Triple Rewind of Unite 500W Motor

Discussion in 'Electric Bicycles' started by safe, Mar 28, 2009.

1. safeActive Member

Triple Rewind of Unite 500W Motor

This is sort of a mirror of this thread:

http://www.ebikehub.com/forum/viewtopic.php?f=4&t=886&p=1546#p1546

http://www.motoredbikes.com/attachment.php?attachmentid=16384&d=1238282052.jpg

The idea is that when you alter the way these motors are wound (internally) it radically changes the behavior of the motor.

The short answer... there is a trick here for extreme power... (without overheating)

(I'll get back onto this thread later... follow the link if you are interested)

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2. safeActive Member

Hmmmmm... expected some replies...

Let me repeat what I've discovered here.

Basically the limiting factor for most electric motors is their heating. Heat is produced based on the formula:

Heat = Current * Current * Resistance

...so as you try to increase the current the heat rises dramatically. But resistance can also be a factor. If you could drop the resistance from the typical Unite motors level of about 200 mOhms - 500 mOhms down to the level that most RC motors run at (30 mOhms - 80 mOhms) then you could reduce the heat by that same amount.

The "trick" that I'm using is exploiting the difference beteween a series connected circuit verses a parallel connected one. When you divide the motor coils up into separate parallel winds this divides the current flow and that dramatically reduces the resistance. (for a Triple wind this means that only one third as much current flows through each of the coils in order to achieve the same magnetic field :idea: )

So a 500 watt Unite motor can all of a sudden pull 1500 watts and not overheat. (no need for goofy air blowers to solve the problem you fix it with a change in the motors design) However, you do not ever get something for nothing and the penalty is that the motor now DEMANDS a higher current just to operate. The no load current increases dramatically. All of a sudden you get the added power, but at the expense of "fuel economy".

People who want sheer power should study this.

If it's of any help, on the last Triple rewind I managed to get this bike up to 58 mph on flat land.

Last edited by a moderator: Apr 23, 2009
3. mabmanMember

Hey Safe. I find that all pretty interesting but with the regs being what they are in regards to wattage and top speed for electric motorized bikes what application do you see this used for?

4. safeActive Member

True... however, there are plenty of outlaws around and this will feed their outlaw lifestyle. :devilish:

The law says 750 watts output and that translates to about 1000 watts input. You can take somethng like a 350 watt Unite 1016Z3 and turn it into a very efficient (and cool running) 750 watt motor doing a Triple wind... and I've done that project too.

The whole idea is that the concept is SCALEABLE to whatever you want to do.

...if you want to change the amount of power a motor can create then your choices are overvolting or rewinding. Rewinding has the advantage that the rpm remains the same, so it's a more practical result. (however, rewinding is more technical than simply adding more batteries)

I'm just making people aware of the dimensions available to them.

Better to "know" than not to "know". :whistling:

----------------------------------------

There are hub motor people and RC motor people that pride themselves in big power output and this shows how the humble little Unite motor can deliver performance that equals what these more expensive options can achieve.

You can buy this 500 watt Unite motor for \$44.49

http://www.monsterscooterparts.com/ramxmo.html

-----------------------------------------

There is also a "stealth" aspect to this trick. You can rewind the motor and nothing is visibly changed. The humble little WalMart ebike can all of a sudden produce twice the power without adding any heat related problems. For those that want more power, but want to appear legal this also is a good thing to do. (overvolting can be detected, but this cannot without taking the motor apart) Those that want to seriously trick out their WalMart bike might overvolt and rewind at the same time while increasing the battery. That way you increase the speed and power at the same time. Many ebikes are designed to pull more current (stock) than the motor is ideally designed for. Going from Single to Double often can increase power while improving efficiency (no load current increases however) without needing to change the controller at all.

There are many options to pick from...

Ebike motor and battery design is an artform... you have many choices that you can pick from and it's up to you to design a custom configuration that fits the needs you have for the bike.

Last edited: Mar 29, 2009
5. mabmanMember

Thanks for that explanation. I am a bit in the dark about electric currently but see the need for it for some markets. Having the most efficient motor for the best price is certainly the way to go as I see bikes like the \$8k Optibike as nothing more than a rich boys toy and not the answer to get more people involved in using them as cheap efficient transport. Keep up the good work.

6. safeActive Member

The Optibike is like the Tesla Roadster... they are both technically brilliant and too expensive for the masses.

Eventually the technology will trickle down to the more entry level ebikes.

But in some cases, for something like a WalMart ebike, the low tech, poor performing technology makes more sense because of the price.

-------------------------------

The Optibike demonstrates the perfect application of all known technologies applied in the most artistic way. While I'm sure someday it will be eclipsed (advances are inevitable) it represents a high standard for the rest of us.

Rewinding a motor is a way to reconfigure the "cheap stuff" to do things that it wasn't really designed for. Like overvolting it's a way to alter the performance of something that comes with performance that is poor.

It's really all about the \$\$\$... rewinding makes for the poor mans "hot rod"...
.

Last edited: Mar 29, 2009
7. beast775Guest

technical

i would like to know how to wind a motor like that?is there a low budget explanation?does this mean you have to upgrade the output shaft for more demand of power and or torque?thanks.

Last edited by a moderator: Mar 29, 2009
8. safeActive Member

This is now my third rewind of a motor into a Triple.

This was my second rewind project from a Single to a Triple... the MY1016Z3:

http://www.motoredbikes.com/attachment.php?attachmentid=16415&stc=1&d=1238356334.jpg

...if you look carefully at the photo you can see the three layers of windings one on top of the other all connected at the center three times. A Single wind only connects the wires at the center once, but a Double does it twice and a Triple does it three times. With each connection it divides the current and that reduces the overall motor resistance. (it's like a series set of resistors verses a parallel set of resistors... the parallel has less resistance as a circuit)

I've taken these Unite motors to way beyond their ratings and the bearings never fail. The MOST likely thing to fail is always the brushes because they carry the current. This is why the brushless motor is really the way to go in the long term. But for a cheap way to get to big power this is the way to go. (that and overvolting)

Just watch the thread develop... I tend to do things slowly so it might take a week or more before it's done. It's hard to say... I'm not in a big hurry. (so you need to be patient and just watch)

The original thread is here:

http://www.ebikehub.com/forum/viewto...6&p=1546#p1546

...and this is a mirror to allow people to discuss what I'm doing from this forum. I'm kind of doing this in a sloppy way, but maybe afterwards I'll redo it as a clean "Build Tutorial". However, as the weather gets better I tend to not want to post as much as I'd rather be working on the bikes.
.

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9. ozzyu812Member

Your work is truly amazing!

I can't understand going through all that trouble with the motors. I have run winding machines before and its not really something I could image doing it by hand. Why not just buy a 1500w motor? Power to weight? I don't think so because your running SLA's. Cost? Obviously not because, it looks like your spending a ton of money? Hiding form the electric bike police? It doesn't look like that bike is trying to hide.

One thing for sure I don't have to understand it, just admire it!

10. AussieJesterMember

Excellent stuff safe...

ozzyu812 you will be VERY surprised how much money
safe doesnt spend he is probably the most frugal guy i have
ever met LoL...he is all about doing thing 'cheaply' everything
you see was done by him in his garage at home alot of the parts
were sourced from curbside You might also be surprised to hear
he doesn't have a 'flash' mig welder like some of us
:: puts up hand :: lol the bikes pictured were all
welded with oxy an acetylene welder!

The first bike pictures in the OP (with fairing) was made
to meet Federal U.S law ie. 750watt max with
operational pedals... bike pictured second was the first bike which
is LEGAL in the state where safe resides, it wouldn't be
classed as 'legal' in all U.S states.

Sure these bikes aren't going to be great for general commuting,
that's not what they are designed for, if you want a bike to run to
the shops a mountain bike would be the better choice obviously.
These bikes are all about speed/fun...GREAT 'toy' to
add to the garage IMHO has been an eye opener watching safe
put these bikes together to, breaking something fixing it modifying
it to work better and be stronger etc...it is a learning process i guess
and interesting to follow IMO... ANYONE that takes on the challenge of
building a bike from scratch getz my respect without question, i
know how difficult it is and the headaches and problems
encountered :: sigh :: in the end though when you do have a finished
bike and take a step back to marvel on your achievements it is a
GREAT feeling knowing YOU made it ;-)

Shall continue to follow with interest keep up the excellent
work mate ;-)

KiM

11. safeActive Member

Thanks for the compliments AussieJester, and I return them all in praise of your own custom made Trike.

This is a photo of the core after having sanded the old paper insulation material from out between the grooves and then applying a thin layer of epoxy into the grooves followed by a layer of high heat black paint to make it look clean and smooth. The core is now ready to be wound.

For more information be sure to follow the mirror site as well:

http://www.ebikehub.com/forum/viewtopic.php?f=4&t=886&p=1586#p1586

Last edited by a moderator: Apr 23, 2009

13. AussieJesterMember

Better than a "bought one" safe ... might be just the ticket for my next ride
if i go ahead with what i was discussing with you yesterday :: wink ::

KiM

14. safeActive Member

The 200C wire is the highest temperature wire (short of some specialized ceramic covered wire) that you can buy. I'd guess the stock wires are probably near the low end of the temperature rating. This is why you can blast huge amounts of current through the motor and the color of the coils doesn't change.

Between the naturally lowered heating due to the motor redesign and the increase in quality of the wire the only thing left to fail is the brushes.

The main thing is that you can get RC motor like performance out of the low cost Unite motor.

And the BEST thing is that there are Unite motors with BUILT IN geardowns like the MY1016Z3:

http://tncscooters.com/images/106115.gif

...or the MY1018Z:

http://tncscooters.com/images/106118.gif

...and it's these motors that really are at the greatest need for a rewind because they tend to be weak motors. Geardowns are essential to get the rpms down low enough to match the pedal rate which is 100 rpm maximum. This is another reason that overvolting does no good... when you overvolt you increase the motor rpm and that screws up any chances of getting your gearing to work right. Going with the Triple wind tends to increase the motor power dramatically, but keeps the rpm low so these geardown motors will be able to be integrated directly with the bicycle chain.

I've done the rewind of the MY1016Z3, but I don't have the bike ready to test it yet...

Last edited by a moderator: Apr 23, 2009
15. skyl4rkGuest

Do you have any advice for rewinding one of these motors to make a generator? Something that would put out about 60V at 3000 rpm? It could be geared up or down so the rpm is not critical.

I guess my question is, if you take a permanent magnet brushed motor rated at 36V, and you want to spin it with a motor to make it generate power at about 60V, how do you calculate how to wind it?

16. safeActive Member

More "turns" means that as a generator it would take fewer rotations of the shaft to generate a given voltage.

Maybe a better way to think of it is that there is such a thing as a constant "K" that for every volt there is a relationship to motor/generator rpm. The faster you spin the "device" as a generator the more voltage you "get". While in the other direction the more voltage you "supply" the more spinning takes place.

So there is a relationship to "turns" and shaft speed.

You would work backwards:

1. Figure out how fast the shaft will be spinning. (which you seem not to care)

2. Divide that speed by the voltage you desire.

3. You now have that constant "K" of volts per rpm and can then figure out how many "turns" you would need to match that constant based on the way your motor is designed. (the strength of the permanent magnets, etc)

...since all this stuff is specific to the motor you are using there is no simple answer. However, you could figure it out.

I seriously doubt that multiple winds are going to help though because that's mainly a thing to do to get extreme power out of lightweight and undersized motors. My guess would be that a Single wind would be the most efficient as a generator.... however... I could be wrong... I haven't thought about it much. :thinking:

17. AussieJesterMember

Don't know if its of any help or not but there are 60v Unite motors already you can buy straight off the shelf, they are alot larger than what safe is working on TNC Scooters have them if your interested, there max rpm is ~3k also I use the 48v version of the motor myself ...

KiM

18. safeActive Member

I've seen those 60V motors over at TNCScooters and they look like the same size as the 1000 watt motors, but they cost \$130. It would be interesting to take one of them apart and see what they are doing.

The old 1200 watt Unite (discontinued) used a Double wind, but was otherwise identical to the other motors which all were Singles.

Generally speaking you tend to create a 60V motor by using MORE turns (so that the constant becomes lower) and having more winds means you get a higher resistance value. So I could guess that the 60V is probably a 1000 watt motor (shell) rewound with about 32 turns in a single wind compared to the 28 turns (or less) you normally get. They might even use thinner wire, but it's also possible they just wind it really tight.

Anyone own a 60V Unite that can tell us?

19. AussieJesterMember

Yeah i would put money on them being identical to the complete 1000watt range with exception to the windings, wouldn't make alot of (business) sense manufacturing different housings and armatures if re-configuring the windings got the required result would it :: wink :: I wonder though why they were discontinued? My thinking is they didn't sell a great deal of them, once you get up over that 48volt territory you starting to"wander" towards some high voltage/amperage levels that most sane people (riding scooters anywayz) would probably steer clear of?

KiM

20. safeActive Member

After the discontinued 1200 watt Unite (Double) I suspect all the motors are now Single winds. Maybe it cost a little more (was more labor intensive) to do the Double winds?

Can anyone name a Unite motor (currently in production) that is anything but a Single?

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When they sell a motor that is "higher voltage" that tends to mean "higher resistance".

Higher resistance usually means more turns for a Single and that's why they end up with moderate no load speed even though they are higher voltage motors.

It's all about how you wire these things... the way they market them makes it seem like they are doing something "special" but it really just comes down to the number of turns, winds and wire thickness.

That's why you can take a low priced motor and rewind it and get something totally different.

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The only other thing is the width of the magnets. I measured the magnets on the 1200/1000 motors and they are 3.5" wide. The 500 motor is only 2.5" wide. So you have to figure that the narrower motor will behave differently.

Last edited: Apr 1, 2009