assembling RC ebike - which bike to choose?

[MrBoots]

Hello everyone. I've been a lurker for quite some time and aside from a few random posts, haven't really been involved with ES. However, I've really appreciated the sheer volume and depth of information available here and I've just been blown away by the technical know-how of everyone here! Anyway, after doing relentless reading of all the RC builds here, I feel like I'm armed with enough info to plunge into my own ebike build.

Right now, because of work, grad classes and frankly, limited funds, I'm only the piecing-together phase. My goal is to build a relatively simple, affordable commuter bike with a range of around 15 miles and a cruising speed of around 25mph. I love zipping around on my bikes. Also, there's nothing worse than sitting in snarling traffic in the Boston commuter rat race. The added health benefits wouldn't hurt either lol.

I'm going the RC route because I'm somewhat familiar with RC products and I've got a small assortment of freewheels, sprockets, tensioners and other bike parts lying around. Also, I'd like to keep the bike as light as possible.

So here's a (tentative) list of the main components I've come up with:

1. Turnigy 63-74 200Kv outrunner (I really liked Scottclarke's set-up because the motor's relatively cheap and I'm not really aiming for a high top speed: 30mph MAX. I'll be fabbing up a seatpost tube mount for this)
2. Turnigy Sentillon 120a HV ESC (I'm aware that some people have had timing issues with this but it's rather cheap and I'm open to upgrading the ESC to a CC unit later on)
3. RC Throttelizer w/ thumb throttle (for reasons I'll list below).
4. 90t sprocket from Monster Scooter Parts -> ACS freewheel -> Surly single-speed rear hub (I'll be employing gwhy!'s BB cup method to mount two freewheels)
5. 11t 10mm bore sprocket (also inspired by Scottclarke's setup).
6. 11.1v 4000mah LiPo's in series

The only problem I'm having now is, I've got a small collection of bikes to install on but not sure which one would work best. Obviously there are trade-off's with each bike but I'd appreciate your feedback on which bike to equip:

My Diamondback Insight is my first choice but because I'll be mounting two freewheels on the rear hub, I'll be ditching all the gears. I actually prefer a single-speed bike for commuting purposes but it'd also be nice to keep the gears since this is really the only multispeed bike I ride regularly and would the best one for the occasionally hilly trail. It's also the only bike I own that's fully-equipped for commuting since it has fenders and a rear rack.

My second choice would be my Schwinn Madison. The thing that concerns me about this bike is the tiny 700c x 23c tires (as opposed to the meatier 32c's on the Diamondback) and the lack of eyelets for a battery rack and I'd prefer not to use a seatpost rack. Also, I think the tendency to go full-throttle while fully tucked in riding the drops might make things really dicey.

Last option would be my GT Avalanche. I figured the meaty tires would help. Plus, it has disc brake mounts so I could easily upgrade if needed. As with the Diamondback, I'd hate to lose the gears and a SS MTB would be slow as molasses without electric boost.

Which bike would make the most sense? Is the ride unbearably-harsh with 700c's beyond 30mph? I'd love to build up a second ebike down the road but for the time being I have to choose one of the three. Anyway, my kit will be coming along very slowly so please have patience. Keep up the great work fellas!

 

[Kepler]

Looks like you have done some great research groundwork before posting. That’s always appreciated as it saves going over lots of well discussed previous topics. I'm a bit like you in that I am quite new to the E-bike seen but have good RC experience before hand. I have 2 major projects under my belt so far, an RC setup and a hub motor setup. My RC setup is on a scooter but is a very similar to what you are proposing. You can find it the thread in the here if you are interested http://endless-sphere.com/forums/viewtopic.php?f=12&t=15030

My tips are. Forget the cheap ESC and go to Castle Creations. Sync issues are a pain. The combination of CC controller, Throttleizer, and Turnigy motor works very well without any sync issues and accelerates from a stand still without complaint. I have tried the cheaper ESC and even with the Throttleizer, they will loose sync especially on start up and they are difficult to get the throttle progression smooth even with the Throttlizer set at its slowest ramp. You can ride around the sync issues of course but it always happens when go to show your creation to someone sending you straight from superstar inventor to amateur tinkerer. If you want to save a bit of cash on the CC ESC, get the HV 85 amp version. I use this one and regularly pull 2.5kW through it on my 6S setup.

Change the bearings in the Turnigy motor. This is not an option, it’s a must. Very cheap and easy to do.

You need more batteries. With your gear ratio, 6 S is your best option but I would go for 2 x 6S 5000mah. This is still nice and light and will give you the range you are after plus a bit more which believe me, you will want. You eat up 15 miles on an E-Bike in no time.

In regards to bikes I would choose the first one if you plan to use for road cruising especially since your not looking for warp speed. Keep in mind brakes are more important then ever to be strong as you will find yourself hauling down form speed much more often then before.

Good luck with the build

 

[johnrobholmes]

I would choose the mountain bike. I have a Madison, and although it is a compliant frame I would rather see better rims and tires for the speed. Also, since you are going to have the extra motor boost it won't be so important to have that uncomfortable tuck position all the time You could keep your front three gears if you just lock the rear derailleur in place and take out a few links.


I second skipping the sentilion, and go straight for a Castle controller. I too have tried and and failed with the turnigy stuff, it just seemed to lose sync when I needed it most. Never happens with the Castle, plus the new ICE controllers have onboard data logging that really makes it shine for troubleshooting and knowledge gains.

Here is the build I am using my ICE HV160 on. Towards the last page http://endless-sphere.com/forums/viewtopic.php?f=6&t=10175

 

[MrBoots]

Gentlemen, thanks a bunch for the tips! I also resized my photos if anyone had issues viewing them.

@ Kepler: I think I'll go ahead and just order a CC ICE 100 since it's only a bit more expensive than the Turnigy ESC. I'm looking to cap my amps at about 80. About the bearings - were they ceramic and where'd you purchase them? BTW, that LiPo alarm is a great idea I'd like to incorporate in my own build. I failed to mentioned that I was planning on running 6S at 22.2v. I was planning on purchasing 8 packs for a total of 16Ah. Scottclarke mentioned that he had reliability issues with the motor when he ran it at more than 24v. What voltage are you running it at and how many miles have you logged on it so far on your scooter?

@ JohnRobHolmes: LOL I just like being as aerodynamic as possible! I do think the MTB will make for the most comfortable ride but I've decided to go with the Diamondback hybrid since it's already my daily commuter - I've upgraded almost every component. Recently upgraded the awful factory Tektro v-brakes to Avid SD7's with Koolstop thinline pads and in addition to the Schwalbe Marathon tires - the bike brakes infinitely better now. I'll be riding without electric assist much of the time and the MTB seems really sluggish by comparison.

 

[gwhy!]

hears my tip ,,
forget rc esc's all together and fit sensors to the motor and use a off the shelf crazyman controller.


edit: and roll with the mountain bike.

 

[TMaster]

Go with the GT Avalanche. I have a 08 Trek Road bike and I've pedaled it up to 34mph on the straits and it is wicked crazy going that fast with those skinny tires and short wheel base.

 

[Kepler]

Gentlemen, thanks a bunch for the tips! I also resized my photos if anyone had issues viewing them.

@ Kepler: I think I'll go ahead and just order a CC ICE 100 since it's only a bit more expensive than the Turnigy ESC. I'm looking to cap my amps at about 80. About the bearings - were they ceramic and where'd you purchase them? BTW, that LiPo alarm is a great idea I'd like to incorporate in my own build. I failed to mentioned that I was planning on running 6S at 22.2v. I was planning on purchasing 8 packs for a total of 16Ah. Scottclarke mentioned that he had reliability issues with the motor when he ran it at more than 24v. What voltage are you running it at and how many miles have you logged on it so far on your scooter?

I figured you were going for 22.2V setup. 8 packs are a lot to manage and fiddily to charge hence the reason I suggested the bigger 6S packs. Not sure if there is an issue getting 6S packs into the US now with some silly rules they have brought in. In regards to bearings, I just installed a set of good quality metal bearings. Ceramic would be better though but $30 bearings I think are overkill in this motor.

24V works best for me also in relation to reliability. Motor stays much cooler at 24V then at the high Volts. I have tried up to 36V in my setup. It was silly fast. I have have logged around 200 hard kms on the scooter without an ESC or motor issue. Both the ESC and motor have done many hours in other projects before this one also.

 

[MrBoots]

Kepler, thanks again for the info. Haven't purchased the batteries yet, but I'll follow your advice and opt for 6s. 3s Lipo's can be had for ridiculously cheap prices but you're right in that it's not worth the extra hassle.

I've been exchanging PM's with a few other members (Jeremy Harris, scottclarke, Dirty-E-Dan and others) and you've all been incredibly helpful. Thanks to all your pioneering, building an ebike seems a little less intimidating for the not-so-technically-inclined like myself.

Anyhow, parts have been coming in sporadically and this is just a 'lil progress report:

I ended up going with the hybrid despite strong recommendations for the MTB. This bike will likely not see speeds above 30mph since it'll mostly be pedal-powered. Additionally, it's a bit lighter than the MTB (have to carry it and out of my apt.) and will mostly be rail trail-bound. I ended up removing the derailleurs/shifters and swapping out my rear wheel in favor of a flip-flop hub-equipped one I had sitting around. Also replaced the crankset and chainrings from a single-speed donor bike. I'm now running a city-friendly 44t/16t single speed combo.

Gone are the monstrous crankset and platform pedals.

Next I tried copying what gwhy! did by mounting two freewheels via bb cup linkage but ran into a bit a snag. Unfortunately, the Dicta-brand freewheel I have doesn't have enough available threads to thread the bb cup. I've ordered a Shimano freewheel that will provide the extra threading (approx. a quarter inch more than the Dicta).

Also, the because the spacing on the hubs are different, the rear axle is a tad too short so I need to get a hold of 145mm+ axle. In the meantime, I fooled around with the 90t sprocket and realized that it has the same threading as a FW/cog. Here, I have it threaded onto the fixie side of the hub. It could be secure to the hub if some of the threading on the sprocket was ground down or sheered off and held in place by a cog ring ala fixie cog. This is cool because I ever decided to fab up a gear reduction unit, I could just attach the motor to the left side of the hub and possibly multispeed functions (probably won't, but it's at least an option).

I plan on mounting the motor directly onto the rear rack. It's pretty strong (rated at carrying 60 lbs.) but could still use extra strengthening. For this, I'll be bolting on a beefy seatpost rack sans rack deck to the current eyelet-mounted rack. The outrunner, in its own turnigy cage, will then be secured by bolted collars and hose clamps to the rack. Fortunately, the side-slots in the rack look to line up perfectly with the freewheel.

Anyway, my ecrazyman controller, hall sensors, throttle and motor should be arriving shortly. I'll keep y'all posted!

 

[MrBoots]

Haven't made much progress with the bike but it should be finished sometime next month. I have all the main components in my possession: motor, sprocket, controller. I'm in the processing of replacing the bearings on the HXT with ceramic ones and re-gluing the magnets with Devcon epoxy. A battery box is in the works too, update should happen soon. I bought a cheapo Schwinn alu seatpost rack from Target and will be using it as a brace for my eye-let mounted rear rack. This combo is incredibly sturdy and stealth so I'm just hoping it can deal with the strain of the motor.

Dual freewheels via BB cup.

Where I'll be mounting the motor.

Thumb throttle and mount for Turnigy Watt Meter to make it easily detachable.

 

[MrBoots]

Now that my tutoring class is over, I've finally found some time to work my bike. My 6-FET ecrazyman controller arrived - per Jeremy Harris' suggestion, 6 new 3077's and modded shunt have been soldered. Controller should be perfect for my 30v needs. Here it is mounted next to the seatpost on the bike. The white foam contraption is just a mock-up for my planned fiberglass battery box. You can also see the gold motor cage for the turnigy motor resting on the bike rack - that'll be secured via collar clamps soon enough.

A closer look at the cage on the rack.

I also disassembled my turnigy 63-74 to re-glue the magnets and replace the bearings with hybrid ceramic ones. I soaked the can in acetone for an entire week before the epoxy finally softened enough for me to pry the magnets off! Leads me to believe the glue was pretty tough and may have been up for the job but alas, I could use the peace of mind. I've used Devcon epoxy on outrunners before and it's never failed me. Best part is, it's very cheap and widely available at dept stores. Supposedly good up to 250 degrees F with bonding strength of 2500 lbs. Here's a pic of the re-glued magnets.

The bearings were surprisingly very easy to replace. I just followed Jeremy Harris's dowel and socket technique. The smaller 15mmx10mmx4mm bearing I pulled out with a J-shaped screw used to tie down car batteries. From there, I inserted a long 8mm socket into the shaft hole and tapped out the two larger 19mm bearings. I bought a set of four hybrid ceramic bearings from Acer Racing for $25 shipped (good deal IMO) and gently tapped them into place with wood dowels.
I've also replaced the larger 35mm bearing with a sealed unit from VXB bearings. Here's a pic with the new bearings in place.

To address side-load on the motor shaft, I actually epoxied another ceramic bearing onto the motor cage. The motor sprocket will be mounted flush, next to the bearing.

I've already mounted the hall sensors on the motor cage and connected everything. Gave the motor a test run this afternoon and it just sounded ferocious at 30v with the hall sensors. Battery on the camera needed to be re-charged so there are a ton of pics I still need to take.