Author Topic: '73 500 - Subframe Fabrication (Read 142936 times)

calj737 · « **Reply #350 on:** July 01, 2015, 10:45:00 AM »

550 was done until the boy clanked it. Re-wired it completely since he mashed the multi-switch and I replaced with m-switches. Modifying the rear set brackets, almost done with that. Carbs are on, synced and just need to weld up the new seat pan and have it reupholstered. I'll paint it this fall.

I am trying like hell to get this bike (500) frame done this month. Got to do the hoop, swing arm and rear set brackets. Then it can be powder coated. The boy won't have the seat and tank done before school though.aybe have the blanks done by Xmas and then can fab and mold them for Spring completion.

SOHC4 Cafe Racer Fan · « **Reply #351 on:** July 01, 2015, 10:48:56 AM »

Slacker kids!! If only he busted out as much work as his old man!

calj737 · « **Reply #352 on:** July 01, 2015, 10:51:51 AM »

Well, can't complain. He and the 16yo are working for a commercial painter 5-6 days a week. Gone by 4:50 every morning and home around 5:30pm. Pretty good money and pretty long days too. Keeps them out of trouble and from underfoot.

SOHC4 Cafe Racer Fan · « **Reply #353 on:** July 01, 2015, 10:56:23 AM »

Quote from: calj737 on July 01, 2015, 10:51:51 AM

Well, can't complain. He and the 16yo are working for a commercial painter 5-6 days a week. Gone by 4:50 every morning and home around 5:30pm. Pretty good money and pretty long days too. Keeps them out of trouble and from underfoot.

Has your daughter fully recovered from the arm break? Is she getting on 2 wheels, too?

calj737 · « **Reply #354 on:** July 01, 2015, 11:12:52 AM »

Not quite yet. The pin was removed a few weeks ago, but she's still in a removable waterproof cast. She is allowed to practice with her soccer team and she still competes on her swim team while wearing it. It throws off her stroke pretty good but it's great exercise nonetheless.

And she hasn't uttered one word of complaint about the whole affair. Impressed with her resolve. Took up writing with her left hand immediately to stay current with her school work and correspondence. She's the least amount of trouble of all the kids and she LOVES a ride on the bikes.

SOHC4 Cafe Racer Fan · « **Reply #355 on:** July 01, 2015, 11:16:41 AM »

Quote from: calj737 on July 01, 2015, 11:12:52 AM

Not quite yet. The pin was removed a few weeks ago, but she's still in a removable waterproof cast. She is allowed to practice with her soccer team and she still competes on her swim team while wearing it. It throws off her stroke pretty good but it's great exercise nonetheless.

And she hasn't uttered one word of complaint about the whole affair. Impressed with her resolve. Took up writing with her left hand immediately to stay current with her school work and correspondence. She's the least amount of trouble of all the kids and she LOVES a ride on the bikes.

I'm sure she will be watching the Final in the World Cup this weekend.

calj737 · « **Reply #356 on:** August 19, 2015, 05:31:40 PM »

Well We have spent the past couple of weekends tinkering with the seat and subframe.

The intent was to completely replace the stock rear with a custom aluminum unit. Obviously you can't weld alloy to steel and the approach of a modern bolted unit was preferred anyway.

The shape was designed by my son, printed and cut out in foam core as a template. Also did a scaled drawing for profile.

Here's step one:

SOHC4 Cafe Racer Fan · « **Reply #357 on:** August 19, 2015, 05:34:27 PM »

Nice job on the bends.

calj737 · « **Reply #358 on:** August 19, 2015, 05:34:54 PM »

Used some heat and a tubing bender to hand shape the tubes

Came out pretty close. TIG welded the rear closed with a miter cut piece, then heat bent the "kick" into the rails.

calj737 · « **Reply #359 on:** August 19, 2015, 05:36:27 PM »

So here's the stock frame after cuts:

And the piece we are fabricating a replacement for:

SOHC4 Cafe Racer Fan · « **Reply #360 on:** August 19, 2015, 05:39:11 PM »

Yeah, that's no easy feat getting those tubes hand bent. Great symmetry.

calj737 · « **Reply #361 on:** August 19, 2015, 05:42:01 PM »

Since these are 1"x0.125 walled 6061 tubes, a solid slug was made to insert into the ends, welded then milled a mortise into

calj737 · « **Reply #362 on:** August 19, 2015, 05:45:06 PM »

And the pieces ready for fitment to the frame. The "tenons" we're milled from cold rolled steel and will be welded to stock frame. A rough mock up-

calj737 · « **Reply #363 on:** August 19, 2015, 05:45:56 PM »

Then weld everything together while bolted in place to keep it all trued up.

Still need to add gussets behind the truss for shock mounts and 2 cross braces and an under seat pan. But I need to wait until the swing arm is done for that.

P.abrera · « **Reply #364 on:** August 19, 2015, 05:47:13 PM »

I like where your goin. Great fab set up

SOHC4 Cafe Racer Fan · « **Reply #365 on:** August 19, 2015, 05:49:28 PM »

Quote from: P.abrera on August 19, 2015, 05:47:13 PM

I like where your goin. Great fab set up

Excellent design and execution.

Tews19 · « **Reply #366 on:** August 19, 2015, 05:49:55 PM »

Cal, what's the weight difference with the modified frame in relation to stock?

calj737 · « **Reply #367 on:** August 19, 2015, 05:52:34 PM »

Shed 4.8# between the stock portion cut off and the current setup. And went from thin, thin thin walled 40 yo tubing and stamped steel to 1/8" walled tubing that's TIG welded. I'd say it's a major upgrade in rigidity and strength. I bet Brent might even like this one (perhaps not the connection technique, but hey it's a street bike)

calj737 · « **Reply #368 on:** August 19, 2015, 05:57:43 PM »

A glimpse of the critical parts of the swing arm:

Started with a 1.75"X1.175" block of 6061. Turned a job onto it to chuck it in the lathe. Centered it up. Then bored a 1.50 hole in it. Milled a chamfer on the edges, split it, then etched index marks in it.

These will be the axle clamps. Styled after a Seely swing arm. Milling internal adjusters from cold rolled next (maybe this weekend, or next week).

Tews19 · « **Reply #369 on:** August 19, 2015, 06:17:43 PM »

UMMM, when do I move in ?

slikwilli420 · « **Reply #370 on:** August 19, 2015, 06:18:06 PM »

Very cool swing arm adjusters. Thinking about putting something like the seeley arm together myself. Any mute details on the arm like specs or materials?

calj737 · « **Reply #371 on:** August 19, 2015, 06:27:38 PM »

Quote from: slikwilli420 on August 19, 2015, 06:18:06 PM

Very cool swing arm adjusters. Thinking about putting something like the seeley arm together myself. Any mute details on the arm like specs or materials?

Well I grabbed some dims from Jaguar, but honestly, my arm will be "styled" off a Seely, but unlike it altogether. I'm using 1.50x0.375" tubing, the adjusters are Octagonal, not hex, currently they're cut to 4" but I may shorten them. I'll use 1.25 cold rolled for the adjusters and open the arm tube so they slide. Stock axle on my bike is 20mm so I need to bite that hole, and slot the legs of the swing arm before I bend them.

The spread and bend will differ too as my is aimed for a 17"x150 tire. It will be very strong and very light. But not a Seely remake.

slikwilli420 · « **Reply #372 on:** August 19, 2015, 06:32:21 PM »

Hold the phone. 0.375 wall tubing, as in 3/8"?? I'm thinking a decimal is in the wrong spot. For an arm like that I would think 0.093-0.120 wall. The seeley arms were only 093 wall.

calj737 · « **Reply #373 on:** August 19, 2015, 06:57:15 PM »

Correct, 0.375 wall. Just because .093 was used, doesn't mean I am. There's virtually no weight detriment but theres huge strength and rigidity benefits to it.

Retro Rocket · « **Reply #374 on:** August 19, 2015, 07:01:38 PM »

Hi Cal, nice work as usual mate. When designing the rear section of the frame, did you factor in shock angle.? If i were going to all the trouble you are, in modifying this frame, I would have been looking at shock angle before welding the pipe from the swingarm pivot area to the rear of the frame..? Somewhere, I have a Yoshimura document from the 1970's about suspension modifications for the period, I'm sure the number Yoshi settled on for the rear shock angle was 36 degrees for optimum rear shock performance, I think Brent mentioned this somewhere when talking suspension on the forum as well, I've looked but can't find it, maybe drag Brent over if you are interested {as anal retentive as me}

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Author Topic: '73 500 - Subframe Fabrication (Read 142936 times)