## Sur-Ron - New Mid drive Bike

General Discussion about large electric scooters and motorcycles and other things with no pedals.
3DTOPO   1 kW

Posts: 437
Joined: Apr 11 2018 2:21am

### Re: Sur-Ron - New Mid drive Bike

motomoto wrote:
Jan 07 2019 9:05am
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?

Jonathan1981   100 W

Posts: 161
Joined: Mar 29 2011 7:48pm

### Re: Sur-Ron - New Mid drive Bike

3DTOPO wrote:
Jan 07 2019 6:17pm
motomoto wrote:
Jan 07 2019 9:05am
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)

3DTOPO   1 kW

Posts: 437
Joined: Apr 11 2018 2:21am

### Re: Sur-Ron - New Mid drive Bike

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-d ... otorcycle/

Love the fat tire on the back!

3DTOPO   1 kW

Posts: 437
Joined: Apr 11 2018 2:21am

### Re: Sur-Ron - New Mid drive Bike

It's interesting they went with a belt drive on a vehicle that is clearly designed for off-road use.

Grantmac   10 kW

Posts: 820
Joined: Oct 22 2018 12:43pm
Location: Victoria, BC

### Re: Sur-Ron - New Mid drive Bike

Belt drives are a Harley signature design feature.

fechter   100 GW

Posts: 15265
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

### Re: Sur-Ron - New Mid drive Bike

The belt looks like it might be made to fit on a Sur-ron. It would sure reduce the noise.
"One test is worth a thousand opinions"

Rix   100 GW

Posts: 9850
Joined: Mar 29 2012 11:26am
Location: Fallon NV USA

### Re: Sur-Ron - New Mid drive Bike

Lelandjt wrote:
Jan 07 2019 4:05pm
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.

Rix   100 GW

Posts: 9850
Joined: Mar 29 2012 11:26am
Location: Fallon NV USA

### Re: Sur-Ron - New Mid drive Bike

3DTOPO wrote:
Jan 07 2019 6:17pm
motomoto wrote:
Jan 07 2019 9:05am
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.

3DTOPO   1 kW

Posts: 437
Joined: Apr 11 2018 2:21am

### Re: Sur-Ron - New Mid drive Bike

Rix wrote:
Jan 07 2019 11:27pm
3DTOPO wrote:
Jan 07 2019 6:17pm
motomoto wrote:
Jan 07 2019 9:05am
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?

Rix   100 GW

Posts: 9850
Joined: Mar 29 2012 11:26am
Location: Fallon NV USA

### Re: Sur-Ron - New Mid drive Bike

Yes I do.

motomoto   1 kW

Posts: 457
Joined: Jun 28 2010 8:22pm

### Re: Sur-Ron - New Mid drive Bike

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.

Flykrisco   1 mW

Posts: 11
Joined: Jan 01 2019 4:30pm
Location: land of milfs and honeys Redondo Beach

### Re: Sur-Ron - New Mid drive Bike

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?

Finer   100 µW

Posts: 9
Joined: Dec 28 2018 9:44am

### Re: Sur-Ron - New Mid drive Bike

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.

Lelandjt   100 mW

Posts: 37
Joined: Dec 07 2018 7:39pm

### Re: Sur-Ron - New Mid drive Bike

Flykrisco wrote:
Jan 09 2019 8:55pm
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.
Last edited by Lelandjt on Jan 10 2019 10:10pm, edited 1 time in total.

Lelandjt   100 mW

Posts: 37
Joined: Dec 07 2018 7:39pm

### Re: Sur-Ron - New Mid drive Bike

Finer wrote:
Jan 10 2019 11:44am
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.

Jammen   1 µW

Posts: 3
Joined: Sep 14 2018 10:00am

### Re: Sur-Ron - New Mid drive Bike

First post! Lurking for awhile, figured I should give back.

Rockshox Coil Spring Boxxer... https://www.amazon.com/dp/B002SR3MB2?re ... b_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!

Paulflieg   10 mW

Posts: 33
Joined: Jan 11 2019 10:30am

### Re: Sur-Ron - New Mid drive Bike

[/img]
Jammen wrote:
Jan 11 2019 10:52am
First post! Lurking for awhile, figured I should give back.

Rockshox Coil Spring Boxxer... https://www.amazon.com/dp/B002SR3MB2?re ... b_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.

JuiceMeUp   1 W

Posts: 50
Joined: Mar 20 2017 2:40am

### Re: Sur-Ron - New Mid drive Bike

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...

Rix   100 GW

Posts: 9850
Joined: Mar 29 2012 11:26am
Location: Fallon NV USA

### Re: Sur-Ron - New Mid drive Bike

JuiceMeUp wrote:
Jan 12 2019 6:49am
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!

Lelandjt   100 mW

Posts: 37
Joined: Dec 07 2018 7:39pm

### Re: Sur-Ron - New Mid drive Bike

JuiceMeUp wrote:
Jan 12 2019 6:49am
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.

Flykrisco   1 mW

Posts: 11
Joined: Jan 01 2019 4:30pm
Location: land of milfs and honeys Redondo Beach

### Re: Sur-Ron - New Mid drive Bike

Paulflieg wrote:
Jan 11 2019 11:04am
[/img]
Jammen wrote:
Jan 11 2019 10:52am
First post! Lurking for awhile, figured I should give back.

Rockshox Coil Spring Boxxer... https://www.amazon.com/dp/B002SR3MB2?re ... b_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

derb   10 mW

Posts: 30
Joined: Oct 30 2015 6:15am
Location: Germany - on the Trail

### Re: Sur-Ron - New Mid drive Bike

At 2500km I changed the chain. As soon as you lift a chain link over half the tooth height on the sprocket, you should renew the chain. The teeth on the sprockets are still looking good and will not be changed yet.

Flykrisco   1 mW

Posts: 11
Joined: Jan 01 2019 4:30pm
Location: land of milfs and honeys Redondo Beach

### Re: Sur-Ron - New Mid drive Bike

Allex wrote:
Nov 16 2018 3:36am
How many Amps did you see during peaks?
Here is a battery case extender with a new hatch. The pack is like 22s10p
Allex. Is this extension available. I'm going to build a new pack and this would be perfect.

Allex   10 GW

Posts: 4151
Joined: Dec 05 2011 8:46am
Location: Stockholm, Sweden

### Re: Sur-Ron - New Mid drive Bike

Flykrisco wrote:
Jan 14 2019 3:03pm
Allex wrote:
Nov 16 2018 3:36am
How many Amps did you see during peaks?
Here is a battery case extender with a new hatch. The pack is like 22s10p
Allex. Is this extension available. I'm going to build a new pack and this would be perfect.
They are still working on the hatch.

freeflow   1 mW

Posts: 18
Joined: Dec 24 2018 5:40pm

### Re: Sur-Ron - New Mid drive Bike

Who's building it? Sur Ron or after market?