Sur-Ron - New Mid drive Bike

motomoto said:
I used to make billet swingarms and frames. The swingarm weighed 1 kg without hardware.GP frame 1.jpg

Wow, that's pretty darn light! Does anyone have an idea how much the stock swingarm weighs? Is there a bearing where the swing arm connects to the frame?

I guess for calculating the force, it seems like the biggest force is the impact from jumping it. How many feet vertical drop could that swingarm withstand?

For a 220-pound rider, plus the 110-pound bike, I calculate that if landed completely on the back wheel from a 9.8-foot drop (3 meters), the swing arm would be subjected to 3,246 foot-pounds. I am guessing the lateral forces for centrifugal force, handling, etc. should probably be, what a half or a quarter of that?

Now, I am considerably lighter than 220 pounds, and never jump more than a couple feet, but that seems like a pretty good design goal. What do others think? How many vertical foot drop should a swingarm be able to take, with how heavy of a rider? What do you think the Sur-Ron was designed for?
 
3DTOPO said:
motomoto said:
I used to make billet swingarms and frames. The swingarm weighed 1 kg without hardware.GP frame 1.jpg

Wow, that's pretty darn light! Does anyone have an idea how much the stock swingarm weighs? Is there a bearing where the swing arm connects to the frame?

I guess for calculating the force, it seems like the biggest force is the impact from jumping it. How many feet vertical drop could that swingarm withstand?

For a 220-pound rider, plus the 110-pound bike, I calculate that if landed completely on the back wheel from a 9.8-foot drop (3 meters), the swing arm would be subjected to 3,246 foot-pounds. I am guessing the lateral forces for centrifugal force, handling, etc. should probably be, what a half or a quarter of that?

Now, I am considerably lighter than 220 pounds, and never jump more than a couple feet, but that seems like a pretty good design goal. What do others think? How many vertical foot drop should a swingarm be able to take, with how heavy of a rider? What do you think the Sur-Ron was designed for?


Swing arm = 5.1lbs
Bare frame = 11 lbs
subframe, with key latch = 3.3 lbs (which is crazy heavy)
 
Thanks Jonathan!

Wow - Harley unveiled 4 new concepts today (two of them are prototypes). One of the prototypes looks like a Sur Ron competitor:

https://electrek.co/2019/01/07/harley-davidson-livewire-e-motorcycle/

HD-Electric-Concept-1.2.jpg


Love the fat tire on the back!

HD-Electric-Concept-1-e1546862767230.jpg
 
It's interesting they went with a belt drive on a vehicle that is clearly designed for off-road use.
 
Lelandjt said:
RE: Swingarm Flex
My cut Shinko 3.5" tire clears the kickstand spring by over 5mm but under hard cornering it hits. The spokes are tight and it has 20psi. That's swingarm flex. I decided to find a smaller, lighter, less grippy tire that doesn't overwork the chassis so hard.

Yah thats frame/swingarm flex causing that. Not surprised you are having a little issue. But thats normal.
 
3DTOPO said:
motomoto said:
I used to make billet swingarms and frames. The swingarm weighed 1 kg without hardware.GP frame 1.jpg

Wow, that's pretty darn light! Does anyone have an idea how much the stock swingarm weighs? Is there a bearing where the swing arm connects to the frame?

I guess for calculating the force, it seems like the biggest force is the impact from jumping it. How many feet vertical drop could that swingarm withstand?

For a 220-pound rider, plus the 110-pound bike, I calculate that if landed completely on the back wheel from a 9.8-foot drop (3 meters), the swing arm would be subjected to 3,246 foot-pounds. I am guessing the lateral forces for centrifugal force, handling, etc. should probably be, what a half or a quarter of that?

Now, I am considerably lighter than 220 pounds, and never jump more than a couple feet, but that seems like a pretty good design goal. What do others think? How many vertical foot drop should a swingarm be able to take, with how heavy of a rider? What do you think the Sur-Ron was designed for?
Nothing wrong with a little over engineering.
 
Rix said:
3DTOPO said:
motomoto said:
I used to make billet swingarms and frames. The swingarm weighed 1 kg without hardware.GP frame 1.jpg

Wow, that's pretty darn light! Does anyone have an idea how much the stock swingarm weighs? Is there a bearing where the swing arm connects to the frame?

I guess for calculating the force, it seems like the biggest force is the impact from jumping it. How many feet vertical drop could that swingarm withstand?

For a 220-pound rider, plus the 110-pound bike, I calculate that if landed completely on the back wheel from a 9.8-foot drop (3 meters), the swing arm would be subjected to 3,246 foot-pounds. I am guessing the lateral forces for centrifugal force, handling, etc. should probably be, what a half or a quarter of that?

Now, I am considerably lighter than 220 pounds, and never jump more than a couple feet, but that seems like a pretty good design goal. What do others think? How many vertical foot drop should a swingarm be able to take, with how heavy of a rider? What do you think the Sur-Ron was designed for?
Nothing wrong with a little over engineering.

Agreed. So you think a 10-foot drop with a 220-pound rider is a good target for a swingarm?
 
I have gone by the "that looks like it would be strong enough" approach in the past, but these days you do finite analysis on the computer model.
 
I weigh about 185 pounds. My rst Fork has about 20% of sag when I sit on it. Right in the ballpark. If I weighed less than 150 lbs I would probably want lighter springs. If I weighed over 200 I would probably want a heavier spring. The compression and rebound clickers offer lots of adjustment. Small clicks, maybe one or two, make a huge difference on how the bike rides.
 
Flykrisco said:
I've looked online everywhere and I can't find information on RST killah fork. I have read it that it is a coil Spring and non adjustable. Does anyone know where you can purchase aftermarket heavier Springs?
I emailed RST and bought a "firm" spring but when I swapped it both it and the stocker had red paint on them and felt the same. They don't make an extra firm. I preloaded the spring with 2 washers between it and the plunger and that made it a little firmer. I poured 50cc of oil in the left leg and 20cc in the right leg and that helped the late stroke spring rate a little and improved lubrication. The damper desperately needs more shims or thicker oil and more pressure but you'll need to find a chuck that fits its weird version of a schrader valve before you open it. I gave up on the stock fork and got an air fork.
 
Finer said:
I weigh about 185 pounds. My rst Fork has about 20% of sag when I sit on it. Right in the ballpark. If I weighed less than 150 lbs I would probably want lighter springs. If I weighed over 200 I would probably want a heavier spring. The compression and rebound clickers offer lots of adjustment. Small clicks, maybe one or two, make a huge difference on how the bike rides.
20% is a lot of fork sag. If you aren't bottoming out and don't mind the steep head angle I guess you're okay but at 170lbs I was diving and sagging all the time and clanking hard off the bottom whenever I jumped. The compression clicker only firms LSC which blows off under impacts. It only helps resist diving under braking.
 
First post! Lurking for awhile, figured I should give back. :wink:

Rockshox Coil Spring Boxxer... https://www.amazon.com/dp/B002SR3MB2?ref=ppx_pop_mob_ap_share

That'll fit in the RST Killah. You'll need to take apart the weird like 6+" preload spacer they have in there and cut a piece of PVC down to 2" or 3". I think it was 1" diameter PVC but double check me.

Huge difference to have the extra firm spring for my 215# self!
 
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Jammen said:
First post! Lurking for awhile, figured I should give back. :wink:

Rockshox Coil Spring Boxxer... https://www.amazon.com/dp/B002SR3MB2?ref=ppx_pop_mob_ap_share

That'll fit in the RST Killah. You'll need to take apart the weird like 6+" preload spacer they have in there and cut a piece of PVC down to 2" or 3". I think it was 1" diameter PVC but double check me.

Huge difference to have the extra firm spring for my 215# self!

All the springs of the Rock Shox Boxxer fit. The same stroke. The length with a modified stop, to adapt to the top cap. The preload is easy to adjust.
 
RST Fork guys:

I pulled apart the right hand fork leg containing the compression dampening mechanism.
I drained and refilled the internal piston with 10 weight oil that was on hand (not sure what stock is).
Made a huge difference to the responsiveness of the compression dampening dial.
It's not a replacement for a stiffer spring, but happy with the 'quick fix' if bottoming out is a problem...
 
JuiceMeUp said:
RST Fork guys:

I pulled apart the right hand fork leg containing the compression dampening mechanism.
I drained and refilled the internal piston with 10 weight oil that was on hand (not sure what stock is).
Made a huge difference to the responsiveness of the compression dampening dial.
It's not a replacement for a stiffer spring, but happy with the 'quick fix' if bottoming out is a problem...

I like it!
 
JuiceMeUp said:
RST Fork guys:

I pulled apart the right hand fork leg containing the compression dampening mechanism.
I drained and refilled the internal piston with 10 weight oil that was on hand (not sure what stock is).
Made a huge difference to the responsiveness of the compression dampening dial.
It's not a replacement for a stiffer spring, but happy with the 'quick fix' if bottoming out is a problem...
How did you repressurize the damper cartridge. That weird version of a schrader valve kept me from opening it. RST told me it comes with 10wt oil so I was gonna fill it with 15 and up the pressure.
 
Paulflieg said:
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Jammen said:
First post! Lurking for awhile, figured I should give back. :wink:

Rockshox Coil Spring Boxxer... https://www.amazon.com/dp/B002SR3MB2?ref=ppx_pop_mob_ap_share

That'll fit in the RST Killah. You'll need to take apart the weird like 6+" preload spacer they have in there and cut a piece of PVC down to 2" or 3". I think it was 1" diameter PVC but double check me.

Huge difference to have the extra firm spring for my 215# self!

All the springs of the Rock Shox Boxxer fit. The same stroke. The length with a modified stop, to adapt to the top cap. The preload is easy to adjust.

That is great news. Thank you so much for the information. I've got a spring on order.

I've got ahold of Alan at electric race technologies and we are working out the details for an asi lipo based power system. I'll post details when we get them worked out
 
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