combatpigg

My Feedback: (3)

A guy posted a video here a few years ago that showed the OS VRDF on a out of production delta with about 36 inches of span IIRC. He hand launched it at part throttle and it was really impressive how well it throttled and how quickly it hit full power when he nailed it. After seeing that plane perform I did a quick check on ebay and those engines were pretty plentifull at what looked like fair prices.

iron eagel

You see them come up on a fairly regular basis, the only downside besides what's been mentioned is they eat a lot of fuel. But they really spool up really good I had one in a df setup years back and it was entertaining.
I am curious how it will work with a prop... (I have the RNV setup for it as well.)

combatpigg

My Feedback: (3)

If I could get one to run decent on FAI fuel, that would satisfy me. $3 / gallon for methanol. It's been a few years since I bought a case of castor from Sig...but it works out to be pretty cheap fuel if that's all you have to buy.
I got a 55 gallon drum of methanol from the local Standard Oil distributor, but sprint car fuel suppliers in some areas will sell smaller quantities..
VP Racing fuel is one dealer.

iron eagel

Setting it up to run on that type of fuel may be the better option as far as cost of operation...

Javier-RCU

My Feedback: (6)

From my own experience...

22% Oil (Sint+Castor)
APC 10x10
MCCoy MC9 Glow Plug
5% or 0% Nitro
No head shim
BVM Pipe
17800 RPM
Do not use spinner a spinner nut will be OK
Take care with the prop balance and check it every landing, when you see little clear veins discard the prop inmediatly.

combatpigg

My Feedback: (3)

That's pretty impressive to be able to burn cheap fuel and to go that fast.
Will the engine have a decent lifespan running at this level of power...?
[I know that question is a matter of opinion, but it's good to hear what people have to say about these engines]

Headhunter70

Some good news here, first I have found a source for carbon props 10x10 and another source where I can get 8x12 or even 8x 13... second good news last week the first Hobby Shop in our country has opened and I can get fuel with nitro :-) I think the Heli mix with 25 % NM and 18,5% oil will do the trick. (Does anyone know Tornado fuel ??) I will test run the engine on Sunday again also using an OPS pipe (open) to check the RPM I can get.
Many of you suggested to run the engine without spinner ? Well the manufacturer of that carbon spinner told me it was tested up to 30.000 RPM, so I hope there will be no problem...
Also the plane where I want to use that engine will look a little strange without spinner

Javier-RCU

My Feedback: (6)

Hi Minister of propaganda!

As you can see on the specs this engine do not have any warranty from OS, so you can guess a short lifespan compared with normal engines. I have some of these on ducted fan aplications running at 24.000 RPM in Dynamax fans but with good lubrication and maintenance you can enjoy this little beast for years.

With regards to the spinner, the problem is when the prop explodes in flight, the backplate of the spinner will cut the engine shaft as a knife in a butter. I have saw a lot of this situations in my flying field.

HEADHUNTER70 with that low oil (18%) and high nitro (25%) you will toast this engine in the first flight. Do not use green fuels with this engine, the oil viscosity in these fuels are useless for the VR-DF. Again use 22% Oil and 5% or less nitro.

Javier

combatpigg

My Feedback: (3)

Wow..! You have such a good memory.... I had to laugh..!
That is a very good endorsement from you. I understand the risks involved, but it is good to hear that this engine can give decent life if it is handled with respect and lots of oil.
If I ever decide to "GO BIG"...this engine might be the one for me. Not to try to set any records, but just to have a popular, low cost engine with lots of spare parts and spare engines floating around the internet.

iron eagel

As long as you use a lot of oil they hold up pretty good.

combatpigg

My Feedback: (3)

I can mix 75% / 25% / 0% for about $12 per gallon and running that mix saves the cost of installing a seperate smoke system.

iron eagel

Your experience with FAI setups will serve you well with one of these engines if you ever decide to go with one, the oil aids both in the lubrication and cooling of these when they are really spinning up.
I was going to use the new one I have in a DF setup originally, but the more I think about it the more I am drawn to putting it in a clean airframe with a prop.

Javier-RCU

My Feedback: (6)

Useing this engine in a clean airframe with a prop from NIB during one or two seasons will ensure a perfect breaking in for a ducted fan setup.

covert action

My Feedback: (2)

Hi all,

I am in the process of building a Parkinson Barracuda with ducted fan with a OS91 VRDF.

Was wondering if anybody has a machined throttle arm made by Jet Model Products (JMP). I understand the stock one that came with the motor sometimes fails, so looking for a better quality one.

Thanks for any help,
Covert Action

kartika

Hi...everybody..I needs your help..

I have OS 91 VR-DF from my friend...I want to use normally airplane not using ducted fan
Can i use this engine for normally propeller 14 X 8 such as others OS 91..??
Best regards,
Kartika

MJD

My Feedback: (1)

No. Not a good choice. Sell it and buy a regular OS .91.

kartika

Thanks for your answers...as i thought before...better just for engines collection
OK..Best regard

MJD

My Feedback: (1)

It is great for small props and going really fast. If you prop it for 17-18k at minimum it should behave nicely. I really don't know exactly how low you can prop it and still have it behave. But loading it down with a 14" prop is exactly what it does not like. It has high timing, and a large carb throat which is only needed for high rpm.

iron eagel

MJD is totally correct this engine loves high rpm. It was designed to spin a 5.25 inch ducted fan setup at rpms reaching into the 20K rpm region and does so very well.
With a good clean airframe, tuned pipe and a small prop I think it would prove to be quite entertaining.

iron eagel

Karitka
It can be used with a prop if setup properly but as it has been mentioned many times in this thread it is a high performance engine which somewhat limits it's applications.
If you would like to try it only use it in an low drag high performance airframe.
As far as how to use it here is some good solid advice.

ORIGINAL: Javier-RCU

From my own experience...

22% Oil (Sint+Castor)
APC 10x10
MCCoy MC9 Glow Plug
5% or 0% Nitro
No head shim
BVM Pipe
17800 RPM
Do not use spinner a spinner nut will be OK
Take care with the prop balance and check it every landing, when you see little clear veins discard the prop immediately.

kartika

Iron eagle....Thanks for your great suggestion
It was broken in and flew as your suggestion.. good run..good idle..
22% castor
Graupner 11 x 11
Glow plug OS 8.
0% nitro, without removing shim
MACS tuned pipe
13200 rpm .(more than enaugh for my plane)

Regards
Kartika

iron eagel

Glad to hear it worked out for you.

kartika

Iron eagle..I have question, what is the difference and uses a round head and a rectangular head on OS 91 VR-DF ?
My friend also gave me new parts of the head (that is round head).
I've read the manual, but the difference was not written down. Do you have experience of using both? as a note on the ground when the temperature at the maximum RPM was 83 deg celcius by using rectangular head.
Thanks

Best regards
Kartika

iron eagel

I have only had the round head ones, it my understanding the head was changed to improve the cooling when used for a DF application, I would think either should work with a prop setup.

MJD

My Feedback: (1)

The RC speed fliers use the round head version in all the pics I have seen. I seriously doubt the square head is of any value for regular prop use, but could be used. (unless it's a pusher maybe..)