Watch gear gearboxes for sale - RC Groups
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Jun 15, 2006, 05:23 PM
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billystiltner's Avatar

Watch gear gearboxes for sale


I have made up some extra watch gear geaboxes and put them up for sale on my website.
2 different units are available.

6:1 Watch Gears
Didel MK04S-10 motor
2.5 x 1.6 Propeller

6.4:1 Watch Gears
Didel MK04-10 Motor
4" x 2.6" Propeller

I'm fixing up my balance to do some thrust tests and add some weights.
You can see the performance of the GBU6010 in my Square5.5 Living Room Looper videos.
I'm pretty sure the units are lighter than others commercially available.

The GBU6010 works well for about 6" span and smaller planes.
The GBU6410 would be an alternate for the Butterfly or Square9 propulsion unit.

Here's a link to my store.

Last edited by billystiltner; Jun 24, 2006 at 10:40 PM.
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Jun 15, 2006, 10:19 PM
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Hows the GBU6410 performance compare to the GB05 with the 4027 cf prop? My modified Square 9 could use just a little more thrust I think.
Jun 16, 2006, 10:06 AM
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Druid, that is a very nice square9!!! whats the weight?
Jun 16, 2006, 12:56 PM
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billystiltner's Avatar
Yes that is a nice square 9. I like the stars on the tissue. You have done a nice job. Even if the thrust is the same with them the GBU6410 weighs less than the GB05. I'm not really trying to compete with that or any other gearbox its just an alternate lighter weight solution for those that want to venture into the super light end of the hobby or just want to spend the extra weight somewhere else. Not that the light side of the hobby is not fun enough as it is. I have lots of fun with my square9 with stock plantraco gear.

I'm still fiddling with my balance so I might not get any good thrust measurements till next week. I've almost got it all setup though. I found out that just adding the big micro clips to the thing will throw the measurements off so I have to come up with some way to add wires to my thrust stand. I think Litz wire along the hinge then solder to 2 copper plates along either side of the main upright. I can then use a rubber band to secure the motor wires to the copper plate to make contact. Then at the base I think I'll add some sort of rods so I can clip the measurement leads.

I'm also going to VA over the weekend so might not answer any emails or fill any orders till next week.

Jun 16, 2006, 03:09 PM
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Jonathan don't have a scale but I think some where between 4 and 5 grams. Weighs
more because of the .9 rx and the Bahoma adapter and micro plugs. This air frame
has a 3" chord the first one had a 3 1/4" chord. I'm going to try another at 2 7/8"
to see if it gets better still.
Jun 16, 2006, 07:43 PM
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billystiltner's Avatar

I just done some thrust measurements.
they were done quickly so I will probably spend some more time next week doing them again. This is a rough idea of the thrust and weight.

Weight - 0.9g
Thrust at 3.6V - 3g
Current at 3.6V - 140ma

For comparison
Plantraco GB05 with 4027 CF prop
Weight 1.1g
Thrust at 3.6V - 2.9g
Current at 3.6V - 160 - 170 ma(the meter went back and forth between 0.16A and 0.17A)

I'm not sure how accurate this is.
Both arms on my thrust stand are 4" but the thrust line sits a bit higher than 4" and the prop is ahead of the hinge line. I might get more accurate readings if I pull on my balance with a string instead of push down with a rod not sure. Also the plantraco motor might be more worn than the motor in the test GBU6410.

I just read a post from Gordon Johnson and he got more thrust with a smaller prop but his gearbox has ball bearings. I'm curious now if the cf tube thrust bearing and ball bearings have that much of an effect. I 'll have to carve a smaller prop and find out next week. I also read in another post that Didel has an 4mm 8.5 ohm motor. I'm also looking into that. Just as soon as I offer a product I'm looking into changeing it. Well maybe I'll just offer one more unit or something who knows.
[edit maybe I misread. The 8.5 ohm motor might have been there 6mm motor]

Last edited by billystiltner; Jun 16, 2006 at 08:04 PM.
Jun 17, 2006, 10:04 AM
Plantraco's Avatar
I think Gordon did get over 4 grams of static thrust with the 4027 CF prop using one of your gearboxes - I seem to recall. So this is great news! It's great that you have them available - I'll be ordering some right away!
Jun 17, 2006, 10:58 AM

Yeah I'm definitely interested in buying that setup we talked about.. I just need a little while to get the monies and such.

You should take some pics to get everyone salivating =] From what I recall, they have a really nice sound to them over plastic, don't they?

Jun 19, 2006, 12:28 AM
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billystiltner's Avatar
That is great.
Gordon got the 4+g of thrust with one of Ralph Bradley's watch gear gearboxes which have ball bearings. My gearboxes have carbon fiber tube thrust bearings. I'm petty sure that the gears in the GBU6410 are the same as in Ralph's gearboxes though.

Thats great also.
Currenlty cameraless but have a few newer photos of the GB6010.
The newer gearboxes have red teflon tubes that acts both as a keeper and a thrust washer. Another difference is the props are more true helical pitch than my previous ones.

Jun 20, 2006, 12:47 PM
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billystiltner's Avatar
A note about the GBU6410. I put it on my Square9 with the plantraco equipment last night and didnt really notice any improvement in performance. I crashed the plane once in the living room and the ply upright slipped off of the motor, the prop did not break. It's kind of like the break away prop on the plantraco GB05. The GBU6410 is really fragile, it will hold up to some living room crashes but you will most likely be better off with the Plantraco GB05 if your plane has a similar wingloading as the Plantraco butterfly. Where you will see improvements in performance is when you pair up the GBU6410 with planes that have a lighter wingloading than the butterfly. I might loose some sales saying this but hey I dont want you guys to think hey my butterfly will perform better with that gearbox and buy it and be dissapointed when you see no improvement in performance.

Now the GBU6010 on the otherhand might be just as fragile but for the size planes it will fly, it is pretty dagone sturdy. I hate to keep pluging to watch my livingroom looper videos but you can see how it holds up to crashes and such in those videos. The prop in the videos was really thin and had been broken several times. The GBU6010 has a lower profile so it doesnt break away on crashes.

Aug 28, 2006, 06:29 PM
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billystiltner's Avatar

I'm almost ready to throw in the towel on these gearboxes but I'm still hanging in there.
I timed how long it takes to make parts and assemble a gearbox and each individual part of construction. It takes 1.5hours per gearbox and 1 hour for the prop. I worked on the gearboxes for 4 days and only had 2 gearboxes assembled but had parts ready for making more. There are snags along the way that can cause much longer time to be spent on each gearbox. I have been trying to formulate tests to be done after a gearbox is done to make sure they are in working order before being shipped out. I'm glad that I have only sold one gearbox and only traded a few becuase my testing has shown that it is really dificult to get consistent assembly. Some of my older gearboxes are slipping. They were glued when my apartment had all the shingles off the roof and it was extremely humid. So I'm looking at better ways to keep the pinion and spur from slipping and a way to test for slippage. The GBU6010 has a mismatch in pinion and spur module but it works out that it is ok. I can get a really smooth running gearbox despite this. The prop size for the GBU6010 is good for really light planes ~2g but with a larger prop it is possible to get a lot more thrust out of the GBU6010 at a price of extra curent draw though. The 30mah lipolies should handle the extra current draw and the motors do not seem to get too hot at 200ma or so. They do get a bit warm at this current draw.

I have found that the 10 ohm motors get more thrust than the 12 ohm motors that is the
10 ohm 4mm x 8mm plantraco motors get more thrust
than the
15 ohm(or12ohm) 4mm x 1mm didel mk04-10 motors

if both motors are geared at 6:1
and a 3.2x2.2 prop is used.

this is contradictory to others findings.
Maybe not though
When the early terts were done with the kokham 20mah lipoly that battery limited the thrust produced by the amount of power it could output

With the new 30 mah lipolies the limiting factor is the voltage with these motors
The 30maH lipoly can put out the current required by the 10ohm motor to make the extra thrust so per V if the power supply is capable the 10 ohm motor does better.

This is probably really confusing.
I might have bad 15 ohm motor and there are other factors that could be causeing the results I 'm getting. I'm still not satisfied with my thrust test stand but here are the conflicting results I got.

Aug 26-06
Didel MK04-10 15 ohm 4mm x 11mm
6:1 gears
3.2"x2" prop
2.8-2.9g thrust

Plantraco 10 ohm 4mm x8mm
6:1 gears
3.2"x2" prop
3g -2.9g thrust

For comparison
Plantraco GB05 with didel mk04-10 motor
MCF 4" cf prop
5:1 gearbox(this might be the culprit of the low thrust results - I got glue in the bearing once and might not have gotten it all cleaned out beacue later I oiled it and other gearboxes. The plantraco gearbox did not do better but others did
3.75-3.8g thrust

Aug 27-06
After oiling gearboxes

Didel MK04-10 15 ohm 4mm x 11mm
6:1 gears
3.2"x2" prop
2.8-3.0g thrust

Plantraco 10 ohm 4mm x8mm
6:1 gears
3.2"x2" prop
3.2g-2.9g thrust

Ther was a slight breeze in the room from the fan but I have found that the thrust tests without the fan the thrust is the average of the upper and lower results I did record the upper and lower thrust.

So you can clearly realize from these tests which may not be accurate* that the 15 ohm motor does best per watt but the 10 ohm motor can provide a bit more thrust if the battery can provide the extra current.

The results could be caused by a barely slipping pinion as well.
I have no way of holding the prop shaft to twist the pinion to se if the joint is good.

Does anyone know how to fit less than 1mm wide jaws onto a shaft to hold it and what kind of metal do you make the jaws from that will hold up to the force required to hold the shaft? There must be a way to do this. I think I might have ruined or at least damaged the brushes by not holding he shafts
while pressing on the pinion.

I might be comparing apples to oranges because I'm using the plantraco 10 ohm motor instead of the Didel 10 ohm motor but I would imagine that the results woul be similar if not better with the Didel 10 ohm motor becaue the Didel 10 ohm motor has a smaller shaft. Good or friction but bad for pinion slipping. I was aggravated at Plantraco at first for sending me the motors with the larger diameter shaft but now I'm thanking them because the 0.7mm shafts allow me to ream the pinions out to be a good tight fit.

I'm thinking of writing an article on how to make these gearboxes instead of selling them. I'll probably make the article regardless if I continue selling the gearboxes or not.
It has been quite a learning experience and I'm still learning.

Since I'm moving I have to close down shop for a couple of weeks but will open back up for business after I get settled. I plan on bringing some gearboxes to NEAT. I'm almost out of pinions so need to sell a gearbox after I treturn so I can reup on watch part soup.

I'll post some new photos soon. The camera is too good it shows all my bad glue mistakes so I'mn rebuilding the gearboxes and cleaning up the excess glue. some of the older gearboxes needed regluing anyways. Duco ha worked fine for the most part but I'm thinking of switchin to either epoxy or CA for gluing the motor shaft to pinion and gluing the propshaft to spur.
Does anyone have any recomendation for which glue to use for brass to stainless steel and brass to carbon fiber joints. The brass cf joint probably only has .0005" or less space between them and the brass-stainless steel joint probably only has .0001" or less so the glue has to be able to penetrate into that small of an area. I think sometimes that the fillet of glue on the outside is the only thing holding the parts in place but recently found that if I glue the female(gear) part it seems that more glue stays inside. I was told to always glue the male(shaft) part with epoxy, that was with a loose fitting part though. This may not be true with such tight fitting parts.

Gosh this is a long post. I think I need to quit drinking coffee. I was still going whn I woke up from the cup I drank last night.

*however I have seen the same kind of results with different gearboxes and even direct drive.

Last edited by billystiltner; Aug 28, 2006 at 06:41 PM.
Aug 28, 2006, 07:00 PM
No more nicotine for me!
micro_builder's Avatar
wow billy, thats quite a post!

all i can say is i'm completely satisfied with my GBU6010, its never failed on me and i've run into more than my fair share of imovable objects. i've broken the prop a couple times, but thats nothing a little dab of CA cant fix. i'm almost shocked that you only sold one and have only done a few trades, even if its impossible to get identicle results from one gearbox to the next, they're still all really nice looking and lighter than mass produced versions.

by the way, your picture taking is getting pretty good. i've found a large magnifying glass between the camera lense and the object can help get a closer image without loss of resolution.

Aug 28, 2006, 07:44 PM
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Dave Wulff's Avatar
Nice camera Billy, don't forget to get some sleep or you will be nodding off at NEAT

Aug 28, 2006, 09:22 PM
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billystiltner's Avatar
Glad you like your gearbox. And thanks for the encouragement.
I think one of the props in the photos is yours just need to get it in the mail.
It ought to fly your square6 really nice. Do you want one with pointy tips or flat tips? The flat tipped one is new but performance doesnt seem any different than the others.

I'm thinking to make kits for them which would be a good way for more folks to have watch gear gearboxes and would take the pressure off of me to get the things working without slipping. Kits would be easier to get mass amounts of them to vendors as well.
It would probably still take about an hour to prepare a kit though but a laser cut upright would make that a lot quicker ahhughm.

Hey Dave
Will do. Cant hardly function without sleep as much as I used to be able to.
The coffee sure helps though.

Have to finish that cessna.


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