Dunno. Not looking for a fight over this, just want to help the guy with my own modest, limited experience, which includes frying one Rossi 81 and one Rossi 65 small heads in my first Byron F16 before I got the right engines.
I guess OS and all the other engine manufacturers felt it was important enough to make two head castings and two versions for all their ducted fan engines, and while YOU may have had luck running Byron fans without the larger head, I think OS, Byron, and the majority of Byron pilots would just say to get the larger head.
Anyway...it's not something worth fighting over, is it? You can have your opinion, too.
Good luck, viper. What is the VX going into?

Hi Tiger, the 46VX is going into a Jet Hangar FJ-3 Fury/F86 but I am building the Naval version. It will have flaps and speed brakes along with the normal functions. I already have everything for the plane but some servos and the front nose strut. I have the main gear oleos and even the drop tanks for it but they will be for show. My second plane will the JHH Phantom with the Dynamax and OS 91. Which I just bought and it will have the scale landing gear struts and wheels.
I just started my turbine fund. I am putting away a certain amount of money each month for a turbine and plane and I plan to fly these two planes for 2 years and get my waiver and turbine and scale plane for it.
Thats my plan anyway
Thanks Joe

EASYTIGER is absolutely right. Even if it's true that some have had luck getting the .91 small head engine to work in a Byrojet fan, it's not supposed to. I'd bet that the small-head engines running in Byrojet setups have a lot of visible signs of overheating, too. Use the large-head for Byrojet applications. There is a good and simple reason for it--the small head doesn't have enough cooling-fin area to dissipate that much heat. The cooling air that the vacuum creates is a fraction of what it is in a tractor-fan setup. How do I know? Burned up an engine back in '93 because I didn't want to buy the large head, even though three different people told me to. Good luck!

Both of those aircraft are great, the JHH F86 is a perfect first jet. Don't forget, Larry Wolf, the JHH guy, is ALWAYS willing to help you out, if you just email or call him.
With the VX, it ought to be spectacular.
If you ever buy a YELLOW aircraft, Shawn Evans will always do the same!

Good plan, by the way. The world needs more SCALE modellers!

Yup Easy, I have known Larry for some time now and he is helping in the construction of my Fury( helping with the speed brakes) He's always been very good to me and I love both Fury's and Phantoms. The turbine I want is his big F15 that is Avonds design. I am thinking of a 30-35 pound turbine but that's a long way off, I will be happy to just get my Fury flying.
Thanks Viper

I also have had considerable experience with the Byron kits and OS91's. I have not had ANY luck when using the small head in the Byrons....period.

I only tried it in 3 of his planes, F16, Mig 15 and the Bullet. All had overheating problems until the large head was installed. An in-flight (BVM) was used on all of them and extra Castor run in the fuel too....

I have found it hard enough to get them to run cool with the large head----4000+ ft altitude most of the time.....Dennis must have the velvet touch to make it work without them......

I am now following "Jackjets" style and adding 6 to 8 oz of Castor to each gallon of fuel for the Byron fans and am having better luck keeping them running with a lot less overheating problems.

Just my experiences....

Rod Springer

You know, I was curious about adding castor oil to my fuel as well. I don't know where to get Wildcat fuel here on the West Coast (Southern California) I ussually fly Power Master 15% Nitro and I add about 3 ounces of Sig Castor too each gallon of fuel. This is just for my regular sport engines. I add about an ounce more to the Powermaster 15% 4 stroke fuel and so far I have had no problems burning up an engine but I don't know what to run in both my OS ducted fan engines if I cant get the Wildcat Jet A. Can I run the Powermaster with the increased Castor oil content in them or should I look for some other type of fuel.
Thanks Joe

I've done just that with the 91, spiked powermaster with some castor. Works fine. But the Wildcat seems to run a little better...at least it makes me FEEL better. With BVM stuff, I only run the wildcat. Order up a case, it goes pretty fast. Or call wildcat and find a local dealer. Call before visiting, though, because just because they stock wildcat does not mean they have jet-a.


But..5% works best for the 91. Don't know about the VX. More nitro on the 91 just leads to more blown plugs, not more power. At least that has been my experience.

Easy Tiger is right.....5% seems to be what the OS91 DF likes..I use the McCoy 9 plugs and now that I am using the huge amount of extra castor oil ( seems like it to me anyway ), the plugs are lasting longer too...

I have been using Byron fuel....same problem finding Wildcat locally, or when I need fuel at the moment.

Oh---one other thing I forgot to mention, some time back there was some discusion about Larry Wolfe always adding an oz or 2 of " turbine oil " to his DF fuel. I am doing that also. So 6 oz of castor and 2 oz of turbine oil is what I have started playing with at the higher altitudes--seems to work just fine--better than before anyway.....


Rod Springer

I'm not trying to pick a fight either. New guys need help from those of us who have the experience to answer their questions. I usually don't have much time to surf the internet because I am working too hard trying to afford my addiction, I mean hobby, but sometimes I feel like pitching in. My buddy Vernon Montgomery and I have each flown ducted fans for over fifteen years. That is over 30 years combined experience (gee, we must be getting old) with Byron jets with Byron fans. We have had a total of 19 Byron d/f aircraft. A total of 24 OS .91 engines, and five Rossi .91 engines (the original Rossi .91, which was a fantastic engine). Only four of the OS engines had the big head. We NEVER had engines that showed any signs of running hot. This is literally after flights that number in the thousands between Vernon, myself, and my two sons, and we fly in the worst of conditions, i.e. we live in the HOT, humid, sunny South.

If you take time to learn how to adjust your engine, you won't have problems. Don't take time, and it won't matter what kind of head you have on it.

To Shaun and EASYTIGER. I am sure you have many years experience with Byron equipment. I am sorry your experience wasn't as good as mine.

Since $60 is peanuts in the jet community, get the big head. Then you will feel that you have done the best you can do.

Viper21 has the best solution: Go tubine

One thing is for sure, I LOVE America. We all have the right to voice our opinions, and can do so without getting shot!

Long live the Red, White, and Blue!!

'Nuff said,
Dennis Lott

Just one more thing...it is not $60 for the head, if you are buying a new engine, usually the two are the same price or $10-20 different. If you have to CONVERT it, it's $60. But usually you can find one for sale for less. I gave one away a few months ago.

Well, I am a ways off from really having to worry about fuel as I am still building my Fury. I just finished sheeting the wing panels and the center section. I am planning to try a pair of those new Hitec thin wing servos for the ailerons on my Fury, I am going to install one in each panel and then one HS 85bb on each flap. So I should have plenty of power and speed. And I am using one HS 85bb on each speed brake in the fuselage between the thrust liner and the fuselage. I will run a metal geared 85 on the nosewheel steering and the rest of the servos will be full size high performance servos except for the Needle valve and the throttle. For those of you that like Fury's here is my color scheme for my plane.
Thanks Joe

I have been flying OS 91s for several years now with NO problems. I use Wildcat 5%, MC-9 plugs, and set it rich. Runs like the proverbial Swiss watch, never a flame out, even when the pipe blew out the back of my Cyclone. Treat it right, and it will run just about forever.

Whats a "Tubine"? Does that involve using a "Tub" pulled behind a boat? Hee Hee

Just kidding, Dennis.

I know little about jets and nothing about helicopters so here's my question. If you need a large head for cooling in some applications why wouldn't a heli type engine with the bigger head work? Some are rated for up to 18,000 rpm.

Helicopter engines are tuned to operate in the 12K to 17K range, depending on the particular engine.

Currently available fans operate at well over 20K. The heli engines would be well past their power peaks. You could do some grinding on the ports to get the power where you want it, I suppose. Some experimentation would be required, and possibly more than one engine before you get it right.

looking at some info from about 1990 out of a Byron kit it shows then rpm max speeds of 16k to 19k for the then present setups. these numbers are for the early 61 to 65 size engines. That was of course for a Byron fan unit. So would a present day heli engine made to turn a max 18k work in their place? Is a heli engine ported different than a plane engine of the same size for different power bands?? For instance MDS sells several engines in the same size for both. Only apperent difference is the bigger head. Isn't 18k a respectable rpm for a guy who doesn't care to rip the sky apart. Just wants to have an easy going jet?

Hi,I just got into jets last year and all of you guy's on RCU have helped me out(A lot of info) and I thank you.The only engines I am runing now is the Rossi's and that I will be buying from now on is the Rossi's and BVM's.I Like the ducted fan's and will most likely not get A turbine becouse I canot aford it. Please keep the info coming and I wll always read it.I have three jets now and I am still buying more stuff to finish them.One is done,one I have all the parts for and the next one I need more parts for it.I know you guy's like the OS but I will stay with the Rossi's and the BVM's and I know somone here goes only by OS but he shure like's to bid A lot on Rossi's on Ebay,I wonder why?,Thank you.

The early byron planes flew with all sorts of weird engines, before purpose-built DF engines were available.
I'm sure you could get your airplane airborne with a heli engine, but I think you will be a lot happier with a purpose-made DF engine and a proper tuned pipe.
If you are on a budget, there are bargains to be had, especially on Rossis.

Mac, you mean me? I did bid on a Rossi 105, never had one, heard one guy say it was okay on the Byron...if I got it for a bargain, I would try it out. That 6.15HP at 24,000 revs is just too tempting, though you rarely hear anything but awful things about that engine!

Thanks for all the information on choice of engines. I'll look for a couple of OS .91's. Large head preferred but will settle for small head.
Do any of you have any recommendations for my completion on my Byron F-16 or TGA F-15. Both have Byron fans. This would be my second attempt for Ducted fan planes. My first was a Parkinson Regal Eagle several years ago. I'll be hoping to fly them off our grass field. Is this possible. I have spring air retracts for both. Any suggestions would help. Maybe I'll get bit by the DF bug and stay this time.
Thanks,
Bob

Pilots,
believe it or not-small head engines WILL work on a Byron fan set up-I have run Rossi and OS engines with small cyl.heads-and they DID NOT overheat-you just have to make sure that you do not run them too lean.Use a on board mixture control. and contrary to what some people have said-the Rossi df engines are very,very good-you just have to know HOW to set them up and run them right.What I do with any DF engine I have is-take it completely apart-check it for F.O.-then make sure the front and rear bearings are "seated" properly-this step alone can give you a extra 1000 rpm-use red Locktite on all the case and carb. bolts-blue Locktite on the cylinder head bolts.If you don't like the Rossi carb-you can adapt a OS.91 carb to the Rossi engine-makes a great engine even better.I use Powermaster 15% with a extra 6ozs. of castor oil and 2 ozs. of Exxon 2380 turbine added.My engines run great.

Jackjet

Hi Scott
Do you still have extra big head for an O.S. 91 ?
Thanks

OMG what a great thread! Telling Dennis Lott how to run a Byron fan!!

Great!! A 15 year old thread reopened. Wonderful.