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View Full Version : Clr size on BT rigid frames



Scoobydude
12-29-2017, 8:54 PM
I might have a lead from someone over at caimag forums on figuring out what size dies are used on rigid pan/knuck frames. I juat tried to see how it would be measuring on a bend i already know on a frame i built and its kind of a bitch if its not close to a 90 degree bend. Would be nice to have the original 48 prints blown up to full scale, id think that would be easy to measure off the prints. I know the bend angles are slightly differant in the front downtubes in pans vs knuckles, but any clr would be nice. Looking for shovel downtube radius,any stock rigid frame rear leg radius, and pan or knuck downtube radius in lower bend.

ncmc47
12-30-2017, 10:17 AM
Chopper handbook used to have 48 rigid frame print that could be down loaded. I haven't been on there for awhile but there's all kinds of useful information on there.

Scoobydude
12-30-2017, 4:53 PM
I think gary says tgey use 4.5" clr dies, not sure but its definatley not acurate for the rear legs, or shovel downtubes. I did 4.5 dies on some sowntubes before and it does look drcent there. The 48 prints dont show the radiuses.

farmall
12-30-2017, 5:42 PM
I don't know anyone with a large enough 3D scanner (or I'd have done it myself) but if you can find someone (maybe put out a Craigslist advert?) you could scan a complete straight frame and import it into CAD.

tomsoftail
12-30-2017, 9:34 PM
would this help? I can email it to you if so..8057980579

Scoobydude
12-30-2017, 10:19 PM
If i had a conplete frame i could just cut out some circles in a bunch of differant radiuses and place them inside all of the bends. I aint got the bread to buy a stock frame or i would do it. Hopefully thats what the guy on caimag is gonna do

I have the cbh prints and their good for dimensional referances, but the dont show radiuses. Ive instagramed and emailed a bunch of guys i thought made their hardtails but it always turns out they cut up a stock frame and used the rear.

Im mostly interested in the rear legs bend, that long radius seems graceful compared to some aftermarket hardtails with tight bends.

Scoobydude
12-30-2017, 10:28 PM
Cbh prints do not show the radiuses.if i had a frame i would just cut out circles with differant radiuses and place them inside thw bends.

Ive asked alot if guys on instagram with the long radius bends in their tails and uts always the rear end of a cut up stock frame .

Heres a link to my caimag forum question
http://www.caimag.com/forum/showthread.php?26645-Dies-for-frame/page3


I was asking if anyone has blown up the original factory blueprint to full scale, the bends are representational of the real deal. A scanned frame would be sweeeet.

ncmc47
12-31-2017, 12:44 PM
I believe the front lower legs to be 3.5 clr, just before they go into the sidecar mounts and a 40 degree bend. I used a card board circle to come up with that. I have read the radius for the rear legs where they curve up to the axle plates is to large a radius for a tube bender. I haven't measured that bend. Hope that helps some.

Zeeman
12-31-2017, 11:32 PM
The die needed to bend shovelhead downtubes is 8 5/8" CLR. The die for the pan/knuck lower frame rail bend just before the sidecar loops is 3" CLR. I forget the radius die needed for the kickup at the rear, but it's pretty large, would need to be custom made.

farmall
01-01-2018, 12:57 PM
xnewmanx has a brilliant and dirt cheap solution for custom dies:

http://www.chopcult.com/forum/showthread.php?t=46266

Scoobydude
02-11-2018, 3:48 PM
I bought a print off tge internet and measured a couple points amd found the scale. It was 2.?? , i forget. I think the entire length of the frame on the paper over the entire actual length gave me about 18th inch off when i printed out the scaled version at a local print shop. They did alot of architectural drawing copies and stuff. Cost me 8 bucks! Then i cut out circles with differant radii.
Seat area - hard to tell with small bend, i think a 9" clr would work at 22 degree
Downtube before castibg - 3" clr at 41 degree
Downtube casting - 38 degree
Rear legs - 9 " clr at 32 degree

Im sure the degrees might be off by one ir two degrees, gary weishaupts prints could confirm . his are very accurate since he plotted his out.

It would be nice to have confirmation from a real frame, since i could not say weather or not the drawing 100% replicates the bend radiusses. Not sure how drafting works, when they draw scale blueprints do they strucly adhere to scaling the drawn bend radii ?

Scoobydude
02-11-2018, 3:49 PM
The die needed to bend shovelhead downtubes is 8 5/8" CLR. The die for the pan/knuck lower frame rail bend just before the sidecar loops is 3" CLR. I forget the radius die needed for the kickup at the rear, but it's pretty large, would need to be custom made.

How did you figure that. Scaling up the print?

Scoobydude
02-11-2018, 3:50 PM
I believe the front lower legs to be 3.5 clr, just before they go into the sidecar mounts and a 40 degree bend. I used a card board circle to come up with that. I have read the radius for the rear legs where they curve up to the axle plates is to large a radius for a tube bender. I haven't measured that bend. Hope that helps some.

It does, thank you