Rod end Bearings

[Akiev]

Could Someone please advise me on which make of Rod End Bearings should be good for the suspension. And also with some research I have found that these rod ends are of many types. Like for load, stainless steel ends, molychrome ends etc.
Which shud be gud enuf!!!!

[Akiev]

Could Someone please advise me on which make of Rod End Bearings should be good for the suspension. And also with some research I have found that these rod ends are of many types. Like for load, stainless steel ends, molychrome ends etc.
Which shud be gud enuf!!!!

[kwancho]

1-2-3 search button.
But, Aurora gives a huuuuge discount. Buy from them.

[Jersey Tom]

And for the love of god don't use them wheelside.

[Mike Cook]

To summarize: (and I will be polite since it's Turkey Day)

Calculate the loads through your a-arms. To do this assume maybe 1.5g grip, and calculate lat and long loads produced by the tire and do the statics to figure out the loads in your a arm members. Don't forget the loads that your push/pull rod put through your a arms.

After knowing the loads, you should be able to choose a specific rod end. In years past we have used 5/16 rod ends on the inboard side without any problems. Depending on your geometry and ball size you could go to 1.4 or 3/16". We used the aurora bearing AM series.

On the outboard side I would recommend using a spherical bearing. If you use a rod end it will be put in bending, and most of the cars I have seen with this configuration either has a huge rod end, or is bent. Our 92' car has this setup with 3/8 rod ends and they bend frequently. If using a spherical bearing there are basically two methods of retaining them. The method we use is to make a cup that welds to your a arm members. The spherical bearing sits in the cup and has a snap on ring to retain it. The other method is to stake the bearing. I don't know much about this process. If you do choose to weld a cup on, I would recommend machining the bore after it is welded, and make the fit like a .0003 press.

In the future please uses the search button, these topics have been covered. Also run your post through a spelling editor to correct your grammar and poor spelling. Your posts don't need to be perfect, but they shouldn't be broken english either. It reflects poorly on yourself and university.

[Jersey Tom]

Mike.. wow.. its like a whole new you.

[Akiev]

Thank you so much for the Information you have given me. (the english spellings too...)

The 'shud', 'gud' and 'enuf' were just a way of typing fast and in short. (Used to msn messenger a lot). I know my spellings well Mr. Mike, it's 'SHOULD', 'GOOD' and 'ENOUGH'. I'll make it a point to use the 'PROPER' form of the word the next time.

We are a first time team and don't have enough guidance and expertise. Your help will be extremely helpful to us. We do not have access to a lot of books and motorsport is not all that encouraged in our country, India

[Rex]

It always cracks me up when people use IM slang words. In the example above, a total savings of about 5 letters was achieved. Not sure about others, but it takes me about 1 second to type 5 letters. Folks' time must be awfully valuable to sacrifice clarity over 1 second of effort.

I heard that New Zealand was actually permitting IM slang on their high school standardized tests. What a shame...

Not to open up a can of worms on an old and always heavily debated topic, but in my experience rod ends outboard are fine as long as you do the math to find appropriately-sized ones. I've seen, driven, and built cars with 3/8-24 threads on the outboard rod ends without any bends or failures. Most recently HXAM-4Ts on upper and lower outboard. I would be interested to hear if folks who have bent or failed them used lower alloy shanks, had heavier cars (mine with the HXAM-4Ts was about 475 lbs as I recall), or if I've just been lucky. Just curious.

[Nitesh]

What college? Seems that a lot of indian teams are jumping into FSAE finally. Which competition are you guys aiming for?

Anyway, DO NOT BE TEMPTED BY THE LOCALY AVAILABLE ROD ENDS. EVEN THE BEST AVAILABLE LOCALLY (IKO) AREN'T GOOD ENOUGH. Take it from someone who has tasted dirt using them.

And do listen to Jersey when he asks you not to use them on wheelside.
Good Luck

[sujaykawale]

hi nitesh.. im from akievs team.
we're from kj somaiya college of engineering, mumbai.
yeah, fsae has grown here! in fact, SAE India is starting a mini baja in india from 2008!

but apart from us, DCE and RV i dont think there are others participating, are there?

which college are you from?

[Nitesh]

there are a couple of IITs and other colleges jumping in. In fact IIT-R had registered for the class 3 for UK this year but couldn't turn up.

I am from DCE. What engine are you using. I've heard that you have CBR 600RR. What year is the engine?

[sujaykawale]

we havent bought it yet.. its a 2004 engine.
weve found a guy here who has a bike he wants to get rid off. so we need to check if everythings fine before splurging.

[Nitesh]

is it the whole bike or just the engine that he is getting rid off? what kind of a price deal are you guys getting, if you don't mind sharing?

[sujaykawale]

its a crashed bike so hes selling it cheap.
were going to buy the whole bike and use what we can (nothing apart from the engine and wiring really)

but studying the chassis and mounting points will be good.

we havent fixed the final price but itll be like 2 lakhs..

[NetKev92]

I just thought I'd respond to one of the notes above. I'm not sure Rod ends are the worst thing to have out at the wheels. They do need to be adequately sized though for the load. They use big ones it looks like on the Atom:

http://gallery.atomclub.com/thumbnails.php?album=48

http://gallery.atomclub.com/displayimage.php?album=48&pos=16

It looks like rod ends, not ball joint fittings. Anyhow, almost any solution can be made to work if you oversize it enough for the loads.

[PatClarke]

And what do you think the Design Judges think about great big industrial strength rod ends being loaded in bending through the threaded shanks? Screwed into a big ugly bush welded into an ugly great wishbone?
Why not try it and see?
I hope you are in my Design stream and I'll tell you http://fsae.com/groupee_common/emoticons/icon_wink.gif
Pat

[Jersey Tom]

I have to admit those are some amateur looking a-arms on the Atom.

[NetKev92]

To be honest, I care a lot more what the car thinks about the rod end. If it holds on and handles the load without fail, it's done its job.

The lack of adjustment for castor angle is the only complaint I have about the Atom's suspension. Camber is essentially all you can adjust unless there are other features built into the upright. The bushings inboard should be very durable. Threads aren't a killer either as long as you account for the stress risers in your sizing. A great number of adjustable pitch aluminum aircraft propellers used aluminum threads to hold up to 40,000 pounds of centrifugal load and the associated bending fatigue loads on the blades. They were still lighter than the steel props of the time despite using a so-called undesirable method of attachment.

[James Waltman]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Jersey Tom:
I have to admit those are some amateur looking a-arms on the Atom. </div></BLOCKQUOTE>

Yeah, those Atom guys are hacks. Right, Jack?

[Jersey Tom]

I'm just sayin.. I wouldn't expect to see that on a production car. I've always seen horizontal or vertical sphericals wheelside on performance cars (outside of fsae).

Yea its probably overbuilt and replaceable, but why not just do it the cleaner way?

[NetKev92]

I don't mind that there may be a better way to do the job. Saying that it doesn't work though and is no good is where I have trouble when there are working examples.

I'm leaning toward rod ends inboard for alignment on my project and ball joints wheelside, but I have Miata uprights and the ball joints for the miata are a pain. The lower is an odd shape for a-arm attachment and the upper is an integral part of the stock a-arm. They're also different size mounts top and bottom in the upright so I can't just buy a handful of lowers to do all four positions. I'm having a hard time finding substitutes because I can't find published dimensions on the taper bores of other makes. Four rod ends might make life easier although I agree that I could maybe do better.

My car is also not an FSAE, but more like a roadgoing Formula 1000 car. I don't much care if people turn up their noses as long as nothing breaks going into the turn. How I get there I'm not sure, but I thought I'd post something I saw while doing research on the problem.

[Steve Yao]

I see where Kevin is coming from and I pretty much agree. It also highlights one of the niggling issues I have with the design event, and it has to do with cost. Cost is no object in teh design event. I included some comments regarding the cost of a component in my chat with a judge during the design event and was told flat out that "there is a separate event for cost, we don't consider that here." A-Arms with rod-ends are cheaper, and easier to make and adjust. However, though they can be sized/overbuilt to maintain reliability, they are still more prone to failure than sphericals. The biggest problem though is simply the fact that they are not the lightest solution. The fact that they are unsprung mass compounds the issue.

Thus, in a pure motorsport, cost-no-object, design event like SAE, the outboard rod-end is a dead-end.

But for the rest of world, if its crap and it works, its not crap.

[Peter]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Jersey Tom:
I'm just sayin.. I wouldn't expect to see that on a production car. I've always seen horizontal or vertical sphericals wheelside on performance cars (outside of fsae).
</div></BLOCKQUOTE>

Nope...

http://www.koenigsegg.com/graphics/enlarge/susp_aarm.jpg


Peter
Delft 2004

[Jersey Tom]

I'll be damned.

[BryanH]

In my exp. driver ability is in inverse proportion to vehicle cost. http://fsae.com/groupee_common/emoticons/icon_smile.gif
Is it possible that the designer intended the upright to break away in an impact with a wall, traffic island, etc so that damage to mountings is mimimised?
The ability to repair the car for another attack on the scenery is much better than taking it home on the trailer.

[jack]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">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 Jersey Tom:
I have to admit those are some amateur looking a-arms on the Atom. </div></BLOCKQUOTE>

Yeah, those Atom guys are hacks. Right, Jack? </div></BLOCKQUOTE>

you will have to ask the british why rod ends on the corners is good idea...

[Parker]

look at the Atom, not even in double shear!!

[adrial]

Rod ends can work JUST FINE if you size them appropriately.

Everybody always talks about the weight savings of going to sphericals. Well, how much is it? Its negligible if you maintain the replaceablity of the bearing. That means retaining the spherical bearing with a snap ring.

If your goal is to make design semi's then you better have sphericals...but dont waste the effort unless you at least have an understanding of every system in your car and know why everything is how it is. In all honesty, I think designing your car with the thought of trying to make design semi's is stupid.

Design your car as YOU think is best! If the judges dont like your rod ends...well I guess you're not going to make design semi's. I guarantee you learned more than someone who designed based on what he/she heard the judges like.

[Jersey Tom]

Sphericals are considerably cheaper to implement, at least for us.

[Matt Gignac]

Even if you do go with sphericals, it's no guarantee of design semis. Let's say you can justify the weight savings, and it amounts to something measurable when you consider all your suspension joints, I wouldn't be surprised if a judge asks "What about adjustability?".

Basically, what you need to do is show a clear progression of your concept of how your way of making a certain component is best to achieve your overall goal.

For instance, if your overall design goal is "design a car with maximum adjustability so the average weekend autocrosser can tune the car for the track conditions", then do rod-ends everywhere and justify it. If your overall design goal is "max weight savings so that we have X performance characteristics", then go with sphericals and justify that.

In either case, make sure your design direction is perfectly aligned with your goal. For instance, if you put rod-ends everywhere, but to adjust camber you need to remove the outboard bolt, twist the rod-end a few turns then re-assemble with a new lock nut, this is no good. You'll likely get "well if the goal was adjustability, why do i need to work so hard to change one parameter". Likewise, if you design for max weight savings as a goal, make sure there are no obvious ways that will save more weight over the design you have, or you'll get called on it. If there are, have a damn good reason why you didn't do it.

At least that's my way of looking at it.

Matt Gignac
McGill Racing Team

[Rex]

Yep, sphericals seem to be almost requisite before the judges will consider your car "upper tier," which I think is a real shame. But it certainly doesn't guarantee a decent design score. One year we did rod ends and caught crap for it at design judging. The next year we spent lots of time making spherical holders that saved weight, etc - and the design judges didn't care one bit. Don't build your car for the design judges - you never know what they'll like or dislike any given year. Using sphericals simply because everyone has been trained for years to say rod ends are evil is not the right answer in my opinion.

[Bill Kunst]

I think I have to go with Tom on this one. Why would you not do spericals? Too hard to make the suspension adjustable otherwise. I feel, and maybe my feelings matter as much as which pop star is turning to porn star, that using rod ends is a bad idea. you can design your suspension mounts and upright to have just as much adjustability, safety (breakaway), and faster adjustability then a rodend.

Anyway, If 50% of the time the judges cared, and the other 50% they were neutral and more interested in other things, why would you chance it to make yourself happy. Well, shit, if you don't agree with the judges, that doesn't qualify you for design finals, just an arguement that you can't win. If you are the suspension engineer for your team, you should be shot for be so arrogant about your design that you won't "compromise" it to try to make design finals.

Anyway, if this is for the weekend autocrosser, how much time are they going to spend adjusting the car for different tracks? Its not like you get a whole lot of adjustment time at the different courses, do you? For those of you that autocross, once you have your car set up, what changes do you make to the car at different courses?

[Rex]

A simple difference of opinions I suppose - I would sooner shoot the suspension engineer for compromising a good rod end design just because some judges dislike it. I have a fundamental problem with changing a well developed engineering decision (be it rod ends or anything else) just to suit design judges. It's not being arrogant, it's making a personal choice.

[Mike Cook]

Guys, give the design judges some credit for once... Just maybe...maybe it is a bad idea to put rod ends outboard and thats why the prefer it. When you do implement sphericals outboard they don't talk about it much because its so god damn obvious to anyone with half a brain to do it that way. If you plan a head, a outboard spherical joint will be lighter and stiffer. Period. If you want to build a crappy car that can be built very quickly, go a head and put rod ends out there. And then come back complaining when the design judges don't like it.

[Rex]

Ha! Strong words there Mike Cook.

Of course a properly designed spherical is lighter and stiffer. I doubt anyone would argue that point with you. I'm just sick of hearing everyone rag on using rod ends when the only basis for their viewpoint is tired old rhetoric. Sure they might break if you pick the wrong ones. So do plenty of other stupidly undersized components. Sure they could be lighter. But so could almost every frame or upright I've ever seen. My point here is simply that saying it's a "bad idea to put rod ends outboard" isn't a justified engineering decision. And I certainly don't think you can say that a team who decides to run rod ends after careful consideration of the pros and cons has put together a crappy car.

[Bill Kunst]

This is sort of stupid. Why would you argue to keep something on a vehicle that has to be "oversized" due to a design issue. Putting threads, anywhere on a vehicle, in bending is stupid. The kind of stupid that forgets to pack a parachute when jumping out of a plane.

If you think that the drive shaft splines need to be larger in diamter than the shaft they drive to avoid stress risers, then you should be against threads in bending. Or better yet, why not make the driveshaft big enough so that it won't break despite its poor design elements?

Let's try to go through this design arguement:

Design judge: "why did you use rod ends outboard?"

Student: "For adjustability"

DJ: "How have you acounted for the stress risers in the thereads?"

Student: "I made it bigger!"

DJ: "Do you think that you could have come up with a better design?"

Student: "I don't like that rhetoric you are using with me!"


Yeah, that has design finals, and overall good design, written all over it.

[Matt Gignac]

But let's say the conversation goes like this:

Student: so we used rod-ends outboard in order to be able to adjust camber easily
Design judge: What about the stress risers due to threads in bending
Student: we went with a larger rod-end to account for this, but the difference in weight between the big rod-end and a properly sized spherical is less than the weight we would need to add for adjustable inboard points (i.e. two 1/4" bolts to adjust each of two inboard brackets, plus shims) or outboard points (some shims and two bolts to hold everything together)

I think if you said this, and came up with the numbers to back it up, you'd leave a positive impression on the judges.

Matt Gignac
McGill Racing Team

[NetKev92]

I've intentionally stayed out of this again for a couple days, but it's interesting to watch the back and forth. On stupidity, I think people ought to be careful calling things stupid that do work. I find it arrogant to assume that successful companies that build and make money on $40k trackday cars or $650,000 are incompetent or stupid designers (although I don't know if the Koenigsegg is making profit yet, Ariel certainly has). Maybe it could be done better, but I get the sense that people like to insult an idea rather than just leaving it at "I wouldn't do it that way and here I'll show you what I think would be better".

I do tend to like Matt's student to judge conversation. The prior looked more like someone with a lip trying to start and simultaneously lose an argument.

This doesn't need to be a competition with contest judges. A good judge may have an opinion, but a good designer will always respect a well-considered design. When I find people who will not listen to or respect any other opinion, these are people that I would rather not work for or with.

The quotes around "oversized" are a bit over the top. There is a proper size for a ball joint to do the job and a proper size for a spherical to do the job. If one is heavier than the other or takes more time to adjust than the other, so be it. Each has its own merits though or nobody would make rod ends.

[Mike Cook]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Matt Gignac:
But let's say the conversation goes like this:

Student: so we used rod-ends outboard in order to be able to adjust camber easily
Design judge: What about the stress risers due to threads in bending
Student: we went with a larger rod-end to account for this, but the difference in weight between the big rod-end and a properly sized spherical is less than the weight we would need to add for adjustable inboard points (i.e. two 1/4" bolts to adjust each of two inboard brackets, plus shims) or outboard points (some shims and two bolts to hold everything together)

I think if you said this, and came up with the numbers to back it up, you'd leave a positive impression on the judges.

Matt Gignac
McGill Racing Team </div></BLOCKQUOTE>

Or they could mention the fact that out board adjustment is unsprung weight.

We could keep arguing and arguing. I guess my point is that there are stiffer/better ways to do outboard balljoints, but they may be more expensive or time consuming.

[John Valerio]

the name of the game here is to do well at competition, is it not? thats usually what you shoot for in any competition, and in fsae you simply will not perform well in design with rod ends in bending. especially not with the increased calibre of cars and level of competition. the judges need to make sure you have all the basics covered in your design before they can really appreciate the detailed work or unique features of your car. and why would you default yourself out of a potential good result in design? i would normally agree with matt and say if you bring numerical justification for any design decision it should be acceptable, but the judges seem particularily harsh on this subject, so run sphericals and the judges will spend less time telling you not to run rod ends in bending, and more time listening to you talk about the design highlights of your car.

[Steve Yao]

Outboard adjustment is unsprung weight, but inboard adjustment buggers up all your carefully design suspension geometry. Your change in camber is now linked to changes in roll center, camber gain.

[B Hise]

If you are smart, changing inboard camber will not adversely affect your suspension geometry (changing outboard camber does similar things). Not by any appreciable amount. Do the analysis. Overall camber gain and TLLTD change throughout the roll angle is negligible and well within compensation via alternate adjustments. Well in our geometry anyway.

We know that inboard camber change forces compromise, as does almost any other suspension change. What's important is to know what each change does to the car and what (if anything) you need to do to maintain your setup goals.

The most important part of the whole deal is to know what your car is really doing. Yes in MATLAB your roll centers, wheel rates and camber gain are x, y, and z. But what are they really? Manufacturing tolerances and deflection can be a bitch and physical testing is the antidote.

- Bryan

[Mike Cook]

zing.

[Steve Yao]

I don't know if the "if you are smart" comment was necessary, but I understand your point. I do understand that suspension design is a large exercise in compromise and there are many variables and infinite combinations of geometries to accomplish your goals.

I simply believe outboard is better option. Inboard adjustment will have a larger impact on the geometric relationship between the suspension points than an outboard adjustment which directs the majority of translation into the upright, instead of both upright and control arm. Especially with an outboard camber adjustment that does not affect sprung or unsprung mass. Like ours. But every team makes their own decisions, and with solid reasoning, is resepected for it.

[jack]

the funny thing about all this is the RMIT car that won detriot last year had no way to adjust camber at all.

[kwancho]

Doesn't changing camber outboard change kingpin angle and scrub radius?

[Kyle Walther]

you can do it where it doesn't change the kingpin

[Bill Kunst]

Either way it changes things, and that can be agreed on. If its negligible or destroys handling all together is probably more a basis of the design. I have seen plenty of designs that use inboard and outboard adjustability, all without using rodends. In both cases, most of the designs did not look like they added significant weight, if any. In either case, I have seen designs that were just as fast in adjustability as a rod end, some faster.

Bill

Oh yeah, how about this for simplicity and adjustability for the weekend autocrosser, the one with so much money they, buy what they want and have no clue what they have:

Using shims, rather then guessing which number of turns you had, or forgot. Pretty easy to stamp/laser a label on the shims. Then they get the pack with the car going from -1 to -5, or whatever, degrees of camber in .5 increments. This seems like it would easily outweigh the benefits of the adjustable rodend.