Stainless Steel Suspension Components

[peter_m7uk]

In order to mount my new Gaz dampers to my Lightweight wishbones to give enough travel,

I am going to do something similar to the Zeemerides. That is, running a tube through the

bottom mounting eye and crushing it flat at each end, then bolting the flats to the wishbone.

I need 1/2" tube for this and I got some 16 gauge stainless from the rack at work, but I

seem to recall discussions about stainless being a poorer choice than standard steel?? I don't

know if this is definitely true or what property of stainless would make it worse, but I'd be

glad to hear any facts on this...

 

Cheers,

 

Pete

[Longboarder]

AVO supply shockers with poly bushes and stainless crush tubes as standard. I don't know what Gaz supply, probably the same. You would use 8.8 high tensile bolts to mount them usually to a U shaped bracket. The mounting bolt is then in double shear and is going to be much stronger than a stainless tube (of unknown brittleness and tensile strength) with flattened ends with a hole drilled through. What you're suggesting will give a much weaker mounting and is not good practice IMO.

 

Nigel

[peter_m7uk]

AVO supply shockers with poly bushes and stainless crush tubes as standard. I don't know what Gaz supply, probably the same. You would use 8.8 high tensile bolts to mount them usually to a U shaped bracket. The mounting bolt is then in double shear and is going to be much stronger than a stainless tube (of unknown brittleness and tensile strength) with flattened ends with a hole drilled through. What you're suggesting will give a much weaker mounting and is not good practice IMO.

 

Nigel

 

 

Thanks for the reply, Nigel. My original question was really a mild v stainless steel comparison, but from what I've

read, stainless is generally stronger than mild in terms of yield strength (when it starts to bend) and ultimate strength

(when it snaps). It is perhaps a bit more brittle (likely to snap without bending) if it's been work hardened, but I suppose "brittle" is a relative term - We're not talking about glass here! I tried crushing a bit of the tube from work

and it certainly didn't seem brittle i.e. It deformed smoothly and without any cracks. So my conclusion, at least, is

that stainless would be ok.

 

As for your points on mounting brackets, I was originally sold a bracket by Robin Hood and bought 1/2" high tensile

bolts to mount the damper bottom with the bolt in double shear. However, this didn't give me enough travel.

Therefore, I looked at the Zeemeride method, which uses the crushed tube approach - Has anyone had their Zeemerides

fail at this mounting point??? I agree that this is a weaker mounting than the bracket and bolt method, but the forces

would be transmitted through such a short section of tube that it would take a really colossal force to actually bend it. For

this reason, I'm inclined to believe that it will be ok. Any further comments are welcome.

 

Pete

[Guest timswait]

Stainless is harder, stronger but less tough (more brittle) than mild steel. It's also worse in fatigue. In your situation fatigue is the most likely failure mode (the ultimate strength is irrelevant, if it deforms enough to get anywhere close to that then you've got a problem), so mild steel would be better.

However I think I'm with Nigel on this, what you're suggesting (if I've understood it correctly) doesn't sound like good engineering practice. Actually I'm not quite sure I have understood it correctly as for all their other faults I've not seen a pair of Zeemers mounted like I think you've described.

[Guest chris brown]

Actually I'm not quite sure I have understood it correctly as for all their other faults I've not seen a pair of Zeemers mounted like I think you've described.

That makes two of us Tim but I have seen others including some tin tops with the flattened tube type of mount. Only it is not quite as easy as just squashing the tube in the vice as the side that mounts to the wishbone is normally in line with one side of the tube with all the bending being done on the other side of the tube only. Also remember this squashing has to be done with the shock or at least the bush in place.

[Guest salty_monk]

SOunds like a PITA to set up to me... If you get the mounting off then the shocks could bind up.

 

You should be able to get required travel using a conventional mounting. How about some pictures, someone will give you some pointers on how to move the mounts to make it work.

 

Dan

[Guest allenr03]

Sorry to gooff on a slight tangent but what is meant by double shear and single shear.I've seen it used before and I think I know but it would be good to have it confirmed!!

 

Cheers

Rich

[Guest salty_monk]

The forces act to try to shear the bolt in two places rather than 1 place (it means the bolt goes through the bracket on both sides rather than just one) as far as I know...

 

Dan

[Guest timswait]

The forces act to try to shear the bolt in two places rather than 1 place (it means the bolt goes through the bracket on both sides rather than just one) as far as I know...

Spot on, in double shear the bolt is supported on both sides of the applied force in single shear it's only supported on one side so must supply a large bending moment to resist this. I think double shear reduces the bending moment on the bolt by something like 4 or 8 times over single shear.

Crushing the tube close to where it goes through the bush might also deform it out of true inside the bush, causing binding and excessive wear.

Another thought: have you actually bought the Gaz dampers yet? Couldn't you just buy shorter ones or if you have already bought them, get them changed?

[Grim]

will this method actually be strong enough??? I'm not convinced

[Guest ScotMac]

Hi Peter, glad to see that you replacing your shocks (dampers). What you are describing is what i call the "butterfly" mount, and what most shock companies call the "t-bar" mount. It is how the l/w does the RH standard lower shock mount for the zeemerides. However, both the shock manufacturers and RH's t-bar's are not crushed tubes. They are a piece of solid round bar that goes thru the shock eye-let, with a flat section on the outside of the eyelet. The RH version of it appears to have possibly welded the flat outside sections to the round bar. Whereas the QA1's that i used simply use a large enough diameter round bar in the center so that they can take off the top and bottom of the round bar on the outside and still have enough material to get a strong mount.

You can see QA1's t-bar on page 53 of this catalog (and on other pages of it):

 

www.qa1.net/pdf_files/drag_racing_street_performance.pdf

 

I strongly believe that a t-bar mount is actually a fine way of mounting the shock. Most shock dealers will actually have an in-house t-bar mount option, so i would check w/ Gaz.

 

Note, i do not believe the 2b's or SS's use the method, hence the confusion.

 

The more traditional U mounting brackets obviously also work fine, and can be done on the l/w. Graham converted his to them...he has a photo of it on his main "l/w defintiive info" thread i believe. However, it WILL make the mounting distance SHORTER, so it may require different length shocks. What it basically entails is that you build bracket that fits into the slot where the end of the shock would fit for the t-bar and also bolts/welds up to the bone where the t-bar would. The standard "U" mount then attached to this bracket, and you have it. It will probably move the mounting of the shock up about 1-2 inches, which may be the problem you are having w/ it.

 

I actually like the t-bar better, than the adaption proposed above, but it does need to be done right. My QA1 mount is 3/4" solid bar in the middle.

 

HTH's. -Scot

[Guest ScotMac]

Oh, you get an even better view of QA1's t-bar mount on page "67" (marked page 67) of the catalog i listed above...here it is again:

 

www.qa1.net/pdf_files/drag_racing_street_performance.pdf

 

And i found a direct picture of it:

 

http://static.summitracing.com/global/imag...l-bar350k_w.jpg

[Longboarder]

Scotmac, the T-bar mount you illustrate I have not seen used before in a coilover installation and would obviously be made of an appropriate material to give a safe fixing. It is the same mounting type as I understand it that Peter was suggesting but a fair step away in execution. The possible advantages I see over the more conventional U bracket and clamped crush tube in this installation would appear to be allowing use of a longer shocker with an increased range of shock movement for the same wheel displacement and at possibly a better angle.

There are a couple of disadvantages that I see over the clamped crush tube method. Firstly location of the shocker along the axis of the T-bar. The photo you point to shows two external circlips and would allow some small movement of the shocker end bush along the axis of the T-bar. Secondly unless the T-bar is an interference fit in the shocker bush there will be some movement along the axis of the shocker of the shocker bush on the T-bar. Both will be over a small range but will cause wear of both components and introduce a small but with use an increasing degree of play into the suspension.

I suspect the T-bar method is a mainstream manufacturing convenience not a performance option. Better design of the installation should negate the advantages of the T-bar in this instance and overall I would still prefer the clamped crush tube mount as being a better performance fixing for the shocker.

Put simply, the bush on T-bar will wear in use and rattle up and down and side to side. Not something I would want on my 'high performance' suspension.

 

Nigel

[Guest timswait]

That T-Bar you show looks like it should do the job, it looks a whole lot more substantial than the flattened tube idea. Does it fit directly into the bush in the shock or does it go inside another tube? If it fits directly into the bush then that should eliminate the slack that Nigel mentions. If it's solid bar then that should be of an equivalent grade to what the high tensile bolt in the U shape bracket set up would have been, so should be OK(it must be, if it's done widely on production cars). If it's a round bar with a flat bit welded on each end then I'd be slightly concerned about the quality of the weld, it would be hard to get a good weld in that situation, and really hard to do without melting the bush in the shock (I assume it has to be done in situ, the flats are too big to go through the hole in the bush - right?)

P.S.

Not something I would want on my 'high performance' suspension

Was it high performance before or after you re-adjusted it on the tyre wall at Barkston?

[Guest ScotMac]

The t-bar fits inside a polyurethane bush in the shock eyelet, and thus has no worse (or better) properties of combating "slop" than the U bracket, in terms of design. In terms of execution, it will combat the slop much better than the RH mount, since the polyurethane bush is probably much better than the questionable material RH used for its "bush".

 

Note, actually the RH t-bar's flats are not too big to fit thru the eyelet (though they are wider than their center round section), so no, they would not need to be welded in situ.

 

-Scot