Latest Chain sizing for mid drives bmx, 420, #40, 219?

[dirkdiggler]

I've got a bht motor that finally needs to be put to use. I bought an enduro frame to build up a bike/mx with a spare motorcycle hub motor. The motor only gets me to 30 mph on 60v of lipo. Somewhat disappointing for me. My cyclone bike goes much better. Plus it seems to slowly accelerate. Definitely won't wheelie on startup. I've tried a few controllers only to get similar results.
So my thought is to add the bht motor that has been lying around. The issue I have is what to do about chain sizing. The motor comes with a 420 size sprocket on a 1/2 motor shaft. The hub motor has a threaded freewheel cassette. I guess I can find a new gear for the motor, switching to bike chain or I can change the freewheel sprocket on the hub to 420. I know lmx uses 415 size with a special hub and sprocket. I think LMX has the hub for like 300 euros. More than I want to spend, I'm doing this on the cheap and I'd lose the hub motor.
I might in the future ditch the hub, but want the extra power and moto wheel for now. Just wish It didn't come with the weight.
Any help would be appreciated. I've searched and read up on chain for the past few days and nothing is getting much clearer. Just looking for a quick and easy solution. I'd love to buy another Cyclone and add it to the bike, but that isn't in the cards right now. I found a few freewheel sprocket carriers that I think will fit on the hub motor, but the sizing does seem iffy. Links, suggestions? I'm still trying to read up on it, I know Recumpence also isn't using standard bike chain, so was going to read through his builds, but so much info to wade through on this site!

 

[bzhwindtalker]

hub only :
http://www.lmxbikes.com/en/spare-parts/18-lmx-rear-hub.html
In pictures the old version, new version has integrated spacers.
We have some of the old hubs in stock, 100€+ ship incl 20% VAT
We also have 38t #420 sprockets made for the BHT and our hubs if you are interested..

I would suggest to stay away from bike chain for offroad. Not for ultimate strength, more for resistance to chain jumping off the sprockets.

 

[dirkdiggler]

I scoured the web :lol: Correct me if I get any of this wrong.

LMX bikes 415 chain
Evolution's Mongoose cx450 #35 chain
Nutspecial's #420?
Skeetab's Genesis #219
Overclocker - NO pics or discussion

Only Nutspecial has a freewheel design.

Someday I will get the LMX bike hub with a rear trials rim with moto tire, but like I said I'm scrounging parts for this build right now and I figure the cost would be around $300 or more to do that. Plus I'll lose the hub motor's extra power - which is debatable.

I dug up an old freewheel with the 4 hole mounting that has been welded so it doesn't freewheel anymore. I"ll try and get a rear 420 size sprocket that mounts to it.

 

[dirkdiggler]

Here is a great diagram for chain sizing:

Bike chain is 1/2" x 3/32" and is used on multiple speed bicycles with derailleurs and cluster sprockets. 1/2" x 3/32" chain has a 1/2" center to center spacing between each link pin, a 3/32" spacing between inner plates, and is approximately 3/8" wide.

 

[nutnspecial]

Okay, so it sounds like you're okay losing pedal function, at least for now. In that case you might want to try the SBP HD freewheel if you want to freewheel. Mine has been holding up very good for a few seasons, against several sets of brakes and tires. I really like not having the bht/drivetrain turning when you're off the throttle.
Otherwise I think you have the right idea with a welded cheap one to integrate a sprocket on the rear wheel.

Regardless, one thing to consider is if the hub cover will take the bht motor torque though. I'm not sure of that, but it would maybe just need some reinforcing?

I would recommend an aluminum sprocket from a gocart place. I bought a few 'blanks' for my #35 drivetrain for something like 30$/pc, and they do alot of tooth counts. I'd imagine they'd also do the other popular sizes like 219 and 4xx. The first 35# aluminum I've used has held up evenly with the 11t front steel cog, though it's about time to replace them and the chain. I'm staying with #35 cuz I like the strength, wear, pricepoint, and weight combo.

I'd recommend an 18fet with up to 20s to get some really good potential from the motor! I'm only running 16s right now, geared for 30mph and it's still great fun though.

 

[dirkdiggler]

Yeah, going to try a pedaless bike. Probably should have just gotten the LMX bike to begin with, but I've had fun building bikes. Building is almost as fun as riding sometimes. I've gone through the typical ES cycle - bought a cheap 1000w rear hub off ebay, then the Bafang 750w, then the Cyclone 3kw. Now on to doing the mx style with BHT!
After searching the interweb, I bought a #420 sprocket 48 tooth.

Should fit the sprocket carrier exactly. I'll use the welded one for now, but will try and get a freewheel in the future when I ax the hub motor. Don't ride dirt bikes, but I don't imagine they use a freewheel. Interesting to see some of the pit bike parts that might fit on this build. Cheaper and heavier than MTB stuff. I know the front forks are super heavy, but for rear suspension might be better with a heavy frame like the enduro (EEB). It would be cool to find a mx rim that would fit into MTB dropouts. That way you could have the beefier rim and have a sprocket carrier built right in.
Next issue I have is the frame. The problem with buying stuff of the net is you can't visualize anything correctly without seeing it. I need to mount the BHT motor somewhere on this white frame:

I can weld a plate on the bottom, but I think it will affect the ground clearance, which is already low due to the 17" motohub. The battery space is weird as it follows the outline of the black cover almost. If I put the motor there, the weight will be higher, but I'm guaranteed not to be hitting the chainstay with the chain line. Not the ideal frame for this! I like the way the LMX shock is mounted, where you can have space to mount the motor on the swingarm. Might need to just modify the BHT cover to reduce some of the bulk.

 

[Overclocker]

Okay, so it sounds like you're okay losing pedal function, at least for now. In that case you might want to try the SBP HD freewheel if you want to freewheel. Mine has been holding up very good for a few seasons, against several sets of brakes and tires. I really like not having the bht/drivetrain turning when you're off the throttle.
Otherwise I think you have the right idea with a welded cheap one to integrate a sprocket on the rear wheel.

Regardless, one thing to consider is if the hub cover will take the bht motor torque though. I'm not sure of that, but it would maybe just need some reinforcing?

I would recommend an aluminum sprocket from a gocart place. I bought a few 'blanks' for my #35 drivetrain for something like 30$/pc, and they do alot of tooth counts. I'd imagine they'd also do the other popular sizes like 219 and 4xx. The first 35# aluminum I've used has held up evenly with the 11t front steel cog, though it's about time to replace them and the chain. I'm staying with #35 cuz I like the strength, wear, pricepoint, and weight combo.

I'd recommend an 18fet with up to 20s to get some really good potential from the motor! I'm only running 16s right now, geared for 30mph and it's still great fun though.

found this at a local shop. aluminum. i'm just a little concerned about the weight of the 415H chain. looks heavy and overkill

here's the dilemma... i can't find #35 aluminum sprockets locally!

oh btw have you tried this calculator?

http://www.recumbents.com/wisil/e-bent/rc_drive/rc_drive_calculator.asp

does it correctly model your BHT's real-world performance?

i'm trying to decide what sprocket combo to use. i'll be using 17s 18650 pack. for max of 50kph (31mph). 22-inch effective wheel size