RC Mid drive project - trial/freeride style

[macribs]

Yes the price is steep. But all things considered, no re build of swing arm centralized motor running via gears to give plenty of torque for even the steepest hills it might be worth th extra pennies. After all, those astro motors are pretty much bullet proof. Astro have higher quality magnets and wiring and can take up to 200 degrees celsius of heat. In that drive unit it seems thermal masses has vastly increased so possible even harder to run into over heat issues.

As it stands now he struggles with heat due to operating motor below the most efficient RPM range. He is reluctant to rebuild the swing arm. And he is close to ditching the mid drive for a powerful hub motor. Seeing all effort and dedication spent on this build it would be sad to see him settling for a hub.It just seems that a 3220 drive unit like this will solves all of his problems.

And who knows - if he is lucky maybe he can get one of those test deals - if he is that lucky he can be beta tester for 400$. Might even be possible to work out a way to get the more powerful 3220.

It just seems that a 3220 drive unit like this will solves all of his problems. But hey that is just one mans thoughts. For all I know maybe those 400$ deals are all gone already, and it seems those are not production ready yet for the public.

That being said I am sure it will be well worth it to do a rebuild of swing arm to fit 120 pro. That motor packs a mean punch.

 

[riba2233]

Yeah but you still have problem with too much torque going through bicycle transmission...

I also vote for rv100 or 120 and modification of existing swing arm. He already has most of stuff ready.

 

[gwhy!1]

he needs a higher kv ( around 120kv ( pref delta) and get the halls out of the motor so it can be tuned correctly.. if he wants to push 7kw reliably.

Edit:
also the close prox of the ali mounting plate may also be heating the motor up

 

[boisrondevens]

Hello Stielz,
Please correct me if I'm wrong, I think you made couples basic mistakes.
1. You may have out a fan but there is not air FLOWING from one side to the other.
2. Rewinding the motor and not knowing the new Kv is bad because you can't reliably calculate the reduction ratio. You are lucky nothing blown yet 
Don't have time to write, got to go back to work…

Nice ride btw :lol:

 

[Stielz]

How difficult would it be to modify the swingarm to fit a RV120? Its definitely not something I could do.

If I can get the full power out of my C80100 I'd be happy for awhile atleast lol. I think I can fit a 2 stage gear reduction in the swingarm, with the jack shaft just behind the motor. Then re-wind the motor again with bigger wire and less turns. The issue is finding the time to do all this. I'm meant to be writing a thesis ATM so just want to get this finished so I can spend more time on that.

Hello Stielz,
Please correct me if I'm wrong, I think you made couples basic mistakes.
1. You may have out a fan but there is not air FLOWING from one side to the other.
2. Rewinding the motor and not knowing the new Kv is bad because you can't reliably calculate the reduction ratio. You are lucky nothing blown yet 
Don't have time to write, got to go back to work…

Nice ride btw :lol:

Some corrections, I did know what the motor kv would be before I did the re-wind. Its 76kv which I geared for a top speed of 70km/h.
As for the fan, I was also skeptical about it making any real difference because of the limited air flow through the end cap. But I was advised that it does make a difference which I have seen, though if the motor were spinning faster it would make more difference.

Keen to see video of your ride in action BTW, maybe that can sway me towards the RV120

he needs a higher kv ( around 120kv ( pref delta) and get the halls out of the motor so it can be tuned correctly.. if he wants to push 7kw reliably.

Edit:
also the close prox of the ali mounting plate may also be heating the motor up

By "tuned correctly", do you mean the hall sensor offset angle? With the adaptto controller you just set this on the keypad, around 15 degrees offset in my case.

I did check the proximity to the mounting plate, no noticeable heat generated in the aluminium and the motor can doesn't get that hot.

 

[Ohbse]

You definitely need to get the RPM's up to get the most from the small motor, that probably requires rewinding based on your current KV as you're not going to be able to double voltage with the controller.

You also need a new seat post, that doesn't look too comfortable! Seat should be parallel with the ground, not crushing your nuts

Looks great, awesome work.

 

[Stielz]

Thanks for the tip, think I can adjust the seat angle so should give that a try

 

[Ohbse]

Thanks for the tip, think I can adjust the seat angle so should give that a try

There are specific posts for laid back style frames that will position your seat correctly. If you do have some angle correction in the current one I doubt it will get you back to flat.

 

[gwhy!1]

he needs a higher kv ( around 120kv ( pref delta) and get the halls out of the motor so it can be tuned correctly.. if he wants to push 7kw reliably.

Edit:
also the close prox of the ali mounting plate may also be heating the motor up

By "tuned correctly", do you mean the hall sensor offset angle? With the adaptto controller you just set this on the keypad, around 15 degrees offset in my case.

I did check the proximity to the mounting plate, no noticeable heat generated in the aluminium and the motor can doesn't get that hot.

I did not know that you could shift the timing with your controller.. cool.. The other thing to consider is the heat effect on the hall sensors when they are internal and this also can cause problem.
What is your no-load current ?.

 

[Stielz]

I am able tune the controller to get very low no-load current but doing this gives far from optimal tuning for on road use.. Accidentally got the motor to 180 degreesC once by tuning for optimal no load power consumption, then doing an acceleration pull on the road

 

[Stielz]

I have a video of it in action.

[youtube]ToSgeMTjNeE[/youtube]

 

[boisrondevens]

Me like

 

[gwhy!1]

I am able tune the controller to get very low no-load current but doing this gives far from optimal tuning for on road use.. Accidentally got the motor to 180 degreesC once by tuning for optimal no load power consumption, then doing an acceleration pull on the road

I have always set for optimal no load current and for me it has always be perfect, it maybe your controller is compensating ( shifting the timing dynamically ) so yes you will need to find the sweet spot for the controller or because you are using a higher voltage than me it may be to do with the upper end rpm, this is unlikely because my motors are wound for 120kv and run on 50v and your motor is a lot lower kv, Or you have some thing else going on under load conditions ( which is a big possibility ( cross talk/jitter/false signals, in sensor signals ).

 

[Stielz]

The controller has a setting called 'ind timing' which is a speed dependent timing adjustment. In my experience when I set this up for lowest current on an nu-loaded motor does not give good results when the motor is loaded.

I think I have the tuning set up pretty good now as the power consumption is around what you'd expect for a given speed. I think the problem is simply that the motor needs to spin faster to get the full power output.

From memory, its got something to do with the max efficiency being the point where the motor iron (or core) losses equal the copper losses. And for this motor that point is probably around 7000 - 8000 RPM

 

[Ratking]

The controller has a setting called 'ind timing' which is a speed dependent timing adjustment. In my experience when I set this up for lowest current on an nu-loaded motor does not give good results when the motor is loaded.

I think I have the tuning set up pretty good now as the power consumption is around what you'd expect for a given speed. I think the problem is simply that the motor needs to spin faster to get the full power output.

From memory, its got something to do with the max efficiency being the point where the motor iron (or core) losses equal the copper losses. And for this motor that point is probably around 7000 - 8000 RPM

Just as a tip, don't demand too much out of this motor after winding it with such a low Kv. I went from 130Kv to 95Kv on my dual motor build and I really felt the difference. Not able to dump as many amps in to the motors, but they stayed cooler and the controller was cooler as well. Even though the drive system have an easier life, it is just not as fun with less punch.

I only have 50v, so you may get more out of your motor, but only more power due to higher rpms

 

[rodgah]

probably around 7000 - 8000 RPM

Im pretty sure it might of been thud that experimented with the max rpm of these motors....from memory the efficiency went out the window close to the factory 130kv wind on 12s so 6500rpm, forgive me if I am wrong. I seem to remember thinking that if I ever rewound mine it would be for the same or a fraction higher kv for 12s because it was based on good testing.

What I can say for certain is that if you are going full throttle in that video on your acceleration then there is something wrong (I am comparing to a CC hv160 though). My dh bike was geared for ~65-70km/h and would easily lift the front wheel off the ground without even full throttle. The same goes for a single 5t delta 3220.....very similar power...though the astro got very hot doing acceleration runs over and over. I never tried to climb a hill like that (in the video) though so my heating on flat ground was minimal given a constant speed etc. Another thing to try is to remove all braking the motor does....since this will heat the motor too....and maybe just a break is all it needs.

https://www.youtube.com/watch?v=N0BnlPL-ips

 

[Stielz]

Sweet, your bike looks like a weapon.

I've found that I need to have the current limits fairly low otherwise the motor overheats after just one burst of acceleration. In my video I'm using 70A battery / 140A phase.

With my re-wound motor, the phase resistance is slightly higher than the stock winding but the motor speed constant is significantly lower and therefore more torque per amp of current through it. I thought the gain in torque per amp would make up for the gain in phase resistance and then some but it seems that's not the case.

You're right, the regen braking does noticeably heat up the motor. When I know that I need to save on temperature rise in the motor I stop using the regen brake then it lasts a bit longer before overheating.

This is a quote from Thuds thread on re-winding these motors http://endless-sphere.com/forums/viewtopic.php?f=30&t=20618

So far, I haven't built a better motor & controller set up than the 6-turn, 2-in hand, 14G, dlrk/wye terminated motor...run the thing with a 12 or 18-FET xie-chang with a 6-Kw limit on 20 LiPo cells & you will not find a better RC power combination [with external hall sensors].

I think the 6T Wye is around 104kv so on 20S lipo thats 7800 RPM.. A bit more than my 4500 RPM

 

[rodgah]

That video isn't mine....just a demonstration of the power you should have. You might have more torque per amp but the higher the rpm, the more multiplication is done via reduction.

Did you weigh the stator before and after rewind?

 

[Stielz]

Yes I did do some weighing. My measurements show the stock wind having 340g of copper, and the re-wind having 380g of copper. Although it should be noted that I weighed the stock wind stator with the phase connector plugs and heat shrink, and the re-wound stator without.

 

[rodgah]

well that blows that theory then.

Try a HV160 just to check that it is not the controller creating the heating. Then I guess you have 2 options, rewind or increase V.

 

[Thud]

Here are my observations for this re-wound motor & its disapointing performance..

Its wound with a single strand of 14 gage wire.....that is only rated for 15amps of current befor it starts heating. With 200c insulation it will do 25amps continuously
https://en.m.wikipedia.org/wiki/American_wire_gauge

Your pumping 3300 watts of energy into a motor set up to receive 1200watts @ 48v. Your going to make heat.
To get that motor near its max rating youll have to adjust the voltage to get it spinning 8k rpms again.
(Edit: reading back i see your running higher voltage the math above is off from an incorect post)

Horse power is a combo of tourqe & rpm's over time....guys throw watt ratings around without any context for the work the motor is performing.

If you want to get 4kw of work out of that motor you need it to spin as fast as is reasonable & from my experiance your target should be about 8000 rpms.

That is a kv of 180 if your going to limit the voltage.

Awsome build though.
Sorry to see you unhappy with the performance.

Edit: Reading back a ways, I see you have a firm grasp of what you need to do.
Good luck &i hope you find time to get it all sorted out.

 

[Folken]

An old thread, but... You are all missing one thing guys: skin effect. There is a reason why motor manufacturers wind with bunches of thin wires instead of one thick wire. Look how thin the stock wires are. Although this rewound motor now has a low DC resistance, the skin effect will increase it when the motor is running, so more heat and less efficiency.
But the build itself is awesome!