# Flying Merkel Ebike and Sidecar with Experimental Motor Design



## deleted_user (Jan 14, 2022)

David_R8 commented on something I had posted on another thread so I thought maybe others may be interested in this long term project I am working on.

So far I am mostly in the design phase and have a few issues to work out and materials to source before I get going in earnest.

*Preamble* (skip if desired):

I wanted to take my dogs along on hikes on old rail trails around Ontario. We tried it a few times and they just can't go very far with the heat and their short little shih tzu legs. So next I figured I'd bike those trails and take the dogs along in a bike trailer. They did not enjoy this. It surmised that it was both too bouncy and they did not like trailing behind., frankly they like to blaze the trail and see where we're headed.

I've also always wanted to own a board track racer but my budget doesn't allow that. I'm on another forum where people often post about constructing custom bike frames. I thought that if they could do it I surely could as well. During my research I stumbled across an early 1900s photo of a dog in a sidecar attached to a Harley. The idea was born to add the sidecar build to the project and revisit the idea of rail trailing with my dogs.
















*The design criteria*

In order to use both Toronto bike paths and most rail trails I'd have to design a pedelec, which is a ebike with pedal sensors that provide feedback on how much power the motor should output to assist the rider. I'd have to be able to convince any authorities that the output was within the required kW rating, which meant that there must not be a throttle on the bike in such usage. I'd use VESC based software controls and a cycle computer (Cycle Analyst) to limit motor output to meet Ontario regulations (with a little cheating for hill climbing because I have many hills near me).

The cycle analyst allows me to easily add a throttle to the bike if I wanted to convert to motor cycle for use where allowed such as on a private track. Since I wanted a board track racer I wanted a motor capable of board track racer speeds IF I desired. I performed a series of calculations and determined that I'd want a motor capable of 4kW continuous output, even if my initial speed controller and battery were not capable of operating at the required amperage. 

I settled for an initial continuous operating current of 25 amps for all components in the system. With that design current and a phaserunner controller from Grin tech (90v, 96 peak amps) I can output ~2kW with a 72 volt battery pack. More than enough power to push me, my bike, sidecar and two small dogs all day long.

That's when I started researching what makes the best proven reliable and powerful DC motor designs. I then tried to take elements from each to design my own motor that I hope can output close to 4kW.  Time will tell.

One remarkable motor design, the Lynch motor, was developed by from someone without any previous knowledge in motor design. When first developed it was exclusively a brushed DC motor of and axial design. Over the past 25 years the technology was improved upon and the IP was bought and sold a few times.  Briggs and Stratton acquired the rights and sold the motors as Etek Motors, they were powerful better replacements for the 6HP gas motors that were Brigg's bread and butter. Needless to say they hindered market development for a long time. It is both the axial design and the unique very robust stator coil design that I wanted from this motor.

Another design element I wanted for my motor was modularity to ease the construction. I also toyed with the idea of Binding Jetting copper printing, except I could not find anyone in Canada that offered binder jet service for copper. The prices from foreign firm was in the many thousands of dollars. Their target market is really more for parts like these:













My Stator coils are more like this:






The illustration below shows the copper stator elements coloured to show the phase winding scheme more clearly. The image also shows the stator core, one of the two rotor hubs, and the splined end of the motor spindle.







The above image shows one things I've done that is unique, which is to put the bike's cranks thru the motor spindle. At the time I thought of this concept I did not think that it had been done before but I discovered a German company (Binova) had indeed done so on a rare ebike conversion kit they'd designed.

It made excellent use of modular construction as well, in fact superior to the best motors I'd seen designed for EV automobiles.

I am making jigs to assemble the motor stator and to cast the stator in resin. This process will also affix the stator to the stator hub on the interior side and the aluminum cooling and mounting ring on the exterior. A cooling loop of copper tubing will also be cast in place for the oil cooling system that will keep the stator under 155 deg C.

I'm also using 3d printed jigs to build the motor's rotors with their magnet arrays. Well actually I will try to make an entirely 3d printed rotor except for the back iron rings and and exterior metal ring to reinforce the rotor's perimeter, and of course the keyless hub that affixes the rotors to the spindle. The idea is to lighten the rotor and provide precise location of the magnet array.
















Below shows the set of spacers that help align and epoxy the magnets in place. They then get removed and the voids filled with epoxy. 







IF the 3D printed parts are not robust enough (carbon fiber reinforced filaments) I'll try to "forged carbon fiber" casting process to make rotors. But I am hopeful that the 3D will work sufficiently well.

below shows where I'm tucking in the cooling tubes between the stator and the exterior mounting ring






Below shows the gates belt cog from the motor to the rear 3 speed hub. The crank side also uses gates belt drive. the driveline lengths are equal in order to ensure that tensioning is not complicated.  The drive ratios have also been carefully calculated to ensure all operating ranges are covered well. I nixed a CVT hub idea because they can't handle the input torque output by the motor.








More to come if people are interested.

I do have issues to solve I'd like input on.

One: 

How to make steel lugs to use to reinforce and braze the tubing together in the period style.  Typically these are investment cast. These don't match any of those cast items found at bike parts suppliers. I supposed I can appeal to CNC mill owners to machine me a set from design I supply. Or I can try to investment cast using an a lower melting point alloy... any ideas of suitable replacement? That would require a major investment on my part. See, I can do puns.

Two: 

How to manufacture about 100 copper coil elements from sheet copper. Initially I was going to use a die punch for this, but when I inquired with a few edm shops none responded to my request for price to machine my die and punch. They must be busy with real customers. My mill is not really suitable for making these parts. But mybe someone with a cnc mill would want to help out?

The dies I have designed for the stator coil elements:





I also need stamped copper plates to make the electrical contacts in a compression type battery pack I am building for other ebikes I am building.

The other option is having the parts cut on a cnc router. Again something I lack... anyone want to help out here?

The battery contact plates, I already 3D printed the stamping moulds to emboss the contact points. I just need cnc router or die set made to punch these too.





I really want to make as many parts for this project as possible, so I may tackle building a rear hub too.


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## David_R8 (Jan 14, 2022)

Exceedingly cool project!
Re the lugs, I think you could easily braze or if you have the equipment TIG weld the tubes together. Some discreet gussets could be added if strength was a concern.


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## deleted_user (Jan 14, 2022)

David_R8 said:


> Exceedingly cool project!
> Re the lugs, I think you could easily braze or if you have the equipment TIG weld the tubes together. Some discreet gussets could be added if strength was a concern.



I could easily just weld the tubes. I just want the lugs for the period look. The bike would look wrong otherwise.

For the same reason I am adding a faux cylinder to the motor to give the period look. I'll use it for a cooling tower for the oil cooling


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## David_R8 (Jan 14, 2022)

I see that some builders are getting 3D metal printed lugs. Likely mucho pesos but maybe an option.








						Atherton Bikes 3D Printed Titanium Lugs
					

They say poachers make the best gamekeepers, so you could probably extend that idiom to bike manufacturing, especially where it comes to UK startup




					3dprinting.com
				











						How 3D printing could revolutionise steel frames
					

Reynolds to invest heavily in additive manufacturing




					www.bikeradar.com


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## deleted_user (Jan 14, 2022)

David_R8 said:


> I see that some builders are getting 3D metal printed lugs. Likely mucho pesos but maybe an option.
> 
> 
> 
> ...



I already checked with my local binder jetting firm. They cater to prototyping market where firms will spend 10K like it is nothing.

This is not possible.

If I can find any scrap maybe I can try to melt ductile iron pipe in a electric melt furnace enough to investment cast?

My last resort will be to cut and weld larger tubing to weld up lugs.


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## Six O Two (Jan 14, 2022)

TorontoBuilder said:


> My last resort will be to cut and weld larger tubing to weld up lugs.


Last resort? That should be your first option, not last. It's pretty straightforward to create a bilaminate style lugs with brass brazing, like Winter Bicycles. Paul Brodie has some videos on this, I'm pretty sure. 


Bilam/ custom lugs by Eric Estlund, on Flickr
I know some builders also tig weld lugs from bits of tubing, and then grind away the welds for a smooth, traditional lug look, and then silver braze the lugs together. That's what Spectrum Cycles used to do when they were still building..

But I did also hear of a some guys who facilitate sintering custom stainless steel lugs in Asia. I think it ends up around $400/lug (which is why I'd be more tempted to go the bilam or TIG route).

This is an awesome project, btw. Can't wait to see the progress.


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## deleted_user (Jan 14, 2022)

Six O Two said:


> Last resort? That should be your first option, not last. It's pretty straightforward to create a bilaminate style lugs with brass brazing, like Winter Bicycles. Paul Brodie has some videos on this, I'm pretty sure.
> 
> 
> Bilam/ custom lugs by Eric Estlund, on Flickr
> ...



you are right... that should be the first option. We do have cheap tig welder which should be enough to weld up lugs, but my tig experience is limited


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## Six O Two (Jan 14, 2022)

Well, the upside to using TIG for building lugs is you get to grind away your welds and no one sees them


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## Chris Cramer (Jan 16, 2022)

Are you designing an e bike with a mid drive motor or a hub motor, and will it only run on a throttle, or will you add a sensor to the cranks?


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## deleted_user (Jan 17, 2022)

Chris Cramer said:


> Are you designing an e bike with a mid drive motor or a hub motor, and will it only run on a throttle, or will you add a sensor to the cranks?



The motor is a middrive, and has a set of cranks that run thru the spindle, and will be a pedelec with hall sensor and magnet array mounted at the crank. I'll still be able to add a throttle option via a cycle analyst if I wanted to use one on occasion.


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## deleted_user (Jan 17, 2022)

So, I am thinking of milling the copper coils I need.





I was thinking of the following:

First I'd clamp a bunch of rectangular copper blanks that have been cut to 65mm x 40mm x 1.6mm together in a jig that holds the parts in compression while also restraining the plates from rotating while being drilled so I can drill 10mm hole thru the copper sheets and then mill a 10mm by 16mm slot.











Then I'd remove the blanks from the jig and clamp about 25 sheets together between two 1/8" thick sacrificial steel 65mm x 40mm plates using two bolts thru the milled slot. 

Then I can mill one long edge flat, then flip to opposite side and mill parallel to dimension. Then rotate to mill other two sides to the right profiles. Finally change tools to mill 2.5mm radius corners. I'd hope that the sacrificial plates help minimize burring and other problems with the laminate edges. 

Finally I'd mill the 3mm slot with a slitting saw. 

Does this sound like the best approach to mill such copper sheets?


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## Tom O (Jan 17, 2022)

I think I would look at waterjet or laser


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## deleted_user (Jan 17, 2022)

Tom O said:


> I think I would look at waterjet or laser



This is why I wish I had desktop waterjet cutter... but 10K.

I'm big into making everything myself and my usual waterjet cutter is good to 3/8" steel plate, not so good on copper sheet with fine detail. The cut pieces fall thru their grid. Local laser cutters charge arm and leg

I also dont want to wait until I have a cnc router


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## Chris Cramer (Jan 17, 2022)

I've cut copper plate with my plasma cutter in very fine detail. Hypertherm's fine cutting consumables work very well for precise cutting as long as the plate is not too thick.
Today I tried to use the machine torch to cut my inch thick hardened steel plate; and even if it started frome an edge it could only cut it if it was first gouged on one side to remove enough material that It has to cut through from the other side.


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## Susquatch (Jan 18, 2022)

TorontoBuilder said:


> I wanted to take my dogs along on hikes on old rail trails around Ontario. We tried it a few times and they just can't go very far with the heat and their short little shih tzu legs.



This is your real problem. 

I'd start by getting real dogs. A real dog would pull the bike for you and eliminate the need for a partial drive system. 

Just kidding but couldn't resist. 

Seriously though, I had to train my dogs NOT to pull me around. Otherwise they did all the work and I was just along for the ride. It wasn't that difficult since they are both well trained to heel. That said, the motor on this system had a different sort of problem. The exhaust system had this peculiar intermittent processing problem that required periodic emptying of the collection system......


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## deleted_user (Jan 18, 2022)

Chris Cramer said:


> I've cut copper plate with my plasma cutter in very fine detail. Hypertherm's fine cutting consumables work very well for precise cutting as long as the plate is not too thick.
> Today I tried to use the machine torch to cut my inch thick hardened steel plate; and even if it started frome an edge it could only cut it if it was first gouged on one side to remove enough material that It has to cut through from the other side.



yeah a plasma cutter is also on my list of "I wants"


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