sub 4 pounds, sub 500w RC mid drive

rastamax said:
So I'd be willing to go to a 32t bike size equivalent chainring cause anymore than that sacrifies ground clearance quite a bit. About a 60t #25,that would give 5:1 to the cranks.
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It would mean a bigger motor and would increase stress on the chain even more.
 
rastamax said:
So basically I was thinking of using a astro 819m-9t and a neugart ple40 at 80:1 reduction and 2:1 going to the cranks for about 100 rpm cadence at 12 volt. Final reduction would have to be adjusted after experimenting a bit I'm sure but it would be close.
Motor is listed at 120gr (?? seems low)
battery:nanotech 3s at 4500mAh/280gr
ple40-80 at 550gr
13t freewheel at 200gr
controller ??30gr
frame mount 250gr ish
total: about 1700gr but it's missing a few parts like throttle, extra chain/chainring...
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Hi All

I have been reading this forum for quite sometime hoping someone would come up with such an idea and actually implement it and it would be commercially viable especially in Europe where the limit is 250 watts for electric assistance. I myself thought about a 1 kg assist including battery motor and transmission which would work though the bike chain like Cyclone (www.cyclone.tw) or John Tetz as below.

Motor - 120g
Gearbox 200g
Controller ?30g
Mounts - ?Carbon fibre - 50g
13/14t freewheel - 100-200g
Battery 400g
plus throttle, extra chain/chainring

John Tetz did this some time ago

http://www.recumbents.com/wisil/tetz/e-assistmetric/

The gearbox he used was much lighter than the Neugart quoted above.

http://www.imsgear.com/en/imsbaseline. IMS gear gearboxes are about 200g.

Look forward to your thoughts. I lack mechanical expertise to connect motor to gearbox but will support this if crowdfunded.

Best wishes

VeloMik
 
The E-ram is coming to market soon.
http://www.b-labs.org/e-ram/
I expect it to be expensive much like a Vivax assist but it looks very promising.

The John Tetz system looks really good. Pretty much shows it is totally doable.
 
rastamax said:
I think a set-up like tangent with near silent operation at power levels that are much more 'bionic' legs than minimoto is pretty ripe to sell alot of units to the mtb scene. bbs units i suppose are the answer but it would be nice to get something that mounts inside the triangle and has better parts quality
Re: sub 4 pounds, sub 500w RC mid drive
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I also think it would sell like hot cake after the initial OMFG Ban all ebikes reaction that is common at the moment.
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if the drive is quiet with batteries that fit in a small camelback then any ban will be unenforcible. A torque sensing mid-drive that can turn a decent 160-200w rider output on a trail ride into downhill speed across singletrack with tacky tires will be a massive gamechanger at trailcentres - the e-ram design does look hopeful!

I now have dreams of turning my local trails with minor altitude into whistler bike park - just need a few extra watts...
 
That E-Ram looks really interesting, like the concept, guess the closest easily obtainable equivalent right now would be a 250w Bafang.

I have an outrunner that I never go around to using, probably an 80A ESC to go with if you can use it, it's the Turnigy C6374-200 that worked pretty well as a Friction Drive (Kepler Drive)

33599583.jpg


(not my photo, just a stock one, can make one if anyone wants)

It is 200 Kv, but if it's useful to ya, let me know, just shipping + what every you think is fair (I paid $60 5yrs ago, never used) here is the modern eqivalent:

http://www.hobbyking.com/hobbyking/...SK3_6374_192kv_Brushless_Outrunner_Motor.html

18129.jpg
 
Iv always fancied that 9235 100kv slim motor for a light build. I envisaged a left hand drive side behind or above the rear wheel axle. As its not sensored I didnt persue it but with a big reduction at low speeds it might be good.

With the batteries if you go lipo you could take 2 sets and a charger. Charge one while your blasting the other. Or just keep extra batteries in a locker?

I put a 250w motor on a couple of bikes and was one of my favorite set ups
24122010047.jpg


an internal geared hub gave me three speeds to
06032011090.jpg
 
robertpaulson said:
just chucking some numbers into a calculator like this (bottom of the page)

http://www.cyclingascents.com/alpedhuez.html#.VpY-HPmyNBc

are you sure sub 500w is going to deliver what you are after? to hit 15mph on a steep fire road i would think you are talking around 800w?
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800? Maybe on a super-ultra light bike, b/c my CA consistently reads 1500 watts going up a 10% hill at ~17mph on my ebike (50lbs) with me (170 lbs rider), gearing makes a difference but not in the power required, just the RPM the motor spins up to...

to simply go up-hill you need gobs of torque, but to go uphill... AND FAST, you need gobs of POWER.

G.
 
hopefully i'm not jumping all over someone elses thread but I think we are after sort of the same thing..

I can consistently put out 250w riding singletrack trails on my MTB, sometimes 350w on a short climb. i'm after assistance that can let me ride a bigger bike (more travel, stickier tyres) faster (so my flat trails become more like a gravity bike park) for more loops, but at the same intensity i currently ride at - personally i think that if someone can make a light, quiet, discrete and torque responsive unit that will retro fit to existing mtb's they will shift huge amounts, even at quite a high price.

I appreciate the trail access issues that plague the USA and probably drive most of the anti e-mtb sentiment, but basically nearly every mtber i know would happily go for an upgrade that gave them bionic legs, which is what this is about, just the noise/system weight/stigma that is currently preventing it - 2 of 3 appear to be right at the technology threshold of vanishing and the 3rd i think will just go away once enough people try the systems.

Digging a bit more and playing with the calc sheet that miles provided, it does seem that 250-500w would provide the extra assistance I need but the more important factor for trail riding (rather than just a lift to the top of the hill) is going to be a spot on torque sensing system, so i'm probably stuck waiting for something like the e-ram or brose to release a standalone unit.

glw plans to the original poster!
 
I'm also looking for a way to build an electric assist mountain bike for technical riding. As fun as it is, I'm not looking for twist and fly but as the OP suggested, just an assist to put in more miles and steeper terrain (so the solution should be fairly light, allow good ground clearance, and provide predictable power assistance). The tangent motors solution is interesting but more power than needed and it looks to be twist and go, not pedal assist. Anyway, I wanted to go on record as looking for a similar solution as the OP.
 
Yes, this idea has interested me for a while; couldn't justify expenditure of a Vivax. The E-ram is interesting and I remember seeing that idea last year, sadly Q factor is large and that is important to me as I would be fitting it to a faired recumbent where space is at a premium. I currently have a TSDZ2 250W mid drive that works well (I have an offset BB so that my shoe doesn't rub when pedalling), but at 3.3kg for the motor is heavier than I'd like. Has anyone contacted Tangent about making a lighter lower powered version?
 
E-ram looks perfect to me. I think the small increase in q-factor should be worth the overall package. Alas, limited bottom bracket options and not available?
 
it looks like the e-ram is now available

http://dienatronic.imb2b.com/sell/index.php?itemid=38430

but no reviews or working units appear to have surfaced yet
 
aja said:
Yes, this idea has interested me for a while; couldn't justify expenditure of a Vivax.
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The price of the Vivax is insane. I've wondered if it might be possible to roll your own. $100-200 for a decent RC outrunner motor. Cycloidal gearbox for single stage 100:1 reduction, even custom made considering today's CNC shops have fairly cheap rates. Off the shelf bevel gears. Cheapish low power ESC. Add a small LiFePO battery pack and charger and it shouldn't be much more than $1000, I would think. Couldn't any of the great thinkers on ES like Kepler put together such a package?
 
Here is another lightweight mid drive similar to eram on crowdfunding platform Indygogo at present. Weight 2kg inc battery. They say they can supply any Q factor or any wheel size. I have no connection with them. Do you all think this is feasible and worthy of crowdfunding?

https://www.indiegogo.com/projects/bimoz-the-world-s-smartest-e-bike-drive#/

Best wishes

Velomik
 
the pulse training idea is a really good one!

Personally i am not an early adopter and would rather wait until its produced and working for a decent period before jumping in. Also not sure on the BB axle type but i have not seen square tapers stand up to decent offroad use for any lenth of time before issues arise, looks like it might be square taper from what i can make out on the pictures.

As soon as someone can make one of these things (light retrofit, properly functional torque sensing, quiet and robust enough for real mtb use)i think they will have a massive sales hit. basically turns every trail network into a downhill park with battery life only limited uplifts..
 
looks like e-ram is about to hit the market

https://translate.google.co.uk/translate?hl=en&sl=de&u=http://www.golem.de/news/e-ram-das-mountainbike-wird-zum-e-bike-umgeruestet-1604-120616.html&prev=search

I know it probably looks rubbish against the more powerful kit, but for me this is the first real kit of this type - super light retrofit torque sensing. I cannot wait, if anyone goes to eurobike this aug I would expect the kit to be launched there.
 
I don't suppose anyone went to eurobike and saw the joy industrial stand? It was next to the scott one and supposedly had the production version of e-ram on display
 
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