Ducati engined café racer
- Thread starter HansS
- Start date
Popeye SXM
Also used for MX
I love your work on the SA, did you have any trouble with distortion after welding? When I made mine I built a jig, a little like yours and when I removed the SA it had a twist. Are you going for twin shocks?. Looking forward to seeing the rest of the frame
Hi thanks.
Farmer92. No I haven't planed for triangulation. My thought is that the SA is from a dirt bike and the forces on the street should be considerable less than it's dimensioned for. I hope im right..
Popeye SXM.
Yep. Rewelded it twice before I got it good enough. It's not twisted. It just got a bit tight between where it mounts on the the engine. But I made it so i will have spacers. So no worries.
Yep I will have twin shocks. Im going old school. RSU fork and twin shocks.
Something like this maybe.
Sent from my SM-J500FN using DO THE TON mobile app
Farmer92. No I haven't planed for triangulation. My thought is that the SA is from a dirt bike and the forces on the street should be considerable less than it's dimensioned for. I hope im right..
Popeye SXM.
Yep. Rewelded it twice before I got it good enough. It's not twisted. It just got a bit tight between where it mounts on the the engine. But I made it so i will have spacers. So no worries.
Yep I will have twin shocks. Im going old school. RSU fork and twin shocks.
Something like this maybe.
Sent from my SM-J500FN using DO THE TON mobile app
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slikwilli420
Been Around the Block
HansS said:
Odd assumption. Don't hope you're right, as that gets people killed. Dirt bikes are not made to hook up instantly like a street bike. Good sticky tires and you may put the arm above its limits. Dirt bike parts dont always translate to street for a number of reasons. Please do your homework and plan on having the arm heat treated afterwards.
Thanks for the input. Tumbs up for having concerns about my safety.
Yes it will be heat treated. I made some calculations but Im not finished with them. Also I discovered things when I cut the SA open that one can't see from the outside.
Casting is really odd. It's very thin just in front of where the shock original mounts.
I have a backup but it's not as pretty as the KTM Swingarm.
Yes it will be heat treated. I made some calculations but Im not finished with them. Also I discovered things when I cut the SA open that one can't see from the outside.
Casting is really odd. It's very thin just in front of where the shock original mounts.
I have a backup but it's not as pretty as the KTM Swingarm.
slikwilli420 said:
See: cush drive hub
farmer92
Coast to Coast
The biggest load on the SA will likely be from the chain pull, luckily that’s usually mostly a compressing force on the SA.
The vertical loading of the SA depends on where you place the shocks.
As you see here, the closer the mounts on the SA are to the frame, the more of a load is placed on the arm itself. If they are in line with the rear axle, there is virtually no load on the SA in that plane. (As long as the are parallel with the direction of travel)
The other loads to worry about are the twisting and sideways bending loads. Both of these are strongly helped by triangulation of the SA either above or below, or both.
One more thing when considering where you mount the rear shocks.
Ideally i suppose you would want to be somewhat in the progressive angles, and defined want to avoid the regressive angles.
The vertical loading of the SA depends on where you place the shocks.
As you see here, the closer the mounts on the SA are to the frame, the more of a load is placed on the arm itself. If they are in line with the rear axle, there is virtually no load on the SA in that plane. (As long as the are parallel with the direction of travel)
The other loads to worry about are the twisting and sideways bending loads. Both of these are strongly helped by triangulation of the SA either above or below, or both.
One more thing when considering where you mount the rear shocks.
Ideally i suppose you would want to be somewhat in the progressive angles, and defined want to avoid the regressive angles.
Popeye SXM
Also used for MX
Ha, It took me a 2nd run with the welder before I was happy too! I still had a little straightening to do. I want to heat treat mine when I am finished so please do keep documenting. I like farmer's post, I think with twin shocks done well and with your fab skills I am sure this will be done superbly, the KTM SA will take the torque/hp of the Duc engine. Love your image, Duc engine with traditional cafe lines 8) 
Got some new parts. Rear shocks So now i can continue with the swingarm. Got them from TEC bike parts. Looks OK. But it's not a Öhlins. They will work just fine for now. And at only 150$ I just couldn't resist.
Sent from my SM-J500FN using DO THE TON mobile app
Sent from my SM-J500FN using DO THE TON mobile app
