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new member stumcgoo, from scotland sent me a pm regarding making a 50mm rim without tig/mig welding the 2 rims together.
we had discussed the possibility over some beers at 12.30pm in cherreuix.
i thought it would be a good little project to put a piece of rim together and see what it takes to take apart.
i trimmed most of the lip of 2 bits of rimand connected them by riveting some 3mm strips across the join. I would plan on putting 1 between each spoke . .
on the faces to be joined I roughed the surface with the wirebrush then put a thin layer of polyester resin/cotton flock, then layed on a layer of 25mm tape and a layer of 50mm tape to each side with just resin.
when its cured for a few days I plan to clamp 1 edge then hang weight off it until it breaks
heres the glassed up test piece, presumably this would be stronger done in epoxy and carbon . my inclination would be to glass the outside of the rim , then lay up the wheel , and do the inside glassing as part of the wheel construction.
my plan now is to cut a ally rinforced section and a un-ally reinforced section and hang some weight off it to see the results. the join surface is 6mm(1/4") so theoretically 100mm length would represent 1"sq so the weight hanging could be expressed as a strain of x psi, ?
any thoughts on that?
Paul, the strength of fibre reinforced packaging tape is immense and hold most stuff together, so I would be very surprised if this fiberglass setup is not strong enough. Even with high tyre pressures I reckon it will hold.
I'm guessing 100's of kgs of weight needed????.
The Ag College just got a TIG welder. NICE!!!!!
[}:)]
So I spent a few hours on it this week repairing aluminium cattle decks in the stock yards.
results are IN!!!!!!!
Excuse the change to inches and pounds, its so i can relate all the measurement to PSI and the tyre pressure.
I cut a 4" piece ,with 2 ally strips and loaded it up with 80, then 200lbs of weight and nothing happened!
I then cut a 2" piece with NO strips and nothing happened. my maths says we now have a strain of 400lbs per square inch!!!!!!!!!!
next step is to reduce it to 1" of strip and add the 80lbs. this resulted in a distortion of the rim section of almost 1/8", but no breakage or cracking of the joint
finally I did the 200lbs test, resulting in a further 1/16" deflection, but the thing held up
if my maths is correct thats 800lbs per square inch!!!
I would appreciate if lachlan , in his capacity as an actual engineer, could check my maths.
of course this now begs the question , why bother with the tig weld?
perhaps you could simply wire the 2 rims with some twist wire to hold the shape then just glue/glass/tape after roughing up with a wire wheel
Great test Paul, no wonder the wheels are hanging together!
I'd still stick to tig in centre - bombproof is good, especially with wheel up.
It shows how Vic's idea of the bike rims / glass combo & your experiments as well have really delivered the goods & made these 5s possible & fun & now it looks like we can trust the structure of the wheels.
Good job guys
I tried just bonding/glassing the rims together a couple of years ago(they where repairable but a pain in the a#$ to do). They blew apart with heat . So I decider to weld them together and that solved the problem. I think the strips and rivets will work fine.
I think the "secret" here might be the use of the the cotton flock as the first layer of material bonding to the roughed up aluminium.
I pulled apart an offcut with plyers and it was really tough to rip off the ally, much tougher than epoxy glue.
cutting through a blob of the stuff with a skinny cutting disc it slows the blade down enough to be noticable.
any other questions stumcgoo
Just a thought here
How about if the two rims were cut down so the spoke holes were left on each half and then a strip of aluminium flat was rolled around and pop riveted through the spoke holes joining the two parts together ?
A bit of epoxy glue could be used as well under the strip
Paul,
A little something else to think about.
Would there be any movement, at all, between the Rims (Flex etc) I am just thinking of the rivets at this point. You don't need any movement at all there.
Pop Rivets are a great bit of kit BUT if they start to work loose they are dangerous.. Point in fact. Years ago in NZ a bloke assembled his Hang Glider "A" Frame (Points under Tension) with Large Pop Rivets.. He was very lucky to survive the Crash..[}:)]
Ron
today did the 1/2" peice test, mounting hole is 1/4 so not alot of meat left, and it still supported the 80lb weight
just relying on polyester,a little cloth and a surface bond orf resinwith some cotton flock in it.. I think that might be 640psi?
all thats left is to use it to tow the landcruiser!!!!!.
personally I would forgrt the rivets and ally and just do it with cotton.
I will test it with some steel rim as well when time permits, in the meantime I plan to make a complete wheel by the system and race test it.
my tig welder is away in madagasgar so its DIY for a while
Where do you get cotton flock Paul ?
Some times asking for things around here all I get is raised eyebrows even somewhat mundane things
I finished the wheel, it came out a bit heavier than my welded rims ,but still lighter than my original domed wheels.
when it came time to balance the took rather a lot of lead bu came up well balanced.
Im looking forward to getting them rolling in september
