Spherical Bearings in A-arms

[D-Train]

Just curious as to what specifications the sphericals in a-arms from other teams are - i.e materials for ball and race. I've found that on disassembly of previous cars, the bearings are always really stiff - do any other teams find this to be a problem? We use Aurora AWC-5T's.

[Alastair Clarke]

Hi,

we've used the Aurora HAB-4T PTFE lined bearings so far, which we've found to be excellent but, as you say, a little stiff. One trick is to spin the balls in the races using a drill for a while to loosen them up. Can't remember where I read this, but it was in a book somewhere.

Cheers

[D-Train]

Thanks Alastair. We have used the PFTE lined bearings but found them to be quite stiff after even relatively few testing hours. I was really surprised at the difference in freedom of movement between 2 different types of bearings we took delivery of today... it really got me thinking about our bearing choices.

I'm assuming most teams simply press in their bearings to housings. Anyone stake the housings, or use any other methods to fix them in place (besides loctite)? I think the pressure from the housings might contribute substantially to this problem.

[Jersey Tom]

This last year was our first year experimenting with spherical bearings in our A-arms. Wish I could tell you which brand bearing we used but I have no idea.

Pressed them into 4130 rings on the ends of our a-arms. They were originally machined well under tolerance, welded to the A-arm, heat treated, and secondary machined.

The trick becomes the tolerancing on the press fit, if you do press them in. For a .750 outer diameter bearing your tolerance limits we decided on for the piece you're pressing it into were roughly .7490 to .7495. Probably wiser is .7495 to .7498 - Doesn't need to be a heavy press since you have such a light axial load and you can use other stuff to beef up the hold.

Couple ways of nailing that. One is an undersize reamer, either specific to that size or a .7500 reamer that's been heavily used and is a bit worn down. Or, get a good boring head with .0001 increments (not a Criterion POS) and dial that in, bore it out with a couple spring passes. Or finally you could use a 3/8 or 1/2 endmill, preferably carbide, 4 flute, light feed and again a couple spring passes. Mic it up and measure the tool dia to within +/- .0001. What's sketchy about that is unless your school has a really top dollar machine (Mori Seiki, Makino, etc...Haas and Fadal are really not that good in terms of accuracy and repeatability) the circular interpolation the machine runs isn't going to be all that great and your piece may be out of round or out of spec on the diameter.

Since we were fairly unsure on how all that would work we also used a set screw from the side and loctite to hold the thing in. With the tolerances we held our bearings didn't slip out of the race at all, and with the exception of 1 stiff one, spun pretty freely.

Another issue is measuring what diameter you're machining accurately. Good dial calipers (Starrett) I'd only trust to within .0005-.0010, and a lot of people don't even use them right. For something like this a pair of ID micrometers is really what you need. We of course didn't have any so what we did was a best effort.

Worst part was our rear lower a-arms, the bearing race sits at a compound angle relative to the plane the rest of the A-arm defines. Spent a couple nights up to 2am dicking around with an adjustable reamer and all sorts of crazy setups just to get ONE to spec. Somehow the other one came out perfectly without us touching it.

We're doing things differently this year, I guarantee you that.

[Mike Cook]

We have pressed ours in against a shoulder and then used a snap ring on the other side. One thing to think about is which direction the axial force will be in and make sure you orient the bearing such that it is pushing against the sholder side, not the snap ring side. I had one pop out on our 05 car... I pressed another one in with some serious locktite. I imagine locktite should be used on all them. Also I machined all of the housings first to spec and then welded them to the a arms with a brass insert in place of the sperical bearing. Worked out pretty good. It sound s alot easier than trying to machine it after the fact on a mill.

[Ben Beacock]

I was speaking with a CART engineer two weekends ago about stiff spherical bearings. Apparently the stiction is greatly reduced in dynamic conditions due to the load on the bearing. He had even run an experiment on the rear a-arms between the spherical bearings and some very expensive needle bearings. The conclusion was that there was no measurable difference to the performance of the car.

[Wilso]

We also use a shoulder to retain the bearing in its primary force direction. Loctite and a press fit were used, however the press fit often ended up a slip fit. We pretty much machined heim joints that fit into an A-arm tube which meant the bearing bore was done on a mill with a boring bar, not super accurate, more like guess and check. Only one bearing has removed itself from its home, and in that case the ball popped out to, we're still not sure which came first, the chicken or the egg.

[Alastair Clarke]

Further to what I said previously - we've now used the staking method of retaining the bearings for 2 years. In our first year, we had bearings come loose. We tracked this down to the plate into which the bearings were staked being under thickness by about 0.015", which meant that the staking wasn't effective. A bit of loctite cured that....

This year, we got the plate thickness right, and followed the instructions in the Aurora catalogue for the bore tolerances and the staking procedure. One thing - stake the bearing, then rotate the whole assembly 90 degrees and repeat. Keep doing this till you're back where you started. Apparently this gives a much more even staked joint. We've had no trouble this year with bearings coming loose.

Hope this helps

[Kevin M]

The easiest way I found to attached them was to machine a sleeve with a shoulder in the lathe that the bearing would have a light press fit into, then weld the sleeve to your a arm, press the bearing in and make a jig that will fit in the press and allow you to crimp the back edge over in three or four places around the edge of the sleeve. This hold the bearing on one side by shoulder and on the other by the crimped over metal. This eliminates any chance of the bearing coming loose, but it also means if you have to replace one it has to be cut out. In the two years we did this we never needed to replace one though.

[rjwoods77]

You have to understand them to break them in correctly. The steel ball, over time, will burnish some of the teflon into the pores of the metal. When this happens the joint will work correctly. Just like any other teflon lined anything. I used .5" rod ends on our baja car in the past and they will never loosen up if you dont do it before you run them. I was told to put a bolt through it and tighten the nut down. Put the excess bolt into a drillpress at low rpm and turn it on. Slowly move the shaft(or whatever the rod end is connected to) through the rod ends angular range until it moves smooth. The goal is to burnish the wroking surface of the ball. Do not, under any circumstances use any kind of lubricant,dry lube,grease or anything with a telfon/ptfe lined bearing. That stuff will keep the telfon from impregnating permenantly. No amount of cleaning will resolve this situation. I was told this years ago and it works perfect. Just go slow and steady. Rush it and you will get the teflon too hot and it will deform permanently. The rod end shouldnt get more than slightly warm when you do this. Youll feel it when it the rod end is working properly. Also, staking is the way to go with sphericals. Call frank @ 610-515-0550. He sells staking tools for these bearings.

[D-Train]

I think we'll definitely be burnishing the teflon in the bearings this year, might have had a lot to do with the problems. Mike - I'm assuming you weld a pre-machined housing to your A-arms - do you find the groove for the snap ring deforms with the heat of welding? Is there much movement of the snap ring in the groove axially?

[Mike Cook]

Out of about 16 a-arms we welded up only one snap ring groove got damaged and I cleaned it up with a dremel. I cut the snap ring grooves to whatever it was suppose to be, so no there was not much play there. There is some gap between the bearing and the snap ring (which might be waht you were actually asking...) but really the snap ring is just there to keep the bearing from falling out, not to hold it in during normal operation.

Speaking of spherical bearings, how many hours do you all get out of them? I'm using the aurora com-5 bearings and just had to replace two after excessive play. We probably have 50-100 hours on the car. Also for rod ends i'm using Am-5's and they seem to need replacing about now. Aurora makes a few series of bearings/rodends that are stronger, has anyone used these? I'm thinking about the COM-KH or COM-E. Thanks

[rjwoods77]

Honestly if you are running anything but a 3 piece bearing you are asking for trouble. The 2 piece bearings arent meant for precision work and are suspect in general. The manufacuring process for them is inferior. I think the am series is entry level at the least. I would use a aerospace grade or performance racing version from aurora. I would also like to note that the hab-t versions are rediculously strong for the size compared to the other joints. Look at the dimensions and you will see that the ref. ball diameters are bigger because of the necks that protrude off of them. They are only 2 dollars more a joint that the aerospace ones. So in all of my designs i eliminated all spacers and just use the width of the hab4-t as the spacer itself. It is worth thew 2 bucks a joint to save the hassle of making and not losing the damn things during assembly and repair. Also my entire car uses those things in every place. All of my joints use .25 bolts with those hab-t bearings. I found that they are stronger than what i need in most places and i can keep the same bolt size, which is already small, throught the car. Also cheaper to buy in bulk in real life and the cost report. Something to consider for all of you.

[D J Yates]

For a staked spherical bearing, which is more likely to fail first under axial load, the ball pressing out of the race or the staked race pressing out of the housing? So far we've used HAB-4T auroras also and had no problems, but the housings have been way over engineered and take far too long to make, so i'm after a simple staked bearing design.

Mike, do you have any pics of your a-arms? I'm just wondering how close you can get the welds to the housing bore without serious distortion and how little material can be used.

BTW, slighly off topic but does anyone have experience using oval/non-circular tubing for their a-arms?

[James Waltman]

Originally posted by Rob Woods:
...Also cheaper to buy in bulk in real life and the cost report...
Real life - Yes
Cost Report - No
4.3.4.2(B)

[D-Train]

We used aerofoil (teardrop) cross sectioned tubing in our A-arms last year. They looked damn hot, but we went back to round tubing this year after one bent in the endurance. The main problem was the forces in each arm member were calculated wrong (they must have neglected pullrod force or something), and the mounting of the pullrods onto the A-arms caused a substantial bending moment. I think they used the wrong moment of area (i.e horizontal, not vertical) to calculate their buckling load capabilities. Also found we saved a considerable amount of weight in the component from last year. Still, asthetically VERY pleasing, and not written off for consideration on future cars.

From reccolection, you might be fairly limited due to size availability too. Also consider you need to explain WHY you went for non-round tubing to the judges - I wouldn't try passing it off as an aerodynamic choice if you have nothing to prove it, and don't know what they'll say if you did it "'cos it looks good"...

[CMURacing - Prometheus]

Originally posted by James Waltman:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Rob Woods:
...Also cheaper to buy in bulk in real life and the cost report...
Real life - Yes
Cost Report - No
4.3.4.2(B) </div></BLOCKQUOTE>

This is why (we at least) have used the Aurora C-series rod-ends and spherical bearings. They're almost $3 cheaper per part, and with 8 pullrod rod ends, 20 a-arm rod ends, and 4 a-arm spherical bearings, that's almost $100 (cost report price). i'd kill for those extra points.

w.r.t. non-round a-arm tubing, auburn? had round tubing they ran through a sheet metal roller to make semi-rectangular tubes. we're looking into this for next year, reason being we have lots of cone impacts and are worried about bending an a-arm around one.

[Denny Trimble]

One advantage of aero / oval section tubing is that it has a lower buckling strength than round tubing of the same stiffness / area / weight.

So, you can design your control arms to have a certain stiffness, and if you hit a wall, the aero section members will buckle at a fairly low load, saving the uprights and frame from damage.

Not that we have many walls to hit. But that's really the only argument for aero tubes I've heard in FSAE. We don't run aero tubes because it's not worth the expense. Also, they are more likely to be damaged by people lifting the car, or a well-placed cone lodged under the arm which lifts the car up. The cones get nice and hard around here in the winter http://fsae.com/groupee_common/emoticons/icon_smile.gif

[D J Yates]

I'm not worried about the capablity of the oval tubes under compression. For a pushrod design, tensile strength is more of an issue. Aero efficiancy isn't a good reason for oval tubes, packaging is my main goal and as Mike pointed out, an oval tube is less likely to bend around a cone. I thought availabiliy may be a problem, so for manufacture, i was thinking about folding 1mm(ish) sheet, welding and grinding the seam.

Back to bearings.

Sorry to nag about this. Is a staked spherical alone strong enough to take the axial loads on the pushrod (or pullrod) loaded a-arm, or is a shoulder required. Obviously, it's dependent on the quality of the bearing race and the staking process, but i'm assuming it's done correctly here.

[Cement Legs]

Can someone explian the staking process a little more clearly?

[Pavan Dendi]

Check out pg. 73 in the Aurora catalog:

http://www.aurorabearing.com/2003-04_Internet_Catalog.pdf

[Dan B]

I used AWC-6TG (if memory serves) bearings on the outer ends of the A-arms. I staked all of them with some staking dies I made per the Aurora catalog out of hardened 4340. The bit that it got staked into (which took way too long to make) was 4130 and finish machined after heat treat. I used a brand new on-size reamer to finish the bore.

The bearings were staked using the staking dies in a hydraulic press using my "calibrated elbow" to determine the correct amount of force. I found (always make spares) that if you stake them too hard they will get very loose (at least they did for me). I put a drop of loctite sleeve retainer in each one for the hell of it.

They held up just find to 2 years of our lower A-arm located pushrod location and aero/gravitational downforce without problems.

[Wizard]

First, I want to say I work for a company that makes spherical staking dies. I want to provide information and not sell a product. The information has been learned from servicing hundreds of suspension components from Club Racers to ALMS teams. The information below should be used as a guide and not the gospel. If anyone has any additional questions about spherical staking I can be reached at ekm24@drexel.edu or if you are interested in purchasing a set of staking dies, Mr. Woods provided the phone # above. John McCrory @ Aurora Bearing is also a great resource for spherical bearing information/questions. Aurora also has an SAE sponsorship, don't remember the exact terms but I think its buy one, get one.

For all those looking into spherical bearings I would suggest looking into either the Aurora Performance Series (PNB & PWB) or Aerospace Series (ANC & AWC). They are the same bearings (minus certifications), but for the smaller bearings you need aerospace. Best quality out there.

Life of spherical bearings really depends on the loading they see. One thing that will shorten the life of a spherical is to pre-loosening the bearing. I would highly recommend against doing this and the cause of the stiction discussed above is either through improper manufacture of the housing or cheap spherical bearings. A spherical that doesn't loosen over time is usually caused by an undersized housing or out of round condition of the housing.

The easiest way to make spherical housings is to machine hoops out of 4130. The ID should be .020-.030 smaller than the bearing OD. The hoop OD should be calculated but if you make the OD that of an available end mill, fish mouthing your tubes becomes an easy task. The thickness needs to be that of your bearing. After welding and normalization you want to fixture your control arms on the mill and bore and chamfer the housing to size. Flip over and chamfer the other side.

The housing bore and chamfer is critical and the tolerances outlined in the Aurora catalog should be followed. I believe the housing OD should be +.0003/-.0002 of the bearing OD. If anything stay on the top end of the tolerance because a little big is better than small. I also recommend using a proper boring head. Once the housing is to specs, you can press the bearing in on the race(sockets work well) with a little Loctite 680 around the housing. The procedure is again outlined in the Aurora catalog.

The staking process is key. You can manufacture dies or purchase them. But proper staking pressure is critical to ensure a sound joint. DJ, you asked which will fail first. Well I have seen a few bearings be pressed out of housing only to find the chamfer was well undersized/non-existent or almost no deformation of the bearing race. Never seen a ball push out completely, a few very deformed and the bearing housing remained in tack. Finding proper staking pressure is key and will take some trial and error (if you purchase our dies we provide proper pressure done through testing). The key is to make sure you have deformed the edge of the race into the chamfer and you have no larger than a .005 gap. To much pressure will actually cause the bearing housing to deform against the ball (i.e. stiction) and to little you run the risk of the bearing getting forced out of the housing.

I hope this helps.

Eric Moyer
High Performance Vehicle Engineering 610-515-0550
Drexel Racing Formula SAE

[Cement Legs]

Is it a real no no to use heat on the housing to expand it while fitting the bearing? I'm thinking a couple hundred degrees tops, and perhaps even precooling the bearing....

[D-Train]

I'm guessing so... I tried putting an old bearing in a drill press at low speed and moving it about - one of them (which was admittedly already quite stiff) started smoking (drill was going around 100rpm), seized up soon after. It seems to have a lot of stiction now. I tried it on a few others though - all of them were much easier to move afterwards. I haven't done this to any of our new ones yet (just stuffing around with old ones so far), and by the sounds of it, it's probably not a good idea (contrary to what I decided after playing around... http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif).

[Wizard]

Mr. Legs,

The housing has to be prepared properly or else you will have excess stiction in the bearing. No heat or cold. A machinist vice with a socket on the housing and a socket on the bearing race works great and if you need more force than what you can generate with the vice handle your bore is to small or out of round.

[D J Yates]

Eric, that was exactly the kind of info i was after, given me plenty to think about. Thanks.

[buddy]

David,

You should check your brake reactions, you'll probably see a-arm compression at some point. Then check weak-axis buckling

buddy

[D J Yates]

Originally posted by buddy:
David,

You should check your brake reactions, you'll probably see a-arm compression at some point. Then check weak-axis buckling

buddy

There is often compression, but when i said that tension is more of a problem, it is. With pushrods at a shallow angle, the reaction is a greater tension in the lower a-arm.

With a braking reaction there is compression in one of the lower arms but therfore, tension in the other, so braking reactions are a mute point.

I did a thourough analysis for a complete set of loadcases/manouvers and overall, for the design of our car, the likely failure mode was a failure of the a lower a-arm member under tension. With non-circular tubing, the buckling failure mode will be reduced, but provided i don't reduce it by more than say 30%, the predicted failure mode is still tension. Meanwhile, increasing the strength in the other direction so making the car more durable to cone (and bollard. - yes, one of our drivers took out a bollard during enduro, plus countless cones) impacts.

From a laymans point of view, buckling would appear to be the obvious problem with skinny a-arms. But as i look into the whole analysis further i keep finding things that are even more likely to fail. For our latest car, i was worried about the hoop stresses caused by an overkill interference fit for the spherical bearing, which increases the chance of a failure under tension.

[buddy]

David,

Your previous post sounded a bit simplistic, but it sounds like you are on top of things.

buddy

[Jevon]

So how does everyone attach the spherical housing to the a-arm tubing? I was planning on attaching the bearing via the stacking procedure discussed previously which means the tubing must be reduced a considerable amount.

I've seen the tubing crimped down to size. Is there a special way to do this? Gradually roll it down or throw it in the vise and crank it down? How did you model this?

I was also thinking of doing it this way. One tube would be attached to the spherical housing then the other attached to them and then everything milled down.

http://www.j9gardens.com/images/Jevon/a-arm.jpg

Thanks for your help.

[D-Train]

I seem to remember Claude Rouelle mentioning something about teams who crimp down the tubing, and I don't think it was good.

We use housings that are about 2mm bigger (axially) than the A-arm tubing to give a good area for welding, though our bearings are just pressed in with loctite. The large housings mean we can't stake them.

[Schumi_Jr]

Jevon,

I like the idea of staking the bearings since you don't need spacers to mount to your clevis. Without spacers the joint is much smaller, lighter and stiffer. The problem with crimping the end of the tube is that you have a stress concentration right at you weld joint from the section change. If you heat treat the a-arm this probably isn't an issue, though.

We crimped the tubes on our inboard joints for our 2005 suspension using a custom die and an arbor press. It was really simple to manufacture and has been trouble-free. Our outboard joint is similar to what Dwayne described but we used snaprings to provide positive retention. Of course, we are changing everything next year http://fsae.com/groupee_common/emoticons/icon_smile.gif Good luck!

[CMURacing - Prometheus]

i know i'm probably going to be revealing a seemingly great idea i'd like to keep for myself, but what about sheet metal a-arms? or maybe really small thin-wall tubing with great big gussets? or maybe aluminum, a la the machined ones we see on the wwu car? this would give you a lot of control over the thickness of the a-arm to which you weld the spherical bearing housing, etc.

anyone already looked into this, and what to steer me away from what i see as an interesting path?

PS: i got this idea from the pagani zonda f on my desktop right now, and also from a ferrari 312/t5 sitting in the basement of the building i'm interning in...both of which have pushrods integrated into the upper a-arm in the rear, another cool idea i think, but possibly not able to be carried over well...

[D-Train]

Sounds like someone might be considering aerofoil... http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

I've seen the A-arm/pushrod design as used in the Zonda, but think it might be a bit heavy for SAE use, and it might be hard to get the motion ratios right without using a bellcrank (consider you ideally have 2 inches wheel movement in total, and want the shock to move throughout it's entire range in that 2 inches). For those who haven't seen it, here's the zonda setup.
http://www.paganiautomobili.it/download/galleria/fn000217.jpg

(EDIT: On second look, might not be so hard to get the motion ratios right... still, looks heavy-ish compared to standard pull/pushrod and bellcrank setup.)

[Jarrod]

heres one example

http://www.davidanderson.org.uk/images/donnington/eagle1%20(Large).jpg

quite common in the 60's 70's on grand prix and also F2, F5000etc, upper wishbone was also a rocker for the spring and shock.

[CMURacing - Prometheus]

I'm not considering aerofoil, we were thinking of the crushed-tube type of assymetric a-arm tubing, but sheet metal seems like another alternative we should look into. i think if we do it right, we can make it stiffer in bending in the wheel motion and cone-striking axes than round tubing, and we wouldn't have to crush the ends to weld on the spherical housing.

[D J Yates]

Originally posted by CMURacing - Prometheus:
I'm not considering aerofoil, we were thinking of the crushed-tube type of assymetric a-arm tubing, but sheet metal seems like another alternative we should look into. i think if we do it right, we can make it stiffer in bending in the wheel motion and cone-striking axes than round tubing, and we wouldn't have to crush the ends to weld on the spherical housing.

That's exactly what i was thinking of doing. I can understand why you didn't want to mention it - it solves so many problems and has some additional positive side effects. With some well made jigs, manufacture should be simple enough. Compared, to what i've done so far, it'll be much cheaper and just as light, if not even more so.

[TG]

Originally posted by D J Yates:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by CMURacing - Prometheus:
I'm not considering aerofoil, we were thinking of the crushed-tube type of assymetric a-arm tubing, but sheet metal seems like another alternative we should look into. i think if we do it right, we can make it stiffer in bending in the wheel motion and cone-striking axes than round tubing, and we wouldn't have to crush the ends to weld on the spherical housing.

That's exactly what i was thinking of doing. I can understand why you didn't want to mention it - it solves so many problems and has some additional positive side effects. With some well made jigs, manufacture should be simple enough. Compared, to what i've done so far, it'll be much cheaper and just as light, if not even more so. </div></BLOCKQUOTE>

I was thinking along these lines, except with carbon that is fused to metal ends for mounting, as it was noted that weight can be an issue. I believe portland saved a few pounds (maybe more, I forgot the number they told me) from each corner by going to carbon tubes over steel ones.

Has anybody tried or know about just forming carbon around a spherical bearing? Maybe a low temp prepreg?

[D J Yates]

When you say fused, how do you mean?

I was discusing carbon fibre with a final year materials student who was doubtful of using an adhesive to join a steel bearing housing to a carbon fibre tube. He explained how the strength of a CF/steel joint was achived by shaping the steel such that the carbon fibres weave around it such that the fibres carry the load, not the adhesive. However, he suggested that if you were going to that much trouble you may as well form the carbon fibre around the bearing.

Contrary to this, i looked into using an adhesive to join a steel housing to carbon tube. I'm confident that it can be made comforatbly strong enough. However, it requires so much machining that it's really not worth it - the CNC technician reckoned about an hour for each housing, plus several tool changes because of wear. Even though our machining time costs the team nothing, with so many machined parts it hurts the cost report severly. If you could use aluminium instead of steel it would be much faster and cheaper.

Has anyone tried using alumiuium to house there spherical bearings? Because it's less stiff than steel it should be much easier to get a desirable and repetable interference fit without requiring a high quality CNC with tiny tolerances. But then obviously strength and stiffness during use becomes more of an issue.

[CMURacing - Prometheus]

the next question is, instead of just sheet metal, what about that structural foam henkel hands out every year (terocore)? or use all aluminum and make a honeycomb structure?

if you want to do carbon, why not take the delft approach and machine aluminum end caps that take all the spherical bearings?

i'm glad you had also thought of this DJ, the fact that two of us came up with it makes it seem like less of a "flux capacitor" idea...

[Chris Boyden]

All capacitors are "flux capacitors" http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Igor]

Maybe a bit on the complex side, but they do work.

http://www.dutracing.nl/pictures/albums/wpw-20050701/normal_PICT3407.JPG

Igor

[TG]

Originally posted by CMURacing - Prometheus:
if you want to do carbon, why not take the delft approach and machine aluminum end caps that take all the spherical bearings?

The Delft approach uses blind bonds... not very good from an engineering stand point. There is a way to do it without the blind bond and are able to rely on the bond. CMU, you saw the links in the other post, same bifusion tech eliminates the blind bonding.

[Cement Legs]

Hey Igor they look nice. You say complicated but ours are basically the same thing, only they are 5 parts welded together so i think you have found a way for us to save a bunch of work..... http://fsae.com/groupee_common/emoticons/icon_smile.gif

Can I ask how much the larger pieces with the pushrod mounts weigh?

[D-Train]

Very clean set up you have there Igor. Do you use carbon or steel tubing with those? And what's the rectangular shaped piece on the part to the left of the picture?

[Cement Legs]

I'm just guessing but it looks like work in progress ???? (and a box of matches http://fsae.com/groupee_common/emoticons/icon_biggrin.gif)

[Igor]

I'm sorry if it looked like I made them. They're from this years Delft car and I'm already an alumnus. Just thought to illustrate the topic.
The parts bond to carbon tubing. The rectangular piece looks indeed like a work in progress.
They look sweet but I think it might be easier to make them in three parts. One square section with two cylinders bonded in.

Igor

[D-Train]

yeah, just thought it might have been some sort of go/no-go gauge. Guess it didn't make much sense being a fully machined part http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif

[D J Yates]

Originally posted by Igor:
I'm sorry if it looked like I made them. They're from this years Delft car and I'm already an alumnus. Just thought to illustrate the topic.
The parts bond to carbon tubing. The rectangular piece looks indeed like a work in progress.
They look sweet but I think it might be easier to make them in three parts. One square section with two cylinders bonded in.

Igor

That is almost exactly how i had designed the housings for this years car. However, after seeing how long it took to make last somthing similar for this years car i'm now going in completely the opposite direction. I belive that i could achieve somthing that performs just as well (maybe even better) yet is cheaper and quicker to manufacture. That said, they do look nice though.

[Mechanicaldan]

As for shaping the 4130 tubing, I just heated each end with a blow torch until it was glowing red and then forged it with a hammer into an oval. I tried to flatten and taper the tube up to about 2 inches from the end. It was kind a zen experience. The tubes were then ground by hand on a grinder to fit the spherical bearing housings that were sitting in a jig. No failure yet.
http://sae.stuorg.iastate.edu/albums/album09/DSC00145.sized.jpg

[kozak]

what is your material thickness on your bearing ring. and you say that you haven't had any failures yet have you tested with the crushed tube design before.

[MH]

Can I ask how much the larger pieces with the pushrod mounts weigh?

The bigger ones weigh 67 grams each. The smaller ones 42. Don't forget, these were designed for a 130 kg car http://fsae.com/groupee_common/emoticons/icon_smile.gif

Actually we got very good feedback from the judges for this solution. They just loved the fact that our carbon wishbones were glued to the aluminium inserts.
The inserts are pretty costly though...

cheers,
Miki Hegedus
Technical Manager DUT Racing 2005

[GTmule]

instead of the pain in the ass machined aluminum bits. What about fabbing up some steel inserts like you made, basically just a standard spherical housing (like Mechanicaldan has pictured up there) and, (using a jig) welding little bits of tube to it. Would that produce the same effect?


speaking of Carbon tubes.

I have this overwhelmind desire to use Graphite Golf shafts for SOMETHING on a car. Either as tension members in the wing mounting, (shortened) as sway bar links, shift linkage bits, I dunno.....but something. They're like 10 bucks and QUITE strong.

What types of adhesives do you use? Hysol type stuff?

Anyway.....

-chuck

[Mechanicaldan]

That picture is from a car that is 2 years old. Same design was used on this year's car. I don't know the thickness, sorry. It's a 1/4" bolt. Eyeball thickness would be about .125".

[MH]

What types of adhesives do you use? Hysol type stuff?


We used 3M Scotch-Weld 9323 B/A. But we're just calling it pink glue http://fsae.com/groupee_common/emoticons/icon_biggrin.gif
Used properly it's one of the strongest adhesives around.

Miki Hegedus
Technical Manager DUT Racing 2005

[Cement Legs]

In spite of the fact that our rod ends are oversized to begin with we have decided to mount spherical bearings in the critical locations. In order of priority what places would most warrant the use of sphericals? Also I just got a price quote for $30 a piece ($CDN), can someone recommend a different distributor because we cant afford to build a car and get rapped at the same time....

[adrial]

Originally posted by Cement Legs:
In spite of the fact that our rod ends are oversized to begin with we have decided to mount spherical bearings in the critical locations. In order of priority what places would most warrant the use of sphericals? Also I just got a price quote for $30 a piece ($CDN), can someone recommend a different distributor because we cant afford to build a car and get rapped at the same time....

The outboard rod end that is supporting the weight of the car should be priority #1 to be a spherical. Priority #2 is the outboard rod end that isn't supporting the weight of the car.

[CMURacing - Prometheus]

the outboard a-arm ends that deal with brake torques are also a problem, especially as you don't want a part to fail under braking.

as for prices, dealing with aurora bearings directly has proven to be the cheapest approach for us.

[Wizard]

If anyone is interested in purchasing staking dies we are starting our yearly run. We typically stock many sizes however if anyone is interested in staking -3 Wide (AWC-3TG) or -3 Narrow (ANC-3TG) or any High Misalignment Bearings please Email ASAP. We typically do not stock these items and we can add these items to our production run.

Prices:
Retail Price $360/set
SAE Price $180/set 1st Set
2 or More Sets is $120/Set

Each set include two dies: One Starter, One Finisher

Eric Moyer
High Performance Vehicle
ekm24@drexel.edu

[rjwoods77]

Hey Eric,

We are going to need staking dies for hab-4t bearings from aurora. What diameter is the die at the pressure point? I need to find out if I have clearance in my holder for them to be used.

[D-Train]

To the teams who run staked sphericals, do most of you just crush the A-arm tubes to get them down to the right thickness, and if so, how long is the crushed region? (EDIT: Just looked back to Mechanicaldan's post. Is 2 inches the norm?) And does this have any major effect on the buckling loads they can withstand?

Anyone doing things differently?

[Wizard]

Originally posted by Rob Woods:
Hey Eric,

We are going to need staking dies for hab-4t bearings from aurora. What diameter is the die at the pressure point? I need to find out if I have clearance in my holder for them to be used.

The OD of a HAB-4TG die (the "G" means grooved for staking) is typically 1" but we could modify the OD for additional clearance. Off the top of my head we could probably make them 7/8" OD. Due to the shallow angle of the second die you would need the full 7/8" clearance, if we make the die walls to thin there are durability issues.

Eric

[rjwoods77]

Originally posted by Wizard:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Rob Woods:
Hey Eric,

We are going to need staking dies for hab-4t bearings from aurora. What diameter is the die at the pressure point? I need to find out if I have clearance in my holder for them to be used.

The OD of a HAB-4TG die (the "G" means grooved for staking) is typically 1" but we could modify the OD for additional clearance. Off the top of my head we could probably make them 7/8" OD. Due to the shallow angle of the second die you would need the full 7/8" clearance, if we make the die walls to thin there are durability issues.

Eric </div></BLOCKQUOTE>



Cool. Be calling you as soon as i get access to my funds.

[Mapes]

what kind of spherical bearings do teams use and from what company do they get them from

[kwancho]

Wargh! You did all the work to find it, so be unlazy and read the thread. People use different bearings for different parts. You need to figure out the forces being put on the bearings, and then when you get a catalogue from a bearing company (*cough* Aurora), you can look at the various max loads for all their bearings.

[SD]

Have any of you had any problems maintaining adequate amounts of misalignment when using the shoulder/press/snapring method of constraint?

[Mapes]

What is the best way to mount a spherical bearing onto the A-arm staking it or some other way

[SD]

The best depends on various factors...

For our team where manufacturing is a large concern the shoulder, press fit and retaining ring is the best method of constraint.

If you read this thread you'll hear a few different views on the subject.

[Wizard]

Mapes,

There is more than one right way to retain a spherical bearing. A staked bearing is traditionally used on inner control arm joints and outer joints when space is an issue (mostly on upper ball joints). The lower joint I mostly see some type of housing in which the bearing is retained by a shoulder and c-clip or two c-clips. The two c-clip method along with some fancy machining can get you a lot of mis-alignment but make sure to use high quality retaining clips.

Proper preparation of both a staked bearing housing and a housing/clip is the same. The bore is critical. To small and you create excess stiction, to big and you have play in the joint. When machining the c-clip goove the distance from the shoulder to the start of the groove is also critical. Typically you run your tolerances on the low side to ensure a bit of clip preload on the bearing.

[Mapes]

Originally posted by Alex Kwan:
Wargh! You did all the work to find it, so be unlazy and read the thread. People use different bearings for different parts. You need to figure out the forces being put on the bearings, and then when you get a catalogue from a bearing company (*cough* Aurora), you can look at the various max loads for all their bearings.

Hey Kwan
I am just a freshmen doing a little bit of research on the subject. I have no clue what to look for and exactly who to get them from so if you could just cut me some slack on the matter.

[kwancho]

Oh, apologies if I came off a little harsh. Hell, I'll be the first to admit I don't know any more than you do. I''m in the same place as you. We're a first year team, and I'm doing the same research you are. Props for finding this thread, but I'm relatively sure the answers to the questions you asked are somewhere in this thread. All the part numbers listed in this thread will make a lot more sense if you get an Aurora catalogue (I've got one sitting next to my desk), and see exactly what bearing they're referring to.

[Wizard]

Mapes,

Aurora has an online catalog and you can also download CAD drawings/models of a majority of their bearings.

http://www.aurorabearing.com/


They also have a CD with all the CAD models, but you have to call to request that. I have extra copies of the catalog/CD if you need them.

Eric

[Mapes]

Originally posted by Wizard:
Mapes,

Aurora has an online catalog and you can also download CAD drawings/models of a majority of their bearings.

http://www.aurorabearing.com/

Hey thanks to kwan and wizard that should help I will look deeper into aurora bearings. Thank you


They also have a CD with all the CAD models, but you have to call to request that. I have extra copies of the catalog/CD if you need them.

Eric

[Mapes]

Eric
Could you tell me where you ordered the CD with the CAD drawings. All I need is the CD I have the catalogue.
Mapes

[Mapes]

I was wandering if anyone knows anything about a company named Bartlett Bearings. If you do do you know if their bearings are quality or not. Also does anyone know if Aurora has the prices for their bearings somewhere on the site or if you have to call to get the price.

Mapes

[Psychosis]

hi guys,
just looking at bearings at the moment, we have a bearing sponsor who don't sell staked bearings, has anyone created a stake groove in their wishbones and a tool to match? my concern is that as you stake it the material is being folded into compression rather than folded out in tension. the alternative is to use circlips, which i think will be a little more complicated (though less permanent) and also increase the depth of the wishbone,
any help would be great,
cheers

[D-Train]

Psychosis - We made an attempt to stake the bearing housings rather than the bearings in a previous year - Colin can probably help me out here. Not really sure how successful it was. Our bearings are press-fitted in with Loctite, and I imagine the staked ones were done the same. The only time I've seen any of our sphericals move in the housings was with a set of arms made up for testing early this year where the reeming job was botched (by yours truly), but no harm came from it.

[Wizard]

Mapes,

You can also download 2D and 3D CAD drawings/models off the Aurora website. If you click "Download CAD Drawings" from the left toolbar on the Aurora main page you can download all the rod end and spherical drawings you could ever need.

Click on Military Specification Units - Spherical Bearings - and there are all the wide and narrow spherical bearings. Remember the Aerospace Sphericals and Perfromance Racing sphericals are identical (aerospace just has certs).

Hope this helps.

Eric

[kozak]

i want to use staked sphericals on the outboard side. how thick should the material be that i press the bearing into. should it be the same height of the bearing, or however much thinner to allow the staked part of the bearing to spread over the surface.

EDIT - nevermind there's a chamfer.

[JesseS]

If you got to aurorabearings.com and download their catalog as a PDF you will find all the information you need in terms of designing a housing for your bearing (assuming you are using an aurora bearing). If you have additional questions send them an e-mail, they are very responsive and helpful.

[kozak]

yeah i looked after i posted and saw the chamfer in the surface.

[Wizard]

Originally posted by kozak:
i want to use staked sphericals on the outboard side. how thick should the material be that i press the bearing into. should it be the same height of the bearing, or however much thinner to allow the staked part of the bearing to spread over the surface.

EDIT - nevermind there's a chamfer.

Kozak,
The housing should be the same thickness of the spherical bearing you are planing on staking.
EXAMPLE: If you were making a housing for a AWC-4TG, your housing thicknes would be 0.327 +/- 0.005. This dimension is critical but what is more critical is that both surfaces are parrallel. This will make it easier to prepare the housing for staking. Refer to my post on page 2 of this topic for more info on spherical bearing staking.

Refer to pages 72-73 of the Aurora Catalog for more info of preparing the housings.

Eric

[RickyRacer]

I was wondering if amyone has had a staked bearing fail on them(come loose). Our tech advisor doesn't want me to use staking, rather machine a small lip on one end and a groove on the other end for spiral locks.
Rick
Long Beach State

[Wizard]

Rick,
I don't know how much experience your advisor has with bearing staking but I have never seen a properly staked bearing "come loose," in terms of the race coming loose from the housing. Spherical bearings that are properly sized will and should become loose (ball to race interface) over time due to Teflon deformation.

I have seen bearings "come loose" and fall out when bearings are just pressed in with some Loctite. I have also seen spherical bearings in a snap ring housing come loose when the spiral ring falls out since the groove was machined improperly.

Proper housing preparation is key no matter if your going to stake the bearing or use a shoulder/snap ring combination. Machine the housing wrong and it doesn't matter how you decided to retain the bearing. Just something to keep in mind when you decide what type of retention method to use, both require time and need to be made to spec to work correctly.

[Moody]

quick question on a great topic: for those using (and staking) Aurora's HAB-4TG bearings, what chamfer are you using? they list 3 different groove types (A,B,C) and each has a different chamfer spec, but there's no clarity as to which one of the three applies to my bearings.

calling aurora only leads me to the CAD CD which doesn't help in regards to housing design - can anyone shed some light on this for me? I know its likely i'm missing something really easy.

[D-Train]

I really doubt a staked spherical would come loose if press fitted in. As I said before, we press fit ours with some bearing retaining compound and have only ever had one move that i've seen, and only after the reeming was rushed and messed up. Mind you, we tend to use as much of an interference fit as possible, provided the bearing still moves in the race freely. Combine the press fit and staking and I'd be confident your bearings aren't going anywhere.

[Wizard]

Moody,
A HAB-4TG is a Type A groove.

Dwayne,
I would look to going away from "as much of an interference fit as possible." If you prepare the housing to spec, the swage will provide more than enough positive retention.

[Omer]

hey guys

what is the distance of your rod end inside the A-arms?

last year team bought 40 rod ends which i beleive has too short thread.

and can please someone explain to me the difference between sphricals and rod ends?
and what makes the difference between rod end in bending to the right way of placing it?

pictures would be very appreciated

[Ryan Stiltner]

Originally posted by Wizard:
Mapes,

You can also download 2D and 3D CAD drawings/models off the Aurora website. If you click "Download CAD Drawings" from the left toolbar on the Aurora main page you can download all the rod end and spherical drawings you could ever need.

Click on Military Specification Units - Spherical Bearings - and there are all the wide and narrow spherical bearings. Remember the Aerospace Sphericals and Perfromance Racing sphericals are identical (aerospace just has certs).

Hope this helps.

Eric



Eric,
I am looking to buy a staking die for the aurora bearings that we purchased. I was wondering if you had any suggestions of where I could buy the tool.

[Wizard]

Ryan,
The company I work for makes staking tools and we have discounts for SAE teams. Give me a call and I can help you out.

High Performance Vehicle Engineering
610-515-0550

If anyone else is interested in staking tools or has any questions regarding bearing staking please feel free to get a hold of me.

We are currently making a run next month due to recent SAE team interest in our dies so I would call if you want a set.

Eric

[Wizard]

If there are any teams out there that are interested in staking dies please contact me ASAP. We are currently finishing up our 2006 production run and NOW is the time to order. We do not stock dies for small bearings (i.e. AWC-4TG and any High Misalignment Bearing), so NOW is the time to order if you need them before comp. Our next full production run isn't until the summer. We do make non-stocked dies when orderd but after we are finished this run the lead time will become 6-8 weeks.

Eric Moyer
610-515-0550
High Performance Vehicle Engineering

[vandit]

for the teams who use/used loctite between spherical bearing and housing ....

today out of curiosity we made tesion test to check the strength of loctite . the spherical bearing gave away at just 2.8KN ... i will briefly put the facts about it

we used M8 spherical bearing in a steel housing having a seat.. not a press fit case , more on finger press fit types (i dont know the tolerance numbers) ... used Loctite 640 and applied to a warm housing... allowed 24 hours for the joint ...

does anyone have idea how much axial load this loctite is supposed to take .... after checking the spec sheet of Loctite 640 , it should take upto 18KN ... either i am misinterpreting the spec sheet ... or their is some serious flaw in ...

[Tom W]

Loctite products are generally extremely sensitive tolerances (they don't like loose fits, check the "Maximum Gap Fill Diameter" they are rated for) and also to any grease/oil/general rubbish left on the bonding surfaces. I think Loctite do their testing in extremely clean environments. In various testing we have never got anywhere near the claimed Loctite stress numbers.

At a guess if you are able to push the bearings into the housings by hand then you have too large a gap to try to fill. If you didn't do any form of surface prep then that would also massively reduce the bond strength.

[vandit]

@ Tom

no we didnt do much great surface preparation ... just cleaned things with acetone for removing dust and etc. i think the problem was loose fit .

i just returned from making another sample . this time i didnt play with the press fit tolerance , i just heated the housing little more to allow the bearing go in with loctite. so i am assuming that once things cool off, it will be kind of press fit with loctite and then tomorrow we will check the force required to snap off ...

actually we are just trying things with last years housing and bearing , no machining access in holidays ...

[JamesCH13]

There is also such a thing as too close of a fit when working with adhesives. I've also read that Loctite 609 is best for a press-fit.