Ultimate Cromotor V4 mod

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bigbr1212   10 mW

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Ultimate Cromotor V4 mod

Post by bigbr1212 » Jun 25 2016 11:05pm

We took a Cromotor V4 and milled down the flux ring and the spoke ridges. Titanium bolts, hybrid ceramic bearings. Vent side covers and countersink holes inside cover to slice the air better and T-9 corrosion protection on the windings. The motor is way lighter plus it looks really cool. I did the work myself. I also did the same thing to a few QS 205 motors
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Ohbse   10 kW

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Re: Ultimate Cromotor V4 mod

Post by Ohbse » Jun 26 2016 12:03am

Obvious question - how much weight did you save?

Any flux leakage? How much meat did you take out of the rim?

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macribs   1.21 GW

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Re: Ultimate Cromotor V4 mod

Post by macribs » Jun 27 2016 6:21pm

Nice work you've done there. *Thumbs up*

Have you done a test ride? How is the heat now with added cooling? Think the shaving of back iron will in any way impact the cooling or do you your vent holes make enough airflow to keep cool? Did you do a "fatbike rim" cut off on the rim as well?

Let us know the weight saving pls.

And tell us more about the bearings. What made you choose that exact bearing, ceramic over traditional steel balls bearing? Do they roll as smooth and long as those inline skates using ceramic bearings?

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spinningmagnets   100 GW

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Re: Ultimate Cromotor V4 mod

Post by spinningmagnets » Jun 27 2016 6:59pm

One of the biggest issues with the big hubs is that many buyers are hesitant to buy from overseas. There's not a huge profit in ordering pallets full and breaking the stock motors down into individual orders, but...if customers could order QS motors and get the modified versions from a US based seller, I think that would go over well.

Ventilating is very good for race motors, but I believe in the long run, non-ventilated hubs with ferro-fluid will prove to be more popular. As to the skeletonizing to shed weight, that's always good for any customer. Of course you have to make what customers want in order to survive. Only time will tell.

devman   10 mW

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Re: Ultimate Cromotor V4 mod

Post by devman » Jul 08 2016 7:30pm

how many mm of steel you are removed from the rotor?

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Schlafmutze   10 W

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Re: Ultimate Cromotor V4 mod

Post by Schlafmutze » Jul 24 2016 12:54pm

Those motors look sick.

Any more information?
Also cromotor V4? I thought the V3 was the newest one, source?

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Offroader   100 MW

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Re: Ultimate Cromotor V4 mod

Post by Offroader » Jul 27 2016 12:13pm

That is interesting about the countersunk holes for better air intake. I wonder how much of a difference it makes.

I do know that for my air cooling mod that I had to drill bigger and more holes because the air flow was not good enough, but I'm pushing a lot of air with my fan.

I'd be interested to know the weight of these motors.

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macribs   1.21 GW

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Re: Ultimate Cromotor V4 mod

Post by macribs » Jul 27 2016 1:31pm

Offroader wrote:That is interesting about the countersunk holes for better air intake. I wonder how much of a difference it makes.

I do know that for my air cooling mod that I had to drill bigger and more holes because the air flow was not good enough, but I'm pushing a lot of air with my fan.

I'd be interested to know the weight of these motors.

Countersunk holes for me means the type of hole you drill if you need ie flush mounted allen screw. Where the radius of the hole closest to the surface where screw will sit flush is larger then the deeper parts of the hole. Then again my english level is probably on par with a 16 year old, as I am not a native english speaker.

I fail to imagine how such a hole will improve air flow? Will the increased radius of the "out side facing" hole create drag or suctions of some sort?
If that is the case, is there a way to quantify the increased flow, or probably better and easier to use temperature as an indicator.
[+] Digression
Man there are so many aspects to learn about e-bikes, tweaking, hot rodding and reliability I kind of get why the major bike and motorcycle companies still are on the fence or using 3rd party enclosed low powered mid motors like Bosch etc. With so many variables in play for powerful, and somewhat reliability for each and every part of motor/controller/batteries/charges most likely even major brands and players don't have all the expertise inhouse today to make affordable high powered e-bikes that can take a beating without bending, twisting or even melting in a ball of fire.

To years into e-bikes, reading up, sketcing, more reading, making mock ups and spending time here on ES I still feel very much like a noobie. There are always new ways, better ways or better parts and ideas to make things accelerate quicker, run faster yet producing less heat or simply better heat removal.

And to think my first thought when joining this wonderful community was to make a one-bike-fits-all-needs :oops: :roll: :oops:
Last edited by macribs on Jul 31 2016 3:46am, edited 1 time in total.

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Offroader   100 MW

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Re: Ultimate Cromotor V4 mod

Post by Offroader » Jul 27 2016 2:44pm

It must make a difference somehow, try breathing through a full straw, then cut 95% of it off. The question is how much of a difference does it make?

I agree, this ebike stuff is overwhelming. I'm not sure if I want to keep up anymore with everything.

What bothers me is I can't get a simple answer for how does the MXUS 3000 compare to a cromotor or QS motor. It is like I have to go do the testing myself to find out.

Ohbse   10 kW

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Re: Ultimate Cromotor V4 mod

Post by Ohbse » Jul 27 2016 8:35pm

Offroader wrote:It must make a difference somehow, try breathing through a full straw, then cut 95% of it off. The question is how much of a difference does it make?

I agree, this ebike stuff is overwhelming. I'm not sure if I want to keep up anymore with everything.

What bothers me is I can't get a simple answer for how does the MXUS 3000 compare to a cromotor or QS motor. It is like I have to go do the testing myself to find out.
15-20% worse, but a similar percentage less mass. Worse torque/amp, worse total heat capacity which in turn results in less peak ability as well as reduced constant power output. If you can improve its heat shedding, you can increase its constant power handling, but that doesn't help for its peak capabilities.

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Offroader   100 MW

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Re: Ultimate Cromotor V4 mod

Post by Offroader » Jul 27 2016 10:29pm

I guess that is best how to look at it, I think it is more like 10% performance loss for a 25% savings in weight. This is because the stator is only about 10% smaller. I don't know how much a difference the extra copper fill makes with peak power.

What kills these QS205 or cromotors is that they waste material making the stator bigger than it has to be and in the central mass of the motor.

I think the QS205 needs to be redesigned for weight savings.

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macribs   1.21 GW

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Re: Ultimate Cromotor V4 mod

Post by macribs » Jul 28 2016 5:15am

Offroader wrote:It must make a difference somehow, try breathing through a full straw, then cut 95% of it off. The question is how much of a difference does it make?

I agree, this ebike stuff is overwhelming. I'm not sure if I want to keep up anymore with everything.

What bothers me is I can't get a simple answer for how does the MXUS 3000 compare to a cromotor or QS motor. It is like I have to go do the testing myself to find out.

We tried a year or two back to raise funds for shipping crom motor and QS 205 to Justin for testing. When no one was committed enough to put some $ into testing - or rather buying those motors the whole project kind of died.

Later I've read that if you ask any motor manufacturer for certain data about their motors the motor spread sheet here on the forum will let you compare your motor of choice against those already are inserted into the spread sheet. It has been a while since I last looked at that file, maybe both QS 205 and MXUS 3000 are entered into the spread sheet? If not you could look at what data you will need for each motor and ask the sellers for that information. I'll think power, heat and torque was amongst the things the spread sheet calculated.

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Offroader   100 MW

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Re: Ultimate Cromotor V4 mod

Post by Offroader » Jul 29 2016 9:25am

I am going to give the Mxus 3000 a try. I am really curious to see if there are benefits of lower weight in the rear.

My reasoning also is that since batteries are getting so large in capacity, I've personally got a whopping 3.3KW pack, a little efficiency savings for a larger heavier motor isn't as important.

For me, if I use a lighter mxus 3000 motor which will not be as efficient or require me to use a little more amps to get the same power as a QS 205, it isn't that big of a deal for me since I have so much battery capacity. The weight savings will be far more advantageous on an off-road performance ebike where suspension matters.

You guys just running on the street, it doesn't really matter all that much having a larger motor in the rear.

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macribs   1.21 GW

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Re: Ultimate Cromotor V4 mod

Post by macribs » Jul 29 2016 3:32pm

Didn't someone shave some backiron off the Mxus 3000? I wonder how much weight is possible to shave off the backiron and possible remove some steel between the spoke holes on the flanges as well. Iirc mxus 3000 is around 9 kilo stock, Imagine getting the weight down by 2 or 3 kilos. Don't know if that is possible, but if anyone remember who did the shaving off the mxus maybe we can find out?

If one could save 2-3 kilos on the motor alone, then a couple of more kilos could be saved lacing up the motor into DH rims and light weight tires.
Even think I saw some titanium spokes somewhere for the weight watchers.

I can testify to that a heavy 205 in a motox rim with a 4 ply michelin is a lot of weight in the rear wheel, on paved roads and gravel roads it is not a problem. But I think I will not be doing any jumping or riding any DH tracks with this setup. I don't even jump down small flight of stairs with this setup. If I need to go down 4-5 steps of stairs on a walkway I slow down to a crawl and ease down each step to avoid damages. Could be interesting to lace up a lightweight wheel/moto/rim combo to test how it will work offroad. At least swapping wheels are easier then building a mid drive.

Then again, I probably will not find time to do a lacing job, shaving off backiron etc before winter hits. Could be a little winter project getting things ready for next spring. Maybe with some sort of swappable car hifi blocks for phase wires, hall sensors and thermistor, clamped to the swing arm or frame. So one would only need a few allen screws to swap wheel/motor or change tire. And no soldering.

Let us know how well the mxus does offroad, Offroad. :)

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Offroader   100 MW

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Re: Ultimate Cromotor V4 mod

Post by Offroader » Jul 31 2016 12:55am

One thing I wonder is why did he use titanium bolts? I would have used aluminum because it is cheaper and lighter.

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