Hillhater
100 TW
No qualms over Rivet & adhesive as it has been the go to construction in the aircraft industry for many years !
10kW, custom cut aluminum frame, QS205, full suspension
- Thread starter owhite
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owhite
100 W
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From BalorNG
Thanks for pointing that out. I can imagine the forces for an "L" shape where both arms are fairly long, how wobble would come into the picture. But in my case one of the lengths of the L shape is fairly short. But I can look at my design and see if I can get a triangle into it. I'd like to possibly just slap something on my existing swingarm, and see if there is a change "before and after".
preciate the suggestion, BalorNG.
Thanks for pointing that out. I can imagine the forces for an "L" shape where both arms are fairly long, how wobble would come into the picture. But in my case one of the lengths of the L shape is fairly short. But I can look at my design and see if I can get a triangle into it. I'd like to possibly just slap something on my existing swingarm, and see if there is a change "before and after".
preciate the suggestion, BalorNG.
owhite
100 W
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I really need to revise my budgetary numbers because I did get into some extra expenses.
As for thicknesses this diagram does not show all the parts, but the colors correspond to black (2mm), green (6.35mm), and blue (9.525mm). Almost all of swingarm #2 parts are 6.35mm. All aluminum is 6061. I LOVED welding it once I got the hang of it. Next go round I'm going to use a little more machining instead of doing some of the bearing holders by hand.
I'm definitely dumping swingarm #1, it's not safe structurally.
mxlemming
100 kW
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- Jul 17, 2020
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Pretty cool. I have a really nice TIG welder, but I am utterly crap with it and have never had the time to learn. One day, I am going to weld up a bike. I think it is an engineering rite of passage to build a bike.
For your swingarm, perhaps take inspiration from he old Santa Cruz super 8 designs with the big ~3 inch tube between the two sides of the swingarm.
Probably telling you to suck eggs, but the torsional stiffness of any closed section is proportional to the wall thickness and the area enclosed by it.
An un-closed section is vastly less stiff.
Get the closed section as close in to the tire as possible, while allowing it to have decent mud clearance, and get the tube as big as possible. Doesn't have to be round, there is no huge advantage of round over square or contoured... just avoid sharp folds where weird edge effects and buckling can occur.
For your swingarm, perhaps take inspiration from he old Santa Cruz super 8 designs with the big ~3 inch tube between the two sides of the swingarm.
Probably telling you to suck eggs, but the torsional stiffness of any closed section is proportional to the wall thickness and the area enclosed by it.
An un-closed section is vastly less stiff.
Get the closed section as close in to the tire as possible, while allowing it to have decent mud clearance, and get the tube as big as possible. Doesn't have to be round, there is no huge advantage of round over square or contoured... just avoid sharp folds where weird edge effects and buckling can occur.
are you welding with MIG or TIG ? you should try to limit the lenght of weldings where possible -
I don't know how you managed the deformations on the piece -
your weldings look very big and I guess the pieces got a lot of heat during the process. Unless you have a post stress relief thermal treatment, the weldings soft the aluminium in the HAZ area, becoming the weakest point.
I don't know how you managed the deformations on the piece -
your weldings look very big and I guess the pieces got a lot of heat during the process. Unless you have a post stress relief thermal treatment, the weldings soft the aluminium in the HAZ area, becoming the weakest point.
owhite
100 W
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I'm not sure what you mean about the deformations.
But I use TIG and agree there is a large HAZ and I currently am assuming that the welds will be weaker. This was my first attempt to make a bike from raw aluminum parts, and I wanted to simply ride it around to see if it would fail. It's a custom bike, and there may be other ways to test it, but i wanted to be able to ride it for fun.
At present I have found one site that might have large enough ovens to heat treat the aluminum, but I'm not familiar enough with the process to know exactly what is involved. I also am prepared to work with a heat treating facility, but because I assume it is expensive I would not do that until I'm done with testing the bike.
BigBlock -- my other thought about heat treatment where I am looking for your opinion is that I view the construction of my bike to be based on using much thicker metals than most mountain bike frames. So yes I agree welding will make everything weaker, but I am hoping that by simply using heavier materials there will reasonable protection.
But I use TIG and agree there is a large HAZ and I currently am assuming that the welds will be weaker. This was my first attempt to make a bike from raw aluminum parts, and I wanted to simply ride it around to see if it would fail. It's a custom bike, and there may be other ways to test it, but i wanted to be able to ride it for fun.
At present I have found one site that might have large enough ovens to heat treat the aluminum, but I'm not familiar enough with the process to know exactly what is involved. I also am prepared to work with a heat treating facility, but because I assume it is expensive I would not do that until I'm done with testing the bike.
BigBlock -- my other thought about heat treatment where I am looking for your opinion is that I view the construction of my bike to be based on using much thicker metals than most mountain bike frames. So yes I agree welding will make everything weaker, but I am hoping that by simply using heavier materials there will reasonable protection.
I agree that heat treatment is too complex and expensive for most DIY builders - it make sense if you weld in a jig that hold firm the part and remove the part from the jig once post treated in the hoven.
Ususally when you weld on aluminum tubes (especially going on the longitudinal plane of the tube) the tube starts to distort compromising your measurements and tollerance. Exepericed welders are able to limit this issue by apply small weldings in a specific pattern and sequence.
If you are not experiencing deformation, you are ok. Using thiker walls will help also to make welding easier.
Ususally when you weld on aluminum tubes (especially going on the longitudinal plane of the tube) the tube starts to distort compromising your measurements and tollerance. Exepericed welders are able to limit this issue by apply small weldings in a specific pattern and sequence.
If you are not experiencing deformation, you are ok. Using thiker walls will help also to make welding easier.
mxlemming
100 kW
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There's nothing magic about heat treatment. No end of people making it sound super complicated but in the end it's literally just heating it to 530 degrees for 1 hour, quench it and then age it at about 230 degrees for 12 hours and you get stress relieved 6061-T6.
It's soft in the middle stage so easy to bend (or straighten out) and you have a few days leeway in between the stages.
It shouldn't be that expensive, you're only renting a few hours in a big oven... But it's a few years since i had anything heat treated and it wasn't as big as your frame.
It's soft in the middle stage so easy to bend (or straighten out) and you have a few days leeway in between the stages.
It shouldn't be that expensive, you're only renting a few hours in a big oven... But it's a few years since i had anything heat treated and it wasn't as big as your frame.
mxlemming
100 kW
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It shouldn't sag provided you support it in sensible places. Try to get it put in the oven upright and without having it rest on important bits like the head tube or bearing races. When it comes out from the first heat treat it will be fairly soft (like 1/3 the final strength) so it's possible to bend it straight...
I presume you used a sensible grade filler rod?
I presume you used a sensible grade filler rod?
