Extending outrunner cables

[BMX]

Hi,

Discovered this board a few months ago and its a gold mine of helpful info, thanks so much to all those who have contributed so much.

Sorry to start with what is probably a ludicrously simple question, but I cant seem to find the answer elsewhere.

I am on my first build using an RC outrunner motor (Turnigy SK64 - 74 - 170) and an RC speed controller (Turnigy 80A super brain). Not trying to get maximum power out of the motor so just on 22 volts right now (but planning to go up to 30volts eventually). I should be OK with the mechanical stuff, but it would be very convenient to mount the speed control further from the motor than the length of the stock wires, is this an issue in terms of impedence etc? Should I try to minimise the length of the extension? Or is it unimportant (within reason)? another couple of feet would be very helpful.

George

 

[dontsendbubbamail]

Extending the wires between the motor and the esc is OK. Keep the wires between the battery as short as possible and add extra caps.

Bubba

 

[BMX]

So I extended the ESC cables by about 10inches and strapped everything to the bike to try.

Almost immediately the ESC seemed to lose sync. So I stopped and picked up the back wheel of the bike and the motor was "freaking out" trying to run, then stopping suddenly. Servo tester was fully "off" at this point.

I then disconnected the battery and turned round to roll home. After 20 yards or so the motor beeped like at start up and light came on on the servo tester (direct drive at this stage 9.5:1 reduction)!

Connected the ESC back to the computer and am looking at the settings. I have turned off the brake (had it on "hard brake" since I have given up my rear disc to fit the drive) and am wondering whether to change the frequency. (8kHz now, 12 and 16 are the other options). Advance is on "auto" as well, can I play with this to help things?

I am not giving the motor much stress at start up (downhill and pedalling) and am bringing the throttle in very slowly.

Is it possible that the cable extension is to blame (partially or entirely)?

Thanks

George

 

[fechter]

Long motor wires shouldn't screw up anything as far as I know. It will increase losses, but generally takes a lot of stress off the controller due to the resistance.

Hard brake could fry something. Stopping a bike is not anything like stopping an airplane propeller.

You could have a loose connection somewhere. This is a common problem.

If you don't get anywhere with that, try going back to the short wires and see if that clears the problem.

 

[BMX]

Thanks,

Bit difficult to go back top the short wires as there is no way to get the setup on the bike that way.

Took the brake off and put the PWM up to 16kHz bike seemed a little less inclined to cogging, but still very problematic, speed controller got pretty hot. I guess I will try going back down to 8 still with the brake off and see how that goes.

What does adjusting the timing do? If I retard it slightly might that help?

Thanks

George

 

[recumpence]

George,

You want the pwm at 8khz for that motor. The motor timing should be low. The issue is not your wire length. It could be a connector to the motor. However, I am willing to bet it is your controller. Some controllers are not up to the task of running an E-bike.

Matt

 

[AussieJester]

^^ BMX recumpence is the guru of RC motors on ebikes
so I would be listening to da man, Castle Creation HV110 ESC would be the shot
for your setup i think, recumpence sells them for very competitive
price also. You can get a throttleiser that consists of a BEC, servo tester
and current limiting, allows you to plug ESC and throttle into the throttliser
EVLogix is the member to see for these retail ~100 bucks IIRC? Of course
the other option is fitting hall sensors to the motor and running a 'normal'
ebike controller. something members have been doing with their rc setups for few months now with much success...

Best of luck anywayz

KiM

 

[BMX]

Thanks for the help.

I put the timing back to 8kHz and left the brake off, also put the timing to low. Definitely the best it has been, less heat build up in the ESC but still very bad cogging followed by a screech and nasty beeps from the motor, only possible to remedy by disconnecting power. I also have the current limiting set to super cautious, so maybe letting it take more current will help, worth a try I guess if I have to replace it anyway....

I went for the speed controller before finding this board and have since read a lot on here so was thinking of a Castle and Throteliser, build quality on the Turigny motor is pretty shocking too so I may simply replace everything

Shame to have to spend the money, and even worse to have the wait for it all to be sent to the UK. Is there anyway I can buy throtteliser, esc and a motor (Medium sized-ish Astro?) from one place to save paying three lots of shipping?

On the plus side the drive seems to be holding up fairly well, so that is something, I will try to get some photos up soon...

Thanks

George

 

[recumpence]

The motor may be OK, even though it looks low quality. I can supply you with the Astro motor if you would like one.

Also, I am willing to collect the parts you are looking for and send them together if you want a Castle controller. The few bucks I make on the controller will make it worth my while to collect the throttlizer and a motor if you want a different one.

The only down side with Astro motors is the wait. They take about 6 weekd to have made at this point.

Matt

 

[BMX]

Thanks Matt,

The Turigny motor has a slightly oversize hole in the outer can for the axle to fit into. The result of this is that the can runs slightly eccentric (0.2-0.4mm at a guess). I could potentially shim this somehow, but I doubt it would be very satisfactory. I also wonder if the variation in gap between coils and magnets (as the can rotates) is adding to the confusion of the ESC...

I saw the Astro group buy thread and a 3210 would have suited me I think, but I wasnt sure by how much I had missed the boat. If you do it again or have spare stock (at non-group buy prices obviously) I am definitely interested.

Sorry to seem dim, but after wading through lots of the great threads on here I am slightly suffering information overload, I probably saw everything I needed to know elsewhere but I didnt recognise the importance at the time. Do you have a website of the stuff you make/sell?

George

 

[BMX]

Well that about wraps it up for the motor.

Tried another little test run and almost immediately had a nasty sound, turned out that the outer part of the can had moved even more off centre and was now rubbing. Took it off to find the typical loose magnet/ chuff all epoxy scenario as well and at least one un-stuck magnet.

I have a smaller (but higher kV Turigny 50-65D 270kV) I can try in it's place but the gearing is going to be pretty high for that (6000rpm @ 22V with 9.5:1 on 26" wheel = 50mph so at least twice the gear I want) ... Might try epoxying the magnets and reaming and shimming the can end on the damaged motor, but I suspect that I wont be able to reduce the eccentricity much.

George

 

[Kepler]

You are going through problems many of us have already enounted with cheap RC gear so your not Robinson Crusoe here. My experience is that you can make that motor work. I have used that motor sucsessfully in a stand up scooter setup but there was no way it would work with cheap Hobby City ESCs (I tried quite a few of them) Best results were with a Castle Creations ESC and Trottleizer setup but you can also get it work with just the CC ESC and servo tester setup. Problem with the second setup is that you don't have any current control and the RC type controllers will just keep on piling in the current as you twist the throttle. Good for wicked acceleration, not so good for sync issues. When running just the ESC and servo tester, I found that a switching in a resistor that limited the pot output to around 2.5K acted as sudo current control and helped the sync issue quite a bit. You can then setup a switch which gives you full pot range for speed. I think Matt posted how to set this up a while back and shouldnt be too hard to find.

As a sucker for punishment, I have ordered one of the Turnigy K Force 100 amp ESC to try with my friction drive. Hopefully the faster CPU and and super slow ramp will make it more Castle Creations like but I wont be holding breath. Worth a go though for $60 US and I have RC models I can use it in if it doesn't suit my drive. The Castle Creations ICE series of ESCs are not to badly priced also and if you dont need anymore then 8S, these could be a good option.

 

[recumpence]

Thanks Matt,

The Turigny motor has a slightly oversize hole in the outer can for the axle to fit into. The result of this is that the can runs slightly eccentric (0.2-0.4mm at a guess). I could potentially shim this somehow, but I doubt it would be very satisfactory. I also wonder if the variation in gap between coils and magnets (as the can rotates) is adding to the confusion of the ESC...

I saw the Astro group buy thread and a 3210 would have suited me I think, but I wasnt sure by how much I had missed the boat. If you do it again or have spare stock (at non-group buy prices obviously) I am definitely interested.

Sorry to seem dim, but after wading through lots of the great threads on here I am slightly suffering information overload, I probably saw everything I needed to know elsewhere but I didnt recognise the importance at the time. Do you have a website of the stuff you make/sell?

George

I have a couple 3210s ordered for myself. I may be willing to sell one to you. I can also supply you with a Castle controller preprogrammed and ready to go.

I just want to make sure you are setup with the right stuff for your application.

Matt

 

[BMX]

That would be great thank you. I will PM you my email.

in the mean time I will play about with the other motor and see what it can do, at this stage I am trying to learn all I can so it is all valuable (if expensive) experience...

George