Steering Gearbox

[Kyle Jeffries]

Due to the location of our steering rack in relation to the front roll hoop/steering wheel, it looks like we're going to need a 90 degree steering gearbox. Does anyone use such a setup or know of a place we can source one? Everything I've found has either been too small, or way too large.

Thanks.

[J. Schmidt]

If you've got the room, use a right-angle drive adapter. Andantex (http://www.andantex.com/) makes some really precise adaptors, but they're heavy.

[Buckingham]

We designed and built a 100 degree box last year for the same reason, with success. The hardest part about using a gearbox is that it requires a fairly rigid mount.

[dartmouth01]

We're looking to use a double u joint, anyone have success with those types? Though our angle is not close to 90 degrees, there are some out there that will do close to that.

[Big D]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by dhaidinger:
The hardest part about using a gearbox is that it requires a fairly rigid mount. <HR></BLOCKQUOTE>
We had such a system on an old car, except for the "rigid mount" part http://fsae.com/groupee_common/emoticons/icon_frown.gif . To be fair, it went to 2 comps, and did a summer of local autocross, but now it is in the scrapyard where it belongs http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif . On it's last day of driving, the bevel gears jumped a tooth while I was cornering.... not the most confidence inspiring thing (haha, how's that for an understeer characteristic?)So if you have to do it, do it as precise, and rigid as you can.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> We're looking to use a double u joint... <HR></BLOCKQUOTE> Our last car has a double U-joint, but only because someone specced it without thinking it through(we could have got away with a single, and no support. With a double, you need a support at the other end of the joint. other than that it works fine.

On both points, I don't see why either is neccessary. You can design to avoid them. We run a bottom monted, front steer rack, and will be running a single U-joint, or perhaps an apex bearing. The only configuration with more angle needed would be bottom/rear steer, but any chassis book I have read reccommends ONLY front/bottom, or top/rear, so you'd need a very good reason to compromise the steering with a gearbox and a non-ideal layout.

[IsheeM]

What do you guys think about the apex universal joint? I noticed they are quite a bit more expensive than standard universal joints. I know they allow the joint to be permanently lubricated but is this make that much difference or are there other benefits that i am just missing?

Thanks,

[Denny Trimble]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by dhaidinger:
Our last car has a double U-joint, but only because someone specced it without thinking it through(we could have got away with a single, and no support. With a double, you need a support at the other end of the joint. other than that it works fine.

On both points, I don't see why either is neccessary. You can design to avoid them. We run a bottom monted, front steer rack, and will be running a single U-joint, or perhaps an apex bearing. The only configuration with more angle needed would be bottom/rear steer, but any chassis book I have read reccommends ONLY front/bottom, or top/rear, so you'd need a very good reason to compromise the steering with a gearbox _and_ a non-ideal layout. <HR></BLOCKQUOTE>

Dan,
Are you aware that the reason those books suggest using a front/low or rear/high rack is excessive compliance in the control arm bearings / bushings? With those configurations, compliance = understeer, which is safe.

However, if you can design the compliance away, you're not locked into those rack locations. Actually, F1 and CART use top/front racks. They see fairly high forces...

Also, a single u-joint steering column is by no means a no-brainer. We've had better luck with straight shafts going to high mounted racks, in terms of steering feel, weight, and complexity.

[Big D]

Denny,
Yes, I know that it's due to flex. And everything is going to have some flex. All I meant was that you need a valid reason to go against that reccomendation. With our cars such as they are, the flex is VERY small, so if you've got a good reason to want a different configuration, you can ignore it.

Mainly, I was saying that anything that forces you to run your steering shaft around a crazy corner, requiring a gearbox or double U-joint, might be a bad idea, and you can probably design around it.

Yours seems like a good call. The less crap you have between your hands and the uprights, the better. Our team has opted for the bottom mount, due to C.G. and more space for the driver's legs, at the cost of some very minimal slop compared to yours. This is why I am interested in the apex bearing, since it looks like it might approach a solid shaft in terms of play.

[alfordda]

We have used those apex u-joints for about three years now, and have not had any problems with them. I think they are a little smoother at high angles than the typical u-joint. With that said we are changing to a top mounted system this year. Mainly because its simpler with our suspension design, not to mention the $150 reduction in the cost report http://fsae.com/groupee_common/emoticons/icon_smile.gif.

[BStoney]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by alfordda:
We have used those apex u-joints for about three years now, and have not had any problems with them. I think they are a little smoother at high angles than the typical u-joint. With that said we are changing to a top mounted system this year. Mainly because its simpler with our suspension design, not to mention the $150 reduction in the cost report http://fsae.com/groupee_common/emoticons/icon_smile.gif. <HR></BLOCKQUOTE>

....my .02....

Not to mention soooo much easier to fixture and get angles correct without the U-Joints. Also, compliance isn't such a huge issue anymore and no need to get the phase right....

[Courtney Waters]

Apex joints are also lighter than the typical universal joint.

[mohab]

when you use apex high angle u joint

does it cause losses in steering torque ??

[mohab]

and how I can calculate losses

[onemaniac]

Originally posted by mohab:
when you use apex high angle u joint

does it cause losses in steering torque ??

Please tell me. What factors resist input torque (in general terms)?
If you can answer that you pretty much answered your question.

[mohab]

1- friction
2- direction analysis

[mohab]

with high angle u-joints (double u joint)
I think losses will be high

the component of force that causes fraction

[mohab]

3- inertia