How to make propellers/gear drives.

[all_fly_all_day]

Hello all, i am what you would call a semi-beginner to R/C. I have bought and flown 3 R/C electric planes, all park flyers. I have now taken an interest in indoor micro-flight. I have plenty of experience with building, but i do not know any "tricks of the trade" or how to make gear drives properly. I am also having trouble in is how to make good ribs, tail surfaces, the outside "frame" of the wing ect...(i think that you can tell by now, those three planes i boutht were RTR and made outta foam:D ) another thing that i was looking into was how to make my own propellers out of balsa and plastic. The propellers that you can buy at the store are too much $$$ for me and i have so much more fun building everything on my plane. the main thing i am stuck on is what kind of bend i should have in it and how to ballence* it right, oh, and i dont know how to make it, lol. I am extremely into indoor flight and would very much appreciate any help:)

Brandon

eat, sleep, and fly...

[dow]

Go to ezonemag-dot-com, under the electric section they have a indoor/micro topic. Scroll down to the bottom of the screen and rearange the threads by number of replies. The second largest thread is on gearboxs. Learn how the search feature works, there has been much written about both topics. By doing this you will learn how to find many things and won't have to wait for someone to answer you directly.

Dave W.

[all_fly_all_day]

Thanks for the reply, i read that thread and i dont understand some of what they are saying. Like do you NEED bearings for the geardrives or can you just make a setup that would lessen the friction. Also, i have tried making my own geardrive and failed:( i dont know what im doing wrong. I have what you would call a 280 size motor, and im not sure how to calculate the ratio. Could anyone help me on this so i could give you a better understanding of how i made it and then maybe you coud help me:D

Thanks again

[frankenfoamy]

A common way to make your own propellers is to find a suitable prop, wax it and lay carbon fiber and epoxy on it. Use a wheel collar as a hub. Blot out as much epoxy as you can with paper towels and then lay a layer of mylar over it until it cures. After the curing, pop it off the mold prop, trim and balance.

[gjohnson]

For a 280 sized motor you can probably use the larger gears from Westech -- available from Dave Lewis http://www.homefly.com and Todd Long http://www.toddsmodels.com. These are 0.5 mod, which simply is a measure of how coarse or fine the teeth are. Dave's site gives exact dimensions and drawings for the gears. The gear that goes on the motor is called the "pinion" gear and the one that goes on the prop shaft is called the "spur" gear. To calculate the gear ratio take the ratio of the teath (doesn't matter what the mod is). So, if you use a 6t pinion and 40t spur, your ratio will be 40/6=6.7 or 6.7:1. That's it.

You can buy ball bearings from both these sources (but Dave has more sizes). These can be put in some type of tubing. An easier way, written up in the Cloud 9 column, is to get some square brass tubing that your metal prop shaft just fits inside. Put a bit of oil or grease on the shaft, make a couple of keepers, and you are in business. I flywith someone who uses these. For keepers he uses wheel collars with a small set screw. Depending on the gear ratio, you may need to space the brass tube away from the motor. Do this with balsa and CA. Some people wrap the whole thing in dental floss and wick som CA on it to glue the whole thing together.

If you have a RC Microflight subscription, go back through old Cloud 9 columns, as several different types of gearboxes are described with photos there.

Regards, Gordon

[all_fly_all_day]

Thanks a lot Gordon,

I might try that. Sounds great.
Does anyone know where to get cheap propellers that would work good on the system that Gordon described to me? My hobby shop has propellers but they are WAY over priced, 7.00 for a plastic 3 in. prop, oh BTW, how do you find out what the ementions are for the prop, i know the first one is the diamiter** of the prop, but im not quite sure about the 2nd one, I can not thank you guys enough for all the help, you are really making this EZ for me:cool:

Brandon

eat-sleep-fly

[Dave Robelen]

Hi Brandon,
The second dimension is the "pitch" of the propeller. This will be given in the same units as the diameter.(diameter in inches, pitch in inches). The actual number is mostly for reference. For example if a 6" pitch propeller could screw through a solid without slipping,it would advance 6" with one rotation. Of course we do not use a propeller this way, but it is important to know that as the number gets larger the plane will generally fly faster (within narrow limits). The diameter basically establishes the "pull" of the propeller, while the pitch sets the speed. I hope this helps.
Regards, Dave

[all_fly_all_day]

Ahhh, ok, very nice way of putting it i do understand it now:)
thanks

I still dont have the picutres of my plane downloaded in my computer yet but i will problably do that tomorrow.

eat-sleep-fly

[gjohnson]

Todds models http://www.toddsmodels.com carries all the GWS props and now the APC props as well. He has adapters for these props too.

Gordon

[Richard Miller]

I stumbled onto the hobbypeople.net site, courtesy of Teoma, and discovered listings of some Cox models, as the Black Maxx. I've been curious as to the absense of Cox in these pages.

Any reason?

-Richard

[rcski]

I never ran a cox before, but of all the people I ever talked to they say their a pain in the butt. I heard they dont run well on regular nitro, you need to buy their fuel. A guy from a LHS in Maine bought one of their planes (Elec) was suppose to be real easy to prep for flying. He did what had to be done, took it out gave it a whirl, the wires where soldered on backwards from the factory. He corrected the problem went out again, gave it a toss and he couldnt get the controls to work. After chasing the plane down he said forget it. He said the box claimed it was a real simple plane to put together and fly. He figured he would maybe sell them, but decided if he had this much of a hassle he was'nt about to have people coming back with these things. In all the years I been flying I have never seen anyone with a cox anything.

[Dave Robelen]

Hello Rcski,
Let me toss in my $.02 worth on this one. When Roy Cox was alive and both owned and managed the business the products were really nice. I am talking about a period from say 1960-1990. The small engines were built of really decent materials, and they were a pleasure to run. Yes, they ran best on the fuel that was designed for them, but that was a really nice product and sold at a fair price.
The Cox business was sold to another company some years ago, and the product line has gone downhill ever since. A shame, because Cox as a name used to be synonomous with quality.
Regards, Dave

[ThunderChicken]

Just FYI, supposedly 30% nitro heli fuel works well in Cox engines.

As I understand it, the biggest difference between Cox fuel and what most of us use is that "standard fuel" over cools these little engines which makes it hard for them to start and keep running. That's why running a high nitro fuel is said to work great.