SJN

One of the guys here put a OS 91 VRDF engine in the laser arrow........sure wakes it up to life compared to installing the reccomended 40 size engine

http://www.youtube.com/watch?v=ldJX0LYFGdg

mk1spitfire

cool, bet he would have preferred a less cloudy day too

soarrich

My Feedback: (98)

Now that's a man's man, holds the tuned pipe barehanded. Cool.

freakingfast

My Feedback: (3)

Very nice! I didn't know the Laser Arrow could take that kind of power, that's a nice surprise.
Whose carbon prop are you using?

My folks from are from Aalborg, DK

SJN

I dont know the details.......just saw the video, and was a little impressed
Try ask in the youtube comments.

lfinney

My Feedback: (44)

cheap easy thrills i like it

iflyg450

My god I wish my arrow moved like that. The YS 45 still moves it pretty good. The arrow is a VERY UNDER RATED DELTA!

Scarub

Wow that thing is insane,Didnt know that style of plane could go that fast.

soarrich

My Feedback: (98)

I thought it would go that fast, until it failed in flight, I guess it's stronger than it looks.

Mike Connor

My Feedback: (5)

No ideal runs for a Doppler check but probably not too far off. Anyone care to quess?

soarrich

My Feedback: (98)

175mph.

Mike Connor

My Feedback: (5)

Lower, much lower.

Mike Connor

My Feedback: (5)

.

combatpigg

My Feedback: (3)

Mike, how could it be running at 28,000?

It looks like a great combo and a lot of fun.... the engine looked almost small on it.

Mike Connor

My Feedback: (5)

Where did you get 28,000? I calculated 17,600 rpm on the pass at 1:17. It sure doesn't sound like your FAI engine. A 9 pitch prop would make things work out about right for 150 mph. Keep in mind that there was not a long straight pass close to the camera for accuracy.

combatpigg

My Feedback: (3)

I must not know how to calculate the rpm. I thought the difference of the 2 frequencies gave the cycles per second?

Mike Connor

My Feedback: (5)

=SUM(60*(2/((1/FComing)+(1/FGoing))))
Here is the Excel spreadsheet formula I wrote with information from HighPlains awhile back.
Frequency coming is the difference in frequency between two lines at the top and and FGoing is the difference in frequency of the same two lines at the bottom. I usually do it accross 5 lines and then divide by 5 for a better resolution. You need the program to do this.

combatpigg

My Feedback: (3)

I see, but too bad it's not as simple as I thought.
I wonder what this engine is capable of? I'd like to see what happens with a 8x10 prop. [sm=tongue_smile.gif]

Mike Connor

My Feedback: (5)

I know the engine is capable and designed for much more rpm. It may be detuned for a reason... like Vne.

combatpigg

My Feedback: (3)

All I've ever heard about DF engines was how tortured they were buried in those jet models. Good reason to pass on any used DF engines for sale, I would think. There are quite a few NIB specimens out there still and the prices are relatively low.

lfinney

My Feedback: (44)

alot of guys are skeered or just ignorant on how to prop high rpm engines, i see this often, poor engines..[:-]

combatpigg

My Feedback: (3)

I just read the engine running advice that Metkemejer gives at the PROFI site. He made it sound like if you force a high timed engine to run below it's tuned RPM, [at full load] the reverse pulse from the exhaust works it's way down the transfers and heats up the case. Nothing good can come of this. Running too short of a system does the same.
The .91 in the video sounded fairly happy being run like a pattern engine...I wonder if he lowered the liner to get the engine to run more like a normal engine?
I've run the FAI engine with the liner lowered and it runs just like a $150 engine this way.

rumpeden

Hi
It´s me flying the Laser Arrow on the video. Regarding the prop, I have bought this recommended by others flying this engine on the Speed Cobra from Fliegerland, which I have one of laying arround waiting to be finished. I also have a 8x10 or 12 for the engine, and will check performance.
Regarding the setup, I had to put some weight in the "tail" for balancing the CG and moved reciever battery all the way out just in front of the trailing edge. It ended up 500 grams heavier than the manual says, but it is not a problem as it still "floats" in for landings.

combatpigg

My Feedback: (3)

It sure is impressive to see that engine obediently idling until you are ready to open it up.
The plane looks SUPER!
Nice job of flying it.
Is this your first plane for that engine?
I'll bet a 8 inch diameter prop lets that engine really unload.
Does this engine have a mixture control valve that you can operate when the plane is flying?

rumpeden

Thanks

It is the first plane for it, but I bought the engine second hand. The needle is "remote" meaning that it is connected via silicone tube as on the OS FX series. It is possible to connect a servo, but I do not think it is necessary.

The Prop. guy can be found here http://www.rc-network.de/forum/index.php (Dr. Topspeed)

I see now that the other prop I have, is 9,1x 12,75. It should be "state of the art" with very thin blades and moulded in special carbon so that the tips doesn´t fly arround my ears [8D]

Price was approx. 20 euro/pcs.