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E-flite . Next D . Fast Lad Performance

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e-Electric Motors & Controllers > Motor sizes
 
 
Sparkhead
Key Veteran
Location: Melbourne Australia

Can anyone tell me what the numbers on motors mean. I have a Twist 37 but some people call it a 3700. What does this stand for? I'm new to electrics and hove no idea what all these figures mean.


Mick.

Robbe & Futaba.
01-11-2004 Over year old.
 
 
Buzzsaw46
Veteran
Location: Spring Valley, MN.

The Twist 37/3700 spins @ 3700rpm per volt, has nothing to do with size. This is common for Kontronics they aslo make a Fun 480 which is the same size but without the fins and they are also rated by KV=rpm/volt so a Fun 480 28 spins at 2800rpm per volt. The 480 part of the number does refer to the size and it's about the same size as a speed 480 long can brushed motor. Each manufacturer comes up with their own sizing numbers so it is very hard to tell just by the model number how the motor compares to other manufacturers. for an exapmle an Aveox 27/26/1.5 would be very close to the same as a Fun 480 33 but unless you look at the data sheets you wouldnt know it just by model number. It would be nice if they could do a more standard sizeing so it would be easier to comapre across differant manufacturers, I like the first part of the aveox and the second part of Kontronics methods. Aveox uses the dimensions in the 27/26, 27mm diameter can 26mm long stator but the 1.5 refers to the number of turns so no idea how many rpm per volt, the Kontronic's Twist gives no indication of the size but 37 tells the rpm/volt. than you throw Hackers in and a B40-xxL would be about the same size as both the 27/26 and the Fun480 but just make every thing more confusing. Bottom line is you have to look for detailed specs for each motor and figure it out from there.
01-11-2004 Over year old.
 
 
Sparkhead
Key Veteran
Location: Melbourne Australia

Thanks for the info, so I can assume that my twist 37 on a 10 cell pack does 3700x12=44,400RPM. So now I can work out some pinion sizes. Is there any loss factor that I have to calculate into the equasion when working out the RPM?


Mick.

Robbe & Futaba.
01-11-2004 Over year old.
 
 
Buzzsaw46
Veteran
Location: Spring Valley, MN.

Here is a good way to calculate pinion gears, I copied it from a differant forum I just used it to figure out the power sytem for my Eolo and it worked out just fine. there is a better sytem if you have the spread sheet program exell(sp) but this works for me.



Take the voltage you expect the battery to supply under load ( 3S LiPoly will be about 10.5 volts). Multiply the KV times the voltage and you will know what the motor should be turning. The motor will be the most efficient at 90% of that rpm and up. Since you need a little “head room” for voltage drop, stay between 90 – 95%. Divide this motor rpm by the wanted head speed (around 2100) and you will have the gear ratio. Divide 180 (the number of teeth on the Hornet main gear) by this ratio number and the answer will be the teeth on the pinion.

Example;

The 010 has a KV of 3570 x 10.5 volts =37485.
Subtract 5% from 37485 = 35611
Divide 35611 by 2100 head speed = 16.96 gear ratio 16.96 to 1
180 teeth on main gear divided by 16.96 gear ratio = 10.61 pinion teeth

I would use an 11 tooth pinion and you will be able to use a slightly higher head speed.

Actually an 11 tooth will put the motor at 95% with a head speed of 2176
Or to look at another way an 11 tooth pinion with a 2100 head speed will have the motor running at 91.6% of it’s rated KV (still OK).
01-12-2004 Over year old.
 
 
Sparkhead
Key Veteran
Location: Melbourne Australia

Thanks, very good explination. Do you take off about 5% of the total battery voltage on all types of batteries or just for Lipo's.

3s= 11.1v - 5%=10.545v.

Is this the same for my Nimh's?

10cell pack Nimh 2150 mAh= 12v - 5%=11.4v.


Mick.

Robbe & Futaba.
01-12-2004 Over year old.
 
 
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e-Electric Motors & Controllers > Motor sizes
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