Light dirt bike, QS 120 70h motor, custom steel frame

[Overclocker]

so after nearly 2 years w/ my GNG kit I've decided to do another build. design goals:

1) 50kph MAX, must climb very well
2) single-stage reduction for simplicity/reliability
3) no pedals
4) 18s, 40ah, 18650 pack, no BMS
5) moped rear wheel 17x2.5 knobby, DH MTB front wheel 26x2.35
6) custom steel frame

already got some parts ready now i need pointers on selecting the proper sprockets combination. i was thinking of using #35 chain


PRICES (philippine pesos) & WEIGHTS:
- knobby tire (Fuji Tire "Wing2000") 17"x2.5": 1970g == P450
- 17" tube: 420g == P85
- 1.4x17" rim: 880g == 400
- 1.2x17" lightweight rim: 680g
- rear hub: 580g == P1150
- 10-gauge spokes/nipples 36pcs: 540g == P250
- RST R-One Pro: 3190g
- Marzocchi Drop Off Triple: 3470g
- Rockshox Domain RC dual-crown w/ direct-mount and headset: 3700g
- DNM RCP-2 rear shock: 830g == P4995
- BHT motor: 5.25kg
- #420 chain: 770g
- Specialized Butcher DH 26x2.3: 1250g
- Maxxis freeride tube 26": 270g
- Jetset Down-Z 26" DH rim: 800g

 

[Overclocker]

It looks nice and not too bulky for ebike.
I've weight my bicycle rim (regular bicycle wheel) with hub without tire and it weights 900 grams.
What is your:
hub weight,
rim weight with spokes,
tire weight,
and rim diameter?

How does it look compared with regular bicycle wheel? In case you got some laying around wheel to compare.

I also feel that i got to use light motorcycle or pit bike rim instead bicycle rim. When i look to my bicycle rim i can't believe that it might cope with more than 2kw mid drive, but maybe i just too precocious

downhill mtb components are tough but i'm going w/ light-moto rear wheel this time because MTB tires wear out too quickly and i need a wheel that's smaller than MTB 26"

this is 17" x 1.4" rim

here are the weights:

a) knobby tire 17"x2.5": 1970g
b) tube: 420g
c) rim: 880g
d) hub: 580g
e) 36 spokes/nipples: 540g


tire is about twice the weight of a wire-bead downhill tire. for just 1kg more you get a lot better flat resistance and tread life

rim weight is actually competitive w/ a wide DH rim

hub is about 200g more than a downhill rear hub

i'll be using MTB rotor:

 

[skeetab5780]

Its gonna look funny with 17" rear and 26" mtb front. Do you have any pics of your frame?

I will be following this build, I wish I could weld effectively. I also like that hub looks nice!

 

[minde28383]

Thank you for weights and measurements. I too plan to build my custom scooter frame and I'm thinking to use the same motor BHT 1000w from e-bike-diffusion.com
where did you get hub and rim?
It surprises me that bicycle rotor fits mini mc hub.

 

[minde28383]

i just found that BHT 1000w is out of stock.

 

[skeetab5780]

Ya im not sure how many BHT's your gonna find. That website used to just buy them from China after you buy it now from them. I saw one on Ebay last week in France but its gone

 

[Overclocker]

Its gonna look funny with 17" rear and 26" mtb front. Do you have any pics of your frame?

I will be following this build, I wish I could weld effectively. I also like that hub looks nice!

quick and dirty sketch but drawn to scale. rear wheel w/ tire is 22" OD. front is 26" OD. shouldn't look too bad. if it does then i'll use 18" or 19" moto wheel in front

 

[Overclocker]

Thank you for weights and measurements. I too plan to build my custom scooter frame and I'm thinking to use the same motor BHT 1000w from e-bike-diffusion.com
where did you get hub and rim?
It surprises me that bicycle rotor fits mini mc hub.

actually the holes are off just so slightly

got these moto parts from some local shops around here

 

[Overclocker]

i just ordered this cheapo 18-FET controller just to get this project rolling

http://www.aliexpress.com/item/SF-1000W-48V60V-Direct-manufacturers-of-electric-vehicle-controller/32287184540.html

 

[minde28383]

It is really not expensive. On label it says 1000W but when i multiply 60V by 42a it's clearly over 2000W watts. unfortunately you won't be using whole potential of BHT motor but I guess it's nothing to compare with my cheap Chinese 1600W motor.

 

[skeetab5780]

Any updates on this frame? curious as to what its going to look like.

 

[macribs]

1+ to what he said.

 

[999zip999]

Bump

 

[Overclocker]

sorry for the lack of updates! been sidetracked by a few things. anyway here's one half of the battery pack. 17s6p. cells are Amperex ATL INR18650 2200mah. to be paralleled with 17s6p Samsung 26F. combined, these cells should easily provide the 42A needed by the cheapo controller

charging to be handled by this 900W dc-dc digital boost module:

 

[skeetab5780]

Nice those look like the cells in the Greenworks packs!

Any frame updates?

 

[Overclocker]

i just picked up this Rockshox Domain to use instead of the crappy RST R-One heavy steel stanchions perfect for lightweight e-motorcycle 8)

this motor is supposed to be 36KV

i'm getting 2491RPM @ 67.5v, unloaded. close enough

this calculator says i'll get around 28mph or 45kph if i use 13t motor sprocket and 52t wheel sprocket

i think i can finally resume working on this project...

 

[madin88]

following this build^^

 

[skeetab5780]

Ya glad to see some sort of update here! Excited for this build.

 

[Rube]

Looks like some cool ingredients thanks for posting. I will watch with interest.

 

[Overclocker]

capacity testing the Amperex 17s6p pack using 6.8ohm nichrome wire load. i'm getting 826Wh. not bad i suppose for $1 per cell

now assembling another 17s6p pack from used Samsung 26F cells (were previously used w/ the GNG kit):

 

[Altair]

Cool!
What brand is your discharge monitor, it has a nice display.

 

[Overclocker]

Cool!
What brand is your discharge monitor, it has a nice display.

https://www.aliexpress.com/item/DC-6-5-100v-100A-LCD-Combo-Meter-Voltage-current-KWh-Watt-Panel-Meter-12v-24v/32546106421.html

100v 100a external shunt. i'll be using it on this build as well

now cycling these 6 cells to match the capacity/IR of my 96pcs used cells. these six BTW came from the same batch. i just need to wear them out a bit to prevent balancing issues

 

[Overclocker]

finishing pack 1 of 2. 17s6p. no BMS, shown here w/ 18-pin balancing port. sand-filled 40A slow-blow fuse

 

[skeetab5780]

Nice looking battery, Do you have the frame started?

 

[Overclocker]

drilled and tapped the hub to attach the 203mm MTB rotor

i decided to use relatively heavy #420 chain and sprockets to make it as maintenance-free as possible, since i'd be riding this through abrasive sand. the #420 should take a while to wear out

Nice looking battery, Do you have the frame started?

will start soon. it'll have similar layout as the Deller i.e. motor is concentric w/ swingarm pivot