Question About Hub Motor Dropouts

[Ohmy]

Hey everyone.

New here on the forum. I’m looking a motor mount for the motor kit from qs motor shown down below (no hyperlink) for a mini bike I’m trying to build. Where could I get one for it? I’ve been searching online for a bit and couldn’t find anything that met the specs I’m looking for. Vendor also sent me this diagram of the motor.

Any help would be appreciated. Thank you.

QS138 4000W V3 Mid-Drive Motor Controller Kits​

 

[Chalo]

If you can build a minibike, you can make a motor mount. The dimensions are in the drawing.

 

[Ohmy]

If you can build a minibike, you can make a motor mount. The dimensions are in the drawing.

I guess you’re right. I just couldn’t find a suitable mount online. But I’ll try my hand at making my own.

 

[offGridDownUnder]

But I’ll try my hand at making my own.

I made the motor mount for my trike out of 6mm flat plate in 5 pieces + 5mm plate for two small pieces which are then all welded together. I also cut an additional 5 plates that slot into the pieces to hold them securely into (almost) the correct positions. Some quality time with a square and straightedge and a small hammer puts them into alignment before starting a series of tack welds, and then full seam welds.

You can see the motor mount in shiny grey behind the seat of the near trike in this photo. I made early versions from mild steel with slightly thinner webs, and this one is 5083 Al with slightly broader webs, and less than half the weight.

Depending on your situation, it may even make sense to just make the plates involved, without bothering about much accuracy, and then assemble and weld them into place in the shop, as long as you can position and angle the motor accurately.

Note that laser cutting introduces heat and warps the plates. Water cutting appears not to cause that problem.

 

[Ohmy]

I made the motor mount for my trike out of 6mm flat plate in 5 pieces + 5mm plate for two small pieces which are then all welded together. I also cut an additional 5 plates that slot into the pieces to hold them securely into (almost) the correct positions. Some quality time with a square and straightedge and a small hammer puts them into alignment before starting a series of tack welds, and then full seam welds.

You can see the motor mount in shiny grey behind the seat of the near trike in this photo. I made early versions from mild steel with slightly thinner webs, and this one is 5083 Al with slightly broader webs, and less than half the weight.

Depending on your situation, it may even make sense to just make the plates involved, without bothering about much accuracy, and then assemble and weld them into place in the shop, as long as you can position and angle the motor accurately.

Note that laser cutting introduces heat and warps the plates. Water cutting appears not to cause that problem.

View attachment 371505

That looks fantastic. Thanks for the feedback.
I don’t have the space nor the money to procure the necessary tools to do what you’ve done, also I don’t know how to weld. Do you think could get away with bending sheet metal to suit my needs for a mount?

 

[offGridDownUnder]

I don’t know how to weld

Another option is to find someone that will for you. I did.

I can imagine a design that can be formed by bending. You then must fasten pieces in place. But it's all doable, even if the first version is for learning, as was mine.

 

[Ohmy]

Evening!

I’ve been on the fence about what motor I should get for the mini bike I am looking to build. The two options I have are either a mounted, mid-drive dc motor or a hub motor. However, I’m confused about the dropouts. The mini bike has 6.25”/158.75mm dropouts, however, I’m not sure what sort of hub motor would accommodate to these measurements. Some are below or above the 6.25” mark and I don’t know what would fit. I’ve attached some images below with measurements for reference and for an idea at what I’m looking at.

Any help would be appreciated.

Thank you in advance.

 

[qwerkus]

If the axle is long enough (looks like it on your drawing), it doesn't really matter that you have an exotic dropout width. You need at least 12mm protruding on both sides for the bolts. Beware that if you want to use disc brakes at lot of spacer / shims will be required for proper alignment!

 

[Ohmy]

If the axle is long enough (looks like it on your drawing), it doesn't really matter that you have an exotic dropout width. You need at least 12mm protruding on both sides for the bolts. Beware that if you want to use disc brakes at lot of spacer / shims will be required for proper alignment!

That’s pretty helpful, thank you. This is my first project so I have thousands of questions.

 

[ganzey]

the first motor you posted is a 12" Rim diameter, like for a small motorcycle, the second one you posted is an 11" TIRE diameter (ie 6 or 6.5" Wheel like a small scooter). i doubt you will want the first one since it will be way too big. and very heavy. or the second one due to it being too small. Something like a qs205 would probably be a good fit, and they have 150-155mm dropouts.

 

[ljbred08]

Can you post a picture of the minibike? That would help determine sizing as @ganzey was saying.

 

[Ohmy]

Can you post a picture of the minibike? That would help determine sizing as @ganzey was saying.

 

[SlowCo]

You will need to cut those drop outs open to be able to slide a hub motor axle in there. And drill holes to bolt torque arms on them.

 

[Ohmy]

You will need to cut those drop outs open to be able to slide a hub motor axle in there. And drill holes to bolt torque arms on them.

Yeah I figured I would have to. I don’t think it will be too difficult. I’ll make it work. Any idea how to install a disc brake in there, if possible?

 

[SlowCo]

A steel plate/bracket welded or bolted to the frame that mounts the caliper should work if you make it strong enough. And maybe get a controller capable of regen braking so the rear disk is only lightly needed.

 

[Ohmy]

A steel plate/bracket welded or bolted to the frame that mounts the caliper should work if you make it strong enough.

Ok cool. I’ll look up how to do this. Thank you

 

[SlowCo]

And maybe get a controller capable of regen braking so the rear disk is only lightly needed.

 

[Ohmy]

And maybe get a controller capable of regen braking so the rear disk is only lightly needed.

So regen braking limits the need for the brakes? Does it sort of slow down on its own?

 

[amberwolf]

FWIW, that frame doesn't look like those should be dropouts for an axle (it would be a very short bike, with the seat over or even behind the rear axle, if so, making it excessively wheelie-prone).

Plenty of mini bikes I see in image searches *are* that short, but you might consider a different build type depending on what you want it to do for you and under what conditions.

It looks like that would better be used as the pivot point for a swingarm, whose suspension springs would then mount between that swingarm (not present) and the bar across the top of the back end of the frame, or to another frame component that mounts there that is also not present.

 

[amberwolf]

Ok cool. I’ll look up how to do this. Thank you

There is a thread here called The Torque Arm Picture Thread that has a number of examples.

 

[ljbred08]

So regen braking limits the need for the brakes? Does it sort of slow down on its own?

Yes, regen braking electronically slows the motor by using it as a generator to charge the battery. It can be strong enough to almost entirely replace mechanical brakes (the more charging current your battery can take, the stronger you can set regen.) On my minibike, I haven't yet bothered to weld a mount for a disk brake because regen works so well. I should though, because if the controller ever fails while riding I am going to want a mechanical backup!

Based on the pictures, your minibike is small enough that an 11" total diameter scooter motor should work. That's what I have on mine; the nice thing about those is that they are readily available as parts from electric scooters on eBay. Also way faster shipping than getting it from China, and far cheaper! Mine was $110 for a 3000w motor.

Current example listings:

• Electric Bike Hub Motor 60V 4000W for Electric Motorcycle Scooter 6" x 3-1/4" | eBay
• Vsett 11+ Front Electric Motor
• Vsett 11+ Rear Electric Motor
• VARLA SCOOTER Eagle One V2.0/V3.0 Motor with tire ONLY
• Blade GT 11" Hub Wheel Motor 1500 - 2500W 60V Electric Scooter Motor Tubeless

Based on measurements of the motors I have and my dropouts, your 6.25" should be fine. Mine are around 6" and a few washers can fill the gap.

FWIW, that frame doesn't look like those should be dropouts for an axle (it would be a very short bike, with the seat over or even behind the rear axle, if so, making it excessively wheelie-prone).
. . . It looks like that would better be used as the pivot point for a swingarm, whose suspension springs would then mount between that swingarm (not present) and the bar across the top of the back end of the frame, or to another frame component that mounts there that is also not present.

If you want to do any offroad riding this would be a great idea. I plan to eventually do this on mine.

 

[Ohmy]

Yes, regen braking electronically slows the motor by using it as a generator to charge the battery. It can be strong enough to almost entirely replace mechanical brakes (the more charging current your battery can take, the stronger you can set regen.) On my minibike, I haven't yet bothered to weld a mount for a disk brake because regen works so well. I should though, because if the controller ever fails while riding I am going to want a mechanical backup!

Based on the pictures, your minibike is small enough that an 11" total diameter scooter motor should work. That's what I have on mine; the nice thing about those is that they are readily available as parts from electric scooters on eBay. Also way faster shipping than getting it from China, and far cheaper! Mine was $110 for a 3000w motor.

Current example listings:

• Electric Bike Hub Motor 60V 4000W for Electric Motorcycle Scooter 6" x 3-1/4" | eBay
• Vsett 11+ Front Electric Motor
• Vsett 11+ Rear Electric Motor
• VARLA SCOOTER Eagle One V2.0/V3.0 Motor with tire ONLY
• Blade GT 11" Hub Wheel Motor 1500 - 2500W 60V Electric Scooter Motor Tubeless

Based on measurements of the motors I have and my dropouts, your 6.25" should be fine. Mine are around 6" and a few washers can fill the gap.


If you want to do any offroad riding this would be a great idea. I plan to eventually do this on mine.

Yeah I may do regen braking. It’s an idea pitched to me in an earlier comment, do you think a regular disc or rim brake in the front should be fine?
Also I’ve already ordered my motor from Lonnyo Motors. It should be here within a few weeks I think.

 

[ZeroEm]

Yeah I may do regen braking. It’s an idea pitched to me in an earlier comment, do you think a regular disc or rim brake in the front should be fine?
Also I’ve already ordered my motor from Lonnyo Motors. It should be here within a few weeks I think.

Ride a trike and have dual brakes up front and no rear brake mount in the rear, just regen! 9000 miles have not changed my front disc brake pads yet. May need to in a few years.

 

[Ohmy]

Ride a trike and have dual brakes up front and no rear brake mount in the rear, just regen! 9000 miles have not changed my front disc brake pads yet. May need to in a few years.

That’s incredible!