BriKali

Hello,

This is my first time posting. Ihave a few questions about my Novel Big Mig .061 Revlite. Here'sa littlebackground: I have notput it ina plane; Iam only running it on abench; basically Iamperforming dyno tests; I am using 15% nitro fuel. Here are my questions:

1) What is the smallest prop I could use without over-revving the engine?
2) What is the largest prop Icould use without lugging the engine at too low of an rpm?
3) Would a 4.75" x 4" prop be too small? Would a 7" x 4" prop be too big?

I'm not concerned about whether any given size prop would make a plane fly well.My sole purpose in usingdifferent size props is to put different loads on the engine. Basically, Ijust want to make sure I don't ruin my engine

Thanks!
Brian

combatpigg

My Feedback: (3)

The 4.75x4 is actually more prop than a 5x3. The 5x3 is a very good working prop all around.
The 6x3 is the biggest you should run. Running larger invites overheating and advanced crankcase/parts wear.
If you have a speedy design with 150 square inches or less and fairly light, the 4.2x4 is a good prop. The 4 pitch will get your plane up to 100 mph if everything is working well together.

A lot of flyers like the 5.7x3 the most, but they are easy to break. I like the black rubber Cox 5x3 for general use. 1 if these props will last for years.

Don't worry about over revving, just make sure the engine is broke in well enough to run a tank of fuel at full song without getting hot and needing constant adjustment. It should be able to run at a slightly rich scream for a full tank by itself. I safety wire the muffler tight to the case to get consistent air pressure back to the tank.

mtntopgeo

My Feedback: (12)

For a "big" prop, I use a APC 5.7x3 ........... On the small end, a 4.75x4. On 33% nitro, with 25% oil, the big prop allows the engine to spin at 19,000 + RPMs. With the small prop, I've had readings near 24K. These are not hard fast limits, just the area I (and the engine )feel comfy with. Others have used smaller, & larger (but not too much larger) with success. ................ George K.

hllywdb

Hi Brian,

Have to agree with CP on the 5X3 lasting forever. I run a 5.7 X 3 as the largest prop. It tends to give a lot more thrust on verticals than the 5X3, but you will break them easy. Anything larger puts the motor out of it's power range. I also like the 5.5 X 2.5 on planes that can fly a little slower. The small props work good on real clean, fast airplanes.

DeviousDave

Try a 4.5-4.1 Electric pylon prop. IANAL, so throw it away at any sign of stress.

Larry Driskill

Brian, your post and concern for your engine got me to reflecting on AMEs and running them in 1/2A CL Combat in the late 90's. So I dug around in my cabinet and found some notes on setting up the AMEs and their performance. One sheet , in particular, caught my attention.

The data sheet, dated 6 June 97, is for a Zeus .049 and is marked "best in '97". We were using the early model short, lightweight, Zeus crankcase and shaft and replacing all the other parts with newer AME bits.

It was turning a glass prop 32,000 and was making two laps on 35' lines in 3.89 seconds at the '97 AMA Nats. That prop was probably a 4.25X3 fiberglass prop with very thin blades. Fuel is not listed, but I suspect it was 30% to 50% nitro, 20% castor, and the remainder methenol. Most of the parts were modified and we broke some of them . . .

I realize that your engine is larger and a much newer RevLite model, but I'm with Pigg and doubt that you have much risk of hurting it through over-revving with any of the props folks have listed (once it is broken-in and if you run fuel with 20% or more oil and don't let it run too lean).