RC assistance

[two56]

I had a play on a bosch based e-bike which made me want to have a go at building one myself. After having a browse on here I liked the power, lack of weight and relatively budget friendly RC solution. It was supposed to be a quick project...

I started off with a 3.5kg block of aluminium. After a lot of manual milling.

Internals.

Oil filled gearbox.

Initially I used a left hand belt drive (15mm HTD) this didn't even come close to handling the torque.

The final version. (lets face it... probably not)

It's currently only running a 6S 20ah lipo. I've only done a few miles since converting it to a chain final drive. I was surprised at the amount of power the little motor puts out, it pulled to 30mph with the current gearing. The bike weighs 46.5lbs, which is inline with the production bikes. I'm still not convinced the gearbox will last.

I'll add some more information and photos soon.

 

[Hillhater]

Wow !
That is very impressive for a first attempt at an RC mid drive. Did you do all the machining yourself of source the gears readymade ?
Care to elaborate
Motor ?
Controller ?
Any freewheels or clutches in the drive ?
What power level do you plan for it to handle ?

 

[two56]

All the gears and sprockets were bought off the shelf and modified. The casing and axles were machined on my mill and lathe. I've also got a Proxxon MF70 CNC mill, it's a bit like a Dremel on speed, it's not massively accurate but it's good enough for all the bracketry and is far faster than doing it by hand.

Gearbox is 12:1 internally, then 9t to 34t final reduction giving approximately 45:1 overall reduction. Sadly I didn't have room for a gearbox freewheel, I was planning on fitting a roller clutch internally. The crank is freewheeled.

The ESC is a Turnigy TrackStar 1/5th Scale Sensorless 200amp 8s. The first one I had was faulty, it shorted the battery and blew/melted the 8mm connector. I've read a good number of threads about blown controllers, this seemed fairly hardy from it's spec. I know it can't run high voltage which means more current and less efficiency...

Motor wise it's a Turnigy G160 245kv. The high kv meaning I can't really run higher battery voltage without more reduction.

I'm guessing it's pushing 1000 - 1500W, it will lift the front wheel slightly. I'm using a servo tester at the moment as the throttle which is frankly scary. I've wired up an ardunio to a thumb throttle, I just need to fit it.

 

[two56]

I've got a slutter at low RPM, high load. Most of the time it doesn't happen, could anyone give me some pointers as where to look and what to tweak. I've messed around with timing with little effect.

 

[KOMAN]

EXCELENT

 

[recumpence]

[\quote]I've got a slutter at low RPM, high load. Most of the time it doesn't happen, could anyone give me some pointers as where to look and what to tweak. I've messed around with timing with little effect.[/quote]

Crappy controller. Low RPM high load is extremely hard on RC controllers. Castle Creations are the only controllers I have found to tolerate that. Also, some small outrunner motors lose sync easily.

Matt

 

[two56]

The Turnigy motor didn't last more than about 50-60 miles before it started letting go of it's magnets.

I bought an Alien Power 6355 190KV motor, mainly because I was being impatient, and wattage wise it was similar to the Turnigy motor. The nose of the motor needed trimming to fit my gearbox. It's under powered and loses sync, a lot. As Matt said crappy ESC + small outrunner. On the bright side I understand more about how sensorless ESCs work. I've bought a 6374 motor and hopefully this will improve the situation and not destroy the gearbox.

Project No.2 is starting to come together.

 

[two56]

Project No. 2 has made progress.

Hub finished and bearings pressed in.

Pulley drilled and roller clutch pressed in.

All fitted together.

 

[spinningmagnets]

Well done! I have seen 63mm diameter RC motors with a 149-Kv, and Thud has rewound an 8mm diameter RC motor in order to get a lower Kv (as a more powerful option).

 

[boisrondevens]

well done!

 

[Sillyhead]

wow, this looks so simple. Do you have cad files or anything of the parts, I would love to try this drive out/making something similar.

 

[two56]

Mk. 2 is coming together, I just need to build a bike around it. I'm a little concerned about flex in the motor mount and the belt skipping. We'll see... It should hopefully come in around 40lb for the entire bike including batteries. I can already see places to refine the design but overall I'm pretty pleased.

I've only CAD'd the motor mount and parts for the sprocket carrier, TBH they need refining. Everything else has been done on a manual mill and lathe. I'll see how the design works and let people have the drawings if it works.

 

[Ham]

Looking good there...very slick

 

[lcyclist]

two56,

Very elegant design; do you expect spin out issue with the one way bearing because it is only pressed in?
Looking forward to your testing!

 

[spinningmagnets]

The magnets coming loose might be related to higher than expected heat. If that's the case, then using a high-temp epoxy might fix that. However, if the heat is high enough to damage the stock epoxy, you might be also getting the magnets hot enough to get near their de-magnetization point. If you do get the magnets too hot, the Kv (top RPM) will go up, but the power will go down.

Astro uses Samarium Cobalt magnets because they plan on getting their motors hot.

 

[two56]

[youtube]-KfxQYkquis[/youtube]

Piss poor quality video, sorry...

MK2 is running, super happy with it. ~40lbs and 26-27mph top speed. No belt slip and the roller clutch still seems solid.

I think the magnets on MK1 let loose due to poor bonding, the motor never got that hot (warm to the touch) due to the stator being bolted to a huge lump of aluminium, the gearbox. I'm hoping that was the case anyway.

 

[dpeters1]

Awesome project! Are you still only running on 6s? Must be geared pretty high to reach 25mph at that voltage and I'm surprised the extra load isn't drawing too much current.

I'm planning a similar build using a 190kv 6374 motor and would like to avoid multiple battery packs... 6s seems to be the highest voltage readily available.

Also if you have any information on average power draw and/or range that would be greatly appreciated!

 

[ScooterMan101]

? there are 7s and 8 s packs available at Hobby King,
I have some 7s Hobby Lipo Packs, and even bought 2 , 8s packs for a future project
(to make a 16s pack for a small hub motor to run faster)
In regards to chargers there are more 6s chargers available at the lower price points,
However with enough people wanting 7s / 8s chargers they will be available once enough people ask for them.

Contact Hobby King and ask, Contact Buddy RC and ask for 7s /8s chargers

Buddy RC 614-369-1085 Eastern U.S. time zone

For example I called Buddy RC in Columbus Ohio and asked them to order some of the new small DC chargers for 7s and 8s ... they said that they have only gotten a few calls for the 7s / 8s chargers. With enough people asking for them the Mgf will make them .
Here is the link to the charger that would be a perfect travel / on a ride take along DC charger ...
http://www.buddyrc.com/isdt-q6-plus-300w-14a-6s-battery-charger.html
and another one
http://www.buddyrc.com/isdt-sc-608-150w-8a-6s-compact-charger.html

I'm planning a similar build using a 190kv 6374 motor and would like to avoid multiple battery packs... 6s seems to be the highest voltage readily available.

Also if you have any information on average power draw and/or range that would be greatly appreciated!

 

[methods]

Sick!

Love the simplicity of Mk2

Recently I have had the chance to review some mid-drive power-assist bikes that utilized a gear set.
Wow... You can get incredible torque out of very little motor.
It takes some getting use to... after years of direct drive with no gears... you gotta adapt to spanking through the gears to maintain peak torque...

Eliminating the nightmare known as CHAIN is a super win.
The hum of a belt is a very nice sound to hear.

My single attempt at a mid-drive was shelved after the chain (which I had to modify and did so poorly) exploded and wrapped up in the rear wheel.
At 50mph it is an unacceptable failure mode.
I believe a belt eliminates this risk.

Love it - post more.

-methods

 

[two56]

Thank you for all the comments, the more I ride this bike the more I like it. I still need to tidy up a few bits and bobs. I kinda threw it together mid week, the important bits work.

MK2 started out after a work mate had a play on MK1 and wanted some electric power of her own. I started looking at making a friction drive, I like them, but we're in England so have quite a bit of rain which isn't a good mix. I then started thinking about using a separate bottom bracket as a jack shaft... Then thought, sod it, I don't need a jack shaft, the bottom bracket is strong which makes it an ideal idler shaft, keeps it light too. I just needed to pack a lot into a small package.

Most of the plate parts were cut on my tiny CNC mill (Proxxon MF70) as I just can't even come close to creating the shapes I need on the manual mill. The Proxxon has been "improved", but still took 4 - 5 hours to just cut the motor plate.

Better YouTube video, it's a lot of fun.

[youtube]C2EVzRKnNpo[/youtube]

Spec wise...

Motor: Alien Power 240Kv 6374
Battery: 6S 20Ah Multistar
Controller: 200A Turnigy TrackStar
Reduction: 14.1:1

Weight as is, without rear brake, chain, chain ring and mech - 40.8lbs. The bike components are... crap :? so it could be built onto something much lighter, easily 30lbs on a road bike and maybe 35-38lbs on a mountain bike. Although I don't think the style would suit a road bike and it would be frankly scary.

Range wise, I'm not sure, MK1 took me to work 14 miles away and if my memory serves me, used about 80% of the battery. I was using it as pedal assist averaging 25mph. Spec of MK1 and MK2 are similar, battery, motor and controller.

Once I've moved house I'll be getting a proper CNC mill so I expect they'll be a MK2.5

 

[methods]

Yo...
that your back yard dawg?

Eh...
Who mow's that?

Looks like it goes on forever. Definitely need a 6' jump back there someplace

-methods