Electric downhill/freeride bike

[Bjorntsc]

Side by side drag race.
I have made videos before and know that videos do not show acceleration, speed, or bad-ass-ness.
By doing a comparison between a bike most people have ridden and a 4-7kW electric everyone can get I better Idea were these projects stand on the performance end of things.

 

[gwhy!1]

the bike in the vid is about the same get up and go as a 200cc trials bike in second gear, if that helps.

 

[etard]

That bike is geared for like 20 mph Gwhy! :lol:

 

[gwhy!1]

That bike is geared for like 20 mph Gwhy! :lol:

Yes , But thats about what a gas trials bike will do in second

its actually geared for around 22mph to be fair

 

[Bjorntsc]

BTW, how is the belt drive going? :wink:

Any issues to bring up?

 

[Ratking]

BTW, how is the belt drive going? :wink:

Any issues to bring up?

Have not been able to do anything. It's getting cold outside too fast also, I don't like that too much.
I wanted to use the bike all year, but we have to see if handle the cold weather.

I need to do some work that I don't have the equipment to do sort of. They have a cnc mill at the place I work, and if I dare to I could use it as a manual mill. I just don't want to do anything wrong with such expensive stuff. One wrong move and the cutting head may try to get trough the milling board :wink:

I have to see what I can do about this. If I just could learn how to use it I actually have a very capable machine to make everything I could want.

 

[Bjorntsc]

I finished my electric specialized enduro up this winter break. The original bike weighs in at 31.25 #, with a rc drive 39.6 #.
The battery is 12s 2p 5Ah lipo weighs 7 pounds in the backpack. It does 37 mph easily (up small grades) and gets about 12 miles of conservative trail riding, 16 miles conservative in town, 2 DH loops, or 12 miles on road at 35mph.

I now understand why everybody has issues with these. The low weight and small wheel base make these hand to control during acceleration. scarier than a CR250R!

Any news on your build?

Edit: 44.4v 10ah

 

[Ratking]

I finished my electric specialized enduro up this winter break. The original bike weighs in at 31.25 #, with a rc drive 39.6 #.
The battery is 12s 2p 5Ah lipo weighs 7 pounds in the backpack. It does 37 mph easily (up small grades) and gets about 12 miles of conservative trail riding, 16 miles conservative in town, 2 DH loops, or 12 miles on road at 35mph.

I now understand why everybody has issues with these. The low weight and small wheel base make these hand to control during acceleration. scarier than a CR250R!

Any news on your build?

Cool, you finally got yours running
It's amazing how hard it is to get a smooth launch with these little buggers.
I haven't been able to do anything unfortunately, but there is just a matter of time before I get a couple of days at the workshop
I am about to make a new swing arm in aluminum, I plan on taking a couple of pictures of the process

 

[Ratking]

Good news everyone!

Today I have been able to do a couple of important things for this build.
First, I was able to get a permission to use the equipment at a school near where I live. So I finally have a lathe and a mill plus some misc equipment
I also got some aluminum for free, I am pleasantly surprised how nice people are around here. I know that a 120mm thick aluminum bolt is pretty expensive if I had to buy it myself.

I got some work done as-well, I welded a piece of 3mm steel plate to the motor mounts to stiffen them up. I don't know if it had to be done, but I did not like how the sheet metal flexed when force was applied.
The reinforcement sheet I used was actually something I got from the laser cutter. He used the wrong thickness, and had to make another one. Lucky for me :wink:
I will be doing some serious work the next weeks, because I've been waiting for this opportunity a long long time.

 

[litespeed]

What kind of steel and what gauge steel did you use? I keep thinking I want to build a frame.

Tom

 

[Idontwanttopedal]

Hi how build going. Bruno dose a twin esc. Hope to have my buil done soon. I've just got the on 80100 with two speed gearbox

 

[mdd0127]

Beautiful! You're really wanting to make me build a frame! I narrowed a seat pan last night for the 71 Honda Sl350 that's going to be racing the mexican 1000 coming up and got all confident about welding extremely thin steel with the giant mig again. Might have to order some chromo when I start feeling better and get back on my feet. Inspiring build man!

 

[Ratking]

What kind of steel and what gauge steel did you use? I keep thinking I want to build a frame.

Tom

Hello

It is mainly made of 1.5mm steel, but the sheet where the rear shock is attached is 3mm steel. It feels more than strong enough, but I haven't been jumping too much with it yet.

 

[Ratking]

Hi how build going. Bruno dose a twin esc. Hope to have my buil done soon. I've just got the on 80100 with two speed gearbox

I hope I will be able to do much over the next weeks. Unfortunate I have a vacation in a week, so I can't do anything yet.
I have seen brunos esc's, but I will use mye hv160's for now, they have been good for me so far.

I'm following your build with interest, I hope you get it going soon

 

[Ratking]

Beautiful! You're really wanting to make me build a frame! I narrowed a seat pan last night for the 71 Honda Sl350 that's going to be racing the mexican 1000 coming up and got all confident about welding extremely thin steel with the giant mig again. Might have to order some chromo when I start feeling better and get back on my feet. Inspiring build man!

Thank you for the kind words

I hope you do build a frame, I really like your previous work, so I think you would do very good if you made one.
To be able to build a frame that looks like a bike, with good performance and range with a decent design is very challenging and fun.

 

[Ratking]

Here's a drawing of the motor mounts and support bearing for the timing belt pulleys. I want to do this right the first time, so I will try to make a setup that minimizes the flex and movement of the axles when the belt is heavy loaded. I will not tolerate any slippage
The motor mount is a slimmer model of the original mount and will reduce the length of the motor with 7.5mm . The strength will remain the same, but I may get a tad less cooling. I hope to overcome that with a fan on the rotors back(as Thud have done).

The concept is to make a motor mount with the same bolt pattern as the pulley support so the bearing is centered.
I would have to make something anyway, since the motor mounts was too small a diameter.

Please tell me if there are obvious flaws in the design that I can't see. Better now, before I use materials and time to make them

 

[Danny Mayes]

There is not a lot of wrap on that second motor?

Looks like only a quarter/90 deg? i'd be concerned that you will get slip there...

What belt are u using? have you modelled it in your software?

 

[Ratking]

There is not a lot of wrap on that second motor?

Looks like only a quarter/90 deg? i'd be concerned that you will get slip there...

What belt are u using? have you modelled it in your software?

I got help from an engineer with calculating, and it should handle the torque output. I agree with the amount of belt wrap, it is a design flaw, even though I don't see how I could have made it any different without butchering the design.

 

[Ratking]

There is not a lot of wrap on that second motor?

Looks like only a quarter/90 deg? i'd be concerned that you will get slip there...

What belt are u using? have you modelled it in your software?

Here's a picture of the data from the simulation.
There are some slight changes, I used 36t pulleys instead of 40t.
But the simulation is done with a trapezoidal toothing and I am using HTD-5 instead.
From what I have read, the HTD tooth profile is up to 3 times better at handling low speed torque.
I think and hope that I am well within the limitations of the timing belt setup.

 

[Danny Mayes]

I did not realize u were using 25mm wide belt. I think u will be ok. From memory my trapezoid set up with same motors and 50% wrap will do 10kw. Mine is 10mm wide. U are over double the width half the wrap and a higher torque profile. Should be fine...

Good luck!

 

[Danny Mayes]

Just realised u are using 5mm. My belt is T10. Hrmmm, could be borderline. I guess u will see. Do u have a plan B?

 

[Ratking]

Plan B is building a new bike from scratch without any obvious flaws
Else I can turn down the power on the CA v3 that I use. That works very well when other people have tested the bike.

Wanting a narrow frame with lots of power is not an easy job :?

 

[Danny Mayes]

Not easy indeed...

can you wrap your belt another way? under the pulley in question and then around the bigger pulley the opposite way, that would get you much more wrap...

Make sense?

3rd edit - arghh its late and i am not making alot of sense.

What i mean is, in the image above, wehre the belt is straight at the top, wrap it under the second motor (the pulley in question) and have the straight part of the belt at the bottm. I thnk that makes more sense!

D

 

[bandaro]

Don't suppose you could run the belt connecting the motors on the inside, as in a 50t sprocket or something with the inside hollowed out and fixed onto the outside of the motor can, so the belt would be enclosed in the frame itself?

Would this be feasible or put too much force onto the can? heat be an issue?

 

[Ratking]

Not easy indeed...

can you wrap your belt another way? under the pulley in question and then around the bigger pulley the opposite way, that would get you much more wrap...

Make sense?

3rd edit - arghh its late and i am not making alot of sense.

What i mean is, in the image above, wehre the belt is straight at the top, wrap it under the second motor (the pulley in question) and have the straight part of the belt at the bottm. I thnk that makes more sense!

D

That is a good idea, but the pulleys are not lined up properly for that. I would have tried it
Thank you for the input