furball

Just started to build my p-51. Wondering which engine to use. I want plenty of powewr and speed. Does anyone know if the OS 120ax will fit? The dementions are close to the os 91fx.

gmohr

Check through this thread, Furball. There are several people using the 120AX, myself included.

Regards,
George

Mustang Fever

My Feedback: (2)

Yeah, it fits really nicely. I used the Mac's muffler stuck out the side. the 15x10 APC prop is ideal. The engine runs forever on 12 oz of fuel (I used the slim 12 oz).

furball

Thanks for the input. I think thats the engine I will use. That Mac's muffler looks good.

gmohr

Another option is the JTEC inverted Pitts style. Theres some posts back a bit, just do a search on Jtec.

Hey Bob! Lets talk props.... I bought a 16x10 because I love the big disk. Will I be loading it down too much?

Thanks!
George

OSUAV8R

Ok, I finally got the retracts to sit the way I am happy with and the wing is finally one piece.. Iam ready to sheet them... I will try to do it the way the manual says.. wish me luck lol

gmohr

Yeah OSU, that looks cut low enough now!! Good luck on that sheeting... [:@]

Regards,
G

Mustang Fever

My Feedback: (2)

George:

Mine tached about 8300 rpm on 10% at 1200 feet above sea level with the 15x10. OS says you can use a 16x10, but I'm sure the rpm will be down from what I got, meaning less airspeed. Question is how much. Tach it. I think as long as you can get an indicated 65 mph you'll be all right.

gmohr

Ok thanks, Bob. Ever try a 15x12?

Regards,
George

Mustang Fever

My Feedback: (2)

George:

Only one I ever used was the 15x10.

Riddle4U

A lot of posts here involve new engines. Don't over prop a new engine..in fact it always runs the risk of overheating. This is a scale model and there isn't any reason to max out the engine's performance. Just run a mid pitch, mid diameter prop, and enjoy. Let the racers worry about marginal props. I tend to like large prop with fine pitch. It pulls through maneuvers, looks impressive spinning on the ground. Smaller prop with higher pitch lets the engine get into its power band, and speed will be higher (always within manufacturers recommended ranges of course).

Mustang Fever

My Feedback: (2)

That's my HO as well. I've been sticking with the recommended props on my newer OS engines, and have been having very good results. The AX series have be designed with different porting for more torque vs rpm, and better cooling fin design so they can turn a large, relatively coarse pitch prop at lower rpm. I think OS is doing this to promote longer engine life, lower fuel consumption, and less noise. (You won't believe how quiet that 120 is with a 15x10 at full throttle, or how long it will run on only 12 oz of fuel, which is the recommended max tank size.)

These are the engines, props and fuel tank combinations I've experience with recently:

120AX 15x10 12oz 8300rpm (80 mph/11 pounds)

55AX 12x7 10oz 9800 rpm (65mph/6 pounds)

46AX 11x6 8 oz 11000 rpm est (62mph/5 pounds)

All of them are very quiet, and will run for 12-15 minutes during a typical flight without getting dangerously low on fuel. Two of my 55s are hauling around an 18 pound B-25 like it's a toy.

gmohr

Ok guys, that's good advice, thanks!

bluetomcat

Hi All
Sorry havn't posted an update on here in a while I am on hold waiting for my retracts to arrive.
Lado-Tech retracts that is. DO NOT place an order for these retracts. They may look good but actually getting them has proven very difficult indeed. I placed my order on 12th september and I am still waiting....
My P51 just sits there.... both wings separate and fuse half built.....
One day....yes....one day she will fly.

Started the build the same time a Gmohr and he has done fantastically well just wish I was in the same place.

Keep up the good work all

Christian

gmohr

Sorry to hear that, Christian. Word is that if you order when he shows "in stock" you are good (and I got mine quickly that way). There are numerous threads regarding Lado's inability to deliver on backorders for months... very frustrating.

You might just consider another option.

Regards,
G

Riddle4U

Yea, Christian that is a bummer. They seem like they would be interesting units indeed. I, as mentioned in the thread, used the BVM jet retracts which were mentioned in my manual (in the front). My kit was bought years ago, so I don't know if it has changed. I operate these with the Robart cylinders as suggested. They do offer a lot of flexibility since they don't have an "up-stop" and can retract as far into the wing as you need to clear the wheels from the bottom of the wing, which also allows one to use full scale gear doors if so desired (I am going to have inner doors also). Good luck, whichever way you end up going!

OSUAV8R

OK, here are the latest pics on my build. I have the bottom sheeted.. and will put in the retract lines and tubes for the servo wiers.. then sheet the top.

Please excuse the ridiculous gear drawings on the bottom sheeting...it will look way better soon

gmohr

Hey OSU,

I have a suggestion, that you take this opportunity to beef up those retract rails and adjacent ribs with some more structure. Overwhelming opinion is that the stock setup is too weak.

Good luck!
G

OSUAV8R

Hey G,
I will, I have to get some Triangular stock for the ribs, and the CJM retracts have an oleo strut, so the forces transmitted to the structure are much lower... that said.. I do plan on beefing it up

Thanks

Nate

BradSD

My Feedback: (9)

That's my HO as well. I've been sticking with the recommended props on my newer OS engines, and have been having very good results. The AX series have be designed with different porting for more torque vs rpm, and better cooling fin design so they can turn a large, relatively coarse pitch prop at lower rpm. I think OS is doing this to promote longer engine life, lower fuel consumption, and less noise. (You won't believe how quiet that 120 is with a 15x10 at full throttle, or how long it will run on only 12 oz of fuel, which is the recommended max tank size.)

These are the engines, props and fuel tank combinations I've experience with recently:

120AX 15x10 12oz 8300rpm (80 mph/11 pounds)

55AX 12x7 10oz 9800 rpm (65mph/6 pounds)

46AX 11x6 8 oz 11000 rpm est (62mph/5 pounds)

All of them are very quiet, and will run for 12-15 minutes during a typical flight without getting dangerously low on fuel. Two of my 55s are hauling around an 18 pound B-25 like it's a toy.


_____________________________

Bob Hunt


Bob, that is some good info but are you sure the MPH are correct. I once put a GPS inside a Carl Goldberg Cub .40 size with a .70 OS four stroke. I flew the plane pretty much flat and level aside from what ever climb and decent had to be made. Surprisingly the top speed was 99mph, I think these planes are traveling a little faster than we think. I was also shocked at the distance traveled, I dont remember the data on that but it was more than i would have ever guessed.

gmohr

Hey all,

I'm having second thoughts on something.... when constructing the elevator system, I used the stock hardware, including the soldered bellcrank/torque rod and nylon clevis. Now I'm suddenly not sleeping at night worrying about that little nylon clevis giving up on me.

Have you all used that same clevis? Anyone had one fail yet?

Thanks!
George

P.S. This reminds me of my years flying full scale gliders. When I was just getting started taking lessons, a buddy gave me this tiny bolt and I asked, "whats this for?" Turns out it was the elevator horn bolt, and MAN it looked way too small and fragile for my taste HAHAH!

CRJDriver

My Feedback: (57)

Stock setup works perfectly fine with a good silver solder joint. Like I have sid before, mine has lasted over 17 years and still going strong. You will be fine. Get some good sleep!

Chris

FallDownGoBoom

My Feedback: (1)

I won't speak for the Mustang's setup, but I lost a T34 when the plastic clevis pin sheared off inside a metal torque rod. If you've already got things installed, I'd make sure there's no binding when the elevators get pushed up/down. But if you can still get to the inside of the fuselage, I'd use a metal clevis.

OSUAV8R

What about metal to metal electronic noise, with the metal clevis?

gmohr

Well truth be told, I'm totally stuck with the clevis as it is, so I hope I get just a little lucky here... and yeah, metal to metal might not be the best idea anyway.


Off topic warning...

I've put the Mustang on the shelf for the past week so I could screw together my new 3DHS Edge 540, isn't she purty? I hope she stays out of the cornfield longer than her predicessor did...