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Ultimate lightweight wheel-motor concept
- Thread starter speedmd
- Start date
speedmd
10 MW
Thanks miles.
speedmd
10 MW
I did a bit of roughed out modeling on the rotor magnets and it looks like we would be able to fit 11mm wide magnets and still have room for a good size dovetail between them with the custom magnet shape. 12 mm wide magnets will fit also, but leaves little room for a strong mechanical anchor. Still possible. Not sure it would be worth trying to squeeze in larger magnets or what the trade offs would be.
The closer you get to 100% pole coverage (180deg magnet angle), the greater the proportion of the additional flux that gets wasted through leakage.speedmd said:
Another factor is the relationship between pole coverage and torque ripple. For this, the optimum coverage will vary with the slot/pole combination.
speedmd
10 MW
Hi Miles
Not sure I understand the 180 degree magnet angle concept you mention. Your last slot pitch was listed at 12.65mm, with a 2.45mm slot width. We could fit comfortably a 11mm wide magnet and still not fully cover the stator tooth. No change on the 68 pole/ 72 slot arrangement. Not at all sure how one would go about optimizing the magnet width. Very interesting project. Much appreciate the experience.
Not sure I understand the 180 degree magnet angle concept you mention. Your last slot pitch was listed at 12.65mm, with a 2.45mm slot width. We could fit comfortably a 11mm wide magnet and still not fully cover the stator tooth. No change on the 68 pole/ 72 slot arrangement. Not at all sure how one would go about optimizing the magnet width. Very interesting project. Much appreciate the experience.
For curved magnets, pole coverage is often expressed in degrees. 180 degrees being full coverage of the pole.
I chose 10mm square flat magnets, initially, because there was talk of using a stock size.
For custom magnets, we might as well make the face concentric with the stator. They can be any circumferential width that works well. I usually tweak the width to give the lowest torque ripple, as the last step.
I chose 10mm square flat magnets, initially, because there was talk of using a stock size.
For custom magnets, we might as well make the face concentric with the stator. They can be any circumferential width that works well. I usually tweak the width to give the lowest torque ripple, as the last step.
speedmd
10 MW
Thanks Miles. Tooth face width is just over 12mm going by my rough calc. still leaving a bit extra room in the gap size unless one chooses to wrap fatter wire. Will take a look at wider custom ground magnet shape to give it a better look at what real estate is available to anchor them with.
Science Faction
1 W
- Joined
- May 18, 2009
- Messages
- 59
Hi guys
I've been off the sphere for a while and returned to check the progress of this most interesting project.
Is there anything to report?
Cheers
Paul
I've been off the sphere for a while and returned to check the progress of this most interesting project.
Is there anything to report?
Cheers
Paul
speedmd
10 MW
Unfortunately I have been too busy to see any time for this project the last few weeks. Hopefully at some point this summer we can find time to settle on some good options for magnets.
johnrobholmes
10 MW
The original flat magnets would be a fine start. The model already has low torque ripple, and they will be a bit cheaper than curved magnets because of the low waste to make them. Having teeth to key them into the stator will be just as secure as a dovetail in this arrangement.
I should also mention I just got a Mazak QTN250 msy, and could make motor housings as large as 14" diameter.
I should also mention I just got a Mazak QTN250 msy, and could make motor housings as large as 14" diameter.
liveforphysics
100 TW
Awesome! I can get lams quoted in various alloys. I have a bit more free time once again.
Someone give me a drawing and I can have a quote by end of week.
Someone give me a drawing and I can have a quote by end of week.
johnrobholmes
10 MW
Many thanks Miles! Either myself or Luke will get some lamination quotes. I have blocked out machine time on my Mazak in the second week of October (right after conversational programming traning) to start machining housings and will go ahead and order a small amount of magnets.
Hurdles I see- freewheel that is broached. someone making them still? Coil resin setting, not sure if my resin vat is large enough to fit the stator but we can brush it in if the coil depth isn't more than 1/2 inch and wire size isn't smaller than 24g. Sensor mounting, either PCB or slots in the stator will be needed.
Who here wants one? I won't do a batch more than 5 at first, and I can't give a solid estimate of completion or a guarantee of specific performance. We can wind them in-house or send them bare. I anticipate that cobalt lam motors will be about 2.5k each, and m15 steel lam about $2K each after it is all said and done. I'm kinda leaning towards cobalt lams for my own if they aren't too cost prohibitive. I would ask for lamination and magnet costs up front and remainder of payment for protos when they are ready to ship. I will also buffer $200 per motor to miles for his time of engineering the design, even though it is probably terrible pay for the hard work he has done.
Hurdles I see- freewheel that is broached. someone making them still? Coil resin setting, not sure if my resin vat is large enough to fit the stator but we can brush it in if the coil depth isn't more than 1/2 inch and wire size isn't smaller than 24g. Sensor mounting, either PCB or slots in the stator will be needed.
Who here wants one? I won't do a batch more than 5 at first, and I can't give a solid estimate of completion or a guarantee of specific performance. We can wind them in-house or send them bare. I anticipate that cobalt lam motors will be about 2.5k each, and m15 steel lam about $2K each after it is all said and done. I'm kinda leaning towards cobalt lams for my own if they aren't too cost prohibitive. I would ask for lamination and magnet costs up front and remainder of payment for protos when they are ready to ship. I will also buffer $200 per motor to miles for his time of engineering the design, even though it is probably terrible pay for the hard work he has done.
johnrobholmes
10 MW
Miles said:
Which is why I want to give you some if I take any cash to make them
johnrobholmes
10 MW
Sent lam quotes to laser lams in alabama for 29g m15 and 29g Hiperco 50.
johnrobholmes
10 MW
Came back at $5 per lam for stator only, laserlams doesn't think they can do the rotor without damage during deburr. So we may need to increase back iron width a bit for manufacturing reasons.
So if we extrapolate the price it is $200 per rotor for the stator lams only in 29g m15. Won't be a huge price jump for rotor too since the material is already contained in the stator quote.
So if we extrapolate the price it is $200 per rotor for the stator lams only in 29g m15. Won't be a huge price jump for rotor too since the material is already contained in the stator quote.
johnrobholmes
10 MW
Now a hurdle for myself would be lamination stacking and insulation. I think hiring a company that specializes in this would be best, so we will address this very soon when things are closer to coming together.
So far myself and Luke are on the list of people that definitely want a motor. Who else would join? I probably overestimated the cost at $2500, but better to overestimate than to underestimate and have to ask for more to complete them.
So far myself and Luke are on the list of people that definitely want a motor. Who else would join? I probably overestimated the cost at $2500, but better to overestimate than to underestimate and have to ask for more to complete them.
good to see the thread is not dead.
2500$ would be for what?
i guess we should first arrange the case, how the motor will be mounted, protection against mud and water etc etc.
who does the winding? i guess some of us want to do this oneself..
2500$ would be for what?
i guess we should first arrange the case, how the motor will be mounted, protection against mud and water etc etc.
who does the winding? i guess some of us want to do this oneself..
johnrobholmes
10 MW
Forgot to remove the magnets from the CAD, so now we are good for rotor lams too. $275 per motor for lams.
$2500 is an estimate for a fully built motor, wound and ready from Holmes Motion Control. The case design we will pursue is cassette mounted with a torque arm to grab the seat stays or BB stays (or both ideally). Weather sealing is not a difficult task for inrunners, but it is best to assume that crud will get inside and to properly seal the coils / magnets to avoid corrosion and damage from debris ingress.
I haven't seen any housing designs being offered yet, maybe Miles posted one I missed. If nobody else steps up I will do it myself. The key element will be dealing with reaction torque without the motor tilting via bearing play, so a two point frame mount will probably be needed. Bearings will need to be larger in ID than the freewheel, but the rpms are low so they won't be too expensive.
$2500 is an estimate for a fully built motor, wound and ready from Holmes Motion Control. The case design we will pursue is cassette mounted with a torque arm to grab the seat stays or BB stays (or both ideally). Weather sealing is not a difficult task for inrunners, but it is best to assume that crud will get inside and to properly seal the coils / magnets to avoid corrosion and damage from debris ingress.
I haven't seen any housing designs being offered yet, maybe Miles posted one I missed. If nobody else steps up I will do it myself. The key element will be dealing with reaction torque without the motor tilting via bearing play, so a two point frame mount will probably be needed. Bearings will need to be larger in ID than the freewheel, but the rpms are low so they won't be too expensive.
speedmd
10 MW
Page 12 has a few concepts for cases. Some very interesting options.
IMO if crud and mud get inside the motor and between magnets and stator, the anticorrosive coating will be rubbed off soon and bigger particles could also damage the winding insulation or other parts. keep it completely closed would be best.johnrobholmes said:
I am very interested and also want to help building such a motor respectively want to have one, but without a well thought out and designed motor im not very pleased to pay up front.
John, what do you think about using and building the motor around the freewheel i posted on page 12? You will need an additional one to the one in the cassete if you do not want to twist the motor when pedalling.
Or what about brake side mount so we can use regen?
It is good you mentioned the point with the tow-point swingarm mount or BB mount. nobody here have thought of this before and it is not unimportant..
