Direct Drive Genesis

Hmm you guys are making me double take here.

So your saying the LR higher KV motor wont be as powerful as the BHT direct drive? Wonder if I run like a 6:1 ratio instead of the 4:1 I run on the BHT? That's what I was planning on doing.

Now im not sure if I should go thru the bottom bracket or not. I have most of the parts already except the 219 sprocket and 5 bolt adaptor.

I think I should still give it a try since ive never completed a mid thru the crank, but I do hear what you guys are saying it makes perfect sense...the less chain in the equation the better and quieter. Also 415H chain is much stronger than MTB chain

nutspecial said:

Skeetab does that LR motor weigh about the same as bht? If so isn't it kinda major overkill for going thru the crank? I assume bike drivetrains start wearing pretty fast @ 3kw right, and these 11 pounders seem pretty happy even up over 6kw, geared direct on a light ride at up to 0-40mph!!

Btw, it's a nice lookin motor and 2nd genny build so far! 8)

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The LR motor is lighter by feel, I Have no scale I have been meaning to buy a cheap one for this exact reason!

Bht is around 30kV while some lr's I've seen are about 70kV. Provided they weigh about the same you could assume they will be close to the same max capability. There's obviously things like motor efficiency etc, but kV is really just like the motor's inherent gearing. Just like voltage is gearing. So with the mech gearing it should be quite similarly capable if it's about the same copper/iron/design/efficiency.

Imagine if you want to get to 6kw. Typical 18fet controllers good for that can do up to 100v and 100a, not always at the same time. If the motor is 30kv, the reduction will be very managable on 20s and 90a. To get that same 6kw used for a 70kV motor you'll either need alot more reduction to compensate for the much faster motor rpms, or will have run lower voltage and alot more amps. Like 50v nominal and 120a. I guess that's 24fet territory.
If I was trying a 70kV single reduction I'd be prepared to try 48v x 100a on 13/50t, and maybe with a big controller 48v and 125+ amps. If running 20s you could get similar power used with ~15/40t and up to 100a (18fet). For around 0-30mph gearing, the motors seem to be much more capable than the 6kw I've used. 0-40mph and 6kw can make them heat up depending on how much bottom end you use.

As far as crank drive, there's nothing wrong with it, I was just pointing out 11lbs is kinda overkill as the bike drivetrain will not take even half of what the motor is capable of. If the drivetrain was stronger it would be awesome with only 2 or 3 gears, but then you couldn't efficiently input human power as well as 24, 21, or even 7spd.

Thx for the info Nut! appreciate it

What do you guys think about turning the motor around and using a direct drive left hand side and still keep all the gears on the right to pedal?

That could be doable?

Actually it doesn't look like there is enough room to do that.. the chain lines would interfere with the motor

Well if I use the LR motor and mount it above the swingarm about 4" I can make the chain lines work...hmmm

Trying to figure out motor placement ideas after you guys got my brain moving...

The BHT motor is too fat to mount on the swingarm for left side drive

Chainline would be way off if trying to keep regular gearing



Then I thought about mounting the LR motor up like this...it would solve the chainline issues, but make mounting harder.

Once I turn the sprocket around the chainline will work

It wont stick off the other side too bad either

Just got my sprockets ordered for the 219 LR motor. Got a 5 bolt cart carrier adaptor and a few sprockets one 82t one 86t

Interested to see what this does

BHT has a lower kV, which allows it to run a single chain to the rear wheel, so easier to build. Works best at higher volts on a smaller diameter wheel. The LR kit has a higher kV. That means that you really need a jackshaft to use its full potential, but...if you do that you can get the same performance (or better) with a lower voltage battery.

BHT = higher volts, single chain
LR = lower volts, and jackshaft (belt + chain)

I feel like if you run the LR at 8:1 direct as apposed to the 4:1 I run on a BHT it will perform similarly. You all seem to thing different.

Thought?

I understand what spinning magnets is saying. But correct me if I am wrong if a rider wants access to lots of "power", higher voltage and low amps are a much simpler or could I say logical choice. It's the high amp side of controllers which gets bigger and less attractive. How the RC / astro guys go with those tiny little controllers is another field I am scared to venture into.... The complexity is the scary thing for me at least. Only thing I like about low volts is cheap chargers.

Back to mechanics, complexity is not just a concept that you deal with once and for all. It is opening up a multitude of things that if can go wrong eventually will.

The only thing that has not gone wrong in some way on my LR big block and bicycle drive train connected to it is the motor itself and the bracket that holds it to the BB.

That's a fail every few rides and it has never been powered up over 50 degrees celcius! Meaning it's got so much potential to unleash for those with a labor of love.

Back to your placement, if running through the BB and the only place you can install your motor is up high, again I think you haven't really created a better set up than it's "normal" in front of the bb spot. As you know as low as possible is best. Only advantage might be less front wheel dirt to deal with.

If you have access to someone who can customise the swingarm more specifically for the big block though, I think you might be onto something special with a direct say #219 14t to 90t.

The motor width to deal with might be overcome with something like a fat bike rear hub and bottom bracket? Or some crazy bicycle chain jack shaft to send pedal power up and or around the motor area. Would rather have bicycle chain which will barely ever used up high just for legality than a motor up high.....

enough rambling, but this is the area I am very interested in finding solutions to myself. have fun

SHould only depend on the motor kV and the voltage you wanna run. For instance if running 30kV @ 4:1, you'll need > 8:1 for similar gearing on same voltage. Or drop voltage so < 8:1 is doable, (and possibly raise amps to make up for the lost wattage). Stock, the phase wires aren't that large so I'd guess there might be a limit to find soon after 80-100a.

6:1 for 70kV w/12-14s pack should be close enough to 4:1 for 30kV w/20s pack. If not raising the amps you would see about 15% less watts with the lower voltage though.

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My opinions on your previous post questioning application:
I'd stay with right side parallel, you could use my hub design if you want fw the motor side. It would cost 150 min in parts and would require a little machine work. The machined adapter piece could even maybe work out of printable ABS (20$ to print) since it's mostly just under compression and transfering pedal power to the hub. There's a thread with the drawings and materials needed. Requires a 155mm d/o for 8/9spd cassette.

Otherwise I'd still keep away from added chainline and brake complexity of LH. I'd figure how to mount a sprocket direct to the hub behind the fw body and dish the wheel appropriately. Maybe get an aluminum blank #35 for 30-40$ You still might need 150-155mm d/o (which I think you have there). Otherwise you're right, either motor would need raised above the crank chainline. Def doable but not optimal for weight of bracketry and motor weight distribution. Also pita for brakes i would imagine.

ya you pointed out the biggest flaw I saw so far. Losing the rear disc brakes. So I guess I will shy away from that...

skeetab5780 said:

ya you pointed out the biggest flaw I saw so far. Losing the rear disc brakes. So I guess I will shy away from that...

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There is enough room to offset the sprocket toward the spokes to make room for the brake disc. It is tight, but it all fits fine.

Matt

With the 150mm dropout spacing and a 135mm rear hub, you should have a lot of room to play with for a sprocket adapter and rotor on the left side. Using a 50 tooth 219 sprocket, a 203mm brake is outside of the sprocket's radius so they can nest together with very little room. This pic was with a 135mm dropout frame. The caliper hangs over the plane of the sprocket so you are limited to about 50-52 teeth on the rear. 219 chain allows for some very small diameter high tooth count sprockets so its probably the only way to get away with something like this. You could also go to a small rotor 160mm and a large 219 rear like 80-100 teeth and get a whole reduction done in one stage like 13:80 or 13:100. The chain and caliper get in each others' way but sneaking a flat sprocket past the caliper should be easy with 150mm to work with.

BTW, sorry about the swing arm delay. Glad you have more than one bike to keep you busy. On that note, let me know if any of this mock up is going to effect the changes we talked about on the swing arm. I think the modifications were going to limit your rotor size choice.

Seems like a few people are into the left hand direct drive...Let me see how my sprocket carrier fits my hub once i get it. I still want to attempt thru the BB real quick just to see what its like. I seem happy with 20s low amperage so maybe 3000w will be enough to keep me happy. Dont get me wrong I certainly have a need for speed but I miss the hill climbing ability.

For sure try the bottom bracket drive first. Not trying to bias you towards the left side drive. Just didn't want the brake to be your hang up if you go that route.

let me bias you a little.

This is what I discovered 20 minutes ago on my bike. From chain pulling from the bb to one side under 3.5kw.



look at the black link if you can't spot the crack....

LOL wow, that is impressive! How much power/years of use? And what MTb frame is that?

The next thing i havent looked into is my wheel diameters. My old build was based on 17" moped wheels which i have a set of... But if i want to try and keep MTB gears i would much rather a 26" MTB wheel. Im not sure if the 6:1 on the LR will be even close to getting to its comfort range. Even the BHT will be alot faster/less torque than i was used to. Maybe i should try the BHT left hand drive... i should get atleast 5 more mph with the bigger wheels i would imagine.

Thoughts?

Also thought about keeping the motor right hand drive but adding a second sprocket to it that freewheels. So i could still link the pedals to the drivetrain somehow. But the motor would still be direct drive. I think this would be easier with the LR motor since it has more motor shaft haning out of it and if i turn the 219 sprocket around like i was planning there would be room to weld to it.

Thoughts on that?

Thanks guys

Here is a pic from BHT bikes I forgot to post from last year.

Ok so I need a little more room and needed a dual disc hub so I decided to just do a wheel build. I ordered a 24" rim and I have a Voloci wheel hub. I just need to order the spokes, I'm not positive on the flange hub spacing is the reason I haven't yet. Anyone know how to measure it?

I think this will solve a few issues. Now lets hope I can assemble it!

Here is the hub and sprockets

You gotta love that Oset sprocket carrier....so meaty!

Ya I was excited when I found out about the parts they offer.

Did I calculate my spoke lengths wrong? why am I having a hard time finding 220.8mm spokes?

Well I ended up finding 220mm spokes, so hopefully they will be long enough! I may have to build a tight wheel