Please advise me on a homemade motorcycle

I’m convering this too-small-for-me bike into a mid drive with these ingredients:
https://imgur.com/gallery/BhQWNKC

Vesc6
https://trampaboards.com/vesc-6-mkiv-in-cnc-t6-silicone-sealed-aluminium-box-with-genuine-xt90-connectors--vedder-electronic-speed-controller-trampa-special-p-27536.html
(Maybe should go bigger)

https://www.altitudehobbies.com/collections/leopard-airplane-motors/products/leopard-8072-11t-160kv-brushless-airplane-motor
(Maybe I should go bigger. Have to figure the gear ratio then kv)

(100) 26650 A123 green iron cells

https://lunacycle.com/luna-sur-ron-belt-drive-upgrade-kit/








1)
I plan to fill the triangle with a potted block that will include the cells, a motor mount plate, and a shaft on the same plane as the plate to add two pulleys for a double gear reduction drive
Kinda like this
https://lunacycle.com/luna-wolf-v2-52v-battery-pack/
but bigger and will include the motor mount, extra shaft, and some mounting rods I’ll thread so it will attach to the seat and downtube with some plastic plates I’d cast. The interface between the the block and down and seat tube..id add a couple subsequently softer layers to the block I’d paint on.


2)
I figured I could do a single speed chain drive on the right side of the bike as usual and the left side of the bike would have the two belts with one attaching to the rear wheel brake rotor mount. Not thrilled on modifying to attach to the brake rotor mount but seems ok and will figure a one way clutch on the extra shaft


3)
I’m also adding mounting rods to the casting/potting I can thread and attach to compete triangle to the frame by plastic plates I’d cast..one for four bolts attaching to the seat tube and two plates totaling 8 bolts for attaching to the downtube.

Hummina Shadeeba said:

https://www.altitudehobbies.com/collections/leopard-airplane-motors/products/leopard-8072-11t-160kv-brushless-airplane-motor
(Maybe I should go bigger. Have to figure the gear ratio then kv)

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I'm just guessing this relates to drive via propeller, wonder how that would relate to a bicycle type of load. And how do you know how to match gearing to the motor RPM.

altitudehobbies said:

● Max Pull: 15.5kg

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It perplexes me why you'd use a 160kV motor to run a bike at 400-500 wheel RPM. The extreme amount of reduction required seems needlessly complicated and lossy, especially if it's belts.

Balmorhea said:

It perplexes me why you'd use a 160kV motor to run a bike at 400-500 wheel RPM. The extreme amount of reduction required seems needlessly complicated and lossy, especially if it's belts.

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I didn’t do the math but assuming a 26” wheel does 400-500 rpm, for an ideally 40mph max speed,..I’m feeling like adding an extra gear isn’t that complicated: two fixed together pulleys with a sprag gear on a shaft that’s perpendicular to the motor mount plate. The motor mount plate is easy and just would need an appropriately sized threaded hole in it to fix an axle after the casting.


My assumption is there’s a lot more potential in a small motor if you spin it fast. More torque at the wheel and better efficiency, no? What that speed would be I guess would vary on the load and copper loss amount. I understood an equal amount of iron and copper loses would amount to most power and best efficiency by weight or volume of motor. Was just trying to compare using the grin motor simulator. I’d like to see the results because I think a lot of motors could be smaller if they were capable of being geared high enough. What’s the sur Ron gearing after both it’s stages?


I want to match the gearing and kv so I can spin the motor so fast the iron losses start to creep over the copper losses. That’s the most efficient way to run it no?

Imagine i have a .2mm lam motor with iron losses as shown here:
https://cdn.shopify.com/s/files/1/0076/7098/8859/files/8072_new_chart.pdf?159
Why not rewind these motors even higher kv and add as big a gear as I can. 30:1. 40:1. At what point is it detrimental? It should be figureable based on this chart assuming they hit the max speed when using the stated voltage, which makes sense that’s what it is. It will be less efficient running at top speed but on the way up to that speed and with constant hard accelerations it seems more appropriate to gear the bejesus out of these low iron loss motors. The whole speed x torque = power thing. They’re interchangeable with gearing but if u don’t get the motor up to high speed it’s not gunna get it

Losses to belts and a sprag gear will be very low I think.


im on the grin simulator setting up a comparison of geared x10 vs x1 and with the adjusted kv to match the same speed. only obstacle is i cant figure what would be an appropriate resistance for a motor with 10x higher kv.

Hummina Shadeeba said:

My assumption is there’s a lot more potential in a small motor if you spin it fast. More torque at the wheel and better efficiency, no?

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Well, you do start off with proportionally less torque. And then you take a significant efficiency hit with each stage of reduction. So at best, you’re looking at comparable overall efficiency and torque. Power is just torque times RPM, you only have so much power to work with, and you throw a percentage of that amount away with each reduction stage. Multiple reductions means compounded losses. Model airplane motors have great power/weight ratios, but their required reduction stages add weight and subtract power.

But besides that, you incur just a whole lot of noise, wear, maintenance, points of failure, and pinch hazards when you have to stack up reduction stages. You get untangled from all that when you start with a low kV motor.

Balmorhea said:

Hummina Shadeeba said:

My assumption is there’s a lot more potential in a small motor if you spin it fast. More torque at the wheel and better efficiency, no?

Click to expand...

Well, you do start off with proportionally less torque. And then you take a significant efficiency hit with each stage of reduction. So at best, you’re looking at comparable overall efficiency and torque. Power is just torque times RPM, you only have so much power to work with, and you throw a percentage of that amount away with each reduction stage. Multiple reductions means compounded losses. Model airplane motors have great power/weight ratios, but their required reduction stages add weight and subtract power.

But besides that, you incur just a whole lot of noise, wear, maintenance, points of failure, and pinch hazards when you have to stack up reduction stages. You get untangled from all that when you start with a low kV motor.

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I’ll get the grin simulator done as soon as I can figure the simple math telling the resistance of 100kv vs 1000kv. I’ll plug that in and there’s a simple gearing option and put that at 10x. Great program but I still need someone skilled with it to give me like half an hour of answers

But the gearing option on the grin simulator doesn’t seem to have any losses or maybe it does take them into account. I thought a good thin carbon belt like the sur Ron is less resistance than a chain, and a chain is pretty good with a good chain line and big cogs

Maybe it’s a fundamental misunderstanding on my part but can’t I transform that speed with the gearing into torque which would otherwise only be obtained through copper losses.

What percentage of ur motor losses are going to copper, iron, or gearing? I’m guessing unless it’s a mid drive with some huge gearing it’s largely copper losses.

Maybe I should try building a bike with my 32k rpm Dremel instead of carving dropouts with it.

MadRhino said:

Maybe I should try building a bike with my 32k rpm Dremel instead of carving dropouts with it.

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What gearing u chose and why?

I’m looking at jackshafts. Thinking how to incorporate it into the potting. It should be easy enough.

Hummina Shadeeba said:

I’m looking at jackshafts. Thinking how to incorporate it into the potting. It should be easy enough. doing it with belts is more work maybe but worth it.

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Belt drives have larger efficiency losses than chains because of increased surface friction, hysteresis in the rubber, and mandatory high tension which causes more friction in the rotating parts. Manufacturers love to cite efficiency numbers that reflect losses in the belt only, not the whole system. If alignment isn't perfect (shafts parallel, pulleys in exactly the same plane), losses can get much higher than the baseline.

In general, I wouldn't recommend spinning a propeller motor any faster than the manufacturer is recommending one spins a propeller with it. That's what they're designing and testing these motors to do. User thud found that core losses in 80xx outrunners start to become substantial past 8k rpm.

I also wouldn't recommend spinning a motor any faster than would require two stages of gearing. Personally, I'm done with two stages and am looking at one stage only. More stages is a pain and too complicated. It's much easier to buy a bigger motor. You can make torque with copper losses in an overheating small motor, gearing losses and a small motor, or efficiently with a big motor. I like efficient with a big motor.

Note you can also spend weight and money on cooling and extra battery for an inefficient small motor, extra reduction stages for a small motor, or on a big motor. I prefer the big motor.

Hub motors are the best for simplicity and reliability. For some of us, their weight is prohibitively large. Since the motor in the thread below never got built,
https://endless-sphere.com/forums/viewtopic.php?f=30&t=57371&hilit=ultimate+lightweight
we settle for single reduction stages to the rear wheel. My build is still in progress. See madin88's build for inspiration.
https://endless-sphere.com/forums/viewtopic.php?f=30&t=91144&hilit=8057
Also see the LMX64 for how hard chainlines are with mid drives when you don't mount the motor in the rear triangle. The chainstays and BB will probably be in the way. If you tie into the existing pedal drivetrain, then you get to pick two of high power, durability, and pedalability.

https://cdn.shopify.com/s/files/1/0076/7098/8859/files/leopard_full_motor_chart.pdf?137

Balmorhea said:

It perplexes me why you'd use a 160kV motor to run a bike at 400-500 wheel RPM.

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You're killing me, offering the chance to respond to that. But I'll resist.

8-10 years ago those motors were all the rage on ES. I have as many as 3 dozen I never sorted a use for, after reading about all the fires others had. Keep that in mind.

The pdf says that if you use the "1810" version (??) 42 volts will give you 5,800 RPM, 1050w, 25a. So let's go to the opposite end and see the results you want. The 26" wheel at 40mph you would expect to turn 520 times a minute. So a 1:11 gear ratio from the motor to the wheel would provide the proper speed. Dang, meaning a 11t on the motor and a what? 120t on the wheel? How about a 9t on the motor and a 100t on the wheel? Or of course comparable pulleys for a belt drive. Decide for yourself it that's outlandish. I don't think you need that 30-40 reduction. But that's between 11-12s, the motor says you can go 6-13s, so far so good. Keep in mind all those people years ago had theirs within the good range and they were still fire hazards. The conclusion was not enough metal in the motors to dissipate the heat. Remember these are intended to turn propellers as fast as possible, which also provides air circulation to cool it. Don't want it turning so fast for a bike.

But the only lower KV Leopard offers is there 6362 105KV. The "2210" claims 45v, 6600rpm, 990w 22a. Just for comparison. 40v would be under 6,000 rpm, etc.

I wanted to mount something like that on a 20" X-Games bike but there is NOWHERE to put anything on those.

12mm shaft, sounds tough enough.

MadRhino said:

Maybe I should try building a bike with my 32k rpm Dremel instead of carving dropouts with it.

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Yeah, you should. I'm dying to see it. Will this be friction drive? Am I screwing something up thinking that would go 48mph? (Theoretically.)

Dauntless said:

MadRhino said:

Maybe I should try building a bike with my 32k rpm Dremel instead of carving dropouts with it.

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Yeah, you should. I'm dying to see it. Will this be friction drive? Am I screwing something up thinking that would go 48mph? (Theoretically.)

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My poor Dremel had seen enough friction already.
If I would use my Dremel for a motor, it should spin a pump for some hydraulic drive. No more chain wear, use a hose. 3 mph top speed, lots of torque, freaking noise. 8)

A nice adapter:
https://www.ebay.com/itm/New-6-Bolts-Disc-Brake-Adapter-5-8-THICK-Spacer-Threaded-Hub-Freewheel-Aluminum/312146302938?hash=item48ad5e97da:g:HnoAAOSwkkNbDa8v



https://www.bikeradar.com/news/chain-or-belt-drive-which-is-faster/?image=3&type=gallery&gallery=1

At the end it tells how belts can be more efficient with a chain tensioner holding the belt close to the cog so it doesn’t slip and then don’t need the substantial preload on the belt which is its reason for it’s in efficiency. I imagine efficiency also depends on the cog size too with the smaller cogs making it less efficient


Thanks for the relevant input. I’d be doing a two stage gear reduction with a jack shaft. Still think I’ll do it! I will have the motor on a large aluminum plate to keep it cooler at least. Surprised to hear these were bursting into flames. Maybe I’ll add another layer of winding varnish

Dauntless said:

https://cdn.shopify.com/s/files/1/

8-10 years ago those motors were all the rage on ES. I have as many as 3 dozen I never sorted a use for, after reading about all the fires others had. Keep that in mind.

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I’ll buy some if you want to get rid of them. I’ll buy all for the right price.

I think I can get close to 11:1 gearing with the jack shaft and a giant gear on the first stage. The second stage being limited to what I can attach to a bike rear wheel. There’s a lot more teeth options for the front cog(chainring). Maybe they can be drilled to mount to the back but seems unlikely.

There is a problem with most propeller motors: they are not made to stand lateral tension on the axle. Small bearings (if any), weak housings... they are designed to work in a straight line. They are easy to wear and overheat with lateral tension.

I’m still on it! Getting feedback from people who make drag racing cars is nice.


Tell me what you think of the plan at this point:

Single gear reduction. The jack shaft would need adjustability to tension the rear belt and it’s too much complication

I’m going to use more standard pulleys as the gates carbon center track ratio is so limited. I’ll somehow mount a huge pulley to the wheel’s disk brake mounting holes and add a one-way bearing, likely on the motor axle. gunna go for a giant pulley in back and smallest in front.
I think with the motor positioned at the center edge of the front triangle the belt can slip through to rear triangle no problem. It’s a bit of an eyesore the giant cog in back..o well

Why not buy Dauntless' motors, and use them as intended, with propellers?

donn said:

Why not buy Dauntless' motors, and use them as intended, with propellers?

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if I can string 6 together and make a plane I’d fly in otherwise it’s gunna go in the bike. Judging by the amount of people running this style of motor with a tensioned belt in the eskate world it seems worth a shot.

donn said:

Why not buy Dauntless' motors, and use them as intended, with propellers?

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Such fun thoughts, no matter how dangerous it is.

https://www.instructables.com/id/Electric-Propeller-Bike/

Someone was mentioning the bearing problems and that it needs a away to bear the load. I forget the name, but there's a type of bearing I'd use as a mount on either side. It looks like a bell curve, you screw either side to whatever with the shaft through the bearing, there's one on each side of the motor, THAT is the strength. I have outrunners, so there's a base to be secured but the bearing mounts would be in charge.

Your motor has the shaft out on both sides, you can put those bearings right on there.

The exact way to mount these, plus of course my accident, is what stands in the way of using them. There has to be a solid surface on BOTH sides, no flex, etc. Or even a whole housing, if you want to go to the trouble.

https://discourse.odriverobotics.com/t/useful-cad-resources/257/14



I have 12 as pictured, plus 6 8085 with a 250kv I conclude are useless for an electric bike because of the 12,000rpm it would have to turn to keep from burning up. I can think of machine shop solutions to putting one on that old 20" XBike, but I don't have a machine shop. After that I think I also have some 6364 and smaller, not so exciting but I was going to build a board and a few other things.

But the higher the KV, the riskier. The lower the voltage, the lower the RPM, the higher the amperage, the higher the heat. These lightweight outrunners are not tolerant. So on a 26" wheel you want to let that one motor run at 12000rpm while the wheel is turning 600 times a minute or less. That's quite the reduction. In another thread Amberwolf is telling a guy he doesn't want two motors if they're not going to both be running, but maybe with the little RC motors you could have the bigger 48v for speed and the smaller 24v to go considerably slower. Doesn't the Volt do something like that? How you manage which one is running I can't guess.

One big idea I had for them it helps to know 'The Boy Mechanic.' So to build one of the pedal cars you can use one of these small motors that'll tuck away somewhere and go unnoticed. I have some steep hills and I just pedal up them as people watch, so they want to try it. I shut the motor off so they can't accidentally hit the throttle and darn, seems they aren't nearly in such good shape as I am, eh? Maybe even I have some celphone remote so I can suddenly make the throttle go and then stop. Boy, would they be perplexed. Picture the YouTube videos.

the motor in a box is interesting but given how many people run outrunners On skateboards with no backend support why is it needed? Was it the cause of ur accident?! I figure a bigger motor will have bigger bearings and I’ll be ok maybe replace the bearings. Maybe go for the 150cc hobbyking motor or some of the others there. What other source is good or a good motor?


Despite saying it’s a bad idea I’m undeterred and still obsessed with both figuring whats the ideal rpm of the motor (based on its iron losses vs copper), and I want to make the most efficient belt setup with a jack shaft possible. I read if u add belt tensioners and loosen the belt as long as it doesn’t skip its good and most efficient. I believe better than a chain. Close enough. So all off the shelf parts. So for the first gear reduction stage coming off the motor I need a monster cog. On the hunt for the monster cog.


a jack shaft made that goes through a potted battery is slick. Gunna look like a giant clock. If such a cog is possible. Adding the jack shaft...maybe it wouldn’t need to be adjustable and the tensioner wheel on a spring could be tightened and would be adequate. I’ll ask. Hell of a lot easier

@dauntless if u have those motors it seems only a couple kv in stock and maybe would have to rewind anyway. I’ll rewind to match whatever is the biggest cog n gear ratio I can find is how it’s likely to end up. But maybe there’s another motor a bit bigger

Hummina Shadeeba said:

Hum the motor in a box is interesting but given how many people run outrunners On skateboards with no backend support why now? Was it the cause of ur accident?!

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The issue specific to what I'm talking about is to have a bearing at each end. Same as having the motor inbetween these sides in the pic and each side has a bearing. If they were mounted to a skateboard with the two sides detached and the board flexed between them, that would want to bend the shaft, or more likely just damage one or both bearings. The point is to make it not flex. If you wanted just one bearing the main bearing would be between the pulley you put on and the housing, that would help with abuse on the motor itself but I think it would be better to have one on both sides.



I'm not familiar with there being bearings you could just press into the housing, but if so you don't mount the bearing itself to the frame and you just let the housing handle it. I don't know that the stateboarders use any bearings, so they wouldn't be worrying about any of this. The housing is to keep the bearings and the shaft rigid to one another.

Unrelated to the freak accident a few years ago, wasn't supposed to be hurt as bad as I was but it put a crimp on things for awhile, I'm finally riding the bike everyday again and I don't get any more of the cramps in the left arm that were making me drop things. Bending over and crouching, the final frontier, but there's been great progress even there. So I think I can work on stuff again.

https://imgur.com/gallery/EXLRcsO





https://www.profileracing.com/product/freewheel-hub-drive-bi-hub/




And I have some disk brake rotor hole to freewheel mount adapter.

And some bare freewheels with just holes instead of teeth for mounting pulleys.



But first I need to figure and confirm what torque and speed the fat 26”wheel will do (with 12s) before I know what belt is strong enough and what pulleys to get. The speed is easy enough to figure but what torque? Roughly.

https://www.altitudehobbies.com/products/leopard-8072-11t-160kv-brushless-airplane-motor


But my math shows the 160kv and 10:1 and the fat 26” tire and 12a getting 15mph top speed. the 260kv is available and then I could do maybe 8:1 gearing for 40mph but I haven’t bothered with figuring the speed details because it’s brought up the more important original question:
What speed is the most efficient to spin given the no-load losses.. and looking at this chart it’s confusing and the no load losses should be increasing with voltage:
https://cdn.shopify.com/s/files/1/0076/7098/8859/files/8072_new_chart.pdf?159

Regardless the no load losses are a pittance. They make me think I should be spinning the motor wound to something like 800kv at least to get the most out of the motor. The pdf shows top speed at 11000 rpm and under three amps iron losses. Ideally I should have half my losses iron no? Instead of a bigger motor why not just spin what you got faster?


Just bought 2 of their 280kv leopard motors. If u have anything similar u want to possibly sell please speak up. These seem a nice size and maybe I’ll rewind one for 400kv

Hummina Shadeeba said:

But my math shows the 160kv and 10:1 and the fat 26” tire and 12a getting 15mph top speed.

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Huh? Is that at 12v? My understanding is that at 15mph the 26" spins 195rpm. 10:1 means the motor at 1,950rpm. What are you figuring differently?

Hold onto that question. I moved on to another bike within 24 hours.

https://imgur.com/a/YrLViU3

That other bike has 14mm diameter dropouts I realized. I change my mind often and embracing it these days. I should probably be flipping bikes anyway and bike stores are out of bikes around the whole country if not the whole world.

I don’t like adapters. So this new bike can take the dual hub above worst case scenario and thats easy. But I’d likely break the gates centertrack bike intended belts I think so will go for freewheels that are designed to be adaptable, a step above an after-the-fact adapter, which I don’t like to start with.


And will put a disk brake squishy fork n 24”wheel on front.

The speed I’ll go on 12s and the reduction I’ll need to get to 40mph I’ll be figuring and posting my answer here:
https://itstillruns.com/calculate-wheel-speed-tire-diameter-7445086.html
http://www.bikecalc.com/wheel_size_math

24" wheel with 2.2 tire is about 2050mm, which is 6.72 feet circumference.
(Feet per mile)5280/6.72(tire circumference) = 785.7( revolutions per mile)

280kv x 12=3360(max rp.........and heres my mistake multiplying by cells instead of volts! as seems seen. and i continue the math with the 160kv motor instead


160kv x 50v= 8000 (max rpm with 50v)
8000/785.7=...10.8(miles per minute)...x60...610 (mph)

o shit.

with 11s at 46v i get a top speed of 562 miles per hour. ...so 14:1 gear ratio with the 160kv motor and 11s gets me to 40mph

with 10s at 42v....513rpm 12:1 gear ratio i get 42mph.

The reality being maybe it will hit 15% below the no-load speed so on 11s and 12:1 that would be 42mph and going for that

Who knows math? Before can go further I need to figure what torque is produced on the belts if I run a 160kv motor with an 11:1 gear ratio and 80 amps (24” wheel but don’t think it matters) assumIng a 3.3:1 ratio off the motor to the jackshaft and again 3.3:1 to the rear wheel? What if it’s 4:1 off the motor and 2.5:1 to the wheel from the jackshaft?


Wait till u see this thing. Far from done but it’s gunna be spectacularly great or a spectacular disaster with batteries and motor mount plate potted together and bolted to the downtube. I have a fear I should bolt it to the seat tube too but hoping for the best and will be many bolts going the full length of the downtube.

https://imgur.com/a/45YY0SH

The bigger hole is for the jackshaft

Just a sketch and not done. What you think?

https://www.sdp-si.com/D265/PDF/D265T146.pdf