Steering Vibration damper removal

[Walt Fricke]

In the continuing quest for lightening in a track only car, I wonder if anyone has ever removed/replaced the hockey puck shaped vibration isolater in the bottom end of the steering column, just above the steering rack itself.

Here is a straightforward way of doing this, although not the lightest possibility.



If anyone has done something like this, have they promptly regretted it? Instead of more steering precision (or just the same), they got palsied hands or something?

Walt

[Flieger]

I like your idea. I heard of billet Aluminum 914 ones but yours seems simpler and cheaper . I am interested.

[burgermeister]

From a theoretical point of view, you'd loose some straight line stability. Maybe enough to make the car difficult to drive, maybe not. Theory (at least my understanding of it) and practice don't always agree though ..

The puck provides compliance in the steering system, which adds understeer to the car in the linear (low slip angle) range. Wouldn't have much effect under hard cornering - after maybe 5 degrees of twist, it gets quite stiff.

[Flieger]

Is this under the cover in the smugglers box? How easy was this for you to do?

[Oh Haha]

Bump for more info.

[Oh Haha]

I was curious so I removed my puck and set out to try Walt's suggestion. Where I ran into a problem and stopped was that the steering shaft that attaches to the puck is "keyed" for the u-joint bolt.

The 4 bolts that attach the puck to the steering rack are oriented in a "cross" pattern. One pair connects the shaft to the puck, the other connect the puck to the rack.
I suppose you could position the strap bolted to the rack to match the shaft so that the ujoint can be clamped correctly but I didn't attempt it.
( I decided to stop there and bolted the parts back together so I can take a drive today.)

What I DID do was to fill the holes in the puck where the sleeves fit with silicone. There was a thread awhile back about this. Once cured the silicone will add a little more stability to a worn puck.

Sorry, no pics as I was intent on the task and forgot.

[Flieger]

OK, that would explain the billet Aluminum ones. The keying is to account for the angle of the steering wheel shaft to the shaft that goes into the rack.

[wswilburn]

You can pull the piece off the steering rack (right hand piece in Walt's picture) and reposition by 90 deg. It is not keyed.

[Oh Haha]

Originally Posted by wswilburn

You can pull the piece off the steering rack (right hand piece in Walt's picture) and reposition by 90 deg. It is not keyed.

Excellent!! I wasn't sure and ran out of time to mess with it. You will need longer bolts. I measured the length needed get good thread engagement and I found that 50mm thread length will work. I would use a thin washer under the head or at least red Loctite.

On the plus side, I did see a noticeable difference in my steering feel after using the silicone on the sleeve's gaps. I also cleaned and lubed the steering shaft support bearing while I was in there. It seemed a little dry.

[Walt Fricke]

Wayne

I'm glad you didn't try to go farther.

I had to do two things differently for the test piece I took the photo of:

1) I drilled out the threads on the T piece so it could be throughbolted.

2) I used spare CV bolts, as the regular bolts are too short - because they don't go through a full flange on one end.

I didn't blink at drilling out the threads because this is a spare piece.

The rest everyone has figured out. Except I haven't unearthed someone who has done something similar to encourage or warn me off.

I may try this out if I find I can make the switch fast enough at the track. If it does evil things I'd like to be able to swap it back and not lose track time. Maybe for the last session of a test and tune day.

Ultimately (if it works), I'm going to rifle drill the T piece, and then cut its ends off. The stubs of the rod left on the ends will be turned down, and inserted into a suitable length of tube, then welded in place. That will allow the T to mate up with the U directly. Save all that weight, you know.

I did this with the long shaft which runs diagonally. Works fine, saved a few ounces. And I learned something: When using U joints, you must pay attention to their "clocking" The stock ones are at about (from memory) a 30 degree angle from one end to the other. Since I had just welded the splined pieces with no angle between their pinch bolt flats, I got screwy steering motion. I was able to fix this with some selective use of a die grinder so I could turn one end the required number of splines.

Walt

[Oh Haha]

[QUOTE=Walt Fricke;5533115]Wayne
1) I drilled out the threads on the T piece so it could be throughbolted.

Yep, I got that far.

Since I re-installed the puck I simply used longer bolts with a lock nut to attach the t-bar piece.

I see that I left that out of my post.

[burgermeister]

Originally Posted by Oh Haha

The 4 bolts that attach the puck to the steering rack are oriented in a "cross" pattern. One pair connects the shaft to the puck, the other connect the puck to the rack.
I suppose you could position the strap bolted to the rack to match the shaft so that the ujoint can be clamped correctly but I didn't attempt it.
( I decided to stop there and bolted the parts back together so I can take a drive today.)

It seems you could also reorient your steering wheel 90 degrees and leave the piece on the rack as-is. Your steering shaft would be off by 90 degrees, but I don't think that would matter.

[KTL]

I don't think the feel will be messed up in a negative way by doing this. Yes, you will feel much more vibration in the steering wheel, as that's the purpose of the rubber disk- to remove vibration/NVH. However I see the vibration as somewhat of a benefit on a racecar. You can feel more of what's going thru the front wheels and might detect a problem sooner.

Remember that there are u-joint kits available from the go fast companies like SmartRacing- see page 2 "Smooth Steering Upgrade"

http://www.smartracingproducts.com/pdfcat/srp2009_frontaxle.pdf

so it's something that's been done before without negative effects in terms of performance improvement.

[Walt Fricke]

Well, the stock steering wheel could just be reoriented (are the splines even numbered?).

Oh, oh - I counted 31 splines on the U shaped piece. But I think that is the number of splines on the end of the T (my counting and recounting patience has worn out), and as I recall the pinch bolt flat allows maybe three spline positions. More details. You can adjust out a spline's difference with the steering arms, normally.

However, my track car has the early (a '68) steering rack, which is a bit shorter than later racks. I had to add an extra spacer at the rack in order to get enough thread engagement out at the steering arm. I had gotten away with running about 2 threads on one side for a while, but eventually decided that needed to be fixed at the rack side, where there was plenty of engagement. So I don't want to plan on using my adjustments there to recenter the wheel.

A proper quick release (racing) steering wheel is keyed or otherwise so it only goes on in one position. I welded a keyed spline to the steering wheel end of the shaft on my track car, so changes there are a major undertaking.

I have always lusted after the asymetrical Porsche Cup car quick release attachment. However, since I enter the track car over the roll cage (open car), I only pull that wheel (whose centering key has worn and mainly frustrates quick replacement of the wheel) when I have to crawl around by the pedals, so I'm not faced with a panic at the grid with centering the wheel.

Though most aftermarket quick releases for our cars attach onto the stock shaft splines, so if the splines are equal numbers (or the offset one way, offset the other trick would work), that could be worked out. I eventually added paint dots on attachment screws for the one on my SC so I can get it back on straight.

Thanks for the pointer to SmartRacing, Kevin. I though I had their catalog memorized, but they keep coming up with stuff. I'll give Craig a call.

Walt

[Flieger]

So, where is the vibration damper located? Is it accessable under the plastic cover in the smugglers box? Or is it something you acess under the car (as in immediately before the rack)?

[Walt Fricke]

You get at it via the smuggler's box. The U shaped fitting in my photo attaches to the pinion shaft which sticks out of the top rear of the rack assembly just far enough to go through the U and hold a washer and nut. The rubber damper part is as thick as the two cylindrical spacers, and as wide as the T. The rest of the shaft sticks up from this and goes through a rubber mounted bearing, and then connects to the U jointed shaft which diagonals through a trough (with a cover over it) from where the steering column comes through the dash.

It is covered for dust protection (and protection from stuff you are smuggling) by a tubular, semi-conical, ribbed piece of black plastic, so you can't really see it until you get that cover off, which isn't easy as you have to undo the U joint and slip the bearing off first. Then you can pull the cover off.

Take a look at Section 4/3 of a factory parts book. It will give a misimpression of the damper part, though. The diagram shows 2 bolts and 2 sleeve spacers, but there are 4 of each, and the T shaped parts are offset by 90 degrees. the bolts hold a thin flat plate onto the rubber puck, with the metal spacers running down holes in the puck, and 2 go one way, and 2 the other. So turning the steering wheel pushes against the rubber, which in turn pushes against the parts connected to the pinion shaft.

Walt

[burgermeister]

You don't want to adjust for steering wheel off-center with the tie rods. You end up with unequal length tie rods, which gives you different ride steer curves left to right. It makes steering wheel kickback noticeably worse when driving on crappy pavement. So if the splines are not numbered the same, re-orienting the wheel may not work out... if you counted right with 31 splines, even if they are the same you'd be off by 3 degrees at the steering wheel.

One could also use a rag joint, which keeps everything oriented in a stock fashion. For shaft rotation, it's a lot closer to a rigid connection than it is to the rubber isolator, and it allows for some mis-alignment of the rack and the steering shaft. Considering how the rack is attached, and the clamped steering shaft bearing, there has to always be some sort of misalignment due to tolerance stackup, so from that point of view a metallic rigid connection is not ideal.

[Flieger]

I'd rather have a rubber mounted bearing than a rubber coupling taking the torque.

I am going to look into making some Aluminum couplers which will replicate the rubber doughnut's dimensions.

[Brando]

Instead of soft rubber, semi-firm polyurethane?

[Jeff Alton]

Try the SRP smooth steering upgrade, I run it in our race car and it is great.

Cheers