Direct Drive Genesis

[skeetab5780]

Got around to building the 24" rear wheel for the new direct drive setup! Here are a few pictures. I have it pretty darn tru left to right but it has a slight lateral wobble I tried to fix but it should be ok. I am happy with it! Slapped a Maxxis Holy Roller on it and now I want one for the front since its such a sexy looking tire. Then lastly I bolted the 219 86T sprocket on to get an idea of the chainline so I can start lining up the motor for mounting.

Taped a ruler to the swingarm and trued the wheel that way, better than nothing

 

[skeetab5780]

So i have my brother making me a motor mount for the LR motor and my 219 chain will be in the mail this week! I should have some sort of platform to start bolting together before you know it. I think he is using 1/8" steel and is bending it in a bench press to make a 90 then adding one simple gusset and from there i will modify it with my dremmel and hacksaw like usual.

One i figure out how it all bolts together I can line it up and tack weld it to the swingarm. I may drill a bunch of holes in it to lighten it up before i paint it too

 

[skeetab5780]

Brother finally got me the motor mount! He did a pretty sweet job on it!

Now I just need to find the time to get it mocked up to the bike!

 

[DanGT86]

looks nice. Do you still want the shortened arm made? Seems like the motor wouldn't fit if we shorten it like we talked about.

 

[skeetab5780]

Its up to you. I will pay for it. But I don't need it if you do not want to make one

 

[skeetab5780]

After buying a 219 cart sprocket chain. It comes in the mail and it is way too short. So I ordered a chain breaker and a second chain so I could put two of them together. Today I got it cut to size and mounted on the bike so I can get an idea of where I need to secure the motor bracket in place. I had to turn the sprocket of the motor backwards so the chain line would be close to the center but now its too close to the motor shaft bearing. I will need to figure something out with a sprocket adaptor sleeve.

Now that the sprocket is reversed the chain is too close to the motor, I can fix it but will need a new shaft sleeve adaptor

This motor mount bolt will work perfectly for a tensioner pully mount location

 

[skeetab5780]

Had to swap the 86t sprocket out for the 82t with the sprocket carrier since I needed to move my chainline closer to the inside of the wheel to avoid the 219 chain rubbing against the aluminum upper swingarm section. I have it all temporarily mocked up so I can align the motor and finish mounting the bracket to the swingarm. Im sure I will have to buy a larger sprocket since my reduction is not nearly enough. But this is just for mockup purposes.

 

[madin88]

The Question: is the BHT or the LR the better motor?

First of all, for a meaningful comparison (supposed that both motors have similar stator diameter and width), the following thing would need to be done:
Use the SAME reduction on both, than use for instance 100V and 50A on the 30kV BHT
The LR motor has a kV of 70 so the "amp multiplicator" is 7/3. this means on the LR you would need to adjust the voltage by 100 x 3/7 so 43V and the current 50 x 7/3 so 117A

both motor now are spinning at the same RPM and have the same input power of 5000W
now check and compare the output power during riding the bike

For the theoretical stuff you could measure and compare the phase to phase resistance. on the LR motor it should be about 6 times lower.
the thickness of the steel laminations are also important. The thinner they are, the better it is (photos from the inside would be nice).

btw: great thread. looking forward to see the finished bike!

 

[DanGT86]

I've been keeping an eye on this thread for a while and trying to resist the urge to start on something else. I couldn't take it anymore so I started doing some mock-up and ordered a 24" rear wheel for myself.

I've had a 5" transmagnetics motor laying around for awhile. I shortened it a while back for another project so it would fit between standard cranks. It looks like its going to be a super tight fit but the 135mm hub in the 150mm drop outs gives me some wiggle room on the chainline. I'm trying to go left side direct drive so the room to adjust will be needed next to the rear brake. Thanks for the inspiration!

Looks like the only way to get the chainlines to all agree is to do this goofy re-route with the human chain side. That doesn't really bother me since the pedals are rarely used for anything.

 

[skeetab5780]

wow that is a tight fit. I like it! I don't even know if i am going to bother putting pedals on this build. Last build had them but it was under powered. I feel if i put 5kw thru it i will be ok with pegs of some sort.

On a side note i ordered a 90t and 94t sprocket to get closer to my 8:1 ratio i wanted so hopefully it will have enough torque for hills like the BHT did.

 

[DanGT86]

I cant decide if I want to bother with pedals long term. I just wanted to mount the motor as if pedals were going to be on it. That way I can interchange freely between pedals and pegs without having to redo things. Its so hard to package everything past the brake rotor and caliper I'd rather do the chain-line once and be done. I'm not sure the optimal peg placement is at the center of the bottom bracket. With the wide stance of pedals, a rider gets to transfer weight back and forth the whole length of the crank arms. I do wonder where the sweet spot actually is.

My motor is 70kv so with 13:92 I should be about 45-50mph loaded on 20s. That's a bit faster than I want but I have the sprockets already. 35mph tops would be perfect for the 5kw I'm planning. The 52 tooth sprocket in the pic is from when I was planning a 2 stage reduction for a 26"wheel. It fits under the caliper with a 203mm rotor. I got a good deal on a 92 tooth so I'm going to try it in one stage. Good news is the loaded top speed should be exactly the same as my MXUS 3k so I am hoping to do back to back comparisons with the exact same power on the exact same frame. Bad news is the largest off the shelf sprockets are around 103 teeth. So if it runs too hot at low speeds I'm pretty much out of easy options for lower speed. I like the steel swing-arm for weldability. Its way better than when I tried to put this motor on a factory suspension bike that I couldn't weld on.

Happy building!

 

[skeetab5780]

Got my new 219 cart sprockets in the mail yesterday! Now i can try to get the chainline completed and get this thing rolling for testing soon. I got a 90t and a 94t, i think i am going to try out the 94t first since its where the ratio needs to be.

 

[skeetab5780]

 

[spinningmagnets]

is the BHT or the LR the better motor?

The BHT allows a simpler and cheaper drive, because the lower kV means you don't need a jackshaft, but...the LR is "better" because it has a MUCH better efficiency, due to the additional jackshaft providing a higher magnet-speed in the motor.

BHT = cheaper purchase price and simpler drive

LR = More efficiency and less motor/controller/battery heat in the daily usage

If you can afford to buy a new battery once a year, get the BHT, if you want efficiency and long battery life (plus a higher wheel-torque from a lower volatge battery), get the LR

 

[skeetab5780]

There are multiple threads going on of people using the LR motor with no jackshaft so again there is more than one way to do things.

Hopefully I will find out soon which I prefer

 

[skeetab5780]

As expected I had to add a few links to the chain for this huge 94t chainring. It is made much stronger than the other ones from Oset but it is twice as heavy...

At what point do you lose efficiency due to the rotating mass of a oversized sprocket>? I'm sure I will find out

 

[John Bozi]

so excited to see and hear this run!

Very interested to see how you use chain retension system if needed especially when coasting at high speed.

I see one danger here in particular. When the chain drops it jams. Not a big deal with a freewheel unless very unlucky. But with no freewheel it could be an instant skid.

Along the same lines with efficiency, how the motor drag now will reduce it. Also if you use regen how that will go with stopping force.

With a chain running 100% of the time wear on the motor chain and sprockets will probably be doubled (as a flying guess).

Still without freewheels you will be the first to really dump power into this motor beyond any lr mid drive kit could survive.

very very excited.

8)

 

[litespeed]

I've been keeping an eye on this thread for a while and trying to resist the urge to start on something else. I couldn't take it anymore so I started doing some mock-up and ordered a 24" rear wheel for myself.

I've had a 5" transmagnetics motor laying around for awhile. I shortened it a while back for another project so it would fit between standard cranks. It looks like its going to be a super tight fit but the 135mm hub in the 150mm drop outs gives me some wiggle room on the chainline. I'm trying to go left side direct drive so the room to adjust will be needed next to the rear brake. Thanks for the inspiration!

Looks like the only way to get the chainlines to all agree is to do this goofy re-route with the human chain side. That doesn't really bother me since the pedals are rarely used for anything.

Looks like you could simply move the motor up to clear the "human" chain side. Not sure if 2 inches would raise center of gravity enough to be noticed in handling or not.

Tom

 

[DanGT86]

Probably could but that puts the motor at a longer swing when the suspension travels. That room between the tire and the seat tube disappears quickly when the swing arm moves. Its going to be close. I got my sprocket tire and wheel in yesterday so I can do some actual fitment testing to find out. I'll start a new thread on it so I don't distract from this one.

 

[madin88]

is the BHT or the LR the better motor?

The BHT allows a simpler and cheaper drive, because the lower kV means you don't need a jackshaft, but...the LR is "better" because it has a MUCH better efficiency, due to the additional jackshaft providing a higher magnet-speed in the motor.

BHT = cheaper purchase price and simpler drive

LR = More efficiency and less motor/controller/battery heat in the daily usage

If you can afford to buy a new battery once a year, get the BHT, if you want efficiency and long battery life (plus a higher wheel-torque from a lower volatge battery), get the LR

The kV should not be considered for the comparison, because the BHT probabaly also could be wound as 70kV, or the LR motor similar to the BHT's 30 RPM/Volt.
Giving the BHT 7/3 of the voltage and 3/7 of the current from a LR setup, or the LR 7/3 of the current and 3/7 of the voltage from a BHT setup, would have a similar effect as rewinding for same kV.
both motors than would have same input power and same RPM on the motor shaft for a meaningful comparison.

I don't know the stator width and diameter of both motors, but presuming it is identical, the motor with the highest copper fill (lowest phase to phase resistance) and/or thinnest lamination will be the winner.

@DanGT: Nice Transmag setup! I'm excited to see how it works.

Does this motor has strong cogging torque, or can you more spin it easy with your fingers?
I think this could be really important for using regen, or if a freeweel neccessarily should be used or not.

 

[DanGT86]

Cogging torque is insane on it. Not a chance to spin it with fingers. I'm curious how it will pedal with no freewheel. A wheel is a pretty big lever when it comes to regen but through pedals the rider is already overdriving the wheel so it might be pretty tough.

 

[skeetab5780]

Dan what is the weight of that motor?

Im trying to buy a welder at the moment its slowing me down. Im sick of borrowing, trying to shop a good deal locally

 

[DanGT86]

Motor is just under 11 lbs.

Neptronix did a great disassembly and measure thread here:
https://endless-sphere.com/forums/viewtopic.php?f=30&t=50066

If you are shopping for a welder I would suggest you get a 220v rather than a 110. Most people I know have been unhappy with their 110v welders. You always want too much power when welding rather than not enough. I've had really good luck with my Hobart handler 180 welder. Hobart is made by Miller and used to be a cheaper line with less duty cycle and some plastic parts rather than the metal parts in the miller. By the time I bought mine they were both using all metal and the guy at the welding supply place couldn't tell the difference other than the color of the paint. Also make sure you get a gas capable welder. Don't fall for the flux core wire $90 harbor freight deal.

 

[skeetab5780]

Update! Bought a cheap Harbor Freight welder to get this bracket tacked to the swingarm, it was pretty brutal since the welder was really underpowered... but its together as of now and i should be able to get it running for a test run soon!

 

[Dauntless]

Have they made that motor available again, or is it still vaneesh?