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Go Back   Madabout Kitcars Forum > Mad Build Area > Vintage and Classic Roadster Kit Car Builds

Vintage and Classic Roadster Kit Car Builds For Vintage and Classic era kit cars. Post your build reports, problems and progress here

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  #1  
Old 25th October 2016, 09:38
Car photographer Car photographer is offline
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Default Cycle wings - best way to mount them?

Hi everyone, so ever since I finished my Fiorano kit I've been constantly having problems with my wheel arch supports.
They are currently made from steel tube that's welded together, and they seemed pretty strong, but it seems that almost every time I drive the car one of the welds snaps off and the other day the tubeitself actually sheared off.

Does anyone have any ideas of what the best method of attaching the wings could be?
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  #2  
Old 26th October 2016, 05:18
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redratbike redratbike is online now
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Pics would help so we could see the current set up and make suggestions

Last edited by redratbike; 26th October 2016 at 05:21..
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Old 26th October 2016, 21:07
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Ok I'll try and sort some out
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Old 26th October 2016, 23:19
molleur molleur is offline
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Quote:
Originally Posted by Car photographer View Post
Hi everyone, so ever since I finished my Fiorano kit I've been constantly having problems with my wheel arch supports.
They are currently made from steel tube that's welded together, and they seemed pretty strong, but it seems that almost every time I drive the car one of the welds snaps off and the other day the tubeitself actually sheared off.

Does anyone have any ideas of what the best method of attaching the wings could be?
Should you have a good library around, you may try this reference:
Sports Car Bodywork: Construction in Timber, Metal and Plastics
B.W. Locke, 1960 or 1961.
Great old reference, with fold out blueprints. Dreadfully expensive even used.
He shows a foolproof method for exactly what you are looking for.
I (insanely) gave away my copy to a kit manufacturer in Michigan.
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Old 27th October 2016, 19:06
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MartinClan MartinClan is offline
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It's unlikely that tube will be strong enough. It may appear to be stiff, but will inevitably tear at the welds. My Marlin uses solid round bar about 10mm as I remember. Done about 6000 miles with no problem. My Pembleton has 8mm round bar. Too soon to tell if its ok though. But mudgaurds much lighter than Marlin so I am hopefull...

Mudguards that move with the wheels get a lot of pounding. Its a common problem area.

Cheers, Robin
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Old 27th October 2016, 19:43
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Thanks guys, yeah someone said solid bar might work better, also do you think it might help to have a layer of rubber sheet between the brackets where they bolt onto the hubs?
Would this help dampen the vibration?
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Old 27th October 2016, 21:11
molleur molleur is offline
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Quote:
Originally Posted by Car photographer View Post
Thanks guys, yeah someone said solid bar might work better, also do you think it might help to have a layer of rubber sheet between the brackets where they bolt onto the hubs?
Would this help dampen the vibration?
Perhaps, but I see it as adding a lot of additional bouncing on the wings.
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Old 28th October 2016, 21:21
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Seen this ?

http://www.hotrodders.com/scratch-bu...Running_Boards

of course no one has asked who did the welding ? and with what ?

regards Paul
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Old 29th October 2016, 11:46
Mitchelkitman Mitchelkitman is offline
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It can depend on how you are attaching them as to how the design pans out. My experience with stays that clamped on the hub (mgb based kit) was similar (ie welds failed.) To cure it I made some solid round 'plugs' about 4" long which I heated up red and flattened the end and drilled for mounting. The other end of the plug had the last 1.5" turned down so it was tight fit in the steel tube (seamless gas tube) and the parts were brazed together. The logic being that cycle frames (very thin and light) take enormous stresses (think bike forks) and have been traditionally made this way. At the top end I also used a tube bender to bend to 90 degrees so no 'corners' as stress raisers. It worked.
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Old 30th October 2016, 09:17
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Ok, here's some pics.
first one is the hub where the tab that supports the arch bracket is welded. (there's one on the other side of the hub too that's hidden in this shot)
1DSC_0505 by paul ward, on Flickr

and this is the arch support itself - the 'nodular lump at the bottom is the latest temporary repair where the tube sheared off.
DSC_0026 by paul ward, on Flickr

DSC_0025 by paul ward, on Flickr

Last edited by Car photographer; 30th October 2016 at 09:21..
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Old 30th October 2016, 15:45
slickshod slickshod is offline
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Hi Paul are they braking at the weld or across it ? and what method of welding are you using ? could you mount them on rubber bushes to absorb any vibrations ,I had to use this method on a Westfield.
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Old 30th October 2016, 16:51
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Quote:
Originally Posted by slickshod View Post
Hi Paul are they braking at the weld or across it ? and what method of welding are you using ? could you mount them on rubber bushes to absorb any vibrations ,I had to use this method on a Westfield.
Both, they have broke several times, sometimes the welds snapped off and also the tube sheared off
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Old 30th October 2016, 17:36
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Are they tube or solid? I think the welding is causing embrittlement of the steel, leading to the tube breaking in the heat affected zone (ie close to weld). If solid (or tube) you could slot them to take a 6mm plate (nice tight fit in slot) and braze them - look at chainstays or seatstays where they meet the rear dropout on a quality brazed cycle frame. Brazing acts at a lower temperature so doesn't cause the embrittlement problems that welding does - that's why it's been used in bike frames for over a century! Good old-fashioned simple engineering is sometimes the best You may have to replace some of your metal that is already heat affected?
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Old 31st October 2016, 09:06
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Default Welds Fracturing

Totally agree with the above ,stress due to heat is likely causing the brake especially in thin wall tube ,brazing or solid inserts at the weld will solve the issue ,good luck keep at it !
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Old 31st October 2016, 14:22
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You don't say what welding method is being used also what is the thickness of the tube compared with the bracket thickness ?

It is possible you are getting undercuts which reduce the wall thickness at the point of maximum stress i.e the tube/bracket interface ?

If you put a internal sleeve into the tube and tapered the inside end to spread the stress you would double it's thickness at the point of the weld ?

Don't forget if you make one part stronger and unable flex you just move the forces somewhere less strong , sometimes flex is best
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Old 31st October 2016, 16:17
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Thanks for the input everyone
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