Trials Frame Design Help

Unicyclepa,

The materials you are calling out are cheap. My advice to you is go to some local machine shops, and bring prints of your drawings, including notes. Explain what you will be doing and how you plan to do it. Tolerate any “advice” the machinists give you (chances are, actually, a decent amount of it will be good stuff), and then ask them if they might have any drops around the shop that you might be able to take for your project.

I did the above, and got a 2"x5"x22" chunk of 6061-T6, as well as a .5"x24"x24" chunk of the same, and enough tubing for three seat tubes. Total cost: $30.

One other thing is that you will need to figure out a way to reference the location of the bearing holders relative to the crown. They must be exactly the same distance from the crown (we’re talking within around 0.005", so it could be much worse. I’m currently making an engine where the cylinder bore has tolerances of -0.0000"/+0.0001"). Any error misaligning the bearing holders will manifest itself as a wheel that does not ride straight in the frame. The easiest way to assure alignment is to make each leg and weld it to the bearing holders first (carefully keeping alignment, and minimizing the distortion due to heat). Then make measurements of each leg (they can be relative, so try just mounting an indicator with a stop on a surface plate… any machinist should be able to figure this out). Trim the longer one to the same length as the shorter one, and then tack weld each one flush with the top of the crown. Then use a small rawhide or rubber mallet to tune the alignment, tack weld and tune some more, then do the final welds.

I think you have slightly exaggerated the torlerance of leg length. Though yes its nice to be perfect, but do you really think a frame like a yuni or bedford is that exact? They still work fine.

i have two coke can shims on the left side of my Yuni MUni they are each less than .005" thick. The difference is noticeable on the 26" wheel when tire clearance is an issue. tolarences for a smaller (trials) wheel would probably be larger but not all that much.

My grandfather use to own the only machine shop in my town. he also knows the current owner so i think im gona take my plans up there with him and see what they can do for me

once aghan thanks for the help i really hope this happens

Evan, you may be right, however on my first frame, I just got them within ~1/64, and the had to mess with stacks of shims, which is a pain.

saskatchewanian: Coke cans are exactly 0.005" thick. I have one in front of me, and I use coke cans for 0.005" shim stock in my machine shop all the time. But yes, my experiences with those shims is why I said it matters. I’ve had to shim every frame I own, which has always sucked.

Update

I did some reworking of the crown. Its now 10 mm taller and the leg retention supports where extended by 5 mm. Also all fillets where removed (i like it better without them).

according to inventor without welds it weighs 462g when built of Al 6061 (kh is like 560 I think)

Updated ISO

I know that in solidworks you can put stress tests on it to figure out where the weak points are and how much force is needed to break whatever you’re making. Can you do the same with the program you’re using?

KH -07 frames are 7005 T6 Aluminium.

i think it would make this frame stronger

sorry for the quality, it’s Paint work

that definately looks sweet, and it would be awesome to see it made. I really like the crown defo looks awesome. DO you recon you’ll make it bi-colour?

theres no need for it to be stronger. Have you ever seen a frame break there?

if they do get made color will probably be up to the buyer.

look into this rigid mtb fork it might give you an idea for the designs. just a thought. http://images.google.com/imgres?imgurl=http://www.cyclesurgery.com/ProductImages/433.jpeg&imgrefurl=http://www.cyclesurgery.com/ProductDetails/mcs/productID/1024259&h=200&w=76&sz=4&tbnid=EcWdpU_JUVmR0M:&tbnh=104&tbnw=40&hl=en&start=16&prev=/images%3Fq%3Dpace%2Brigid%2Bfork%26svnum%3D10%26hl%3Den%26client%3Dsafari%26rls%3Den-us%26sa%3DN

That’s turning out way cool. I think you should end up painting it in the colors that are in the last pic.

how much would this unicycle be?

$200ish

each frame will be custom

thats actually a good price, provided that the frame is good and strong. After all the kh trials frame is 199. If these are custom made and weigh less, then that is a good price

mabr 250 with a life time warranty

if it got the lifetime warranty im buying it.

if you start producing will they be ready be next xmas?

i hope