another pit bike conversion qsmotor 2000w

I've been thinking of converting a honda crf50 or similar small bike to electric and wondering if anyone has done anything similar?

I've also taken notice to the qsmotor 138 3000w and the smaller 120 2000w, I see the 2000w version is sold with a 72v 150a controller, does this mean the motor has a peak output of approx 7kw?

I think the 3000w would be overkill as I had read someone was running it at 15kw or more :lol: These motors also come with a 17mm shaft (I think) which fits a standard 420/428 sprocket which a crf50 already uses which is handy..

Does anyone know the kv of the 2000w version? I think I also read somewhere the 3000w version is 73kv

If the 2000w motor is also roughly 73kv and I ran the motor at 48v for 3500 rpm, then with a 13t front sprocket and 36t rear and a 10" wheel does the equate to around 35-40mph? Is that reasonable for this motor? Never been great at gear ratios!

Or would it be better to run 18s 75v with 13t front and 41 rear for around 50mph??

iif anyone has any ideas or info please share, cheers!

Did you do your rpm calculations with a 10" diameter? I believe that's just the rim size, I used an overall tire diameter of 15" and came up with 56 mph at 3500 motor rpm. Also, with that big of a motor, there won't be much room left for batteries in such a small frame.

I don't want to discourage you from doing a conversion, but have you considered OSET at all? I picked up a 20R recently and it's a blast! On full batteries, peak power is almost 5kW (48V, 100A controller).

First question to think about, because battery space is limited, is how fast do you want to go, and how far, under what conditions.

The how fast and what conditions will give you how many wh/mile you'll use.

The how far , multipled by teh wh/mile, will give you the capacity (wh) of the battery you need.

Then the current requirements and voltage needs of the system, will help you pick out the type of cells/battery you will need.

Those together will give you the size of the battery, and the design of the frame will help you figure out if that will fit inside it, or if it has to be fit in side panniers, or even a trailer if it's really big.

Is this a pit bike for an adult or for a child?

PaulM said:

Did you do your rpm calculations with a 10" diameter? I believe that's just the rim size, I used an overall tire diameter of 15" and came up with 56 mph at 3500 motor rpm. Also, with that big of a motor, there won't be much room left for batteries in such a small frame.

I don't want to discourage you from doing a conversion, but have you considered OSET at all? I picked up a 20R recently and it's a blast! On full batteries, peak power is almost 5kW (48V, 100A controller).

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Ah yes you are right! this is here why im asking such things :lol: The smallest front sprocket I have found is 11t but i recall reading somewhere that anything less than a 13t begins to get quite noisy, the largest rear sprocket I can find is a 41t which would drop the speed to around 40mph I think

I think there would be enough room to easily fit 48v 10-15ah lipo, maybe even squeeze 20ah, With a 20c continuous discharge would that keep the lipos happy and not under too much strain? if the controller is only rated at 48v 100a?

Although I have no idea what kind of range I'd get out of that size pack as I have no idea how throttle happy I'd be but I'd imagine only averaging 15-20mph at the very most

I have looked at the oset mx-10 which looks very similar in size as a crf50 but is only 1400w and has a hefty price tag, I also love to tinker and build projects, in the future I'd love to convert a full size mx to electric but for now I want something small to beat around on and experiment with.



Edit;

amberwolf said:

First question to think about, because battery space is limited, is how fast do you want to go, and how far, under what conditions.

The how fast and what conditions will give you how many wh/mile you'll use.

The how far , multipled by teh wh/mile, will give you the capacity (wh) of the battery you need.

Then the current requirements and voltage needs of the system, will help you pick out the type of cells/battery you will need.

Those together will give you the size of the battery, and the design of the frame will help you figure out if that will fit inside it, or if it has to be fit in side panniers, or even a trailer if it's really big.

Click to expand...

I think I can easily fit a 48v 10-15ah lipo pack and with a 20c continuous discharge I think it shouldn't be under too much load?

The conditions will mostly be flat but a mix of mostly dirt and gravel tracks, I cant imagine averaging more than 15-20mph but could be wrong!

I was thinking between 450-700 wh but have no idea what kind of range I'd get from that, I'm not really bothered by a massive run time that said.

Grantmac said:

Is this a pit bike for an adult or for a child?

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An adult (physically at least) :lol:

Consider looking for a KX100/CRF150RB/105SX then. Much more suitable to adults.
10-15kw would move one along smartly to say the least.

Grantmac said:

Consider looking for a KX100/CRF150RB/105SX then. Much more suitable to adults.
10-15kw would move one along smartly to say the least.

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I already have a crf50 to convert and I want a small bike which can be thrown in the boot of the car, I'f the smaller 120 sized motor has a peak output of around 7kw I think it would be a blast to ride too.

Look at the QS1000, they can peak at 6-7kw for a short time.
Also consider raising the seat to add battery space.

Grantmac said:

Look at the QS1000, they can peak at 6-7kw for a short time.
Also consider raising the seat to add battery space.

Click to expand...

At first I thought the 1000w version would be more than enough power for such a little bike however I cant find one which has the 420/428 sprocket shaft anywhere? I can only find the 2000w and 3000w versions with sprocket shaft

Recently received the 2000w motor with votol em100sp controller combo, decided not to convert my crf50 but built up another cheap 10" pit bike to convert, will probably be damn inefficient but should be a lot of fun!

Going to run 3x 6s 20ah turnigy packs as 18s1p for 1330wh weighing 8kg

So I mounted up the motor, just a matter of making some small mounts - 8 in total and a bracket under the frames top tube to mount the controller too, and then finally I knocked up a basic lower frame mount for the time being to mount the batteries, batteries currently fitted super snug with foam in a watertight box, this is not the finished design however, just a mock up/experiment to let me be able to test the bike out!






And I've got to say im completely blown away by this motor! its absolutely overkill for this tiny bike but god damn it is so much fun its hilarious!! The gearing/top speed came out a little higher than i'd imagined at 48mph on gps, I calculated/estimated it to be around 40 but it will powerwheelie the whole time with this gearing and pretty mind blowing acceleration, its incredibly addictive!

The only trouble is 10" wheels don't offer much traction in the dirt and the "sport" mode is almost useless in wet mud but is a heck load of fun roosting the entire time :lol: I honestly don't think any "high end" 4 stroke pit bike engine would have a chance in hell against this set up in terms of acceleration.

Will try and get some riding footage asap!

Then the bike will be stripped down again to paint the frame and redesign the battery frame cradle for something a little sleeker yet stronger

Nice build! :thumb:

Maybe get a 12" rear and a 14" front wheel combo in that bike if it would fit?

SlowCo said:

Nice build! :thumb:

Maybe get a 12" rear and a 14" front wheel combo in that bike if it would fit?

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Thanks bud!

Yeah 12/14 would be far far more suited for this motor although probably still complete overkill, And I am very tempted to build up another chassis in the near future but 10" wheels are such a laugh!

this might possibly be the least efficient bike on endless sphere though hahaha I could be wrong.. I haven't done much testing but with the way I ride it i cant see more than 15-20km range

ZERONEST said:

I haven't done much testing but with the way I ride it i cant see more than 15-20km range

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Time for more battery then...

SlowCo said:

ZERONEST said:

I haven't done much testing but with the way I ride it i cant see more than 15-20km range

Click to expand...

Time for more battery then...

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Seriously! I could fit twice the battery i have under the frame and the motor would not notice the extra weight whatsoever, if i did double the battery it would only be slightly heavier than the bike with the original 4 stroke engine/fuel tank of fuel.

That said though I'm not likely to ride this bike long distances much anyway, and when it comes to riding in woods and small tight tracks 10-15km is a lot of laps to me! :lol:

Before batteries i also need a new charger, my 10a isn't cutting it haha, I knew it wouldn't, its all I had previously.

Am thinking of picking up one of these chargers as I prefer to remove the batteries and balance charge and inspect for damage each and every time, should charge my current pack in 2 hours which I'm fine with although 1 hour would be decent..

https://www.banggood.com/ISDT-T8-BattGo-1000W-30A-Smart-Battery-Balance-Charger-For-1-8S-Lipo-Battery-p-1191860.html?rmmds=search&cur_warehouse=UK

If anyone has any recommendations let me know!



Edit: has any seen/used one of these throttle boxes? which allows you to use the normal cable throttle, I cant find if its a hall or pot throttle but would love to be able to use something like this especially with the low price

https://www.aliexpress.com/item/32954909008.html?spm=a2g0s.9042311.0.0.37ab4c4diIEkju

Had a couple more test rides on this bike now, upped the controller amps to 150 and then realised how completely absurd this motor is for this tiny bike! now dropped it back to 100A and tempted to go further but its so much fun!

Received this throttle, And it works great! much better response than the other one I was using and is great that you can use a much sturdier cable operated throttle

Also got round to finish welding and painting the frame, swapped out the old chain roller for a softer skateboard wheel which i lathed down, this reduced the chain noise quite a bit, I also experimented with 12/13/14t front sprockets and settled on 13t as I hardly noticed any difference compared to 14t, however 12t made a LOT more noise, I was quite surprised..

View attachment 4
View attachment 3



Also printed some basic covers for the left over plugs and connectors




Now that the bulk of the bike is done I will soon start fabricating another battery frame mount for stainless steel as the current one is just a mock up, although I'm still struggling to find watertight containers in the correct size, here's what I'm using at the minute and it works great just a little ugly..



Got some riding clips from the first test ride, ignore the alarm, will get some better footage soon but it has been soppppping wet here in the uk lately, also dark so soon

https://www.instagram.com/p/B5KCogjHaDv/?utm_source=ig_web_copy_link

https://www.instagram.com/p/B5GN-bXnRaH/?utm_source=ig_web_copy_link

[youtube]jRfpKUButGQ[/youtube]

Finally a bit of riding footage from yesterday when there was a break from the rain
[youtube]g4D40K6ezFs[/youtube]

some big roosts from yesterday
[youtube]Y261XT8wYVA[/youtube]

Awesome project! Curious what the cable throttle converter is? Could you share the model? Thinking about doing a CRF50 myself. Looking at the QS 1000W 72V 428 with the EM50SP controller. Thanks

foxfrey said:

Curious what the cable throttle converter is? Could you share the model?

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https://www.aliexpress.com/item/4000768288652.html?spm=a2g0s.8937460.0.0.25912e0eftn2Py