albietz

I have a question about installing a prop. on an OS engine (0.55AX). The engine is installed on an airboat so I'm not very familiar with the best way to address this issue. I figured the rc plane guys would be the best experts. I'm installing an APC prop. with a tru-turn aluminum spinner. I can't get the adapter nut to be tight enough so that the prop. doesn't spin on it's own while the motor shaft remains stationary. I believe the nut is bottoming out on the motor shaft and that's why I can't get the prop to stop moving. Does anyone have any suggestions on what I could use as a safe spacer? Thanks

jetmech05

do have the thrust washer? It should be spinner back plate, prop, thrust washer. then nut...the thrust washer is about the size of the prop hub in diameter

BarracudaHockey

My Feedback: (11)

You should have the spinner backplate, then the prop, then a 1mm to 1.5mm thick thrust washer, then the prop nut.

If you have all that then unless you're using a very thin electric prop, you should be able to get it tight.

albietz

Yes, I have the engine hub with the knurled face against the spinner back plate, followed by the prop, and finally the washer with the nut fitting into it's center. The propeller that is have an an APC 10x6 and imprinted on the packaging is that it's for 50-60 2 cycle engines. It does have a narrower hub than the master airscrew 3 blade prop. that I also have on hand.

Gray Beard

My Feedback: (-1)

Bit small for the .55.

JohnBuckner

My Feedback: (1)

The APC 10-6 C-2 is almost 1/16 th narrower than the APC 11 inch C-2 hubs. That prop is to light in diameter and or pitch.

If you really want to run that size then your options are to use an additional washer behind the spinner with this presenting the possibility of slippage problems or to run an eleven inch APC cut down to that diameter.

An ideal prop for that engine is an eleven inch and either seven or eight inch pitch (yup eight inch pitch).

John

albietz

It's a 10x6 four blade.

albietz

Thanks for the feedback. Not sure what's the best prop. option, so I have either 10 or 11" diameters with different pitches and also numbers of blades. Have done some reading and it seems like everyone would have their own opinion as to what prop works best in their situation with an engine this size. Figured I would just start plaing around, but came across this prop. slippage issue as soon as I got started. I was thinking another washer might work, but wanted some other input before I started experimenting.

JohnBuckner

My Feedback: (1)

Yup thats right but try reading the manual for that engine (OS has an opinion too) you might just be surprised.

John

JohnBuckner

My Feedback: (1)

Then your option is to use a washer behind the spinner back plate and that is about it when using an undersized hub.

John

albietz

Yeah, that's what it sounds like. Thanks

jaka

Hi!
I use a 0,4mm ply washer between the engine drive washer and the Tru Turn spinner backplate.

albietz

Thanks for the response. I'll have to give it a shot.

rgburrill

I just looked at the OS page and the picture of the 55AX.  I do not see how your nut would not go down all the way.  The picture shows the nut to within 1/8" if the thrust washer with no prop at all. 

SRQFlyer

My Feedback: (17)

I would guess it is the spinner adapter nut that is bottoming out. Maybe a regular nut and then the spinner nut would work, or the "long" version of the Tru-Turn nut?

Jim

scaleman57

My Feedback: (23)

Hey Al what i do is take my dremel put a carbide cutting wheel on it trim 1/4 inch off offof the shaft , problem solved.Not all guys will agree but I do it all the time.

BarracudaHockey

My Feedback: (11)

I didn't think of that, are you using the spinner adapater as the prop nut? That makes sense now.


If you can use the prop nut, then put the spinner adapter on the end.

Don't cut the crankshaft.

biam

I agree with John, an 11x7 0r 8 is all I ever used on my tower .46 engine, with good results.

Gray Beard

My Feedback: (-1)

When we talk about different prop sizes for planes we are working within the engines rpm range too. By changing lengths and pitch it effects how well the engine pulls the plane. The manufacture of the engines gives us a starting point of sizes then we test different pitches and lengths to decide what prop works best for the plane/engine combo. Going too small takes the engine over it's working rpm range, too big and it lugs the engine down too much. This is what you will see when plane guys are talking about prop sizes. A 10 inch prop with the small pitch on a .55 engine could over rev it and cause problems. Running more blades like you are can compensate for a bigger prop. Check to see what rpms your engine is running just to be safe.

CGRetired

My Feedback: (1)

One important point here is to undersatand that the manufactuers specs list HP at a certain RPM. For the most part, this RPM is not a typical nor a nominal RPM for that engine. Smaller engines will operate at higher RPMs than larger engines.

Noise does not equal power.

Having a prop that allows a high level or RPM, although it may reach the theoritical nominal for that engine (what the manufacturer states, in other words) is usualally not a practical operating RPM for that, or any engine.

A .55, for instance may say 2.2 HP at 15000 RPM (this is not what they say, but is just an example) a practical max RPM for that engine may be 11,000 RPM. So, select a prop that will give you the best performance at that RPM.

This takes trial and error and a little time to organize the stats for your particular engine and then select the prop to work with it.

CGr.

freakingfast

My Feedback: (3)

An APC four blade????

Gray Beard

My Feedback: (-1)

Yep, they make them, you just don't see them often.

freakingfast

My Feedback: (3)

Old, old stock. Discontinued for years.

JohnBuckner

My Feedback: (1)

Not only discontinued but possibly a safety hazard as well:

http://www.apcprop.com/v/Clearance/clearance.html

freakingfast

My Feedback: (3)

He may be OK with the 55AX and a 10X6 4 blade. It will not see over 14k static (calculated) and the engine will never fully unload on the airboat (it'll blow over first if it's a traditional Everglades design). The prop will most likely break if it contacts solid water at speed.

A better choice is the 3 blade Master Airscrew 10x7. The 55 with stock muffler and baffle was 11,700 (tested) and with a "tuned muffler" it jumped to 14,000 backed off 300 rpm rich on 15% fuel. The wide blades of the M.S. should offer a lot of punch to get the boat on top of the water quickly. They are more forgiving for impact than APC.