Help mounting a 6x3 apc prop (hole is larger than mounting screw)

layback209 Fri Oct 13, 2017 9:11 pm

Howdy Folks, hoping to bend this forums ear to help answer a dumb question of mine, i did some searching on google and in this forum but did not come up with a clear answer.

I have a few APC 6x3 props that i would like to mount on my 0.049 teedee or blackwidow but the prop mounting hole diameter is too large for the engines prop bolt. Is there some kind of spacer you can make to center it? appreciated any guidance you can provide to me. I seen a photo in this forum of a number of different 6x3 brands and the APC one had what appeared to be a metal spacer (perhaps tube or cone shaped...not sure) to center it. I certainly dont have a lathe to make one...

Cheers,

Derek

batjac Fri Oct 13, 2017 9:45 pm

Hi, Derek. Welcome to the Forum. The easiest way to center it is to use a short piece of small fuel tubing to go over the 5-40 prop screw. the fuel tubing will squeeze and center the prop. There used to be a guy who machined bushings for the APC props to work with the 5-40 screw and sell them on eBay or by email. I have one of his bushings, but he doesn't sell them on eBay anymore. At least, I haven't seen him sell anything for a long time. I don't remember his name.

If someone else knows his name and email address, I'd be eternally grateful. Or at least 'till Christmas...

The Festive Mark

Oldenginerod Fri Oct 13, 2017 9:47 pm

Mark got in ahead of me, but here is the message that I was sending when he chimed in.

A small length of plastic or rubber tubing of the right inner and outer diameters is fine. As long as the prop is centred then once tightened the bush (tubing) doesn't carry any load anyway. Even a small piece of heat-shrink tubing will work if you need something real thin.

Rod

Ken Cook Fri Oct 13, 2017 11:28 pm

Mark, I designed the bushing for the prop. I did this for 1/2A combat because changing a prop with a piece of tubing on it was a pain in the rear. I needed something that could be done quickly. I made one here at home and Mike Parkin made them for me. Seeing that he was already selling on Ebay, I told him it was a good idea to sell them. The rough length of rod he needed to begin with was of a special size and he needed to buy a certain length. He purchased the length and I bought the majority of the bushings. What was left were sold. Mike was in the process of a major upgrade of machinery. The jobs he was doing has consumed a lot of his time. Ken

batjac Sat Oct 14, 2017 1:04 pm

*** SIGH ***

I guess I'll just have to keep careful track of where the one I have is at all times.... Ah, well. Thanks for the info, Ken. And thanks for getting Mike to make the run he did. At least I have plenty of small fuel tubing for the rest of my props. Fuel tube works.

The Resigned Mark

fredvon4 Sat Oct 14, 2017 1:55 pm

Hey Mark...I got lucky and actually got a few of the last run of the bushings last time offered

Happy to send you one..just PM

BTW any spacer/bushing need NOT be full Prop hub length...just enough diameter to fit hub and bolt

I find the K&S tubing assortment to have quite a few small length pieces that work ok...in fact more than once I ganged up severl different diameters of tubing to fit the prop bolt and then large enough to center a over reamed prop hub hole

roddie Sat Oct 14, 2017 2:36 pm

batjac wrote:*** SIGH ***

I guess I'll just have to keep careful track of where the one I have is at all times.... Ah, well. Thanks for the info, Ken. And thanks for getting Mike to make the run he did. At least I have plenty of small fuel tubing for the rest of my props. Fuel tube works.

The Resigned Mark

I keep a zip-seal bag of short telescoping alloy tubing bushings to bush my prop-hubs... along with spare varying-length/size prop-screws. I keep that bag with my props. That's one way to keep track so I don't misplace small items.

What you "could do" Mark.. is to thread a small "zip-tie" through the eye of that bushing and zip it closed a few clicks. It's a lot harder to lose something when it's easier to see.. and won't inadvertently roll off a table or bench. Just cut the tie with scissors when you're ready to use it.. and have another new zip-tie ready for when you take it out of service.

andrew Sat Oct 14, 2017 3:09 pm

The prop shaft holes in the smaller APC props may not be centered or perfectly perpendicular to the hub due to the hand drilling process used after the props come from the mold. The recess in the hub is, however, centered since it is part of the molding process. The bushings mentioned use this recess for centering the prop on the shaft.

APC notes the alignment problem in their technical notes and states the hand drilling that's used after molding.

batjac Sat Oct 14, 2017 10:08 pm

andrew wrote:The prop shaft holes in the smaller APC props may not be centered or perfectly perpendicular to the hub due to the hand drilling process used after the props come from the mold. The recess in the hub is, however, centered since it is part of the molding process. The bushings mentioned use this recess for centering the prop on the shaft.

APC notes the alignment problem in their technical notes and states the hand drilling that's used after molding.

Yeah. It's awfully strange that a manufacturer that ships thousands of props a month wouldn't have some sort of simple drilling jig that would center on the molded recess to drill an accurate center hole...

The Jaded Mark

layback209 Sun Oct 15, 2017 12:37 am

Thanks for the feedback. I never thought of trying fuel tubing for centering.

I thought it was odd for an manufacturer to supply a prop but not provide an "OEM" bushing/correct hole size to help customers use their product.

Intersting about the center hole being a bit off from factory too I would have never expected that to be a thing either.

The local hobby shop does have a good assortment of k&s tubing as well. Good news Smile

. I'll do some testing and see what works best.

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Help mounting a 6x3 apc prop (hole is larger than mounting screw)

Help mounting a 6x3 apc prop (hole is larger than mounting screw)

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