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Dec 28, 2001, 05:34 PM
Only nerd in the village

Pager motor test results

Here are the results of my pager motor tests for your viewing pleasure:

Motor: Pager motor from BG Micro (USD 1.75)
Gear: 4:1 using module 0.25 gears from WES (USD 3.00)
Prop: U-80 (USD 1.00)
Total weight: 3 grams

Volts: 4.95
Amps: 0.30
Thrust (grams): 9.5

Volts: 3.75
Amps: 0.22
Thrust (grams): 5.5

Volts: 2.50
Amps: 0.15
Thrust (grams): 3.0

Conclusion: This is a very powerful little motor when used with 4 cells and the low current consumption would indicate that it is reasonably effiecient. Motor barely gets warm and I checked the brushes in one after an hour of running and they still loked fine. I have tried a larger gear ratio and larger props, but performance increase was not worth the extra effort IMHO. The motor likes to rev and does NOT like a heavy prop. Since the motor works best with 4 cells it can either be used with a DC-DC converter running from 1 cell or in multis running of 4 cells. A twin with 4x70mah NiMH should work well because current consumption is with the capabilities of the small NiMHs.

I hope you find this information useful.

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Dec 29, 2001, 04:33 AM
Registered User
jberg's Avatar

yes, that is very useful. I believe that I can soon build a DC-DC-booster/ESC combination that is quite powerful and efficient (I'm fighting with the software at the moment). With that one would be very independent from a certain input voltage level to power the higher-voltage pager motors. Plus, the output is DC, so no problems with coreless motors.

Where do you get the U-80 props from? What all-up weight do you believe to lift with ~10g of thrust? 25g? Maybe 30g?
Dec 29, 2001, 12:33 PM
Only nerd in the village
Hi Jochen

I'd like to hear more about your DC/DC converter.

I got my U-80 props from Free Flight supplies in the UK. I will be ordering some stuff from Flitehook soon and they also have U-80 props. I can send you their pricelist and you can put whatever you need on my order. I have some more pager motors on the way from the US and can spare a few if you are interested. I'm also waiting for some of the small GWS props to see how they compare to the U-80.

I memory serves me right the geared KP-00 in my 24 gram model produces app. 8-9 grams of thrust and this is adequate. In terms of power 1.5 to 2 watts is sufficient for 25 grams model weight.


Dec 29, 2001, 01:49 PM
Registered User
jberg's Avatar

my booster can pull up to 2A from any source, takes away 20-25% of power and puts the rest out at almost whatever voltage level you want. I designed it originally to supply a 1524 with 9-10V and 0.9A from two Tadiran cells as a power system for a "Tiny". That would be about the maximum power. All lower power and voltage levels are easier, of course, and will give better efficiency. Think of 5V/0.6A for a very long time to an N-20 from one of the Li-Polymer cells you know very well - you get it? (BTW, it's a real pity that the Tadirans are discontinued, their quite low inner resistance would have been a great advantage.) Weight will be at about 3g (booster and ESC). But - it does not yet work completely as I want it to. I'm working on it (job comes first ).

Think farther: a dual actuator driver made from one PIC soldered to the back end of a GWS R4P receiver, supplied by the same 5V that drive the N-20 or pager motor - the only missing thing here is *time* at the moment.

Dividing shipping costs from USA or whereever by two and adding 1,50 Euro for a "Päckchen" would be a great idea. I am strongly interested in the pricelist (you still have my email and snailmail address?).