My DIY Luna Cycle Bafang HD is finished!

Sin Saint

New Member
Region
USA
It was perfect, all gears easily accessed. Then I changed to a 42T Chainring from Luna Cycle. Perfect chain line also.
Thanks for the info sir. Do you like the 42 or 46 better with the 11-34? I have a Mongoose Juneau to use as my donor bike for a BBSHD build. I think its about the same thing as a dolomite. It comes stock with the 14-28 freewheel also. I'd like to have a top speed around 20-25mph and be able to climb a few hills.
 

Tom@WashDC

Active Member
Region
USA
City
Loudoun County, VA
Thanks for the info sir. Do you like the 42 or 46 better with the 11-34? I have a Mongoose Juneau to use as my donor bike for a BBSHD build. I think its about the same thing as a dolomite. It comes stock with the 14-28 freewheel also. I'd like to have a top speed around 20-25mph and be able to climb a few hills.
I have fiddled with the Luna 30T Mighty Mini, 40T, 42T and stock Bafang 46T chain ring. The Bafang 46T will not hold the chain consistently. The 42T is where I am sticking. Coupled with the 14-28 you can go anywhere and the stock freewheel gears seems really durable. The Luna 42T Chain line has a perfect off-set. (see pics) The 30 and the 40 had enough of an angle to cause the gears to ghost shift and grind and chatter.

I've been running the 42T with the stock 14-28 Mongoose Freewheel and it works perfectly. Comfortable top speed is about 18-20 MPH. 21-25mph, I am pedaling quickly but the motor is really spinning where it should be. I have my speed limited to 25MPH as I do not fancy dying on the road. I avoid roads and traffic as best I can.

I've got the DNP 11-34 Freewheel from Amazon that I tried earlier with the 30, 40, and 46 chainring, but I have not tried it with the 42T yet. Since the chain-line was previously less than ideal and I was getting ghost-shifting, I tried shifting the DNP 11-34 freewheel outwards with a 3mm spacer (upon advice from my local LBS) and used the 40T chainring. The gear setup for speed (11T) and climbing (34T)was excellent but I managed to completely strip the threads on the hub while climbing a 45 degree hill. Turns out losing 3MM of threads on the hub was critical under so much power. So I figured i would order a Cassette-type hub to replace the freewheel hub. No such luck. There are no fat bike cassette hubs that will fit that bike (190MM) and rim with 36 spokes in the US at this time. They are all 32 spokes. So I managed to call Pacific Cycle, the distributor for Mongoose and they shipped an entire back wheel and hub for $39.00!

So now I am running the Luna 42T with the stock 14-28 freewheel and it works great. Totally satisfied.

But.... in my never ending quest to improve upon my project, I've ordered a Shimano Type 36 spoke cassette hub from AliExpress which should be here in a week. Now that I have a near perfect chain-line, I want to try a 10/11 speed SRAM/Shimano 11-42 or 11-46 rear cassette and upgrade from the Tourney Derailleur and shifter to a higher quality.

This bike build by the way is a monstrous beast! There really is no place I cannot go, and I get a lot of looks and compliments.

Let me know if you need any help on the install ~Tom


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Sin Saint

New Member
Region
USA
Great info thanks so much. I'll stick with the stock freewheel and grab a 42 chainring when I order my motor. Your chain alignment looks very close to the stock chainring.
 

Sin Saint

New Member
Region
USA
Hey Tom I finished my build today and took it for a test ride. You were right. Chain line is perfect with the Luna 42t chainring. My first test run hit 27 mph throttle only with the stock 14-28 freewheel. The next gear down topped out at 17mph throttle only. Gearing seems perfect for me. The bike is an aluminum framed Mongoose Juneau.
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Tom@WashDC

Active Member
Region
USA
City
Loudoun County, VA
Sin Saint, your build looks great! Looks like a very capable monster and I am very envious of your 52V battery! Glad the chain line works well for you. That bike will go anywhere you want it to go, Be careful it will tempt you to do challenging things :) I always ride with elbow pads.

I put some metal fenders on my bike. The plastic ones I had did not last but a few rides. Bolton Bikes has a sweet deal for $49.00. I had to buy $20 worth of additional mounting hardware but the fenders are very sturdy and do not rattle, and they keep me and the bike clean and dry.

I also added the Bafang Thumb Throttle, I find it more comfortable and easier to use especially while riding over rough ground.


PowerTripCycles turned me on to an inexpensive rear rack by Ibera which I have just ordered.


Congrats on the slick build. Keep us posted after you've ridden it nice and hard. ~Tom
 

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Sin Saint

New Member
Region
USA
Hey Tom, I hadn't paid much attn and thought the Juneau came with the same 14-28 freewheel found on the dolomite. It doesn't. When I started riding it I realized it has an 8 speed. I counted 11-34t. Maybe you could get a wheel and shifter from them cheap idk. My bike isn't pretty anymore. It's covered in mud!