Small CV's/Uni Joints for Steering System

[RonBurgundy01]

Hi all,

This is really for any/all the Aussie teams on here but all/any help would be awesome.

This year we are going to run a floor mounted rack and obviously unless you create the thing like a go kart (i get sick of telling people it's not so i definately don't want it to look like one) then you need some way of running the steering column from the wheel to the floor (about 90 degrees)

I have seen plenty of teams running small little CV's i think (possibly UJ's but can't tell coz they have a boot over them). I am just wondering (from the aussie teams) where abouts in Aus it is possible to get an item this small?

I am assuming the use of CV's mainly because using a UJ would give uneven velocities while turning the wheel hence creating a notchy feel to the steering??? Is this true??

My last quesiton is...with a pair of small CV's (providing they're available) is it actually possible to run a near 90 degree angle in their stock form or do you have to make a custom housing for them??

The option of using a 90degree bevel box is not out of the quesiton, we have some gears suitable but it's a lot of time, effort and dificulty in mounting (triangulation on chassis) that could be solved by a simple joint.

Hope someone out there can help me!!

Cheers

Matt

[RonBurgundy01]

Hi all,

This is really for any/all the Aussie teams on here but all/any help would be awesome.

This year we are going to run a floor mounted rack and obviously unless you create the thing like a go kart (i get sick of telling people it's not so i definately don't want it to look like one) then you need some way of running the steering column from the wheel to the floor (about 90 degrees)

I have seen plenty of teams running small little CV's i think (possibly UJ's but can't tell coz they have a boot over them). I am just wondering (from the aussie teams) where abouts in Aus it is possible to get an item this small?

I am assuming the use of CV's mainly because using a UJ would give uneven velocities while turning the wheel hence creating a notchy feel to the steering??? Is this true??

My last quesiton is...with a pair of small CV's (providing they're available) is it actually possible to run a near 90 degree angle in their stock form or do you have to make a custom housing for them??

The option of using a 90degree bevel box is not out of the quesiton, we have some gears suitable but it's a lot of time, effort and dificulty in mounting (triangulation on chassis) that could be solved by a simple joint.

Hope someone out there can help me!!

Cheers

Matt

[PedalOnTheRight]

Does anyone know where to pick some up in the States too??

As far as the 90 deg bend goes, if you secured it correctly for and aft of the CV joint, it might work. CV and UJs aren't usually meant to work at extreme angles like that (just think of your socket wrench CV and trying to turn it at 90deg). So if you can stil minimize bump steer by moving the rack in a direction so as to create a better angle, do it.

Also, in thinking about it, if you lengthened the steering arm attached to the rack, and made the one attached to the steering wheel shorter, you could definately reduce that angle a bit, although I understand the frame is possibly in the way.

I'd say that having a right angled CV joint would not hold up too well under the stress of rookie drivers!

eej

[Antti Mikkonen]

In states summit racing (http://www.summitracing.com) and search U-joint

[james17]

As far as I know, best thing to suit your application would be the apex covered universal joint. We have used these in the past and have never had an issue with improper feeling in the steering system or failure. They bend to (I think) around 35*, here is a link to the site.
http://www.pegasusautoracing.com/productselection.asp?Product=1490
Think about tilting the rack around the centerline of the tierods, then you could very easily get away with a single joint.

[John_Burford]

Do not use these particular u-joints in steering systems. Although they are very convenient and light weight; they DO have lots of lash, and do not have adequate wear resistance. I have used these in several cars and been dissapointed. If you have to use this U-joint find the 7/8" size availible at Aircraft spuce.

Even though there is a torque spec on these U-joints, they are design for AXIAL LOADS.

John Burford


As far as I know, best thing to suit your application would be the apex covered universal joint. We have used these in the past and have never had an issue with improper feeling in the steering system or failure. They bend to (I think) around 35*, here is a link to the site.
http://www.pegasusautoracing.com/productselection.asp?Product=1490
Think about tilting the rack around the centerline of the tierods, then you could very easily get away with a single joint.

[Dan Nauts]

We're just installing our second custom made 90 degree miter box to our floor mount steering rack. A huge PITA, but way better than running a u-joint at high angle (which I find can get notchy)

We chose not to run 2 universal joints due to the rearward location of our rack, or relative horizontal location of the rack to the steering wheel. High angles would've been needed on the joints.

The decision was also based on the fact that the additional universal joint would require a shaft support on the "middle" shaft, that in our setup, would require the support to be located far off any tubing, so system stiffness was the concern.

[Scotty]

They are Apex joints and we have a pretty good stock of them.Here is a link to what we have.

http://www.taylor-race.com/subcat1.cfm?category=Special%20Parts

[SpdRcr]

http://www.cooperpowertools.com/brands/apex/univ_joints.htm

[Richard Pare]

The Apex booted joints in 3/4" are way more than adequate for your steering. Most small-bore formula car builders have been using that piece for about 25 years with years of life before they need replacing.

To get a near-90-degree bend, you'll need at least 2 joints.

[Cory M]

USA- Aircraft Spruce

UK- Trident

[james17]

[QUOTE]Originally posted by John_Burford:
Do not use these particular u-joints in steering systems. Although they are very convenient and light weight; they DO have lots of lash, and do not have adequate wear resistance. I have used these in several cars and been dissapointed. If you have to use this U-joint find the 7/8" size availible at Aircraft spuce.

Even though there is a torque spec on these U-joints, they are design for AXIAL LOADS.

John Burford
[QUOTE]

I'm kind of curious what situation you are using the Apex joints in that could cause such issues, I just went out and grabbed the wheel of our 2004 car to see if there was any slop in the joints and felt none at all. I can see the issue you bring up if you go past the recommended max. angles, but otherwise I see now way to have these issues.

[John_Burford]

I've seen between 1 to 3 degrees of lash in a new Apex u-joint. Depending on the steering effort designed into the car the lash grows over time. One of the Detroit area schools had 5 to 8 degrees of lash in their 99 car.

I think 3 degrees or less of steering lash is good. 3 to 5 degrees is tolerable for an older car used to train new drives. Above 5 degrees is unacceptable.

Steering lash and friction have a profound on get better lap times out of your top drivers. I've found most FSAE driver won't complain about steering lash or fiction. When their adrenalin is up they don't notice, but get rid of lash and friction in all your driver control especially steer and the stop watch will tell you it was a problem.

John Burford



<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">[QUOTE]Originally posted by John_Burford:
Do not use these particular u-joints in steering systems. Although they are very convenient and light weight; they DO have lots of lash, and do not have adequate wear resistance. I have used these in several cars and been dissapointed. If you have to use this U-joint find the 7/8" size availible at Aircraft spuce.

Even though there is a torque spec on these U-joints, they are design for AXIAL LOADS.

John Burford
[QUOTE]

I'm kind of curious what situation you are using the Apex joints in that could cause such issues, I just went out and grabbed the wheel of our 2004 car to see if there was any slop in the joints and felt none at all. I can see the issue you bring up if you go past the recommended max. angles, but otherwise I see now way to have these issues. </div></BLOCKQUOTE>

[Garlic]

I've seen generic 'cheap-o' versions of the APEX joints that looked identical but had poor lash and build quality.

I've used the real thing and there was nowhere near 2 degree of lash...

[Richard Pare]

There are some counterfeits out there that I wouldn't put on anything.

Genuine Apex joints are built to MS specifications, and lash is one of them. Apex joints are THE standard for steering systems on formula cars.

[RonBurgundy01]

Thanks to all who have entered into this discusion, it has provided a really good bit of light into the problem we face.

What i have taken out of this is

-Apex joints seem to be the acceptable and most widely used product for the application

-They are bloody expensive!

-Dont skimp on the quality of the joint though as they provide too much lash in the steering system when 7 degrees is the limit? (I am pretty sure that's the rule)

-A steering box is damn hard to intergrate into the chassis!

I do have another quesiton though. If using an apex joint on say maybe a 40 degree angle (probably our best case situation) is it required to support the shaft in the middle where it runs down between your legs? I would assume no since it is basically under pure torsion however it is probably not a wise idea to skimp in the size of this member?! And if it does have to be supported...that really sux! The think would be harder to get in and out of than a sprint car!

Once again thanks to all who have inputed info into this thread, very much appreciated.

Cheers

Matty

[Cement Legs]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by RonBurgundy01:
Hi all,

This is really for any/all the Aussie teams on here...

Matt </div></BLOCKQUOTE>

Why is the car upside down. Couldnt resist http://fsae.com/groupee_common/emoticons/icon_razz.gif

[RonBurgundy01]

Legs...you idiot!!!

That was so lame and stupid that i really had to burst out laughing!

Keep up the good work champ

Matty

[Jarrod]

the apex joints won't do 40deg, 35 is the limit, they get very notchy past that (we had ours at about 32). If the rack is mounted rigidly, and the pinion and upper steering column are well supported (ie bearings, with a decent centre spacing) with the joints right next to the mounts at either end, the intermediate shaft can float, but everything needs to be very well made. The apex joints are expensive, but everything else i have looked at for industrial applications, including expensive needle roller units, were absolutely terrible in terms of freeplay, and not all that much cheaper.

[Wes]

Our team runs a 90 degree gear box to a floor mounted rack. The gear box is rated at less than 1.5 degrees of backlash. Combined with some play in the rack and quick release, i would estimate our total play at around 3 degrees. This is ideal for us due to the rearward mounting of the rack.

[drivetrainUW-Platt]

gokart thing? are you talkin about formula sae or some other project? either way, a U joint would be ok if its not too small of an angle your turning. Aas far as the "not constant velocity" part of a u joint, your will be turning it at 2 rpm so that wouldnt be a problem. Most manufacturers will give specs on safe angles for there joints so look at those as well.

[RonBurgundy01]

Mike,

I do appologize for my mistake on the very opening part of this post. What i should have said was...

"i get sick of people telling me it is a go kart so i don't want it to look like one"

This is what happens when you put a post on here at 2am in the morning after no sleep for 40 something hours and in the middle of procrastinating over writing your thesis!

Matty