"How To" wrap a rotor magnet...

[lincpimp]

Not sure if this is a true "how to" but I guess the info may be useful. Fisrt time I have done this, so not sure if it is the correct way or not. Here we go.

So I decided to wrap the magnet of my hacker b50 5s motor with kevlar thread. I will be using this motor on 3s lipo in my speed 10th scale, so magnet reinforcement seems like a good idea.

I scoured ebay for kevlar thread and found some. The seller also had something called vectran, which is supposed to be superior to kevlar, so I bought it.

Heres the link : http://cgi.ebay.com/ws/eBayISAPI.dll...MEWN:IT&ih=023

When I received the package today I had a look and the vectran is thinner than the kevlar, so I decided to use it as the air gap between the magnet and winding is tight on the b50 motor.

Heres a pic of the rotor before:



Heres a pic of my supplies, 30min epoxy, 80 grit sandpaper, vectran thread, shrink tubing, and paint stick:



Rotor after light sanding:



Rotor after application of mixed epoxy and wrap of vectran, I wrapped it as evenly as possible, but the vectran is very fine, and not woven together so it was difficult to make it overlap much:





Heatshrink applied over rotor and heated up to hopefully hold it all together while drying. Also hoping it forces out any excess epoxy.





I will cut the heatshrink off tomorrow and see how it looks. I will also balance the rotor, not really sure how to do that, may have to sand some of the epoxy off...

[What's_nitro?]

Very interesting... I may have to try that with my Feigaos if it works out for you.

[BL_RV0]

Cool. Let is know how it turns out.

[JERRY2KONE]

hey Linc how goes it? So is the shrinkwrap just for helping with the form of the whole project, and then you take it off?? Or does it stay on the rotor?? Do you have any tech data that can give us some kind of idea how much protection this will provide versis not doing it? I am just curious how much of an advantage this might give, and how it may affect the performance & efficiancy of the motor.. Looks like a fun job and if it does give an advantage worth the work, then you have just taught us all how to do it. Nice tutorial/how to. Not bad for a pimp without any monkies to help out.

[BrianG]

linc, couldn't you put the rotor on some type of lathe and gently scrape the rotor? This would remove any high spots and balance it at the same time, no?

[Tempted]

Originally Posted by BrianG

linc, couldn't you put the rotor on some type of lathe and gently scrape the rotor? This would remove any high spots and balance it at the same time, no?

Nah, it wouldn't balance it just smooth it. Different density between the epoxy and rotor so for that to work you would have to grind away all the epoxy. Easiest way to balance is to put it in extremely smooth bearings and spin it. Where it stops, lightly sand the bottom a bit. Spin it again and see what happens. Do that until the rotor doesn't stop in the same place every time and your done. There are more precise ways but nothing without a sophisticated machine that I am aware of.

[lincpimp]

Originally Posted by JERRY2KONE

hey Linc how goes it? So is the shrinkwrap just for helping with the form of the whole project, and then you take it off?? Or does it stay on the rotor?? Do you have any tech data that can give us some kind of idea how much protection this will provide versis not doing it? I am just curious how much of an advantage this might give, and how it may affect the performance & efficiancy of the motor.. Looks like a fun job and if it does give an advantage worth the work, then you have just taught us all how to do it. Nice tutorial/how to. Not bad for a pimp without any monkies to help out.

Not sure if it will do much. Hopwfully it will hold the magnet together, as the one piece magnets tend to come apart. I am not sure if I should have wrapeed the rotor first, then applied the epoxy.

Originally Posted by BrianG

linc, couldn't you put the rotor on some type of lathe and gently scrape the rotor? This would remove any high spots and balance it at the same time, no?

It would true it but I am not sure if my wrapping method is precise enough for that to perfectly balance it.

Originally Posted by Tempted

Nah, it wouldn't balance it just smooth it. Different density between the epoxy and rotor so for that to work you would have to grind away all the epoxy. Easiest way to balance is to put it in extremely smooth bearings and spin it. Where it stops, lightly sand the bottom a bit. Spin it again and see what happens. Do that until the rotor doesn't stop in the same place every time and your done. There are more precise ways but nothing without a sophisticated machine that I am aware of.

I plan to use my prop balancer to balnce this rotor, and just sand it as you suggest. We will see how that works.

[lutach]

Linc, you did it like most place will tell you to do it. You'll have a little access and that can be removed. I can't wait to see how it looks.

(Off-Topic: How's the 100A ESC doing in the crawler?)

[mohanjude]

James

I asked the forum on help with my damaged 1521 rotor. I applied epoxy on the magnet and it worked. However I got scared as after a 5 min run when I took the rotor out the epoxy was getting soft. I remember somebody talking about heat resistant epoxy. Dont know where to find the stuff. The epoxy you used on your picture is exactly the same stuff I used. Dont know if it will soften once the rotor is spinning at 30k rpm and the heat is high. Last question - do you think you will have enough clearance?

Mohan

[Tempted]

I would use a balloon. You can melt it off with a lighter without hurting the epoxy. Just pull as much off first, then burn the remaining a little at a time. Keep the rotor dunked in water as soon as you burn the balloon and it should be just fine.

Edit- I was just thinking, exactly how important is the exterior wrap? Just let the epoxy dry and sand it smooth.

[lincpimp]

Originally Posted by JERRY2KONE

Good info Linc. Maybe you need to coat the inside of the shrinkwrap with something to keep it from sticking to the epoxy, hence making it easier to remove after the epoxy has hardened/dried. I am not sure what you can use without affecting the epoxy itself, like WD40, or Pam, or some other kind of releasing agent. The proceedure is kind of interesting to watch from the outside perspective. Thank you for sharing this with us.

If I used the plastic type of heatshrink, such as the type used on lipos, I feel it would be easy to remove. I only had the rubber type and did not even think that the epoxy would stick to it...

Originally Posted by brushlessboy16

I was wondering if that was going to happen..

Why not a later of way paper or something?

I may use some plastic wrap, as what's_nitro suggests.

Originally Posted by What's_nitro?

Even better, use plastic sandwich wrap. It's very thin and also impermeable. Wax paper might still allow some epoxy to get through and stick it all together, plus it's much thicker than the plastic wrap.

I may try this out on something other than a magnet and see how it does.

Originally Posted by Tempted

I would use a balloon. You can melt it off with a lighter without hurting the epoxy. Just pull as much off first, then burn the remaining a little at a time. Keep the rotor dunked in water as soon as you burn the balloon and it should be just fine.

Edit- I was just thinking, exactly how important is the exterior wrap? Just let the epoxy dry and sand it smooth.

I may just try to do it without using shrink. With a thin coating of epoxy and tightly wrapping the thread, the epoxy flowed thru nicely. I need a better method of holding the rotor while wrapping. Guess I will have to enlist the help of the bench vise...

[Tempted]

You could also run the rotor off of a low speed motor or lathe once you get the epoxy done. It would prevent running and may even help with balancing.

[lincpimp]

Originally Posted by Tempted

You could also run the rotor off of a low speed motor or lathe once you get the epoxy done. It would prevent running and may even help with balancing.

I just use enough epoxy to coat the thread. My main issue is how to balance the rotor once the wrap is done...

[Tempted]

I'm stumped there. The only way I can think of has already been mentioned. Your prop balancer would be about the best choice and just sand the epoxy until it doesn't stop in the same place.

[BL_RV0]

How is it coming along? Has the second coat dried yet?