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Guys
I am having some brackets made to replace the U clamp that holds the front wing stays to the upright. Idea is 2 half moon sections of 20mm alloy or stainless with high tensile bolts to suit. I should have these some time next week and be able to give you guys some kind of costs if you are interested in some.
I am comming to the conclusion that it is the half moon sadles that come with the U clamps that are the problem.
To start with they are soft pressed metal and the edge that butts up to the wing stay is not flat to start with. As Robin pointed out the wing stay bars are nearly horizontal so any wing movement from side to side causes the flat mounting plate to rock against the saddle which deforms and the bolts come loose. Once it starts to loosen it only gets worse as the amplitude of the wing vibration increases.
I think Stuart's suggestion above or the 'double clamp' technique is the way to go?
Looks good Stuart - I take it that the small cap head bolt in the centre is to lock the clamp in place on the upright.
Did you make a depression / pit / hole in the upright for the bolt to rest in, or is it just the pressure of the bolt and the clamp stoping it from rotating?
I did some digging on the subject of torsion bars (which the wing stays effectively are). The spring rate is proportional to the 4th power of the radius (minus the 4th power of the inner radius for hollow bars) It might explain why Marlin went from a small radius solid bar to the larger radius hollow tube. It would certainly reduce the bouncing (caused by the wing stay twisting). Its a pity they didn't get it right - I think it would have been a much better solution.
Some calcs:
Solid bar 10mm. Stiffness = 10,000 (somethings)
Hollow bar 16mm wall 2mm?. Stiffness = 27120 (somethings)
The hollow tube is 3 times stiffer.....
I still have the (unused) hollow wing stays. Perhaps a hybrid would be a good solution?
Stuart - do you intend to make some more of your clamps? I would be interested in a cost....
Wings do still bounce a little but no where near as bad as before. The Bolt in the centre is a locking bolt which i have ground to a point so it bites into the upright.
I will get a cost for anyone thats interested.
that is a very elegant solution, well done!
Are your BMW uprights the narower 45mm diameter version? Something to keep in mind if you are ordering anymore.
I've also been experimenting with a different mod which i needed to get done before the London-Brighton run this weekend. I'll take some pics later.
Note for GOO: Jason, have you had any news from Marlin on their new version?
Note for GOO: Jason, have you had any news from Marlin on their new version?
Nope. Still waiting for my silencers and my bumpers as well. I like the look of stuart's solution, but I'll hold off for now as I don't know what the mounting holes / general layout of the new stays look like.
that is a very elegant solution, well done!
Are your BMW uprights the narower 45mm diameter version? Something to keep in mind if you are ordering anymore.
I've also been experimenting with a different mod which i needed to get done before the London-Brighton run this weekend. I'll take some pics later.
Note for GOO: Jason, have you had any news from Marlin on their new version?
...peter
Forgot to tell everyone. When I asked Terry about the "new" wing stays she said "what new wing stays". She said that they weren't doing any development on the E30 version as they didn't have one (an E30 based Sportster) in the workshop to work on at the moment. She offered to have a look at the problem on my car - if I were to drive the car down to them.
I was specifically told by Mark when I picked up my bodywork that he'd binned all the old stock, and was redesigning the stays and I'd get a pair of the new ones when they where ready.
Hmmph. The answer phone is on, and Terry is away until the 11th. There's a mobile number for Mark on the message - does not knowing what's going on count as 'urgent'?
Guess what turned up today? Yup, my silencers and the wing stays. They're exactly the same as the ones you guys have, and have been supplied with 48mm pipe clamps.
So I guess I'll be interested in a pair of clamps if the price is right, Stuart.
I have 325i uprights - I'll measure them up tommorow, but I guess they're the same size as Robin's.
I've binned the half moon pressed metal saddles as i think they are too soft and deform.
I've replaced them with a 6mm thick mild steel plate.
I've used better quality 3/8" diameter exhaust clamp 'u' bolts and locktight
I've used two 'u' bolts on the basis that if one comes losse the other might hang on (per Robin's suggestion). It also means there is significantly more surface area clamped to the upright. The 6mm plate deforms very slightly under full torque on the bolts which I detected as the gap between the wing stay and the wheel rim changes by a few millimetre as you tighten the 'u'bolts.
I've separated the fixing to the wing stays so that any movement here isn't transmitted to the 'u' bolts.
I've used 10mm fixing bolts which gives more head surface area than the 8mm original mounting.
I need to clean up and re-painted everything now...and nowhere near as elegant as Stuart's solution.
I've binned the half moon pressed metal saddles as i think they are too soft and deform.
I've replaced them with a 6mm thick mild steel plate.
I've used better quality 3/8" diameter exhaust clamp 'u' bolts and locktight
I've used two 'u' bolts on the basis that if one comes losse the other might hang on (per Robin's suggestion). It also means there is significantly more surface area clamped to the upright. The 6mm plate deforms very slightly under full torque on the bolts which I detected as the gap between the wing stay and the wheel rim changes by a few millimetre as you tighten the 'u'bolts.
I've separated the fixing to the wing stays so that any movement here isn't transmitted to the 'u' bolts.
I've used 10mm fixing bolts which gives more head surface area than the 8mm original mounting.
Yup, no issues at all. First time i've done that kind of distance without any issues so, so far very good.
The journey down to Brighton was mostly B and C roads and I did the last part of the journey back on the M25 so they had a throughly good vibration test. Just need a coat of paint.
Mine seems ok with the lighter wings on the u clamps still at the moment. 
