rear hub question

[Frank]

assume:
o "bolt-on" cv's/tripods
o (2) deep groove bearings in upright
o spacer between inner races of dreep groove bearings
o two parts transmit the torque from the cv to the wheel ("stubshaft" and "hub")

there's a few ways to transmit the torque from the stubshaft to the hub...

spline
dowels / drive pins
capscrews
key

i hate the capscrew method even more than the key

my question is...

for the teams going this way....

do you find the dowel option lighter / cheaper / easier...?
or is there complications?

kind regards

Frank

[Frank]

assume:
o "bolt-on" cv's/tripods
o (2) deep groove bearings in upright
o spacer between inner races of dreep groove bearings
o two parts transmit the torque from the cv to the wheel ("stubshaft" and "hub")

there's a few ways to transmit the torque from the stubshaft to the hub...

spline
dowels / drive pins
capscrews
key

i hate the capscrew method even more than the key

my question is...

for the teams going this way....

do you find the dowel option lighter / cheaper / easier...?
or is there complications?

kind regards

Frank

[Z]

I am curious as to how FSAE teams do this too...

I can't see the dowel approach being strong enough, especially if using smallish ID ball bearings (how big Frank?). A keyway? Aaack!

The "standard" production car method of an external spline of the CV stubshaft fitting in an internal spline on the hub, which in turn sits in the ID's of the bearings, seems ok to me.

There is also the possibility of a "face spline" (very efficient way of joining two shafts for torque/bending/etc.), but this would require a separate method for clamping the bearing ID's (eg. a standard ring nut from the bearing suppliers).

So how do you guys do it???

Z

[Denny Trimble]

We do splines. The only machining operation we farm out to sponsors...

[Travis Garrison]

Splines are definitely a good way to go, if you can't afford proffesionaly splined stuff, but have CNC access you might look into sinusoidal splines...

http://dot.etec.wwu.edu/fsae/images/Sinusoidal%20spline%20on%20cv%20tripod_JPG.jpg

[Agent4573]

We send our stuff out to get splined also.

[ben]

We machined the tripod CV profile into the hub and then used the disc bell to clamp against the inner bearing. We did it in steel for two years and the team this year did them in 7075 aluminium and hard anodised it with no problems.

Ben

[Rob.C]

indeed we did ben!

the cv sections were cnc cut into the central peice of our 3 piece hubs, then hard annodised, and have very little signs of wear, deffinitely the lightest way we have found of getting the drive across the back end!

however, inboard end was done using the manufacturers splines.

[kozak]

Do you have any pics of that?

[Rob.C]

i dont have any here, i will have a look in the lab tomorrow! and i may post one on here tomorrow, if i can find a suitable one!

[kwancho]

Yeah, I'd be really interested in seeing what that looks like. Thanks!

[Z]

Travis,

Nice work. Is that actually an unfinished axle or just a demo piece? Is that the tripod housing at the far end? What mates to the (tapered?) five-lobed spline at this end?

Wish I could hold it, touch it... http://fsae.com/groupee_common/emoticons/icon_smile.gif


Ben and Rob.C,

I guess you used large diameter "thin ring" (68- or 69- series) DG ball bearings? If so, what size? Expensive??

Z

[Travis Garrison]

Z,

That is a finished axle, with integrated tripod housing on the end...not a work of art or anything, but it got the job done, and was about a pound or so lighter than the other options open to us (mainly shaved VW CV's). WWU has been doing that sort of axle since ~1996 on the formula cars...

The tapered spline mounts to an aluminum hub:

http://dot.etec.wwu.edu/fsae/images/CV%20joint%20tripod%20with%20hub_JPG.jpg

http://dot.etec.wwu.edu/fsae/images/Tripod%20housings%20with%20splines_JPG.jpg

[Frank]

after looking at the whole design again

i figure the bearings need to get bigger because the pins need considerable PCD

the net result for me was no weight saving at all

i LUV those sinusoidal thingies!!!!

any chance of a pic of those parts Ben & Rob C?

[James Waltman]

A few more pictures to show off the sinusoidal splines:
http://dot.etec.wwu.edu/fsae/HostedPics/Viking35/hubs-stubs-cvs/DSC01524.JPG
http://dot.etec.wwu.edu/fsae/HostedPics/Viking35/hubs-stubs-cvs/Assembly.JPG
http://dot.etec.wwu.edu/fsae/HostedPics/Viking35/hubs-stubs-cvs/Rear_corner_full_test_fit.jpg

They are very cool and they are relatively easy to manufacture. The same tapered end mill can cut the male and female profile.

[Erich Ohlde]

Do you make your own tripods or buy some? What material do you use for the tripods? and how do you keep it from chewing up the surface that the tripod rides on?

[Denny Trimble]

The tripods are machined into the shafts.

How did you adjust wheel bearing preload? I'd assume the tapered sinusoidal spline is torqued down good and tight, but what puts preload on the wheel bearings? Or is it a double-row bearing?

[mtg]

Wusses, outsourcing splines. What, you don't like spending an entire night tweaking the cutter in 0.0005" increments to get a good fit? http://fsae.com/groupee_common/emoticons/icon_smile.gif

I did the tripod housings and halfshafts on the 2005 UMR car, and I used a bolt interface between the outboard tripod housing and the hub. It worked pretty good, and they only weighed 1/3 lb each.

[Z]

Travis/James,

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Denny Trimble:
How did you adjust wheel bearing preload? I'd assume the tapered sinusoidal spline is torqued down good and tight, but what puts preload on the wheel bearings? Or is it a double-row bearing? </div></BLOCKQUOTE>

And even if it is a double row bearing, it would have to be clamped up reasonably tight to avoid fretting... So what locates the bearings to the axle shaft? Also do you use some kind of boot over the tripod joint?

BTW I'm liking that twin-tube chassis the more I see it http://fsae.com/groupee_common/emoticons/icon_smile.gif

Z

[Rob.C]

i believe the bearings on our hubs are 95mm OD 618 series INA bearings, as for price, all i have to say is SPONSORSHIP! http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

i have a couple of pictures, but how do i put them on here?? not got a clue!

[scooter2131]

James,

Do you have any more picture of your rear end. It's not really important, I'm just curious as to where you're putting your driveshafts. I may not be able to tell just from the perspective of your last pic.

Also, how did integrated calipers and rim mounted discs work out for you?

[Travis Garrison]

Denny, Z,

One of the axle has a step (visible in the pictures) just after the tripod housing, and we threaded the other end and used a large aluminum nut to sinch it down from the other side.

So I guess I lied...those axles in the pictures aren't quite done...I don't seem to have any pictures of the complted setup (at least no closeups) James might...

Z,

Yes they take a boot to cover up the CV...

That chassis weighed ~55lbs with roll hoops, but should have weight 49 were it not for a layup error. (if .075" thick tubes are good, why not go for .120"? http://fsae.com/groupee_common/emoticons/icon_smile.gif ) Fillament wound tubes and simple bulkheads = $1,700 chassis http://fsae.com/groupee_common/emoticons/icon_smile.gif Hell if we had gone to 13" wheels we could have even had something resembling a traditional suspension geometery.

Scooter,
http://dot.etec.wwu.edu/fsae/SharedPictures/V35%20Complete/rear%20view%20of%20car.jpg

As for the integrated caliper and rim, well if you don't care about scrub radius they work fine. You could make them work OK on a 13" rim with a small upright...but on a 10" they probably weren't worth it. Really they are unnessicary IMO, none of us could use enough of the brakes to justify anything that radical, and they forced a lot of compromises onto the suspension.

[kozak]

why do you taper the sinusoidal splines, is it for better fitting. and for the pic of the unfinished rear drive line and upright i suppose you have a spacer between the end of the splines and the upright bearing, or did i miss something.

[Travis Garrison]

Kozak,

Not a spacer, an aluminum nut...that exposed portion of shaft actually gets threaded, and a nut is put on it to lock it in place.

The taper is just a convenient way to lock everything down tight.

[jack]

if there was no taper, it would be impossible to get the splines "tight". one small disadvantage of the taper setup, is that they eventually wear out (think square taper mountain bike cranks).

[kozak]

ok, so the bolt holds it on one side and the nut pinches it on the other. and the splines want to keep pulling apart is that why they wear.

[Travis Garrison]

Jack, Kozak

The splines don't wear out terribly quickly...V28's were still in good shape when I left, the aluminum hub on V35 started to seat a little deeper when we insisted on taking it on and off several times a week towards the end of the build...but thats about it. Normal driving didn't appear to cause undue wear and tear...they just didn't like excessive #'s of rebuilds...I beleive it was the action of tearing them down and putting them back together, and scraping aluminum out of the way in the process that did it. However they never actually got sloppy or anything.

Frank,

I appologize for hijacking the thread. Not my intention...hopefully you got the info you wanted by now..

[Cement Legs]

[QUOTE]Originally posted by Travis Garrison:
Jack, Kozak

...I beleive it was the action of tearing them down and putting them back together, and scraping aluminum out of the way in the process that did it. However they never actually got sloppy or anything.

Frank, QUOTE]

Did you guys mark the original orientation of the male W.R.T. to female components before disasembling and rebuilding? I've looked at your design before and while we are still hoping to be able to afford to have the spline work contracted out, the sinusoidal splines are within our ability.

[Travis Garrison]

No, we never did...They aren't directional in any way so it shouldn't matter, but I suppose there's a chance that might have helped.

[Denny Trimble]

Just because the joint could be tightened further as time went on, doesn't mean it was wearing out. More likely, the aluminum was yielding slightly, which isn't the end of the world.

You are asking that interface to take a lot of force:
-tapered press fit force
-drive / brake torque
-cornering moments
-vertical, lateral, and longitudinal loads

And, it's constantly rotating just for fun.

I know Travis hates the hubs on the '05 UW car because they took so long to make, but they don't have a joint there. The stubshaft splines only see torque, not bending, and the hub consists of the wheel flange and bearing mount shaft. So, all the wheel loads are fed to the bearings by a single piece, instead of through a joint. Same idea as most production car FWD hubs, but way cooler... http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Z]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Rob.C:
i believe the bearings on our hubs are 95mm OD 618 series INA bearings, as for price, all i have to say is SPONSORSHIP! http://fsae.com/groupee_common/emoticons/icon_biggrin.gif </div></BLOCKQUOTE>
I'm guessing they are 6815's (5x15=75mm ID, 95mm OD, 10mm wide)?


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">i have a couple of pictures, but how do i put them on here?? not got a clue! </div></BLOCKQUOTE>
Me neither??? Any quick tips on pics, anyone???

Z

[adrial]

We did it the same way as Ben C...

If you email me the pictures I can post them, adrialk@gmail.com. You have to host the pics somewhere and then post a link or type it in as follows: http://www.awesomepictures.com/mypicture.jpg

Here is a link to the picture...as it is a little large:
http://www.rfr.rutgers.edu/gallery/Building%20RFR052/DSCF3615.JPG
We used the 6815s...

Here is the upright, I changed the upper BJ bolts to hex heads soon after:
http://stoopidsavant.com/v-web/gallery/albums/050501rfr/IMG_8331.sized.jpg

[Pavan Dendi]

For those that hard anodize...are you able to specify the thickness of the process when you send it off? Is this something that can be controlled reliably or did it take some test pieces to figure out pre-anodized bearing surface diameters?

Assuming that the thickness can be controlled, are there any ill effects of going with a thicker "coat"?

adrial, those are gorgeous uprights. Were they done in-house? Am I correct in assuming there's a spacer in there to keep the bearings separated?

[Wilso]

adrial,
Another question, when you press the wheel studs into the hub, how does the head sit against the back of the hub with that radius there?
BTW, really nice looking parts.

[adrial]

Thank you for the compliments...they along with the front uprights/hubs were my pride and joy for '05.

Most of the machining for the uprights was done using an Alumni's CNC, but this year they will be done in house. The hubs were hand lathed and then the hub face was cnc milled.

There is no spacer between the bearings, rather there is a lip machined into the upright. A spacer between the two inner races would be a good idea to distribute the load to both the bearings during pressing, but I didn't do that and have had no issues.

A flat surface was machined into that radius (using long 3/4" end mill) for the head of the press in stud to sit against. They aren't quite done yet in that picture.

[EliseS2]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Travis Garrison:
Z,

That chassis weighed ~55lbs with roll hoops, but should have weight 49 were it not for a layup error. (if .075" thick tubes are good, why not go for .120"? http://fsae.com/groupee_common/emoticons/icon_smile.gif ) Fillament wound tubes and simple bulkheads = $1,700 chassis http://fsae.com/groupee_common/emoticons/icon_smile.gif Hell if we had gone to 13" wheels we could have even had something resembling a traditional suspension geometery.

</div></BLOCKQUOTE>

I will once again proclaim my love for the chassis.

[CMURacing - Prometheus]

a bearing question:

adrial above talks about not using a spacer for the inner race of his DG ball bearings. have any other teams done this and gotten away with it? deep grooves' don't like a whole lot of misalignment, but does this just mess with bearing life, or do they actually have a possibility of seizing?