Billville

4 Blade on .60 size P-51’s – Solutions to problems…


Anybody other than me thinking of solving this problem… how to make a 4 blade fly fast and look right on

.60 size Mustangs?

Starting with a clean sheet of paper, ideally, I’d like to use a YS 1.40 – to the new 1.70 for power and 4 BIG paddles up front.
I’m looking for speeds equal to or better than with YS 110 and YS 140 with a 2 blade.

I’m willing to invest in the R and D to make it happen- gear drive, etc.

Yea, I know, keep dreamin’- right?

Right now, I'm working on solving the problem of noseovers by designing a movable C G - a sliding batt tray to be moved aft upon landings after the tail is down.


I’d be interested in constructive comments relating to the problems involved and possible solutions. Thanks, Bill

Super Sabre

You can use a 15.5x12 if you use the RCV120-SP http://www.rcvengines.com/rcv120sp.htm

If you plan on using an ARF, you'll have to midofy the firewall prior to installation.

SS

P-51B

My Feedback: (5)

You could also use an electric motor.

Billville

Thanks, but gotta go fuel for this project.

... also - the RCV 120 would be the easiest - but I don't think the power is there to get the speed I'm looking for and a 15.5 doesn't look big enough to me.

It sure would be easy, though. Bill

saramos

RCV and electric are the only two real solutions I know of. I think anything else is just dreaming.

Scott

ticketec

My Feedback: (2)

Are you getting at that you want to pay someone to machine you up a reduction gear setup?

check out solo prop's for the spinny bit up front.

Hope you pockets are deep.......

TopShelf

My Feedback: (4)

This http://www.warbirdpropdrives.com/ is what you would need to accomplish but on a smaller scale.

Kent

attwooddrow

My Feedback: (75)

I have a rcv 120 on a Top Flite P-47 with a Solo hub and four blades set at 18" dia. and 10 pitch. I have not flown the plane as it's not completed yet. However, I am getting rpm's of 7100 to 7300 on the test bench.Blades look real scale to.

TLH101

My Feedback: (90)

Lets see, a .60 size Mustang will have a wingspan of about ~65". That will require a ~19.5" prop to be "scale" size. Now it generally takes a 45-50cc engine to tur a 20" 2 blade prop. Now with 4 blades, how much will it take, even with reduction and bunch of pitch.
The key is, he want's a scale size prop, and he also wants speed. Somehow, I just cannot see that happening.

attwooddrow:
If an RCV 1.20 will turn an18x10 4blade prop at 7K, I would say maybe your tach is set on the wrong blade count. RCV site shows about 6K with a 18x12 or 20x12 2 blade.

attwooddrow

My Feedback: (75)

Tach's working fine. I have 2 120 SP's and 1 90 SP going into a Brian Taylor 190 I'm also working on right now. The 90 when being broke in w/ a 18 x 12 2 blade was running rich and still had over 7k. These engines have more power than you would think.

Kmot

My Feedback: (24)

Bill, I think this would be an incedibly awesome thing to accomplish. I believe you would be better advised to work on a remotely contrallable variable pitch blade before a sliding cg however. Best of luck!

Billville

Hi - thanks for your interest. We both fly at the Basin, I believe.

Here's the deal with my thinking...

I'm not convinced that with todays technology and manufacturing processes - CNC - that the idea is crazy. Somewhere in my mind, I think it can be accomplished by thinking differently.

I'm interested in the possibility of mfg and selling a kit or parts to make it happen.


I think you know how many guys would LOVE this to exist.


The sliding batt tray is only to solve the noseover problem created by main landing gear placement and added nose weight from the prop, gear drive, or Variable Pitch hub or whatever it will take to make this deal work. - You don't think a movable cg will work? I can get 15 inches of travel aft. I think that's plenty to keep the nose down after the tail is down on landings without adding much weight.

Remote variable pitch is the kind of thinking that may help to create a solution to the problem of no big and fast four blades in the sky.

Waddya think? Bill
_____________________________

Billville

No, I can do that myself for free out of scrap lying around.

Kmot

My Feedback: (24)

Bill, I was not discounting your sliding battery tray. I am sure it would be a nice function to have. But it would be simple to make. A remotely controllable variable pitch prop in the .60 size you are thinking of would be an engineering exercise, for sure. I only meant that is where your R&D time would be better spent.

Yes, the basin is one of my fields.

Billville

An all composite 46 size Mustang with an RCV 120 w/4 blades is an interesting idea.

I like the high wing loading aspect of it as models are not nearly heavy enough. This will most likely be the platform I will start with.

I will build the airframe to suit the engine so as to address the problems that need to be solved. Bill

SCALECRAFT

My Feedback: (13)

I believe it can be done. Its going to take time and testing.

Heres what I have so far. The RCV 120 with a 20 X 10 scale carbon 109F/G 3 blade we made could only get up to 3500 rpms. The RCV has 2:1 gear down but only 1.89 bhp.

The 109 blade supports allow "on ground" pitch adjustment.

The RCV manuel says 15 X 10 maxon a 3 or four blade if I remember correctly. Manuels on line for RCV.

Then I assembled a economical gear down system with an OS 108, that I have not tried as of yet.

One thing we have been able to do successfully is make our own scale (any) carbon/composite props. The do not flex as plastic/glass filled or wood prop so they do load the engine down since they do not lose their pitch at high rpms.

Now how to get a bunch of ponies/torque into a small engine to turn one of these close to scale size and looking props with good performance.

Nose over, this I thinks will come with practice once the prop system is operational.

Steve

Trollmaster

Now not thinking this anywhere close to "through" you could get some ideas with an RC helicopter swashplate collective pitch setup??

saramos

Steve,

Perhaps you could add a fan to the back of that gear reducer and help cool the engine in the cowl. Is that something you machined up yourself? What's the gear ratio?

Scott

SCALECRAFT

My Feedback: (13)

Hi Scott

Yes, if you look at it closely, its basically an alum I beam and a few alum plates. Although I'm not a machinist, I have a mini lathe and mill from Harbour frieght.

Each machine ia about the cost of a large set of retracts and its uses are unlimited.

Gear ratio is 1.7 : 1, just used what I had on hand, no other reason.

Problem at this point is the belt is too narrow, a wider belt would be better. I can tighten this belt, but the extra load on the bearing would cause premature failure of the bearings i think.

Steve

SCALECRAFT

My Feedback: (13)

Oh, the cooling problem. On the BF109G, some models had oversize oil coolers at the bottom of the cowl, I think that along with a few "tricks" and also flying in wheather no hotter that 80 degrees should avoid overheating.

Or i can make a fan. Who knows it may sound like a mini supercharger like the full scale.

Steve

Billville

[quote]ORIGINAL: SCALECRAFT


Now how to get a bunch of ponies/torque into a small engine to turn one of these close to scale size and looking props with good performance.



Steve
[/quote

Hi, guys...

Lately I've been thinking that part of the solution may be to go to a bigger engine, and design the airframe around it.

Part of the problem of fitting oversize engines in the past has been that the combination is mis-matched.

I'll bet the reason we don't have 4 blade rc mustangs is due to return on investment constraints and not technology. Nobody has put their mind to it yet, and made it happen.

A well designed 60 size P-51 with a YS 170 or Moki 210 would work - IF IT'S DESIGNED AS SUCH.

Or . . . a 46 size with an RCV 120.

The wing loading will be closer to scale, and the problems inherent in a 'heavy" plane can be solved by designing FOR a heavy plane.


I'm interested in you guy's feedback. Bill

Richard L.

My Feedback: (24)

7100 - 7300 rpm at the prop hub = 14200 - 14600 rpm at the crank, which is not good.

Something does not look right. I would try another tach set on FOUR BLADES.

jaka

Hi!
Heavy!??? All models should be built as light as possible to fly well.
4 -blade scale size prop for a small .40 size model is just not possible.
Sorry!

tahustvedt

Swinging scale size props is perfectly realistic and very satisfying to fly with on a scale model. Basically you need to reduce the rpm and increase the torque of the output shaft somehow and increase the pitch of the prop. the solution is not to cram a much more powerful and bigger engine in the nose. I have two planes with big multi-bladed props and used different approaches to the problem. My 1/6 scale Spitfire swings a five blade 19" DIY propeller and my 1/6 scale P-40 swings a three blade 20" Soloprop propeller.

I made a belt drive for my 1/6 scale P-40. It's electric, but there's no reason why a custom belt drive system can't be built for a glow engine. Basically you need to know what RPM the engine likes to operate at efficiently, how much power it produces, and then adapt the prop rpm and pitch to achieve a high enough pitch speed and the right power level. Or you can just test different gear ratios and measure and see what works for the engine, and then calculate the pitch speed from that. I usually end up testing different gear ratios anyway so it's a good idea to order a few different pulleys/gears.

www.sdp-si.com has a large selection of pulleys, belts, gears, shafts and bearings. Everything you need. It's not going to be a budget project, but it's fun. My next project is a constant speed propeller for the P-40, and then a counter rotating gearbox for the Spitfire.

tahustvedt

Hi. I like what you have done. Your prop is very impressive, I remember seeing pictures of it here some time back I think (?). I also had problems with the torque overcoming the belt grip. What I did was add a support-wheel on the loose end of the belt, the side of the belt that is not under tension while the motor is under load. This increased the contact-area on the smaller pulley and instantly fixed all skipping without overtightening the belt. You can see the bolt with the two bearings that act as a third pulley in one of my pictures above. It's a very simple solution and it's not under a lot of stress because it's only supporting the loose side of the belt apart from when the prop is windmilling and I don't think that's going to cause problems.