Best rear suspension system for a rear hub motor?

[dotrick]

Hello,

I'm looking for the best rear suspension system for my new homemade frame ?

I saw several systems : here
- Single pivot,
- Unified Rear Triangle,
- Four-Bar
- Virtual Pivot Point,
- Monolink

I have a rear hub motor, the TC100 (11kg). The top speed is about 100kph. This frame should be able to go on the road, trail, small jump, wheelie not for downhill.

I saw these systems : several pictures.It's a great configuration to get more space for battery, but is it good? It's an old frame..

What is your recommendations?

Thank you!

 

[spinningmagnets]

If you are making your own frame, you have lots of options. I recommend ChroMo, but that's just a personal preference over aluminum frames, both have their benefits. Guys with rear hubs like how "near silent" they can be, guys with mid-drives like how well they climb steep stuff very slowly when desired without stressing the battery or overheating the motor.

The frame I would most like to build is a hub-motor used as a non-hub, driving a jackshaft that is concentric (having the same centers) as the frame pivot. Rectangular battery pack that is integral to the downtube, like Rodgahs "Big Hit FSR". Here are two bikes that really impress me:

Rodgahs enormous battery pack downtube housing: http://www.electricbike.com/big-hit-fsr/

And the "Specialized Supercharged" http://www.electricbike.com/specialized-super-charged/

 

[madin88]

Hi dotrick,

thx for the link to the different suspension type. Its very interesting.

There are truly a lot of options / differnt types of bike frame out there. With your powerful hub motor you should also look to a swingarm where you can install good torque arms. Your motor produces about 200Nm torque at 200A Phase (ebikes.ca calculator). I dont know how many amps you are running but for 100kmh i think so keep this in mind.

On my bike (you know my thread ) i have a four bar suspension and the comfort (up to 75kmh with 21,6" od wheel) is ok. As i said i mainly choosed this frame because of the option to mount good torque arms.

The most motorcycle use a suspension which is same like Single Pivot or Unified RT so i think this will give you the best suspension at high speed. Also the properties of damper, spring, rebound does matter (high speed needs fast rebound as far as i know).

br
martin

 

[dotrick]

@spinningmagnets
These ebikes are very impressive! The "Big Hit Fsr" has a good frame for battery! I Like it. It looks like the Stealth Bomber...
I found another frame, a German frame (Propain-bikes.com). I don't know if it's good, but i like it. It's a freeride frame.

@madin88
I will do my own swingarm more like a motorbike.

If you use a motorbike suspension, you will probably have good performance for high speed but not when you use the pedals.
The DH Freeride bikes system minimizes the interaction between the working suspension and pedal forces.

Ebike is an hybrid between little motorbike and bicycle. Ebike suspension should be an hybrid too, no?

 

[SHARKBITEATTACK]

I would think the good ol single pivot would be best, just like a motorcycle uses. I could be wrong but I thought all those other designs were made just to take down pedal bob

 

[full-throttle]

Does it need to be super-efficient under pedaling forces? If not then don't bother with anything else than a single pivot.

It's funny that you worry about suspension design while determined to use a 11kg hubby :lol:

 

[dotrick]

Does it need to be super-efficient under pedaling forces? If not then don't bother with anything else than a single pivot.

It's funny that you worry about suspension design while determined to use a 11kg hubby :lol:

What do you want to tell me? The suspension will not be very good because of the 11kg of the hub? What is the maximum hub weight for an ebike of 30Kg? :?

Thanx,

 

[full-throttle]

What do you want to tell me? The suspension will not be very good because of the 11kg of the hub?

Something like that
Ever heard the term unsprung mass?

.. lighter wheels are sought especially for high-performance applications..
..high unsprung mass can lead to severe wheel hop, compromising traction and steering control..

 

[madin88]

lighter wheels are sought especially for high-performance applications..
..high unsprung mass can lead to severe wheel hop, compromising traction and steering control..

yes thats the problem with heavy hubs. If you have the skills built your hubmotor in the frame and make a chaindrive.
Big tires and low air pressure will help a bit to reduce wheel hop, but this will cause in lower efficiency.

 

[dogman dan]

This problem is why I chose to run a lighter rear hubmtor, use a slow winding to tame the hills, an live with less speed. I just didn't like a 25 pound 5304 in the dirt.

But it's true, the bike I had then was a piece of crap. So that didn't help any. So the short answer is, you will need a good suspension. Cheap stuff will not feel as good.

With my 15 pound hubbie, I am now using a single pivot bike. Since it's a good bike, it's suspension performance is not bad. It has a very long shock, so it's got decent travel. But I do like the extra travel you get from a short shock with a pivot link, like 4 bar pivot or the specialized fsr. For sure, for pedaling the link tames pedal bob very nice, allowing a more cushy suspension setup. Previously I used a cheap 4 bar suspension bike, but upgraded both shocks. My fsr remains a pedaler. When I want a beautiful handling ride, I pedal it.

But once you slap a big heavy hubmotor on that bike, you can't set up so cushy anymore IMO. You need to crank down the preloads and the rebound enough to compensate for the 30 pounds or so of motor and battery. Just like the same tuning would not work for a 200 pound rider that hopped on a 150 pound riders bike.

So once I stiffen up the rear to handle the hubmotor, I have to also stiffen up the front shock too.

 

[Drunkskunk]

Unsprung weight is the enemy, but it can be managed well. I've got 40lbs of motor and wheel on the end of a long arm suspension, and It floats over both the small stuff and huge hits.

The intagrated swingarm is the optimum design for a hubmotor, but the pivot point may be hard to build. The next best design is the single pivot. Its robust, stable, and predictable, and the linear motion makes tuning the shock a breeze. You can check out my build thread for a worst case scenario of unsprung weight on a long arm suspension. And yet the bike handles anything I throw at it smoothly.

 

[circuit]

I can confirm that heavy hub will cause many problems, whatever suspension you use. I had a crystalyte x5 hub (11kg) in my bike along with quite good suspension. The wheel was wobbling around at speeds, especially in corners, where it felt like going on flat tire. It was so bad that I ditched whole bike.
If you need good suspension and handling, choose mid drive and keep your wheels as light as possible.

 

[zombiess]

If you are not dead set on building your own there are now several custom ebike specific frame kits available.

Greyborg Warp <-- I sell these and it is the lowest cost option as far as I know
Phasor Cycles
Torque Raptor

All 3 of these use the same general type of rear suspension setup and all have > 6" travel.

Just wanted to offer up some ready to go alternatives for you. If you are building your own it's always good to look at what others are doing and already have working, nothing wrong with borrowing a design concept for a DIY project.

BTW as far as the unsprung weight goes with a large hub motor, I have not noticed any issues on my own bike, but I only have 12 miles on it so far and I am not a suspension connoisseur. I can tell you that riding my bike feels a lot like riding a gas dirt bike. I don't do jumps because I don't know how to, but I can easily go over stuff at 30mph with my current setup that my other ebikes couldn't dream of handling. Hitting a 5" curb dead on at 15mph is a minor event at best.

Double squish rules

 

[dotrick]

The intagrated swingarm is the optimum design for a hubmotor, but the pivot point may be hard to build.

What is it?

If you are not dead set on building your own there are now several custom ebike specific frame kits available.

Great! Thank you, I didn't know 2 of these 3 frames!
Yes, I did many measures on existing MTB, ebike to do my own frame! It's difficult for me, I'm not a mechanician!
I started my solidworks design . I use a single pivot. The suspension travel (rear and front) will be between 150 and 200mm.

 

[dotrick]

I can confirm that heavy hub will cause many problems, whatever suspension you use. I had a crystalyte x5 hub (11kg) in my bike along with quite good suspension.

OK. I don't understand why many people choose Hub motor instead fixed motor on frame. Yes, it's not good to have weight on wheel...

 

[zombiess]

I can confirm that heavy hub will cause many problems, whatever suspension you use. I had a crystalyte x5 hub (11kg) in my bike along with quite good suspension.

OK. I don't understand why many people choose Hub motor instead fixed motor on frame. Yes, it's not good to have weight on wheel...

If you can't figure out why most people use hub motors.... Here is a clue... It's simple :lol:

 

[dogman dan]

It is a fairly simple way to build an e bike, using a hubmotor. And avoids the problem of bike chain being too weak for really powerful motors.

A wobble with a hubmotor that felt like a flat tire in the corners sounds more like a problem humbmotor than a hubmotor problem. Some of the old 5300 motors had some sloppy machining.

Mine, I just didn't like the feel of it in dirt on singletracks. I decided I liked a lighter hub than more power. On street, I love my 25 pound 5304 hubmotor on the Full suspension longtail. Its not so heavy that a few washboards on a dirt road are a problem.

 

[snellemin]

Keep the suspension as simple as possible and tuning it will be a breeze. I don't see the point of going fancy with suspension designs for an e-bike, when pedaling is secondary.

I have the Torque Raptor frame that I'm building up, since Zombies didn't have the Greyborg in stock when I wanted to build a nice ebike. I also have a old Fuji mtb that uses the same type of suspension and I have used a hubmotor and a mid-drive on that same bike.
I prefer the mid-drive setup for the single track trails I ride on. I just don't go fast enough for a hub motor to be superior and efficient. With fast I mean over 25 mph. I'm using the same controller and battery power on the mid drive as I did with the hub motor. Power consumption is about the same on the same course with both setups. The big difference is that the mid drive is easier to handle, excelerates faster and climbs better.
But as mentioned before, the hub motor is easiest the build. The mid-drive is more complex, but superior on the trails.
However, the hard tail EVG with hub motor is my favorite for onroad speeding.

 

[madin88]

If the rim is centered well and the wheels are balanced, there are near to zero comfort losses on street riding. In curves as well no mentionable issues, but i can only speak for my bike with 21,6" od tire up to 80kmh.
Balancing and smoothly running tires are very important for comfortable riding. Especially heavy motorcycle tires can wobble a lot. Balancing i did with "try and error" method until quite all of wobble is gone. This takes some time but its worth it.

 

[dotrick]

If the rim is centered well and the wheels are balanced, there are near to zero comfort losses on street riding.

The same for my setup. My rear wheel is not a perfect circle. I have an error of about 3-4mm on the diameter. I rode at 90kph on a perfect road, and no problem.

But as mentioned before, the hub motor is easiest the build. The mid-drive is more complex, but superior on the trails.However, the hard tail EVG with hub motor is my favorite for onroad speeding.

OK, I have to think a frame with two configurations... Hub motor and Mid-drive !

 

[dotrick]

Ok, my Big Hub motor is not good for my rear suspension...

Do you know a mid drive who have the same power as mine (TC100 - see below)?

I' m thinking about a configuration with a mid drive with a hub at rear.

 

[madin88]

>90kmh are very much for a bicycle. If you are going to build a daily use bike and not want to break records you should set it up with lower speed.
You also should keep in mind you need very much Ah for riding longer time at this high speed. At hill climbing the motor will take tons of amps and overheat soon in a 26" wheel.

I would say stay with your TC100 and built your bike for <80kmh max but very solid (good suspension, rims, brake etc). With this you will have more fun instead of only high and dangerous topspeed.
If you have some engineering skills take a high kv hubmotor and mount it to the frame with about 1:2 geard chaindrive but this is very much work..
Or lace your motor in smaller rim (watch out that the pedals do not touch the bottom). This is only a bit lacing work and will also help to make your motor more efficient.

 

[dotrick]

>90kmh are very much for a bicycle.

Yes, but I like it!

If you have some engineering skills take a high kv hubmotor and mount it to the frame with about 1:2 geard chaindrive but this is very much work.

Yes, I think about it...

About a system with 2 gears. First gear 1:2, I will have a better efficiency under 50kph, more torque, 400Nm Wheelie Wheelie Wheelie... And with the second gear 1:1 for top speed.

 

[madin88]

About a system with 2 gears. First gear 1:2, I will have a better efficiency under 50kph, more torque, 400Nm Wheelie Wheelie Wheelie... And with the second gear 1:1 for top speed.

i don't know if a bicycle chain and bicycle cassete can handle the torque and if so it would not be very durable. Shifting under load would be also a problem. 400Nm -> the bike only would throw you off :lol:

maybe the NuVinci CVP kit is something for you:

http://www.nuvinci.com/09_lev_kit.asp
http://www.utahtrikes.com/PRODINFO-Nuvinci_Developer_Kit.html

speed ratio: 0,5 - 1,75 autoshift
power: 5kw continuos

sounds not bad

 

[dotrick]

Hey madin88, my ES friends!

thank you for your answers! :wink:

i don't know if a bicycle chain and bicycle cassete can handle the torque and if so it would not be very durable. Shifting under load would be also a problem.

I think about a BMX FreeWheel and Chain, I think it's better than MTB stuf... And sure, no shift under load!

400Nm -> the bike only would throw you off :lol:

No, you have the throttle to adjust the inclination...

Thank you for the NuVinci links. CVT is a good solution. I like [/quote]