20 inch full suspension street build (now with twin motors)

[recumpence]

I have been doing a bit of experimenting.

Today I removed one motor to compare efficiency. Oddly enough, the efficiency is nearly identical to the twin motor setup. That seems strange to me.

Also, I have been doing more and more CA programming and I am sneaking up on the "Perfect" program settings for this bike.

Matt

 

[pendragon8000]

Oddly enough, the efficiency is nearly identical to the twin motor setup.

would this be that the motors have a set efficiency. and having 2 of them they are just as efficient but there's twice as much power in and out. or is this power consumption cruising at a set speed?

 

[DanGT86]

I have been doing a bit of experimenting.

Today I removed one motor to compare efficiency. Oddly enough, the efficiency is nearly identical to the twin motor setup. That seems strange to me.

Matt

That does seem strange as the demand on that one motor per given power output should have doubled. Maybe the slight efficiency loss from running the single motor a little harder was canceled out by the gains from having one less pulley and fan creating drag. I would suspect at those high rpms on the primary reduction a little belt friction goes a long way towards the efficiency.

On a long ride at high power the extra thermal mass of 2 motors would help with efficiency as the motors get hotter correct? That is of course if you could resist running it twice as hard with 2 motors. Doesn't look like the type of bike you build to go easy on.

Interesting stuff. Glad you are always testing out so many different setups.

 

[Thud]

Seems perfectly logical...
2 motors drawing a set amount of current sharing the load at a given speed.....

1 motor drawing the same amount of current as two motors to do the same amount of work.

with variables in reduction losses, additional load losses with the single motor...it would be very nearly the same power consumption.

where you expect to see dramatic variance will be max acceleration rates & efficacy hits at the extreme ends of the operational envelope

 

[recumpence]

Good call, Thud. I concur.

Matt

 

[recumpence]

https://youtu.be/SiiNORLzA18

Sorry it took so long to post this. This is a video I made immediately after setting up the Delta/Wye switching on the bike. This is the original twin motor system. The bike, now, has three motors (but is not 100% up and running with three motors yet).

Enjoy the video!

Matt

 

[Stielz]

Three motors Cant wait to see how that beast goes!

 

[recumpence]

You and me both......

 

[recumpence]

Hey Guys,

It's been a while since the last update on this bike.

A couple months ago I installed three motors. It was explosively powerful, for sure. However, in the interest of experimentation I decided to go down to a single motor for grins. I have to tell you, this bike is a joy to ride even with one motor. It is geared for 40 mph hot off the charger (38mph for most of the charge). I love it! With this gearing, it will pull wheelies with hard throttle at any speed under 10mph. But, they are plenty controllable and it never catches me off guard. It is lighter, more efficient, and much easier to ride.

I think I will keep it like this for a while.

Matt

 

[DanGT86]

Cool, thanks for doing that research. Many times the insanity to push the limits of power whith the maturity to turn it down are not traits found together in one brain. Very cool exploration of both ends of the spectrum.

Guess it is a bit of a waste to design a two wheeled frame just to spend all your time on the rear one.

 

[MitchJi]

It is geared for 40 mph hot off the charger (38mph for most of the charge). I love it! With this gearing, it will pull wheelies with hard throttle at any speed under 10mph. But, they are plenty controllable and it never catches me off guard. It is lighter, more efficient, and much easier to ride.

Cool, thanks for doing that research. Many times the insanity to push the limits of power with the maturity to turn it down are not traits found together in one brain. Very cool exploration of both ends of the spectrum.

Both ends of the spectrum :lol:

 

[LightningRods]

Very fun, creative, over the top build. I would expect nothing less from you Matt.

 

[recumpence]

Just a quick update.

I have been riding and riding and riding this thing. I LOVE this bike! I have an LED headlight on it now, so I ride it at every opportunity.

No problems yet.

Matt

 

[DanGT86]

This is more of a motor theory question but given your background with multiple motors I thought you might have some insight. I'm curious, when you set up twin motors that are fixed to each other via timing belts, do you make any effort to time the phases? I can imagine there could be a difference in the torque by timing the motors so the phases are pulsed in sync vs alternating. Given the high rpm though, I'm not sure it would be perceptible. I'm picturing it being the difference between 6 phases vs 3 double strong phases. Much like the way a single cylinder 600cc motorcycle feels totally different then a 600cc inline 4cyl.

My thought process is likely a gross oversimplification of what is actually going on inside a motor but I thought you may have experimented with it.

 

[recumpence]

With two motors and two controllers, the system automatically self balances. Timing would only be an issue if you wanted to run two motors with one controller.

Matt

 

[DanGT86]

I get that the power would balance automatically since the current can vary. I guess i'm wondering more about having the stator poles alignment with the magnets identical between both motors vs staggered. Once the belt is intalled that relationship cant change. Seems like it could change the peak power and torque points by a few rpm or maybe have an effect on the current available to each controller due to tadem "firing" of the phases.

 

[recumpence]

I get that the power would balance automatically since the current can vary. I guess i'm wondering more about having the stator poles alignment with the magnets identical between both motors vs staggered. Once the belt is intalled that relationship cant change. Seems like it could change the peak power and torque points by a few rpm or maybe have an effect on the current available to each controller due to tadem "firing" of the phases.

I've never noticed a difference no matter how they are timed.

Matt

 

[recumpence]

Hey Guys,

With the Raptor sold, I was looking at possibly building another twin motor dirt bike similar to the Raptor, but a touch lighter, and a touch smaller, with twin 3215 motors instead of twin 3220s. After some thought I realized that this 20 inch bike in this thread would be a very good platform to convert. So, I wanted your input. What I am looking to do is go back to twin motors, install 24 inch wheels (I prefer 24s on off-road bikes), and fabricated a motor cover. This would be 1/10 the amount of work versus building a new bike (not to mention the cost savings). Besides, I never ride this bike anymore now that I have my Mountaincycle.

What are your thoughts?

Matt

 

[ScooterMan101]

With the Abundance of 26 inch Full Suspension Bikes available, used and old stock in bike shops, 26 inch would be the way to go.

Unless you want yourself to be the one to ride such a 2 motor system.

 

[recumpence]

With the Abundance of 26 inch Full Suspension Bikes available, used and old stock in bike shops, 26 inch would be the way to go.

Unless you want yourself to be the one to ride such a 2 motor system.

Ahh, yes, this is a bike for me personally. I love 24 inch wheels.

 

[motomech]

I have a 2WD based on a mountain bike that had 26" wheels, that has been converted to 24" wheels;



I had to install a crankset w/ shorter crank arms because of pedal strikes while cornering. Other than that, it has worked out well.

 

[DanGT86]

Hey Guys,

With the Raptor sold, I was looking at possibly building another twin motor dirt bike similar to the Raptor, but a touch lighter, and a touch smaller, with twin 3215 motors instead of twin 3220s. After some thought I realized that this 20 inch bike in this thread would be a very good platform to convert. So, I wanted your input. What I am looking to do is go back to twin motors, install 24 inch wheels (I prefer 24s on off-road bikes), and fabricated a motor cover. This would be 1/10 the amount of work versus building a new bike (not to mention the cost savings). Besides, I never ride this bike anymore now that I have my Mountaincycle.

What are your thoughts?

Matt

The first thing that comes to mind would be the frame geometry based on the changes you made. That being said you would be the guy to ask about it since you designed and built it. Is there going to be adequate ground clearance for your intended use? Didn't you reduce the total suspension travel for on-road use? Sometimes working with what you have seems cheaper until you end up changing every single part. I have fallen into that trap before. That bike is a bit of an exception to the normal rule because of the bolt on head tube and seat bracket. I can't imagine you wouldn't be able to set it up any way you needed.

I love 24" wheels. I'm 6' tall so I like the room that large frames have but prefer small wheels. The 26" and larger just feel clumsy like I'm on stilts. Add in the monster torque your bikes put out and an the shorter spoke length of smaller wheels has to really tighten the feel of everything. I am always frustrated by the lack of tire, rim, and tube choices in 24" though. I just bent my Alex DX32 24" 36 hole rim and apparently its the last one on earth so now I have to buy new spokes if I want to keep the hub motor.

I am surprised that you would go dual 3215. It seems like there would be some overlap where a single 3220 with a fan would be more efficient in terms of weight cost and packaging at about the same power as dual 3215s. What would lead you to the dual 3215s? I'm asking out of curiosity not as a suggestion.

Before you take it apart you should bring it down to Saint Louis for our 1/5th mile oval track ebike race on May 27th. Sprocket for 55-60mph and it would be about perfect.

 

[recumpence]

Hey Guys,

With the Raptor sold, I was looking at possibly building another twin motor dirt bike similar to the Raptor, but a touch lighter, and a touch smaller, with twin 3215 motors instead of twin 3220s. After some thought I realized that this 20 inch bike in this thread would be a very good platform to convert. So, I wanted your input. What I am looking to do is go back to twin motors, install 24 inch wheels (I prefer 24s on off-road bikes), and fabricated a motor cover. This would be 1/10 the amount of work versus building a new bike (not to mention the cost savings). Besides, I never ride this bike anymore now that I have my Mountaincycle.

What are your thoughts?

Matt

The first thing that comes to mind would be the frame geometry based on the changes you made. That being said you would be the guy to ask about it since you designed and built it. Is there going to be adequate ground clearance for your intended use? Didn't you reduce the total suspension travel for on-road use? Sometimes working with what you have seems cheaper until you end up changing every single part. I have fallen into that trap before. That bike is a bit of an exception to the normal rule because of the bolt on head tube and seat bracket. I can't imagine you wouldn't be able to set it up any way you needed.

I love 24" wheels. I'm 6' tall so I like the room that large frames have but prefer small wheels. The 26" and larger just feel clumsy like I'm on stilts. Add in the monster torque your bikes put out and an the shorter spoke length of smaller wheels has to really tighten the feel of everything. I am always frustrated by the lack of tire, rim, and tube choices in 24" though. I just bent my Alex DX32 24" 36 hole rim and apparently its the last one on earth so now I have to buy new spokes if I want to keep the hub motor.

I am surprised that you would go dual 3215. It seems like there would be some overlap where a single 3220 with a fan would be more efficient in terms of weight cost and packaging at about the same power as dual 3215s. What would lead you to the dual 3215s? I'm asking out of curiosity not as a suggestion.

Before you take it apart you should bring it down to Saint Louis for our 1/5th mile oval track ebike race on May 27th. Sprocket for 55-60mph and it would be about perfect.

Thanks for the input. Yes, it is easy to change the geometry for larger wheels and longer travel. No problem there.

The reason for dual 3215s is lessening the torque a touch over twin 3220s, but also to ease the load on the controllers. One controller with a crazy high kv 3220 is super hard on the controller.

I have been invited to the race. I do not think I can get away from my business though.

Matt

 

[DanGT86]

Had not thought about it from the controller perspective on the 3215s. That makes a lot of sense.

I'm glad you heard about the race. Last year we were all racing hub motors. It would have been cool to see you represent the mid-drives on the track. I'm hoping to get my RC mid-drive project ready for the track by then but I have a lot of small bugs to work out and a 2 year old so time is hard to come by. Speaking of mid drives, as I built my RC Drive unit it slowly evolved into somewhat of a copy of your V4 drive. Sorry about that. I'm not selling them so I didn't feel too bad about it. There are just only so many ways to mount motors, tension belts, and have adjustability enough for a bike. You used up a lot of the good ideas first.

Here is my RC drive if you are curious.
https://endless-sphere.com/forums/viewtopic.php?f=28&t=87934&p=1287900#p1287900

The race seems like it will be an annual thing so maybe you should start thinking about an optimal oval track setup now The track is always there and open to the public so if you find yourself passing through Saint Louis bring a bike with you. There are no employees and no fence around it. As long as its not reserved for an event that day its just in a field right off the highway like a public park.