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 Post subject: Shortening a Miata rack
PostPosted: Tue Oct 30, 2007 9:26 am 
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Joined: Tue Oct 30, 2007 9:19 am
Posts: 2
Hello All,

I am looking for any information about shortening a Miata Steering rack.
I did a preliminary search and found a couple of references to shortening a rack but no solid info.

Can anyone point me to some?

Thanks,

Nathan


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 Post subject:
PostPosted: Tue Oct 30, 2007 10:48 am 
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Location: Charleston, WV
Well the reason there is such little information on this is probably because it's a bit of a sketchy proceedure. If you don't do it just right, it could come apart and kill you and knows who else. Nobody wants to get sued, especially me.

However this picture shows basically how I did it. The only purpose of this crude drawing is to show how I went about shortening my Miata rack. It is not a how-to.


*disclaimer*-
Do not attempt to shorten a steering rack in this fashion. If you try to do it this way, and die, it is your own fault- I told you not to. By shortening a factory steering rack in this fashion, you are ageeing to meet with disaster and other unknown consequences of such disaster at any point in your future.


Attachments:
miatarackshortening.JPG
miatarackshortening.JPG [ 41.78 KiB | Viewed 7456 times ]

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 Post subject:
PostPosted: Tue Oct 30, 2007 10:57 am 
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Joined: Tue Oct 30, 2007 9:19 am
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Thanks for your reply. I will not take you post as "instructions".

I understand that modifying a rack is sketchy. But after all, we are building suspension components whos failure would likely be just as disasterous.

But like I said, point taken.

-Nathan


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 Post subject:
PostPosted: Tue Oct 30, 2007 10:59 am 
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It's sad that we must preface our advice with, essentially, "don't do this".

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 Post subject: Seals in shortened rack?
PostPosted: Sun Feb 17, 2008 5:22 pm 
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I've taken the plunge and cut my rack housing down. I'm gearing up to weld it back together. I'm not sure about the seals just right of the cast section. I've tried to pull, pry, and push them out, without budging it. I did manage to break and the green nylon-esque ring, but that's it.

Welding the housing would destroy the seal, I'm sure. Any advice on removing this seal?

A thought crosses my mind that this seal may not be critical for a depowered rack. Anyone have any idea on that idea?


Attachments:
File comment: Sorry for the cruddy photo. Can't find the focus menu on my cell phone. ;-)
Photo_021708_005.jpg
Photo_021708_005.jpg [ 71.66 KiB | Viewed 7123 times ]

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 Post subject: How to cut the rack?
PostPosted: Sun Feb 17, 2008 6:13 pm 
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Next question...how did you guys cut the rack? I had no trouble with the housing on the band saw, but it wouldn't so much as scratch the rack.

-dave "wishing he had a bigger lathe" hempy

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 Post subject:
PostPosted: Sun Feb 17, 2008 8:23 pm 
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Location: Charleston, WV
I used a 14" chopsaw. As for the seal, I'm not sure which one you are showing in the pic. What part of the rack is that? The only seal I removed was the one on the rack itself.

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 Post subject:
PostPosted: Sun Feb 17, 2008 8:51 pm 
I had my rack itself cut on a lathe, by cutting off one end, and then had the cut end re-threaded to take the ball joint (I used a GM rack, though). That made sure it was perfectly straight. They cut the housing on a lathe, too, and TIG-welded it back together while it was in the lathe. Came out perfect...even with a micrometer, there is no run-out or out-of-true at all. It cost about $80 to have it done, but I figure it was money well-spent.
Steering is just as important as brakes IMHO, and a failure in either at speed would be unpleasant :no:

Not a good place to save money... :shock:


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 Post subject:
PostPosted: Sun Feb 17, 2008 11:40 pm 
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Joined: Thu Dec 06, 2007 1:31 am
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Location: Nebraska
I just finished mine about 1/2 hour ago.

dhempy, I saw that same seal. I tried to pry it out but it wouldn't come. I pried out the green ring, popped out the spring in the seal and just left it.

I cut my shaft with a die grinder with a cutoff wheel, squared it up on the belt sander and beveled the cut there as well. Clamped it in the "V" of some 1" angle iron to hold it straight made a couple of tacks with the TIG, rotating and clamping until it was all welded. Came out nice and straight. With the TIG I was able to leave the weld subsurface so no grinding on the shaft. I cut the shaft at the large groove after the seal is removed and went inboard 5.5".

I cut the tube on the inboard cut right flush with face of the 90* fitting first and then outboard 5.5". It made it easier to clamp the outher piece into the band saw as well.

That put the cut about 1/2" from the end of the bushing that goes inside.

Deburred everything, slid the bushing into the tube and the whole works into the rest of the housing, took two hose clamps and three pieces of 1/2" stock and clamped them on either side of the cut. That, with the bushing inside kept it nice and straight.

Did the Flyin' Miata depower while I was at it and everything came out perfect.

Well, almost perfect. The first rack I tried to do (off of a 96) was not the same. It didn't have the big bushing. There wasn't ANYTHING in the end of the tube, so if you cut off the seal, there wasn't anything to hold the shaft from slopping around. There wasn't a snap ring in the end of the tube and I couldn't figure out how to get it apart, so I figured I'd cut it in half, as I needed to anyway. So scrapped that rack. Good thing I had a spare.

One key to knowing which one won't work--instead of having a snap ring that hold in the pinion shaft, there are two allen head bolts that hold the split casting together. I couldn't see any way to shorten this rack. Just a word of caution.


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 Post subject:
PostPosted: Mon Feb 18, 2008 1:16 am 
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chetcpo wrote:
I used a 14" chopsaw.


Ahh...I'll give the chopsaw a spin tomorrow. Thanks! :-)

Quote:
As for the seal, I'm not sure which one you are showing in the pic. What part of the rack is that? The only seal I removed was the one on the rack itself.



The casting is almost visible in the vice in the photo above. The photo below highlights the seal location with a yellow arrow. Before you cut your housing, you probably stuck a ruler down in the housing to figure out how far down you could cut. That seal is the thing the ruler would have landed on.

I went ahead and tacked the housing back together. I put the slug and the rack back in, which held things pretty well aligned on the passenger side. I hung it vertically in the vice, and wedged some toothpicks in the driver's end at the bottom, which has a lot more slop. The toothpicks held the rack centered so I could tack the housing. The photo below is just prior to tacking.

I frankly forgot about the rubber seal when I tacked the housing. :oops: I can grind the tacks off if I need to take it out...but unless someone says otherwise, I think I'll just let it burn up in there. My hunch is that it is for sealing steering fluid, and is not critical for the now-manual rack. Opinions?


-dave "needs a shorter shaft" hempy


Attachments:
Photo_021708_099.rack.jpg
Photo_021708_099.rack.jpg [ 70.12 KiB | Viewed 7058 times ]

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...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
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 Post subject:
PostPosted: Mon Feb 18, 2008 1:22 am 
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Location: Lexington, KY
I've been thinking about shortening the rack more than 6". While I'm not going that route (this iteration), I think it you could get 8" pretty easily, and almost 10" with a bit more work. The slug could have its middle removed, just like we do for the housing. You could get maybe another 2" out of there, retaining the inboard seal end and the outboard c-clip end.

If you wanted still more, I think you could take a section out of the housing between the casting and the seal (yellow arrow) for another 1.5" or so. I'm not quite sure what's going on in there, as you can't see in that part, so there could be obstacles to taking length out there.

One issue to consider is just how narrow you're comfortable having the seals supporting the rack. One thing that surprised me is that there is no outboard support on the driver's side. (either that, or I've lost a part...not uncommon!) The passenger end has the seal 3" in at the end of the slug, but the outboard end has a large gap between the rack and the housing.

What this means to me is that the shortened rack is supported by seals with a spread of about 2". This would have been 8" of supported range in the Miata. The extent of this support range is shown (approximately) in red below. 2" strikes me as a very narrow mount for something like a steering rack.

I wonder if it would be worthwhile to shorten the slug to draw the seal out a few inches for a wider support base? I'm not sure why the slug is so long. I wonder if it is to reduce the fluid area to match the stroke. Or maybe keep the seal that much further from contaminants creeping in from the world?

I'm not sure if the pinion interface counts as a support point or not. If so, that would add perhaps another 6 or 7 inches, both for the stock and shortened configuration.

Having said all that, I slid the rack in and pushed and pulled pretty hard. I could detect no play whatsoever, even with the short range of support. This really surprised me.

Now I'm not too darned worried about all this, given the success so many other builders have had with the system. Just burning a few brainwaves.

I am trying very hard to shake the "paralysis by analysis" I've been in the past few months and get back to making some real progress. Junior was inspirational on the phone today, pointing out that "pretty good" is better than "perfect" if "perfect" never gets done. Plus, it really won't be that hard to rip it all out and redo systems if I get it on the road and find some issues.


ramble, ramble...wonder how much work I could have gotten done while typing this...ramble, ramble...


-dave "maybe i think too much" hempy

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...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
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 Post subject:
PostPosted: Mon Feb 18, 2008 1:46 am 
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As someone told me, "Walk a line between doing it right and getting it done."

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 Post subject:
PostPosted: Mon Feb 18, 2008 10:23 am 
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Joined: Tue Aug 07, 2007 1:34 pm
Posts: 45
Location: CHINA GROVE NC
I realize the "Locost Spirit" is a spirit of adventure and exploration into new things, but on this topic I would move carefully when shortening a steering box. In my area or on Ebay, you can get a quick ratio, easily rebuildable, Coleman or Sweet (non power assist) for a price that might be worth while. I work in a machine shop and would not shorten a Mazda rack for the price I can get a racing rack. Just make sure you get one in decent condition from a reputable person - a wrecked and improperly "fixed" one is worthless as is and is possible going to cost more than a new one to fix.

My intention is not to throw a damper on the Locost Spirit especially if steering boxes are your "thing". But I have found in my experience (gearboxes are my "thing"), my limited time and aboundant creativity have lead me to projects that in the end were 1) a great learning experience, 2) a time consuming reinvention of the wheel, ie lots of time creating a one-of something when an expert had them sitting on the shelves. When I look at projects like this I think of the lesson from the talented and creative guy who made his own ball bearings........

Anyway, lots of luck and please get the parts CRACK TESTED MORE THAN ONCE !!


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 Post subject:
PostPosted: Mon Feb 18, 2008 10:52 am 
I must not have spent enough time thinking about this. I cut my rack with a bandsaw, and chamfered the edges before welding it together. Straightness was taken care of with a vise and some careful checking with a straightedge. Took about as much time as selecting an aftermarket rack out of a catalog, and was a whole lot less money.

The various seals are there to keep power steering fluid inside, yes. And it's possible to disassemble the later racks to depower them although you may have to refer to a real manual instead of the internets.

PPAM20, there's a difference between a steering box and a steering rack. Just FYI.


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 Post subject:
PostPosted: Mon Feb 18, 2008 7:29 pm 
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Location: CHINA GROVE NC
Sorry for the rack/box thing if it confused anyone.

But my major point guys is be especially carefull here. Its not a good sign when you can't get through the rack with a bandsaw and then are going to weld on it. Yes it is possible but be carefull - you don't want a fatique crack to get started in the end of the rack itself - it will be a far worse failure than a pinion failure.

The only way I've seen racks shortened (that I would trust) is exactly like zetec7 posted earlier. The rack remaines straight. The body if you are carefull can be straight or straight enough.

I have seen a good variation in zetec7's method where a machined sleeve holding the outside bushing and wiper was pressed and welded to the shortened tube.

Anyhow, I rarely get on a soapbox but I felt I needed to speak up on this one


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