Jan 10, 2002, 07:55 AM
in persuit of low wing loading
Gordon Johnson's Avatar

Gearbox Construction Techniques

Ralph, Jun, and others have posted details about building gearboxes in other threads. On Ralph's advice, I've purchased servo gear sets. As he found, the JR gear sets provide quite a few gears that are compatible with the Kenway gears. I'll post details about which gear set part number and what you get later. I didn't have much luck with Futaba gear sets providing gears that are compatible with Kenway gears. As soon as my order from Dave Lewis comes in I'll have a reasonably good starter set of the WES gears and the 2mm and 1.5mm id bearings.

But, I have questions. I thought I'd start by reposting Jun's gearbox making technique. I've replicated the part of rolling paper by using grocery bag paper. What I haven't been able to do is find any plastic tubes from liquid soap dispensers large enough to take the 5mm od bearings I get from Dave Lewis. Jun, could you tell me what size bearings you use, and what brand liquid soap has the right size plastic tubes (otherwise I'm going to be getting some strange looks in the grocery store). Also, it would be great if you could post the picture of your gearbox here again.

Dave Lewis is including plans for a two-stage gearbox in with my order, and I think I have sufficient gears to attempt one. I'll post details here on my progress.

Ralph, please jump in with whatever techniques you've learned.

Jun Nolasco quote from KP-00 vs KR1 thread

For the motor mount, I use rolled calling card paper 3/8" wide. I roll the paper around the motor for 1 1/2 to 2 loops, putting some thick CA on the overlap (normal glue or paste will also work just fine). I make sure the motor has a loose fit on the rolled paper. I then remove the motor and saturate the roll with thin CA and leave to dry. This gives me the ability to replace motors at will.

For the plastic tube, I use the ones normally found inside lotion and similar bottles. The ones I have work great on 5mm and 6mm outer diameter bearings. In fact, my wife even saves them for me.

You can also use rolled paper for the tube, built similarly to the motor mount described above.

For the spacer, I use a slightly thicker piece of balsa. I put a bit of thick CA on both sides and sandwich it between the motor mount and bearing tube. I then press on the fully assembled contraption until I achieve the proper gear mesh. I then tie several loops of unwaxed dental floss around the whole thing to keep everything in place. Finally, I remove the motor with pinion, bearings, shaft with spur gear, and saturate the dental floss and balsa spacer with thin CA.

Once things have dried, you end up with a very light but strong gearbox. I have yet to break any of the ones I have built.
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Jan 10, 2002, 10:17 AM
registered user
DNA's Avatar
The white tube holding the bearings is a piece of a Bic pen.
Jan 10, 2002, 05:37 PM
Heli Bouncer
Looooeeee!'s Avatar

I seem to think, fact I'm pretty sure the poly tubes you want are from those gallon containers of orange based abrasive hand cleaner. GoJo makes these products I want to call this stuff agent orange, but....???

Jan 10, 2002, 10:24 PM
Registered User
nolasco's Avatar

I have looked at all lotion and liquid soap dispensers here at home to figure out where the plastic tubes really came from. Unfortunately, the only thing I am sure about is where they did not come from. It's certainly not Vaseline, St. Yves, or Soft Soap. But, my wife says they most likely came from Bath and Body Works liquid soap dispensers. In any case, I use those tubes on 6mm outer diameter ball bearings. Funny thing though is that some tubes are a tight fit while other are loose.

For 5mm outer diameter ball bearings, I use the tube that comes with those toy propellers found in my LHS.

Here is a photo of another of my gearboxes. It works for DC5-2.4, N20, and GWS motors using 48 and 50-tooth spur gears and 9 and 10-tooth pinions. Other gear ratios might also fit.

Jun Nolasco
Jan 10, 2002, 10:31 PM
Registered User
nolasco's Avatar
Oops! Here's the image.

Jun Nolasco
Jan 11, 2002, 06:50 AM
in persuit of low wing loading
Gordon Johnson's Avatar
DNA, thanks for the Bic pen tip. I've already cut one up and it looks like it will work.

Jun, thanks, this will give my wife an excuse to visit Bath & Body Works.

Looee, hmmm, Agent Orange ...
Jan 11, 2002, 07:48 AM

agent Orange

I Think that it's the stuff called Fast Orange
Jan 12, 2002, 06:39 AM
Old Desert Rat
Arizona Chuck's Avatar
I know this isn't a gear box but will a O ring box do?? I was playing around and can up with a belt drive on the cheap Johnson motor. The belt drive works good but I'm not happy with the motor yet, to many amps and no poop.
I made the pulleys out of 1/8" Plexiglas cutting the "v" with my drill and a rat tail file. I press fit to the shaft. The shaft is in a CF tube. 3/1 ratio.
Jan 12, 2002, 08:25 AM
Registered User
Arizona Chuck

Looks nice, how do you cut the perfect circles?

Jan 12, 2002, 09:13 AM
Registered User

Belt drive

Is not as effecient as gears but it is really quiet
On little motors we used the ortho bands which are like mini rubber bands
Pullies - Guess who has a metal working lathe,
Jan 12, 2002, 09:20 AM
Only nerd in the village

Re: Belt drive

Originally posted by aeronutz
Pullies - Guess who has a metal working lathe,
I do!

How much less efficient than gears do you think it is? I still have a belt drive in mind for pagers since a 2-stage gearbox will also suffer from efficiency losses.

Jan 12, 2002, 10:02 AM
RPV builder & operator
Pierre Audette's Avatar

Re: Re: Belt drive


How much less efficient than gears do you think it is? I still have a belt drive in mind for pagers since a 2-stage gearbox will also suffer from efficiency losses.

Don't know, but I'd say it's caused by belt slippage, and the additional side loads on the pulleys/bushings from the tension in the belt.
Jan 12, 2002, 03:48 PM
Old Desert Rat
Arizona Chuck's Avatar
I drilled the center hole first and draw the circle with a compass then carefully cut them out with a scroll saw. Then I chucked it in my hand drill and held it against the belt sander to round it.
Jan 13, 2002, 07:06 AM
Registered User
jberg's Avatar

be sure to wear SAFETY GLASSES when turning plexiglass pulleys with your power drill! I once had to wait several hours in the emergency ambulance until somebody pulled a small piece of plastic out of my eye. Not mentioning that that hurts, at least that is time wasted that could better be used to build models!
Jan 13, 2002, 01:35 PM
Registered User

Super gearing

Yes, you can have big gear ratios and if the power you are transmitting is small anyway there is not too much loss because of the sideways thrust on the bearings caused by the belt tension.
Andrew H gave me some silicon plastic tube which fits over the 1mm motor shaft, the ortho band seem sticky so I dont think there is much slipage going on.
I think this would better suit pager motors at hi revs and low power, so if the little pully is say Dia, 1mm and the biggy is say eh, 20mm what is the gear ratio?
20 to 1 sounds about right?
If it is a tight fit in your plane, 'turn the motor round' so the big pully is nearer the tail end.
My test one used a plasic pully made from a wheel thing I found in a craft shop, this was my uncivilised pre-lathe era!

What we need is someone clever like Andrew H, who as luck would have it will be testing a four engine micro plane on Saturday which is destined to have four highly geared pagers in it.

I was designing a super effecent carbon prop today too .... its all starting to come togther again


Ps Dr Chris has a lathe too, and some pagers.

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