wirnik

Hi!

For me, ducted fan unit with OS-max 91 is to expensive.
Is there any possibility to build fan unit or use Ramtec's fan unit with regular prop. engine (12000rpm)?
Have you ever seen sth. like that?

I think, that I can use fan with gear, witch can make high enough rpms. Is it right thinking?



PS. I know, that I can use normal engine with propeller outside of plane, but I don't want to.

JWN

My Feedback: (42)

Solid gear drives do not work on single cylinder engines. The power pulse rattles the gears and causes early failures. Besides, by the time you designed, built and perfect a gear drive, you will have far more money invested than if you were to just buy a DF engine to start with. One more item to keep in mind is that you are going to have to use a far larger engine than a .91 before you have enough power to spin the rotor at a high enough RPM to make a decent amount of thrust. Bigger engine means, again, more $$$.

John

wirnik

ok - but rc helicopter also have gear and it works ok.
and I don't need so much power as developed by OS MAX 91 with duct. fan unit.
I was thinking about gear for increasing rpms, not the power.
do you know is there a possibility, to create fan for engine witch is working 10.000- 14.000 rpm?
and one more question: how will be working ducted fan unit for OS MAX-91 df with OS-MAX 91 fx?
I am asking so strange questions, because in Poland OS MAX 91 df with fan unit is unavailable, and if I want to import it, after duty and tax will be costing 800$...

Wayne H

Yeah! How cool would a 25cc weed-eater type engine ducted fan be!!

trioval00

My Feedback: (17)

correct me if i am wrong, but you need that power to get the rpm's.

go ahead and try it, but if you are trying to save money, forget it, jwn is right, setting up that gear drive will cost you alot more money then a good fan and motor

look in the classified section for a use motor and fan, i picked up a byron fan and a new os91 for about 265.00 a few months ago at a flea market

mark

BalsaBob

My Feedback: (24)

A company called Combat Models use to make an F16 that used a regular piston engine mounted just inside the fuse (at the rear). I believe it used a regular prop that was cut down a bit (to fit inside the fuse). The airplane was primarily foam (and then glassed). I saw one fly once...... not terribly fast, but it flew OK. I am not sure if Combat Models is still in business or not. Bob

patf

My Feedback: (4)

wirnik,

you might check around for a motor called or by angstrom. it was a 90 size russian made motor that was a monster. the german's were importing and running them for a while in their ramtec units. might be something you can get a hold of for a reasonable price.

Razor-RCU

My Feedback: (50)

The Combat Models F-16N ran a YS-45 and a pusher prop (10x7/8) just outside the tail-cone... At < 8lbs. they fly very well but the foam dents easily-

Combat Models may still be in business but they do not act as if they are- worst customer service I have ever seen!

Cheers!
james

JWN

My Feedback: (42)

Helicopters have a clutch between the engine and the gears. This absorbs a lot of the high shock power pulse which is a detriment to gears. They also use a nylon gear and reduce the RPM's instead of increase as you are talking about. Next, you say you simply want to increase RPM's, not power. Well, you are going to LOSE power through the gears even if they were 1:1 and it will take MORE power to increase the RPM's of the fan. A .91 FX simply will not turn the fan fast enough to produce any useable thrust in a model which a fan of this size will fit in.

John