Extending propellor on crankshaft by adding washers

[Allen Eshleman]

I have a beautiful 2nd hand Banshee.  The original owner had an LA 40 on it.  I put a Brodak 40 on it using the same holes.  However, with a normal installation the driver washer is too short because the installed propeller rubs against the front of the plane.  I know that one solution would be to drill new holes and move the engine out. The other would be to install an LA 40.  However, I was wondering if just adding to flat washers between the drive washer - the one that has a grated face that usually touches faces with the prop, will work. Will the propeller slip, even if it is drawn really tight?

[Steve Berry]

The more accepted solution is to simply use a prop shaft extension, such as this one:

https://brodak.com/fox-prop-shaft-extensions-10-32-thread-x-3-4-long-1.html

Lots of places to get one, and Jim Lee (see Vendors Corner) may already have one ready to go for the Brodak 40.

Steve


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[Robert Zambelli]

Not intended to be a dumb answer but why not just trim off a bit from the front of the fuselage?

If not, how thick would the spacer have to be to clear the fuselage?

Steel washers would almost definitely slip.

[Dave_Trible]

Yeah I'd just sand or shave a little off the airplane-especially a profile.   You will struggle to keep the prop on tight stacking washers.

Dave

[Colin McRae]

I have a Banshee that ran an OS 40 LA. Way too much engine for it. Plus, really nose heavy especially with the OS stock muffler. I had to add a lot of tail lead to CG balance.

I ended up switching to an OS Max 30 plus I moved the engine back a bit so I could get rid of the tail lead.

A friend of mine runs a 25 LA with success.

[Colin McRae]

Yeah I'd just sand or shave a little off the airplane-especially a profile.   You will struggle to keep the prop on tight stacking washers.

Dave

Plus, if there is any prop (and or spinner imbalance), moving the prop out will increase load on the bearing potentially adding to wear.

[Motorman]

Don't do it.

[Doug Moisuk]

Take the engine off, fill the holes. Move the engine forward, mark the hole location drill into the mounts not all the way threw and use a brace inserts.

[Dave Rigotti]

Use self adhesive sandpaper to the faces of the two washers like 120 grit. Go fly it....

[Dan McEntee]

   If you only need .030" (1/32") or a fuzz more, just make a shim disk from sandpaper. If you are using a spinner, put the shim between the spinner back place and the drive hub. You can layout one in pencil on the back of a sheet of sandpaper with a good center mark. Punch the center hole 1/4" and then cut out the disc. If not quite enough, make two of them. Make sure the shaft threads still go through the nut.
   Type at you later,
  Dan McEntee

[Motorman]

Cut out a disk of G-10 material and glue it on the back of the prop hub.

[jerry v]

Use the aluminum backplate from suitable spinner. Cut the plate to the diameter same size like the engine backplate. Usually the spinner backplate has the knurling on the engine side and the prop side.

Jerry

[Allen Eshleman]

Thanks for all the suggestions.  I am considering shortening the front of the fuselage.  The B-40 is lighter and I think less powerful than the LA 40. As for now, I think that's what I'll try next.

Thanks again.  I see other options here also. 

[Brett Buck]

I have a beautiful 2nd hand Banshee.  The original owner had an LA 40 on it.  I put a Brodak 40 on it using the same holes.  However, with a normal installation the driver washer is too short because the installed propeller rubs against the front of the plane.  I know that one solution would be to drill new holes and move the engine out. The other would be to install an LA 40.  However, I was wondering if just adding to flat washers between the drive washer - the one that has a grated face that usually touches faces with the prop, will work. Will the propeller slip, even if it is drawn really tight?

    I use plywood washers for exactly that sort of thing.  My current airplane has a 1/64 plywood washer between the thrust washer and the spinner backplate, and I have a stack of them in my toolbox.

     Brett

[Allen Eshleman]

Do you make those wood washers or buy them.  If you buy them, where?

[Brett Buck]

Do you make those wood washers or buy them.  If you buy them, where?

  I make them. They are only 1/64" so I cut them approximately round with a pair of scissors, and carve out the center hole with an exact knife to a little over 3/8 to get them over the end of the spigot on the crankshaft. They are not particularly round or uniform, how out of balance can a ring of 1 1/4 diameter 1/64 ply be?

    Brett

[Allen Eshleman]

Do you use several at a time? Where do you get 1/64 plywood.  I see packs of them on Amazon.  Looks like they're basswood.

[Brett Buck]

Do you use several at a time? Where do you get 1/64 plywood.  I see packs of them on Amazon.  Looks like they're basswood.

  1/64 plywood is a common hobby shop item (and one of the more useful products you can have around!). It's great for lots of things, pretty heavy for the dimensions, but so useful I always have some with me. I use it for fuse doublers, edging cowl/hatchs, great for repairs, as well.  This seems a little expensive, but expedient:

https://www.amazon.com/Midwest-Products-Birch-Plywood-24-Inch/dp/B000BQT8GU/ref=sr_1_2?crid=1MX8L4MCROA7U&dib=eyJ2IjoiMSJ9.I43a8yTsx4a6wsW31LcfNoYS8AqT9vp8ZBpnX2v5_lsTro0znhA_pn1H80xWU0pKPRiEgX6lm96BenPyTs1nwtgq3F3DcJdDSVCk6SRMmsRqJhm0rn9HSFBpwOp6DipCSsN1GFLYASdtA63-ev06TsQrkSx2xxlpF1YDbzxYCSGjrla6K9cVa7DG0-lRLOcllECzMygitzeFJrmD-N4R_kohhYhsL3_JIsPEyTbseEilYsvCnnWq3Aaw_Yh-bmERLOz7sEjVcMDNmFv0qVErcRBEhJzhDsGs9k6J94NgGs4.OgrzXvMFXCAnim_ehnN0o0S0IS3pGAjaDSTBIZHAtNM&dib_tag=se&keywords=1%2F64+plywood&qid=1747073425&sprefix=1%2F64+plywood%2Caps%2C177&sr=8-2

      Brett

[Allen Eshleman]

I ordered a sheet of that.  I will try this before doing surgery on the plane.

[Dan McEntee]

Do you use several at a time? Where do you get 1/64 plywood.  I see packs of them on Amazon.  Looks like they're basswood.

    It's hard for some to comprehend the concept but 1/64" plywood is just that, plywood that is .015" (approx.) thick and made up of 3 players of wood!! It is handy, amazing stuff and once you use it and learn to work with it you won't ever be without a sheet or two around the shop. It's insanely expensive these days and was always pricey but well worth the extra expense to have on hand. SIG used to handle it, Midwest, and some of the other wood suppliers. It would generally come in 6" by 10" sheets, but also larger at 12"by 24" and 12" by 36 or 48".
  Type at you later,
   Dan McEntee

[John Carrodus]

As Brett Buck said, I also have used 1/64 th hard plywood. Works a treat, no problems at all. Easy solutions are often the quickest way to the party

[BillLee]

Back in my Fast Rat days, I used a 1/8" aluminum spacer behind the prop on my models. The models were made to fit an HP 40 which had a longer 'snout' then the K&B 40s or the K&B 6.5. In spite of no knurling or other treatments, they worked just fine, even in that very high horsepower/high RPM environment. Keep the prop tight.

[Howard Rush]

A 1/64” plywood disc behind the prop can shush some cases of prop buzzing. I got this advice from Matt Piatkowski via Paul Walker. It works.

[Brett Buck]

A 1/64” plywood disc behind the prop can shush some cases of prop buzzing. I got this advice from Matt Piatkowski via Paul Walker. It works.

     Prop buzzing?  I am curious which of the many strange sounds coming out the front of an electric you mean.

       Brett

[Ken Culbertson]

     Prop buzzing?  I am curious which of the many strange sounds coming out the front of an electric you mean.

       Brett

I thought this was IC but I have noticed a lot of very strange, what I assume are prop tip noises that are not drowned out by the motor like they are in IC.  You can almost fly some maneuvers by sound.  Twins add another pleasant sound when they harmonize!  Would love to hear a quartet someday.

I wonder if the plywood or sandpaper washers would work on Electric.  Don't see why they wouldn't.

Ken

[Howard Rush]

It’s maybe the same noise you get from blade tips not in the same plane.  The noise in corners is different.

[Brett Buck]

It’s maybe the same noise you get from blade tips not in the same plane.  The noise in corners is different.

     I would expect adding things to the stack would tend to make it worse (mistrack more and move the principle axes) rather than better. Maybe that is the effect - without, the prop tips run in the same plane, with, sometimes, they are out-of-plane and don't interfere with each other as much.

     I note that there are people who are convinced that you should run slightly different pitch on each blade of a propellor. The explanations for that one were, charitably, vague.

    Brett

[Lauri Malila]

It’s maybe the same noise you get from blade tips not in the same plane.  The noise in corners is different…

The whole model is a resonance box and every model absorbs or reinforces the vibroacustic signals differently.
Now, when you squeeze something (in this case a softer washer) to the interface of resonator and amplifier, it’s no surprise you can hear the difference.
Aircraft plywood is propably just fine, I’d propably glue gf or cotton/phenolic washers to the prop. Or even better, add a steel shim between front bearing and cone. L

[Ken Culbertson]

Although I have used them in the past, I am not a fan of washers, especially on collets.  From what I gather re-reading this thread the amount of space needed is relatively small.  My approach, and I have a spinner backplate dedicated to this task is to treat it as if it were a new build.  I glue a layer of heavy construction paper and some 100 grit sandpaper to the back of a 2 1/2" spinner backplate and use it to form the spinner gap gradually tightening the prop until there is no more sanding as you rotate it. You could easily shorten the nose this way with no damage to the rest of the fuselage.  Just refinish the part sanded off which will not be visible anyway with the spinner on.  Handy when you want to change engine down/out thrust or need a larger gap for electric cooling.

Ken

[Dave_Trible]

Jim Lee makes a handy tool just for this.   I slips over the engine shaft and has a nice knurled aluminum handle to spin around and sand the nose off.   In the long ago past I used some plywood washers at times my issue was oil soaking and uneven crushing when tightened down so that the prop and spinner wasn't running true.   I have a few larger nylon washers I got at Ace Hardware that I use sometimes.   They tighten up evenly and are impervious to oil or, er, electron slime.......I still sand the nose rings down if need be so that I won't have to find my washers...

Dave