electric trials / freeride build "gasles"

[Mitch3514]

well the first lot of parts for this build have been dragged out,



the frame is of a 94 gasgas contact (unused believe it or not) and the swing arm a newer alloy design
overall i aim to build a medium weight electric bike capable of fairly heavy off road use, and something around the 5kw peak mark should suffice.
specifically wanting torque for trials style riding below 10km/h with a top speed of around 40km/h. single speed transmission.

plenty of decisions to me made yet and i encourage you guys to have an input as I'm new to the electric bike game.

here's a list of details I'm yet to fully decide on:

forks- mountain bike forks of some sort. done

rims + tires- (most likely dh mountain bike ones)

motor- (5kw peak, relatively light , low rpm)

inverter/controller-

battery arrangement / capacity-

motor mounting- alloy, using existing attachments where possible

pedals or no pedals- at this stage I'm set on retrofitting a BB crank set, simply due to the fact that ''motorbiking'' in my area would be quickly shut down however a strange looking electric mountain bike will be a little easier to pass off with the locals.


i first aim to build up a rolling chassie as light as possible and then adding the power system.
i will add cad files of my designs as we go, tho don't expect progress to be exciting as this is a weekend project more or less (and money for components is limited )



Mitch

 

[christerljung]

That's a really serious ebike project! The rigid frame invites to a heavier more gas-lookalike build, maybe mx-wheels and tyres? Then 5kw would be minimum. On the other hand the idea of keeping it as light as possible with DH-wheels you got plenty of room for batteries and would have a long range bike.
I would recommend a GNG-450 motor with a Lyen or kelly controller. 18S or 24S. No reduction, just one chain and a big rear sprocket.
Or maybe a second hand geared hub, midmounted.

Good luck! Keep us updated 8)

 

[Mitch3514]

yep, plenty of space for the elecs, that's what I'm thinking

ill keep it as light as can be, I'm heading into the workshop tomorrow to begin modifying the frame. step one- removing dead weight. aim to knock a kg off to 11kg with swing arm.

at this point my estimated weight is 42kg which i suspect is well on the light side, but here's how I've broken it up:

frame: 8kg
swing arm: 3kg
wheels- 5kg
forks- 3kg
shock- 1kg
motor- 5kg
motor mount assembly+ battery housing + inverter mount - 4kg
inverter- 2kg
battery (lipo) -6kg
chain, sprocket additional -1kg
bottom bracket, pedal assembly, 2kg
wiring- 1kg
handle bars, throttle, ect- 1kg

mitch

 

[gwhy!1]

well the first lot of parts for this build have been dragged out,



the frame is of a 94 gasgas contact (unused believe it or not) and the swing arm a newer alloy design
overall i aim to build a medium weight electric bike capable of fairly heavy off road use, and something around the 5kw peak mark should suffice.
plenty of decisions to me made yet and i encourage you guys to have an input as I'm new to the electric bike game.

here's a list of details I'm yet to fully decide on:

forks- mountain bike forks of some sort.

rims + tires- (most likely dh mountain bike ones)

motor- (5kw peak, relatively light , low rpm)

inverter/controller-

battery arrangement / capacity-

motor mounting- alloy, using existing attachments where possible

pedals or no pedals- at this stage I'm set on retrofitting a BB crank set, simply due to the fact that ''motorbiking'' in my area would be quickly shut down however a strange looking electric mountain bike will be a little easier to pass off with the locals.


i first aim to build up a rolling chassie as light as possible and then adding the power system.
i will add cad files of my designs as we go, tho don't expect progress to be exciting as this is a weekend project more or less (and money for components is limited )

Mitch

Now that propper eye candy... where on earth did you get a unused contact frame!!! ( where is you location ) I will be watching this with interest. Give some info on what will you be aiming for as regards top speed as this will determine drive train components,motor and controller. I dont know if you have clocked one of my threads http://endless-sphere.com/forums/viewtopic.php?f=12&t=32042&start=25, I may be able to give you some pointers

 

[Mitch3514]

haha don't tell me I'll be making enemies of every trials rider here by hacking at this frame!
it was out the back of a trials shop in Sydney since the shop started in the early 90's. how it came to me was I posted in the trials aus forum and Paul from 'the hell team' was kind enough to let it go.
i live in Melbourne, Victoria
i plan on doing essentially trials riding with it so a top speed of 40km/h would be enough. plenty of torque for the slow stuff is the main goal but with enough speed for a mx style burn around as well..

i have noticed your trials conversion that's one of the reasons i went ahead with this project!

a question to do with the suspension, i have come to realize that these bikes use a coupling that connects between the swingarm and frame where the shock mounts in between the two. i cant get hold of one for this model bike so my options are, machining the part which i cant do easily, or simply using the swing arm upside down and mounting the shock more traditionally; here's a pic of what i mean:



solution:



can you see any issues with doing this in terms of the geometry?

cheers,
Mitch

 

[gwhy!1]

, Yes please dont cut it up ( but you do what you gotta do, just let it go to waste ) ,

It will be quite difficult to come to a compromise on top speed/torque if you want to use it for serious trials and also ranting it like a mx I think if you are aiming for 5kw of power you maybe able to get the top speed upto around the mid to late 20mph mark but this will seriously knock the torque needed for anything other than easy/entry level trials. 6kw with a top speed of around 22mph is very nearly spot on for most trials sections , but this again also depends on the final weight of the bike with the rider on board. You can pick up the linkage second hand on ebay for the bottom mount it will be just a matter of bideing your time and waiting till one comes along. I would have thought that running the swingarm upside down would cause a few geo problems and will also effect the rear shock performance but having said that a direct linkage is always better from a maintenance point of view, so I would say try it , unless you are a very good trials rider or have no other bike to compare it with you may not even notice the difference, the rear shock performance will be effected but this may not be a issue if your only doing light trials stuff, You can also look out for a sherco ( from 1999-upto around 2003 model) linkage as this should be identical ( if not identical, it should be useable ).

 

[Mitch3514]

yep 6kw peak at 22mph sounds about right for what I'm after

hmm motor options, here's my thoughts

gng kit motor- light weight but I'm doubtful of its ability to handle this current

mid mounted hub motor- seems to be the heavy but cheap alt

rc setup- gwhy, you seem to be having allot of success with this. although running two motors coupled together introduces another component to fail under load..well unless built very well. Id rather avoid this with a single motor, controller and direct drive.

I've noticed gng sell a number of larger motors similar to that in the 450w kit, perhaps this with the right Kelly controller will suit my application,
http://www.gngebike.com/48v800w-brushless


Mitch

 

[speedmd]

I would go much larger higher torque motor for trials riding. Something like the 5-7.5kw golden

would think is possibly a good size for the frame and you would not have to rev the shit out of it to get over stuff.

 

[speedmd]

I would go much larger higher torque motor for trials riding. Something like the 5-7.5kw golden

would think is possibly a good size for the frame and you would not have to rev the shit out of it to get over stuff.

 

[jansevr]

john in cr's motor might be of some interest to you: http://endless-sphere.com/forums/viewtopic.php?f=31&t=40859

and here is a build with it: http://endless-sphere.com/forums/viewtopic.php?f=28&t=45165

this is probably the best motor out there as far as design goes - look at that amount of copper! you might want to talk to john about the specifics as far as power goes, but it should be able to handle the power you need no problem. there is no possible way a gng should be used on a build of this scale/power. hubmotor conversions are possible for mid mount but i think john's motor will be the best bet as far as power/efficiency/price.

 

[Mitch3514]

yep,
really interested in johns motor, could be spot on for this project .
ill build up the frame first then come to that decision.
cheers,
Mitch

 

[bzhwindtalker]

Following with interest! Very similar aim as my LMX project. The GNG 450 wont' be enougth motor for a 45kg bike. I went with a 9C used as mid drive for mine, on 22S and rewired delta for more rpm.
I'm more after enduro/freeride stuff so the geometry will be less suited for trials but i like to clim a rock from times to times

here's my frame, work in progress

My current bike with the gng motor as a simgle speed does nice trials with 45kph top speed too :

Suscribed,
Adam

 

[Mitch3514]

nice work Adam,

yeah so i can see ! great work with those videos too! i can really see your other passion coming out there. i was thinking of maybe even doing some aerial trail riding filming using a gopro attached to my fpv/uav quad for something new. could be pretty cool!

anyway as for the motors, yeah for sure with the gng 450 being to small. was thinking maybe the larger one but i noticed you considered that with your build and ended up with the 9c anyway. also i do like the look of gwhy's setup, using rc with hall sensors..

when i get time ill do some proper research and come to a decision, as for now trying to find 10 year old bike parts is keeping me well occupied!

Mitch

 

[Idontwanttopedal]

How about a ca12095 from Bruno they are 80kv which might help with gearing

 

[Mitch3514]

this weekend's task:



after hours of fiddeling around with a kx65 linkage the conclusion was to make one. time to test the welding skills i suppose

 

[Mitch3514]

update:
swing arm linkage is fab'd, will post pictures when i head home this weekend. As for the geom i did my best to estimate given the shock specifications and what i could fit between these very different parts. But learning as i go, of course..

also just picked up a new part, these forks should be strong enough without adding too much weight:


currently deciding on wheels as the quicker this thing is rolling the quicker i can get onto motor selection/installation and all the hard stuff.
At this point I'm looking to follow Adam's solution using a motorcycle front for the rear wheel and dh front wheel. this looks like a good compromise between weight and strength. either way a mtb wheel needs to be in the front.

hopefully with semester one complete next week ill be able to get this bike looking a little more functional

mitch

 

[speedmd]

Hi Mitch

I would go with dual triple clamp style forks rather than a single fork crown style if you want to do trials. Much stronger. For light trials duty, the ones you have should hold up but keep a eye on them.

 

[Mitch3514]

i haven't had much trials experience at all so i think these will get me through to later on like you say. but yep well noted!
cheers,
Mitch

 

[speedmd]

Hi Mitch

They will work great on most stuff. You will notice the flex if you start bouncing on the front wheel or bouncing into hard objects with most of your weight.

Should be of little issue with most free riding. Look forward to seeing the build.

cheers

 

[John in CR]

Actually it's our MiniMonster that may be the perfect motor for this dual purpose rig. Use low speed mode for the trials and switch to high for MX type riding. Use high voltage, so you can keep current lower and avoid the issues of high current heating up the speed switching mechanism. Compact and easily trimmed down to under 9kg, and the series/parallel switch of the windings makes it perfect for your needs. Gear it down to a top speed of 60-70kph in high and you'll have great rock crawling with a 30-35kph top speed in low, especially with a 30s battery. Geared for 80kph max on 20s the Mini hauls a 170kg load up a 25% grade in low completely stress free, so imagine your lighter load volted up and geared down.

There's a group of guys that do trials riding just up the hill from my house with trails cut into the side of the mountain. Those slopes are way way too steep for me to even think of riding, otherwise I'd build one for myself and get those guys into electric trials bikes.

John

 

[speedmd]

There's a group of guys that do trials riding just up the hill from my house with trails cut into the side of the mountain. Those slopes are way way too steep for me to even think of riding, otherwise I'd build one for myself and get those guys into electric trials bikes.

John

Hi John

Great that you have this near by. I rode a old OSSA M.A.R. for years. Lots of fun. Thinking best approach would be to add a hand operated clutch to a mid drive setup using something like your motor. Two,- possibly three speeds will cover it well. You need all the pop you can get out a drive train, from a dead or near dead stop to develop the lift needed to get up the big steps with some control . Too timid or weak and you fall backwards near the top.

 

[John in CR]

There's a group of guys that do trials riding just up the hill from my house with trails cut into the side of the mountain. Those slopes are way way too steep for me to even think of riding, otherwise I'd build one for myself and get those guys into electric trials bikes.

John

Hi John

Great that you have this near by. I rode a old OSSA M.A.R. for years. Lots of fun. Thinking best approach would be to add a hand operated clutch to a mid drive setup using something like your motor. Two,- possibly three speeds will cover it well. You need all the pop you can get out a drive train, from a dead or near dead stop to develop the lift needed to get up the big steps with some control . Too timid or weak and you fall backwards near the top.

I wouldn't try to climb these without ropes tied to me, much less try riding a bike up one. I'm not sure which would be worse, going up or looking over almost a sheer cliff and going down. They make it look easy though.

 

[gwhy!1]

 

[Mitch3514]

hey speed,

by hand operated clutch are you referring to a mechanical clutch or an electronic one like in gwhy's build?
i do like the sound of multiple speed settings too!
mitch

 

[Mitch3514]

and gwhy! that pic looks to be a of a gagas contact am i correct?