want2race
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| posted on 14/9/08 at 10:31 PM |
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Cycling wing arms? How strong
I made some out of 9mm Cold rolled steel this weekend mounted to a plate that bolts to the upright. The bad thing is if I flick them or rev the engine
at idle, i get a large amount of vibrations though them.
Anyone have any ideas or logic on how to stiffen these bastards?
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Andi
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| posted on 14/9/08 at 11:06 PM |
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Do you have a photo?
And does this happen with the wings on?
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Paul TigerB6
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| posted on 14/9/08 at 11:18 PM |
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There is quite a lot of lift generated by the wheel arches at speed so you can be sure they will lift if they arent stiff enough. If they are
vibrating simply by revving the engine then i'd be worried myself.
I saw a figure of 40kg of lift generated the other day on here so give your stays a good pull and see how much they flex. If its much then you might
want to look at using heavier duty / larger diameter tubing
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want2race
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| posted on 15/9/08 at 02:16 AM |
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Heres some pics
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scutter
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| posted on 15/9/08 at 05:35 AM |
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I think you need to find a way of bracing them, with them only having one mounting point they are bound to vibrate.
Are there any other mounting holes around to use?
ATB Dan.
The less I worked, the more i liked it.
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britishtrident
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| posted on 15/9/08 at 07:47 AM |
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As above --- also try think in terms of stiffness not brute strength.
What you want to do is make the supports stiff enough to raise the natural frequency the wing vibrates at above the frequecies of vibration of the
road and engine.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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MikeRJ
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| posted on 15/9/08 at 07:52 AM |
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Cutting slots in the inside edge of the wings is a mistake IMO, you lose rigidity in the wing itself and the GRP will be prone to cracking from that
point.
Interesting top wishbone design though, camber and castor adjustable.
[Edited on 15/9/08 by MikeRJ]
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Richard Quinn
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| posted on 15/9/08 at 10:34 AM |
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quote:
Originally posted by MikeRJ
Cutting slots in the inside edge of the wings is a mistake IMO, you lose rigidity in the wing itself and the GRP will be prone to cracking from that
point.
Interesting top wishbone design though, camber and castor adjustable.
[Edited on 15/9/08 by MikeRJ]
It may be my eyes but those wings don't give the impression that GRP cracking will be much of an issue
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andylancaster3000
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| posted on 15/9/08 at 10:35 AM |
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This is how we did ours. They finished very stiff (you can almost sit on them!) and there doesn't seem to be much movement at high speed at all.
Being tubular they aren't to heavy either.
Earlier in build to show a little more detail:
I can't remember what the two different tube sizes are off hand but the upper one is a close sliding fit into the lower part in each
'prong'
HTH
Andy
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hellier0437
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| posted on 15/9/08 at 03:29 PM |
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how did you bend the tubing?
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britishtrident
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| posted on 15/9/08 at 04:18 PM |
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quote:
Originally posted by Richard Quinn
quote:
Originally posted by MikeRJ
Cutting slots in the inside edge of the wings is a mistake IMO, you lose rigidity in the wing itself and the GRP will be prone to cracking from that
point.
Interesting top wishbone design though, camber and castor adjustable.
[Edited on 15/9/08 by MikeRJ]
It may be my eyes but those wings don't give the impression that GRP cracking will be much of an issue
True but sharp cornered slots in aluminum alloy sheet are still really bad news more so than in GRP --- of course sharp corners in highly stresed
steel parts like wishbones aren't a good idea either.
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want2race
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| posted on 15/9/08 at 05:50 PM |
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quote:
Originally posted by hellier0437
how did you bend the tubing?
I used a rod bender
[Edited on 15/9/08 by want2race]
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andylancaster3000
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| posted on 16/9/08 at 12:13 AM |
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Used a mechanical type tube bender similar to the type used by plumbers for copper pipe but much large with formers for different sized tubes.
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want2race
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| posted on 16/9/08 at 01:25 PM |
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So whats the black art?
Using 2 mounting points? I'm really confused why this didnt get the job done.
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TheGecko
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| posted on 16/9/08 at 01:38 PM |
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quote:
Originally posted by want2race
So whats the black art?
Using 2 mounting points? I'm really confused why this didnt get the job done.
In my opinion (for whatever that's worth!) the single mounting point is the main problem. The arms supporting the guard are ~12" long so
they've got lots of leverage to exert on that poor single mounting point. Two mounts, as far apart as possible, will make a difference. Either
pick up at the bottom ball joint or the caliper mount holes or the backing plate holes (if there are any).
Mostly unrelated - those are nice guards. Did you make them yourself? I ask as I'm currently looking at what would be involved in rolling my
own front and rear guards from ali.
Dominic
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want2race
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| posted on 16/9/08 at 04:46 PM |
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quote:
Originally posted by TheGecko
quote:
Originally posted by want2race
So whats the black art?
Using 2 mounting points? I'm really confused why this didnt get the job done.
In my opinion (for whatever that's worth!) the single mounting point is the main problem. The arms supporting the guard are ~12" long so
they've got lots of leverage to exert on that poor single mounting point. Two mounts, as far apart as possible, will make a difference. Either
pick up at the bottom ball joint or the caliper mount holes or the backing plate holes (if there are any).
Mostly unrelated - those are nice guards. Did you make them yourself? I ask as I'm currently looking at what would be involved in rolling my
own front and rear guards from ali.
Dominic
Thanks for your advice! Im going to play with this when I get home tonight
The guards are galvanized steel. They are made for a trailer and work pretty well. I will trim them a bit to cut down on the "scoop
effect" but just want everything to work right now!
Oh ye.. total cost $22 a piece @ a trailer supply shop
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want2race
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| posted on 24/9/08 at 10:11 PM |
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I added a second point from the brake caliper bolt. Its not much stuffer. I am considering 13mm tubing for the redesign.
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