Converting to steering rack
Converting to steering rack
I'd like to convert my w201 to a steering rack to make space for the downpipe. I know nothing about doing this other than it's easy to do it wrong. There's very little info out there to do this so I was wondering if anyone here has done it before or if anyone knows any details?
I'd like to use a BMW rack as they're supposed to have a good ratio and plenty of lock.
Not sure where to put this thread so iI'll put it here as it's the most viewed section lol.
I'd like to convert my w201 to a steering rack to make space for the downpipe. I know nothing about doing this other than it's easy to do it wrong. There's very little info out there to do this so I was wondering if anyone here has done it before or if anyone knows any details?
I'd like to use a BMW rack as they're supposed to have a good ratio and plenty of lock.
(03-01-2014, 02:09 PM)hooblah Not sure where to put this thread so iI'll put it here as it's the most viewed section lol.
I'd like to convert my w201 to a steering rack to make space for the downpipe. I know nothing about doing this other than it's easy to do it wrong. There's very little info out there to do this so I was wondering if anyone here has done it before or if anyone knows any details?
I'd like to use a BMW rack as they're supposed to have a good ratio and plenty of lock.
There is someone who converted a w201 to a rack. i believe the person was swapping a LSx engine and needed the space, also a W210 rack was used at their mounting design is fairly easy to work with. Lots of work to get it wright .
Duncansport
03-01-2014, 03:06 PM #2(03-01-2014, 02:09 PM)hooblah Not sure where to put this thread so iI'll put it here as it's the most viewed section lol.
I'd like to convert my w201 to a steering rack to make space for the downpipe. I know nothing about doing this other than it's easy to do it wrong. There's very little info out there to do this so I was wondering if anyone here has done it before or if anyone knows any details?
I'd like to use a BMW rack as they're supposed to have a good ratio and plenty of lock.
There is someone who converted a w201 to a rack. i believe the person was swapping a LSx engine and needed the space, also a W210 rack was used at their mounting design is fairly easy to work with. Lots of work to get it wright .
The length of the rack should be such that the inner pivots of the tie rods intersects a line drawn between the upper and lower control arm pivot points. I have NFI how you find the UCA pivot point on a strut front end. The shortcut would be to center the steering wheel and find this line by observing the LCA bushings and the inner tie rod ends. Another shortcut would be to just find a rack that puts the centerline of the inner tie rod ends the same distance that the drag link does on your chassis. The caveat with the second shortcut is that if you raise or lower the rack from the place the drag link was, this distance changes. Long, thorough bumpsteer article: http://www.circletrack.com/chassistech/c...gines.html
Moving the rack fore and aft in the chassis changes ackermann. Getting this wrong could be worse than getting bump steer messed up. I would say to just position the rack in the same place, fore and aft-wise, in the chassis as the drag link but the drag link behaves differently. It moves fore and aft as you steer due to the arcs of the pitman and idler arms so it's current position may very well not be the best place for the rack. Ackermann article from same great source: http://www.circletrack.com/chassistech/c...ng_system/
Clear as mud?
raysorenson
03-01-2014, 08:05 PM #5The tie rods should point to the instant center. This is pretty easy on both short/long arm front ends and strut front ends.
The length of the rack should be such that the inner pivots of the tie rods intersects a line drawn between the upper and lower control arm pivot points. I have NFI how you find the UCA pivot point on a strut front end. The shortcut would be to center the steering wheel and find this line by observing the LCA bushings and the inner tie rod ends. Another shortcut would be to just find a rack that puts the centerline of the inner tie rod ends the same distance that the drag link does on your chassis. The caveat with the second shortcut is that if you raise or lower the rack from the place the drag link was, this distance changes. Long, thorough bumpsteer article: http://www.circletrack.com/chassistech/c...gines.html
Moving the rack fore and aft in the chassis changes ackermann. Getting this wrong could be worse than getting bump steer messed up. I would say to just position the rack in the same place, fore and aft-wise, in the chassis as the drag link but the drag link behaves differently. It moves fore and aft as you steer due to the arcs of the pitman and idler arms so it's current position may very well not be the best place for the rack. Ackermann article from same great source: http://www.circletrack.com/chassistech/c...ng_system/
Clear as mud?
Ive been doing some reading up on this and it looks like I need to start off with a rack thats quite narrow; i.e. one that has its inner tie rod pivots no wider than the wishbone pivots when on full lock. This is to combat bump steer.
Ive spoken to HughF regarding this and he reached the same conclusion. So his w210 rack plan is off the cards and a different rack is being sourced.
It also looks as though the hubs will have to be changed for those off a car with a rack due to Ackermann, or want of correct Ackermann.
Hmm yes sort of lol.
Ive been doing some reading up on this and it looks like I need to start off with a rack thats quite narrow; i.e. one that has its inner tie rod pivots no wider than the wishbone pivots when on full lock. This is to combat bump steer.
Ive spoken to HughF regarding this and he reached the same conclusion. So his w210 rack plan is off the cards and a different rack is being sourced.
It also looks as though the hubs will have to be changed for those off a car with a rack due to Ackermann, or want of correct Ackermann.
I've been thinking that it would be a good idea to fab an adjustable rack mount. If you could adjust the rack fore/aft after installation you could dial in the amount of ackermann you like. More ackermann would be great for autoX and help get a nose-heavy car rotating, less would be more stable for tracking. To take care of bump steer, use heim joints for outer tie rod ends and adjust them up and down with spacers to adjust bump steer.
raysorenson
03-05-2014, 07:24 PM #7What is it about rack hubs that differs from worm and sector hub setups?
I've been thinking that it would be a good idea to fab an adjustable rack mount. If you could adjust the rack fore/aft after installation you could dial in the amount of ackermann you like. More ackermann would be great for autoX and help get a nose-heavy car rotating, less would be more stable for tracking. To take care of bump steer, use heim joints for outer tie rod ends and adjust them up and down with spacers to adjust bump steer.
Ray, the 2nd link you posted explains in perfectly, although it did take a few attempts at reading it to understand it fully. You asking me that question leads me to think you didnt read it yourself lol
But the difference between rack and box hubs is the angle of the steering arms on the hubs.
A rack system has steering arms that are angled 'straight ahead', this is fine and produces no Ackermann when used with a steering rack as the motion of the rack is linear and both hubs steer at an equal number of degrees.
A box system has steering arms that are angled towards the car. The reason for this is to cancel out the Ackermann produced by the drag link setup.
So, using the standard hubs meant for the drag link system with a steering rack would mean excessive Ackermann. And the opposite is true for a system that uses rack hubs with a steering box.
Now this has been cleared up im either going to have to find some different hubs or modify my existing ones
Ok so after further reading it looks as though you want to minimise Ackermann effect.
Ray, the 2nd link you posted explains in perfectly, although it did take a few attempts at reading it to understand it fully. You asking me that question leads me to think you didnt read it yourself lol
But the difference between rack and box hubs is the angle of the steering arms on the hubs.
A rack system has steering arms that are angled 'straight ahead', this is fine and produces no Ackermann when used with a steering rack as the motion of the rack is linear and both hubs steer at an equal number of degrees.
A box system has steering arms that are angled towards the car. The reason for this is to cancel out the Ackermann produced by the drag link setup.
So, using the standard hubs meant for the drag link system with a steering rack would mean excessive Ackermann. And the opposite is true for a system that uses rack hubs with a steering box.
Now this has been cleared up im either going to have to find some different hubs or modify my existing ones
![[Image: SU1HMDE1MDgtMjAxMzA0MTctMTkwOS5qcGc_zpse9059da4.jpg]](http://s1213.photobucket.com/user/mantahead1/media/SU1HMDE1MDgtMjAxMzA0MTctMTkwOS5qcGc_zpse9059da4.jpg.html)
![[Image: SU1HMDE0MTItMjAxMzAzMjItMTQyMi5qcGc_zps8b041c4d.jpg]](http://s1213.photobucket.com/user/mantahead1/media/SU1HMDE0MTItMjAxMzAzMjItMTQyMi5qcGc_zps8b041c4d.jpg.html)
think i ended up with about 6 degrees ackerman
hub wasn't finished in that pic, needs beefed up a bit.
i decided against the e300 rack also as it looks to take up even more room than the steering box.
if you had the right exhaust manifold that goes up towards bonnet and keep the turbo low, you should have room for downpipe. i'm running 4 inch down pipe on RHD w202
![[Image: SU1HMDE0MDctMjAxMzAzMTktMTIzNi5qcGc_zpsb58c017b.jpg]](http://s1213.photobucket.com/user/mantahead1/media/SU1HMDE0MDctMjAxMzAzMTktMTIzNi5qcGc_zpsb58c017b.jpg.html)
think i ended up with about 6 degrees ackerman
hub wasn't finished in that pic, needs beefed up a bit.
i decided against the e300 rack also as it looks to take up even more room than the steering box.
if you had the right exhaust manifold that goes up towards bonnet and keep the turbo low, you should have room for downpipe. i'm running 4 inch down pipe on RHD w202
The steering arms are probably forged and can be bent with heat. Verify they're forged vs cast using common methods before trying this.
I would caution against being ackermann averse. No ackermann setups get a lot of talk on the intarwebs, and it seems to work good on F1 cars but almost all other race cars use it. The reason front toe out is used for Autocross is because most production cars doesn't have enough ackermann for optimal traction for hard cornering below 50mph.
raysorenson
03-06-2014, 06:36 PM #10It's been several months since I've done my ackermann research, so no encyclopedic knowledge of all the ins and outs here. I just remember those articles from a few months ago and they were enough to talk me out of trying what I was thinking about doing! :-) Thanks for explaining that to me.
The steering arms are probably forged and can be bent with heat. Verify they're forged vs cast using common methods before trying this.
I would caution against being ackermann averse. No ackermann setups get a lot of talk on the intarwebs, and it seems to work good on F1 cars but almost all other race cars use it. The reason front toe out is used for Autocross is because most production cars doesn't have enough ackermann for optimal traction for hard cornering below 50mph.
Mantahead did you modify the steering setup to gain Ackermann? What difference has it made?
I need to figure out if there are any implications with the length of the steering arms but ive read a fair few articles and theres no mention of it anywhere.
Hmm ok so Ackermann or no Ackermann? Im getting mixed opinions here so im not sure. My car will mainly be used as a daily with the occasional track day.
Mantahead did you modify the steering setup to gain Ackermann? What difference has it made?
I need to figure out if there are any implications with the length of the steering arms but ive read a fair few articles and theres no mention of it anywhere.
i have seen nissan skyline hubs welded and they moved the track rod end closer to centre for more lock, problem was, the rack went over centre so the inside wheel flopped about on full lock, to overcome this the track rod end location was then moved closer to the brake disc(steering rack at rear of subframe) next problem, the car then had reverse ackermann, solution was go back to the first way but move the steering rack back to stop the arm going over centre.
when they had reverse ackermann, they just used loads of toe out to help overcome it.
hope this makes sense.
i just tried to keep ackermann standard. i just wanted more lock.
i have seen nissan skyline hubs welded and they moved the track rod end closer to centre for more lock, problem was, the rack went over centre so the inside wheel flopped about on full lock, to overcome this the track rod end location was then moved closer to the brake disc(steering rack at rear of subframe) next problem, the car then had reverse ackermann, solution was go back to the first way but move the steering rack back to stop the arm going over centre.
when they had reverse ackermann, they just used loads of toe out to help overcome it.
hope this makes sense.
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