M100 Motor with 6.6:1 Gearing - RC Groups
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Feb 10, 2003, 09:57 AM
Registered User

M100 Motor with 6.6:1 Gearing

A discussion was started at the top of page 14 of the following thread about the concept of installing an M100 motor in a 6.6:1 GWS EPS gearbox so that it could swing a larger prop than the 7.2x4.2 prop that comes with the M100 gearbox's 3.89:1 gearing. From page 14 to page 23 of the thread, results started coming in, and preliminary indications are that this could be a great combination for producing more thrust at less current than the standard M100 package. I thought it was time to give this subject its own thread for those who may not find the information buried at the end of a thread on a different subject. So, if anyone has any comments about this power combination after reading the following thread, please post them here.

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Feb 10, 2003, 11:24 AM
Live to ride... and fly!
Tres Wright's Avatar
Can you give a synopsis on how people are getting the 6.6:1 gearing (any mods required to get it into the GWS box)? I'm sure it's in that thread somewhere, but it's like that CD Rom thread, too big to extract any info from! I've got 3- M100's that are without homes since I started converting to 010's, but one is about to go in my Elipstik. Sounds like the gearing test might be worth a shot!
Feb 10, 2003, 11:36 AM
Registered User
I agree, the M100 is a great little motor, but it spins so fast that it's never been a drop in replacement for the old 280 without changing the reduction ratio. Fortunately it does fit into a GWS IPS100C gearbox with a good selection of ratios. I wish there was a chart similar to the ones on GWS website showing the motor with each prop and gearbox combo. I hope we can get enough feed back to build a database like that.

With careful matching of prop and gearing, it can be made to work well at 3.5 - 4 amps, and run on 2 cell Kokam 1020's. This is originally a 2.4 volt motor, but seems to have very good life on 2 cell lithiums if kept under 4.5 A. I wouldn't expect it to live long on higher cell counts.

Its a high revver, and I'm also trying to find a good direct drive prop that will keep it under 4 amps. I had to cut a GWS 5x3 down to 3 1/4 to get the load down. I also use a de-pitched 5x3, but I still had to cut that down to 4 1/2! I'll try a 4 x 2 1/2 next. Anyone know of another brand that is known to work?

Dave also brought up the possibility of using the larger sizes of GWS direct drive props (up to 12x8) with a gearbox. These props make slightly less thrust than the regular geared props, but use much less current. There may be some promising combinations there?
Feb 10, 2003, 01:47 PM
Registered User
Tres, here's what genebond had to say about his conversion, along with a photo:

Here's a picture of the conversion in process, to show how simple it is. The only thing I did was swap the pinion over (used a little CA on the M100 shaft), Waller out the mounting holes on the frame, and mount the M100 motor with (I think) 2.6mm x 1/4" screws. I had some screws the right size, but too long, so I cut them down.
Feb 10, 2003, 03:42 PM
Crash Master
Gene Bond's Avatar
Hey guys. Taking a little break from work, here, and figured I'd check in. (Don't tell any of my employees, they think I'm downloading porn )

Sorry for the lousy picture. I think my camera may need to find a new home.

I hacked this together on the spur of the moment, on a wild hair to power one of GPW's Albatross 3D's, thinking it'd be a nice cheap and fast platform for testing, ultimately to be used in the 'Low Budget IFOish' I've been pondering on.

My Albatross 3D started at 8.75oz, and has since had about 1-1.5 ounces of hot glue added to it This power system, M100/EPS-D/12x6/QC830, seems to be producing about 9-10 ounces of thrust, as it will just hover, and sort-of pull out of a vertical on a good moment. It performs a little better on 8x300NH, or 7x150NC. Have yet to really get info on 950prismatic's or 1200LI's. I KNOW what will happen on K1020's, and therefore will avoid it at all costs Actually, they hopefully will be here soon (Come on Troy, I ordered them Saturday night, why aren't they here yet? )

Anyway, more torture testing to come. And, an indoor meet next week. I wonder what it'd do on a 6.5oz LadyBug........ Hmmmm.....

Anybody have the specs on this, so I can send them to Pedro for Pcalc?
Feb 10, 2003, 09:36 PM
Registered User

M-100s out of stock

It sounds like bad news for all of us wanting to jump right on the M-100/EPS-D band wagon. I ordered 3 motors yesterday but got a call from Mark today stating that they are currently out of stock and would be unavailable for at least "several weeks".

I'm sure that the demand will go through the roof if testing proves them to have longevity with the EPS set up.

Hugh Mason
Newark Electric Flyers
Feb 13, 2003, 10:31 PM
Registered User
I received some props today, and having prepared a test bed for the M100, proceeded to run some tests with the EPS-100c gearbox, D gearing. I used two sets of 2s Kokam 1020's paralleled as a power source, and recorded Whattmeter data. For continuity, I drained the packs to 8.1-8.2v resting voltage. I did notice that a pack at a given resting voltage can be more or less depleted before the voltage changes, and that probably affected the results somewhat. The voltages given in the chart below are those observed under load.

To complete the test bed, I made a device to measure relative thrusts and used it to compare the thrust of the various props in this 6.6:1 gearing. It does seem to work fairly well; multiple trials with the same prop gave reproducible results. I calibrated it with known weights, holding the device vertically. Then I ran the original stock 280 motor in the Thrust-O-Meter and compared the results with the GWS power chart for that motor, gearbox, prop combo. This gave a correction to my calibration which I applied to the M100 data. By my best estimation, the correction is slightly conservative. Its accuracy does require that I have duplicated the conditions in the power chart, which happens to use 7.2v for its test. By coincidence, the loaded voltage while I was testing the stock 280 was 7.2v, so no interpolation was required to interpret the chart. And, the whattmeter showed the same current and computed watts as were in the chart for a given prop, so I feel fairly confident about the final calibration.

That said, I should add that the apparatus is a little sloppy, so don't regard the thrust data to be much more than approximate. I should show a picture of the Thrust-O-Meter so you can see what we're dealing with here:
Last edited by Jim Jernigan; Feb 13, 2003 at 11:24 PM.
Feb 13, 2003, 10:43 PM
Registered User
kevin b berger's Avatar

This is a must have!

OK, I see you have been keeping your top secret thrust test rig under wraps, but now that it has been exposed, you must tell us all how it is done! It does indeed look like a finely calibrated set-up, and we must have the detailed parts list and assembly instructions so that we can validate and verify!

No really, it actually looks pretty cool.

I was following the M100 threads a while back, and have done quite a bit myself with the Johnson 4046, was it ever determined they were the same motor? I can post some pretty good data on the 4046.
Feb 13, 2003, 11:10 PM
Registered User
Here are the data. Since I've not had success tabulating data in these posts, I'll just put it in order, one prop at a time. (BTW, all the props are RS- no Hyper drive) Order of info is: Prop size, loaded voltage, amps, watts, thrust, and efficiency in gm/watt.

M100 Motor with EPS-100C "D" gearbox

14x10, 6.4v, 5.0A, 33W, 10.6oz, 9.1g/watt
14x70, 6.5v, 4.2A, 29W, 10.95oz, 10.7g/watt
13x65, 6.7v, 4.0A, 28W, 10.6oz, 10.7g/watt
13x90, 6.5v, 4.7A, 32W, 9.89oz, 8.8g/watt
12x60, 7.1v, 3.8A, 28W, 10.25oz, 10.4g/watt
12x80, 7.1v, 4.1A, 30W, 10.06oz, 9.5g/watt
11x47, 7.4v, 2.7A, 21W, 8.47oz, 11.4g/watt
11x80, 7.1v, 3.7A, 27W, 9.01oz, 9.5g/watt
10x80, 7.2v, 2.8A, 21W, 8.12oz, 11.0g/watt
10x47, 7.3v, 2.3A, 18W, 7.76oz, 12.2g/watt

The first thing that I notice is that genebond has been right on with his selection of the 12x6 prop. Another thing is that the numbers indicate that further reduction would yield improved efficiency. The EPS-100C with its stock 280 motor is much more efficient with this D gearing.

Again I will caution that there is unknown error with these figures, especially the thrust. But if they are in the ballpark, the M100 with EPS gearing seems to be a great choice for the Mini IFO, IFO, and whatever lies in between!
Feb 13, 2003, 11:29 PM
Registered User
Kevin I don't know if the Johnson 4046 is the same as the M100. If it is, and you have data, that would be great! I hope the M100 becomes available soon.
Feb 14, 2003, 12:00 AM
Heli Bouncer
Looooeeee!'s Avatar

Electronic Gldmine..

I thought I'd pop in here with this tidbit. It appears that the 2 motored car mirror adjuster from Electronic goldmine uses the same size motor.

Notice that I did NOT say that they are one and the same. The EG motors are definately much lower Kv. They appear to be the same case and back plate size. Another thing, If you have an old M100 that you've been treating nicely by keeping the current down, and it is getting on in its brush wear, you can use the G4046/Johnson 250 backplate with its new brushes on the M100, *IF* its commutator is in fair shape.

I believe that the M100 is a Johnson 200, It even appears to have the same gauge wire. so if your feeling real ambitious you might want to try rewinding the EG mirror motors with the un wound wire from you gutted G4046.

BTW Jim Jernigan, could you post some readings from your drive with a GWS 9X7? I want to compare to my 7:1 M100 drive.

Here is the Electronic Goldmine link, for the mirror motors.

Feb 14, 2003, 12:31 AM
Crash Master
Gene Bond's Avatar
Jim: Thanks for the data. I don't deserve the credit for picking the 12x6, I think it was Dave... I just decided to try it, and liked it!

Based on my real world testing, the thrust number you have jives pretty close. I'd like to be able to interpolate some of these numbers, but my brain is mush right now.

BTW, Dave, the 12x8 from Bals Products WAS the RS, not the HD

I think I'm going to run some numbers to see what I can come up with for a 10x4.7 prop for the Mini IFO, since that's all the prop it can handle.
Feb 14, 2003, 02:30 AM
Senior Gravity Checker
The m100 is shorter in length and has less stator material that the G4046. The G4046 also has larger magnets and more copper wire on it. The comm and brushes are the same.

I posted the procedure for grafting a new comm on the m100 from the g4046. just do a search.

For those that feel it's too much work....you can mail your old m100's to me . You can never get too much of a good thing!.. -Ken
Feb 14, 2003, 09:34 AM
Registered User
So I win the Lucky Guess! award for estimating the 12x6 would be the best prop for this combo. Thanks for the confirmation, Jim. That's my reward for spending way too many hours reading about combinations that have worked for others, and trying to extrapolate how that would apply to untried combinations.

If further reduction would yield improved efficiency, and your aircraft can handle a larger diameter prop than 12 inches, you could always go with one of the long axial distance EPS-
DX or EPS-STD gearboxes: E=7.75:1, F=9.00:1, G=10.66:1 and H=13.00:1. I'm using a cut-down (excess plastic cut away) EPS-STD-D (6.6:1) gearbox with the bushings replaced with bearings (STD=bushings and DX=bearings).
Feb 14, 2003, 09:40 AM
Live to ride... and fly!
Tres Wright's Avatar
Thanks to all of you for the great info! Those numbers certainly look impressive. I think the stock M100 with stock prop was giving me 5 or 6 ounces of thrust at over 3 amps, so changing the ratio and prop are wielding double the thrust at nearly the same amp draw! Very nice!

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