My RC Mid Drive with Single Stage Reduction

[Ehead]

I'm still fiddling around with the spacing on the main chain rings. Here is the rebel gear mounted and the Morezone bag from Amazon that fits the 4s 8000 fairly well. It is the small size and is a very tight fit with foam around the battery which is good. I couldn't use the box I had for the battery. I don't want any movement inside the bag. Magura Twist Grip tomorrow, shifters and tires Friday.

Just FYI,I had to cut a bit off the front derailleur so it wouldn't hit the motor chain when shifting into high gear...

Let us know what you think of the Magura. I've heard they are nice, but expensive.

Ah..I was just mumbling to myself I have to cut the lower area of the front derailleur. I may just go with 22t alone. The spacing on my bike chain rings are really close so I'll have to address this issue. I cut some large washers in half to space the Rebel ring but its not enough. If I flip the rebel around it gives me the gap but seems to hit the main chain. My crank arm is stopping me from spacing anymore. To be expected. trial and error. Not a big deal. I'll know more when I get the shifters.
Yes the Magura is 55 but the Domino is 90. So I bought 2 tires and the Magura instead of just the Domino. I hope I won't have the dead spot in the beginning of the throttle.

 

[oaktsh]

Just received my 90T Rebel Gear chain ring, completely CNC by them - cost extra for the additional CNC set up and cuts but I think it is well worth the time saving. Appears to be of very nice quality. 112 grams final weight.

 

[tentman]

Nice work Oaktsh.

Just to swing the conversation a little (again, I'm a slow learner) - FZ Bob is using a battery pack which I understand will deliver 30 amps (30C ??) with a burst capacity of 40C.

Are there battery packs "out there" in the same 4S to 8S low voltage style that would deliver say 45 C with a burst to say 60??

Or individual batteries that could be built into such a pack??

Would anything else in the energy foodchain (e.g. controller) limit the ability to use those sort of amps at low voltages??

Thanks

Oops Edit - I see now what "C " rating means - so what is the limiting factor in going for as many amps as a motor will "supposedly" handle

 

[fixvid]

Just received my 90T Rebel Gear chain ring, completely CNC by them - cost extra for the additional CNC set up and cuts but I think it is well worth the time saving. Appears to be of very nice quality. 112 grams final weight.

That chainring is dope, but i feel that thickness is overkill, seems like 6mm thick. We are talking about 500w not 2kw, with 4mm thicknes it could be made 33% lighter.

How much was the final cost?

Just to swing the conversation a little (again, I'm a slow learner) - FZ Bob is using a battery pack which I understand will deliver 30 amps (30C ??) with a burst capacity of 40C.

Are there battery packs "out there" in the same 4S to 8S low voltage style that would deliver say 45 C with a burst to say 60??

The VESC 4.12 as i understand could suck 27A continously from battery without cooling. FZBob set battery limit to 45A. Which should be good for short climbs. You would need a battery which can supply at least 30A continously for this setup.

If a Lipo has 5Ah capacity with 6C discharge rating it means that it can deliver 5*6 = 30A continously. If a Lipo has 10Ah capacity with just 3C rating you get the same 10*3 = 30A discharge capability..

 

[FZBob]

FZ Bob is using a battery pack which I understand will deliver 30 amps (30C ??) with a burst capacity of 40C.

Some thoughts for those that are new to the battery side of things. E-Bike batteries contain lots of energy, and can be dangerous. People have burned down their houses! I'm not going to provide a complete guide to safety, as there is a lot of information on the net. Please do your research! LiFePO 4 batteries are a safer alternative, compared to Li ion, at a slight weight penalty. I believe fixvid is running 5s LiFePo4, and that may be a good way to go.

My battery pack is 8Ah, rated for 30c. That means that IN THEORY it could deliver 240 Amps "safely". I would never go near that rating! I take data every ride from my watt meter, and the most I have ever seen is 35 Amps. Remember - the battery does not determine how many Amps it delivers, it determines the voltage. The resistance (impedence) of the load determines how many Amps are drawn (I=V/R...). If a Li battery is shorted, it will deliver thousands of Amps, very briefly, and then bad things will happen. By the way, for that reason, I run a 40 Amp fuse fairly close to the battery.

I would recommend a wattmeter. They provide lots of interesting data, and are fun to watch if the ride gets boring.
Something like this, there are a bunch on the net.
https://hobbyking.com/en_us/turnigy-180a-watt-meter-and-power-analyzer.html
I have seen some with remote sensing, so you don't need to run 4 bulky power wires up to the handlebars. It is possible to extract the sensing element from this unit, and remote mount it, but it's not trivial.

For Li ion, I would recommend one of these low voltage alarms. If any cell goes low, it screams at you! Amazing for under $3. Just 7 grams and a bit bigger than a postage stamp. Plugs in to the balance leads. Loud as hell.
https://hobbyking.com/en_us/hobbykingtm-lipoly-low-voltage-alarm-2s-4s.html

Also, make sure that the VESC low voltage cutoff is set correctly. I believe the VESC interface has a nifty little calculator built in.

Make sure batteries have physical protection against impacts and punctures.

Know how to charge and store safely!

If I missed or screwed up anything, please correct me. Also, if anyone has good links to battery info or safety, please post...

 

[FZBob]

That chainring is dope, but i feel that thickness is overkill, seems like 6mm thick. We are talking about 500w not 2kw, with 4mm thicknes it could be made 33% lighter.

I agree. I was surprised when mine came in so thick. It worked out OK for me, as I didn't need spacers and the ledge prevented my bike chain from dropping between the chain rings if I over-shifted from the 22 to the 40T. However, I can see that if running smaller than 40T, the extra thickness would get in the way.

I think around 3mm thick would probably work, as long as it is not being bashed into rocks much. Might be worth requesting that, and seeing what Rebel Gears says. Possibly they have thin blanks, or can turn the whole thing down.

 

[fixvid]

I would recommend a wattmeter. They provide lots of interesting data, and are fun to watch if the ride gets boring.

What about connecting the hm-10 Bluetooth module to vesc? Then stream all logging data to smartphone and possibly change settings also.

I bought the hm-10 but didn't have the time to hook it up. It's not rocket science and every useful information can be displayed on smartphone. I'll get back with a how to if I manage to make it work.

https://banggood.app.link/wRpGv7PF7W

I think it can be bought cheaper than this around 4-5usd.

 

[falcongsr]

On my VESC I am using a https://metr.at/ bluetooth module with their iphone app. Much more expensive, but it just works and the web interface to review your ride data is worth the premium.

edit - I should mention the metr app allows you to save and recall different current limits so you can dial in your power levels on the fly. On my road bike (friction drive, not chain drive) I am limiting to 6A which at 6S is 150W which is enough to get me over 20mph.

 

[fixvid]

The Metr.at dongle and app is nice but comes with a price premum. I'll say if someone has less money and wants to tinker a little bit the hm-10 should be good also. There is a free app developed by a guy whose name i don't remember now.

Some thoughts for those that are new to the battery side of things. E-Bike batteries contain lots of energy, and can be dangerous. People have burned down their houses! I'm not going to provide a complete guide to safety, as there is a lot of information on the net. Please do your research! LiFePO 4 batteries are a safer alternative, compared to Li ion, at a slight weight penalty. I believe fixvid is running 5s LiFePo4, and that may be a good way to go.

LiFePo4 are indeed very safe, but i would say that good quality cylindrical li-ion cells will make no harm. I threw old sony cells in the middle of a big fire and there was no boom at all, just a little bit of hiss... very dissapointing.

The problem with LiFePo4 is the low energy density. Around half of that of the best cylindrical li-ions. So the next step for me will be to upgrade battery, 4s6p, around 1.2kg, with 3300mAh cells.

I can recommend this BMS, it's very good:
https://www.aliexpress.com/item/32832316893.html

It can be set up for 3-4-5s, 2.8v discharge cutoff, it can handle a LOT of current, price is good,etc... no need for buzzers.

 

[bose]

Why not go with a tool battery? The Bosch 18V 6Ah - easy fast charging with minimum hassle and danger. Makita also has premium batteries for their 18V tools.

3D print an interface board and Bob’s your uncle.

If you need bigger range - bring an extra battery in a backpack or saddle bag and snap on in seconds.

 

[fixvid]

Why not go with a tool battery? The Bosch 18V 6Ah - easy fast charging with minimum hassle and danger. Makita also has premium batteries for their 18V tools.

3D print an interface board and Bob’s your uncle.

If you need bigger range - bring an extra battery in a backpack or saddle bag and snap on in seconds.

That was the first thing which I thought about when read about FZBob's light ebike

I have one 6ah Bosch and a lot of Makita batteries, but I came to the conclusion that this bike should need at least 2 batteries in parallel. Than I started to think about a good space management inside the frame triangle with 2 batteries but I didn't solve this equation really well. My frame has limited space inside the triangle. I may still think about this solution but for now a custom shape battery is much more suitable for my frame.

There is one more thing.. Bosch and Makita communicate with the tool to cut off power supply when depleted.. In our case the vesc can do the cutoff, but cell level discharge cutoff is still missing. That bms which I posted is a bulletproof solution.

 

[FZBob]

On my VESC I am using a https://metr.at/ bluetooth module with their iphone app. Much more expensive, but it just works and the web interface to review your ride data is worth the premium.

edit - I should mention the metr app allows you to save and recall different current limits so you can dial in your power levels on the fly. On my road bike (friction drive, not chain drive) I am limiting to 6A which at 6S is 150W which is enough to get me over 20mph.

I really like this! Which means I have questions...


Can I see this on my laptop after the ride, or just on my phone? Can it display Watts and Watt Hours?

Is it as simple as plugging the metr into the VESC, downloading an App, press run and go for a ride? Or would I need to configure a bunch of arcane parameters, download patches, fix conflicts, etc, etc? (When I first got my VESC, it took me about 4 days to get it to communicate to just one of my computers/devices (out of 6). Turned out I had to play with Baud Rate type stuff. Reminded me of the '90's. After that, all was good.)

Am I correct in assuming it gets position, speed and altitude data from GPS?

Do you know if the raw data could be accessed, and be imported to Excel?

Looks like it plugs into the UART/Comm port. I believe that's where my throttle is connected. Did you run into that issue?

 

[Ehead]

All done. Runs great up the steep hills. The only problem I had was the spacing on the middle chain ring and the voltage display leads were too long to get proper power and throttle control so I eliminated it. The Magura Throttle work great. Thanks Bob for all the testing. Enough building for now. I'm off to ride.

 

[cheapcookie]

All done. Runs great up the steep hills. The only problem I had was the spacing on the middle chain ring and the voltage display leads were too long to get proper power and throttle control so I eliminated it. The Magura Throttle work great. Thanks Bob for all the testing. Enough building for now. I'm off to ride.
gopr0298.jpggopr0296.jpg

Very nice, congrats!!!

Consider going DD with disc brake hub sprocket and inverted motor mount !!! Regen braking !!!

 

[FZBob]

All done. Runs great up the steep hills. The only problem I had was the spacing on the middle chain ring and the voltage display leads were too long to get proper power and throttle control so I eliminated it. The Magura Throttle work great. Thanks Bob for all the testing. Enough building for now. I'm off to ride.

Looks good! Now it needs to be dirty!

 

[falcongsr]

Can I see this on my laptop after the ride, or just on my phone? Can it display Watts and Watt Hours?

Is it as simple as plugging the metr into the VESC, downloading an App, press run and go for a ride? Or would I need to configure a bunch of arcane parameters, download patches, fix conflicts, etc, etc? (When I first got my VESC, it took me about 4 days to get it to communicate to just one of my computers/devices (out of 6). Turned out I had to play with Baud Rate type stuff. Reminded me of the '90's. After that, all was good.)

Am I correct in assuming it gets position, speed and altitude data from GPS?

Do you know if the raw data could be accessed, and be imported to Excel?

Looks like it plugs into the UART/Comm port. I believe that's where my throttle is connected. Did you run into that issue?

Yes you can open the page on a computer/laptop and view it. I do this every ride. It shows instantaneous voltage and current so you can calculate power/watts if it's not there already.

If your VESC is configured properly then you just have to hook it up and pair it with your phone. It just worked for me. Kepler might have preconfigured my UART port on the VESC to accept it when I ordered it from him.

Yes I think it gets all the position/alt from the phone/GPS. I assume speed is from GPS as well.

I did some digging on downloading the data, and you can download a .fit file for each ride. You can then convert that file to .csv using some online tools, so you could have all the data in Excel. Here's the howto and example of them using to make overlays for ride videos. https://metr.at/overlay

I am using Kepler's Arduino throttle which connects to the PPM inputs so my UART port was free for bluetooth.

Thanks for this thread and sharing all of your work. I'm slowly pedaling towards a similar solution.

 

[FZBob]

Yes you can open the page on a computer/laptop and view it. I do this every ride. It shows instantaneous voltage and current so you can calculate power/watts if it's not there already.

If your VESC is configured properly then you just have to hook it up and pair it with your phone. It just worked for me. Kepler might have preconfigured my UART port on the VESC to accept it when I ordered it from him.

Yes I think it gets all the position/alt from the phone/GPS. I assume speed is from GPS as well.

I did some digging on downloading the data, and you can download a .fit file for each ride. You can then convert that file to .csv using some online tools, so you could have all the data in Excel. Here's the howto and example of them using to make overlays for ride videos. https://metr.at/overlay

I am using Kepler's Arduino throttle which connects to the PPM inputs so my UART port was free for bluetooth.

Thanks for this thread and sharing all of your work. I'm slowly pedaling towards a similar solution.

Cool! I've been writing the data (peak values only...) in a notebook after each ride, then typing it into Excel.

So if I can figure out the throttle, I'll be set. With luck, I could just build a breakout cable. I would guess that the throttle could share power and ground with the metr. I would also hope that the throttle pin would not be needed by the metr. I'll see if I can find more info.

By the way, did you use the PCB antenna, or the big optional antenna? I would prefer the PCB antenna. My battery/electronics bag is pretty stuffed.

 

[FZBob]

So if I can figure out the throttle, I'll be set. With luck, I could just build a breakout cable. I would guess that the throttle could share power and ground with the metr. I would also hope that the throttle pin would not be needed by the metr. I'll see if I can find more info.

By the way, did you use the PCB antenna, or the big optional antenna? I would prefer the PCB antenna. My battery/electronics bag is pretty stuffed.

I sent an E-mail to support@metr.at:
"I would like to purchase a metr unit to interface with my VESC on my E-Bike. However, it looks like it plugs into the UART/Comm port on the VESC. I have a Hall throttle which uses ground, 3.3v and ADC on the UART/Comm port. Can the metr and hall throttle share the port? If so, how? Would a breakout cable work, where Ground and 3.3V are shared? Does the metr use the ADC pin?"

and got a quick response:
"Metr Pro doesn’t use ADC port.
Only four pins: 3.3V, GND, TX and RX need to be connected. The cable uses 7 wires to match ESCs 7 pin connector.
https://metr.at/faq#q32
You will have to replace cables. There are several people (including myself) who did this with e-bike and ADC and it works without any issues."

So it looks like a breakout cable will work. They have 3 antenna options, so I just enquired about that.

 

[falcongsr]

I use the integrated antenna, no need for the range of an external antenna if your phone is with you on the bike.

 

[FZBob]

They have 3 antenna options, so I just enquired about that.

Per metr support:
"PCB antenna should be fine!"

Ordered...

 

[NateTN]

I made a 90t sprocket out of 6061 for testing, I'm still working on the motor mount and waiting on components.

 

[falcongsr]

That is artwork. :thumb:

 

[NateTN]

That is artwork. :thumb:

Thanks!

Its very light, I hope it holds up as I am partial to the look.

If it is functional I'll make another out if 7075-T6 and have it anodized after properly machining the teeth profile.

 

[Kepler]

I would recommend a wattmeter. They provide lots of interesting data, and are fun to watch if the ride gets boring.

What about connecting the hm-10 Bluetooth module to vesc? Then stream all logging data to smartphone and possibly change settings also.

I bought the hm-10 but didn't have the time to hook it up. It's not rocket science and every useful information can be displayed on smartphone. I'll get back with a how to if I manage to make it work.

https://banggood.app.link/wRpGv7PF7W

I think it can be bought cheaper than this around 4-5usd.

A cheap plug and play Bluetooth solution can be bought from Flipsky for $10.



Works perfectly with the the Vesc mobile app. You can then use the real-time data feature as a dashboard and Profiles feature to set power profiles.



Draw back is that the App is Android only and there are a few steps to start seeing the real-time data. Also you need to set your screen to stay live continously or whatever its longest setting is to keep the display up.

The Metr is a better solution but if funds are tight, the Flipsky offering is quite adequate.

 

[fixvid]

I made a 90t sprocket out of 6061 for testing, I'm still working on the motor mount and waiting on components.

That's as light as it can be. It doesn't look more than 75g. Can it withstand the torque ?