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Post  jbanes1961 on Thu Nov 07, 2019 9:17 pm

Prop hub nut 20191122
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Post  jbanes1961 on Thu Nov 07, 2019 9:19 pm

I'm assuming this is the prop hub nut. I'm also assuming that this needs to be removed to service engine. The problem I'm seeing here, is when u try to loosen the nut, it just spins the engine. Am I missing something here?
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Post  NEW222 on Thu Nov 07, 2019 9:54 pm

Yep! Gotta remove the backplate (or tank and backplate if so equipped) first. Second, remove the piston and cylinder assembly (don't ask me how I know this one). From there, there are a couple of options. Option one is to pad the jaws of a vice, re-install the propeller screw, then insert into the vice and slowly and carefully tighten up the vise until the crankshaft pushes free from teh drive washer. Option two is to simply put the propeller screw back in, then lay the engine pointing up on a solid flat surface and strike the propeller screw carefully, and the drive washer will again seperate from the crankshaft. I personally prefer and do the first one in a vice, but have done it both ways without any damage. There are a few threads here explaining this if you want to search 'how to remove drive washer'. Hope this helps.
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Post  NEW222 on Thu Nov 07, 2019 9:58 pm

Forgot to add that a coupel of our sponsors here sell tools specific to doing this particular task, as well as put it back on.

Speaking of putting it back on. Very easy as well. Just insert crankshaft into the crankcase, line up the splines of the drive washer and crankshaft up (you can feel it when it is in place), then using your propeller screw with a propeller on it, put it in and start tightning it up. It will naturally follow its way back onto the crankshaft.
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Post  Marleysky on Thu Nov 07, 2019 10:15 pm

Instructions from Cox International:
Prop hub nut 76664710
Prop hub nut 91cd0410

My question is.....Why do you want to do this? Is it stuck, or castor goo slowing it down?
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Post  jbanes1961 on Thu Nov 07, 2019 10:21 pm

Very good...one last question, can i safely assume that the hub will never just fall off, when u dont want it to? Sounds kinda like a press fit deal...nothing is wrong with engine, I saw in the 50 yr old instructions that u were supposed to check hub for tightness every time before u fly it. Which got me to looking at the set up and seeing possible problems
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Post  944_Jim on Thu Nov 07, 2019 10:47 pm

Sir,
What you are showing us on your engine is the prop drive plate, not a prop hub nut. Some drive plates are hex-shaped, and some are round. They press onto the crank.

The prop hub nut is the black barrel that is being used to re-assemble the drive plate onto the crankshaft on the above image. They are usually used with a spinner. They can work loose through use, so it is prudent to check the prop hub nut to ensure the prop doesn't come flying off the crank.

Go to Cox International and look for the spinners. Each one shows the prop hub nut. The spinner slips over the prop hub nut and snaps into the groove around the prop hub nut's mid-section.

Not every engine will.use a prop hub nut. Some people will use a 5-40 screw and washer to retain the prop. Another spinner (the aluminum.one) is drilled through with a screw securing the spinner onto the prop. Again, look at Cox International's site for that example. Even prop screws can work loose. Check your prop mounting often. Props taste awful.

Enjoy the hobby! Have you got a plane picked yet?

Jim in MS
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Post  jbanes1961 on Fri Nov 08, 2019 7:40 am

Yes I have a plane picked out. P40 Warhawk. Soon as I find one in my price range
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Post  getback on Fri Nov 08, 2019 9:12 am

jbanes1961 wrote:Yes I have a plane picked out. P40 Warhawk. Soon as I find one in my price range
Plastic , balsa , RTF , build ur own , scratch builds ?? and RC / CL ? Very Happy lol!
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Post  jbanes1961 on Fri Nov 08, 2019 10:07 am

Probably start with plastic CL
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Post  944_Jim on Fri Nov 08, 2019 8:30 pm

JBanes...pm your address. I have a few P-40 planes if you want to build a balsa model. Both slabbie wing and profile fuselage, and built up wings and profile fuselage.Prop hub nut Img_2187
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Post  getback on Sat Nov 09, 2019 8:06 am

Take Jim up on that J Balsa flys better and is easier to repair , cost less than Plastic .. The P40 is pretty sought after and can demand some $$$ for fun !! Small Cox Logo
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Post  getback on Sat Nov 09, 2019 8:08 am

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Post  Canso07 on Sat Nov 09, 2019 5:31 pm

I just built this Carl Goldberg 1/2A P-40 in about a week off and on. I traced all the part from the originals, still leaving me a complete kit. Nice easy build just have to add the paint and decals. Bought the decals from Brodak, looks just like the original ones. JBanes you can order the complete kit from Brodak also.

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Prop hub nut 20191112
Prop hub nut 20191111
Prop hub nut 20191110
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Post  Canso07 on Sat Nov 09, 2019 5:32 pm

Prop hub nut 20191113
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Post  jbanes1961 on Sat Nov 09, 2019 7:50 pm

thanks for all the info....
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Post  944_Jim on Sat Nov 09, 2019 8:30 pm

Canso07,
Any chance you scanned the parts into full size PDFs?
I'd like a copy.

I usually scan the plans/build sheet in overlapping sections, and then use stitching software to digitally assemble the prints. From there, print to PDF as different size Iimages to create a full size PDF (just a little math to check percentage scale-up or down).

The CG P-40 begs to be wrapped around a jumping bean wing!


Last edited by 944_Jim on Sun Nov 10, 2019 12:40 pm; edited 1 time in total
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Post  jbanes1961 on Sun Nov 10, 2019 6:00 am

no, i didn't scan them, don't have the scanner and i"m not very computer saavy
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Post  944_Jim on Sun Nov 10, 2019 7:49 am

JBanes,

That was for Canso. If he digitized the patterns, they can be used to scratchbuild.one fairly quickly.

If you wanted to buy a kit like his, then here you go. Brodak reproduces the very same kit with their name on it:
https://brodak.com/catalog/product/view/id/3045/category/900/

You still need to supply your finishing supplies.
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Post  jbanes1961 on Sun Nov 10, 2019 12:42 pm

Ok, thanks Jim, I check it out
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Post  roddie on Sun Nov 10, 2019 4:46 pm

jbanes1961 wrote:Prop hub nut 20191122

Hello jbanes, I like the photo. I LOVE Cox engines! I see that you now have some info. to work with. The Cox .049/.051 engines (all)  utilize a female size 5-40 machine-screw thread for mounting a propeller or drive to the crankshaft.

Your photo shows a nice brass prop. drive-plate. You're correct in that it's splined and a press-fit onto the output-end of the crankshaft. For "Pusher" applications; a thrust-washer (currently available part) can be placed between the drive-plate and the front of the case. This lessens the wear on the front of the case from friction. Installing a thrust-washer is also a smart idea if an electric-starter is ever used on the engine.

I use an electric starter.. and usually apply a drop of oil to the drive-plate/case junction. The Cox Tee Dee .049/.051 aluminum spinner works well for using an electric starter. It's a cone with a through-hole for a longer (approx. 1"L.) 5-40 prop-screw.

Here are two .049 engines with the Tee Dee-style spinner installed (Tee Dee .049 on top/Medallion .049 below)

Prop hub nut Tee_de10

A 1"L. black-oxide 5-40 cap-screw on this one... (I got mine through Fastenal Co.)

Prop hub nut Tee_de11

The spinner's taper ranges approximately .300 to .400" or 7 to 10mm diameter. My homemade electric starter uses 5/16" ID (.312") rubber fuel-tubing to engage this type of spinner.

Prop hub nut Tee_de12

You may want to use a "starter-spring" (currently available part). The hex/cam type is designed for the engine in your photo.. because of its' hex drive-plate. The cam-style spring assy. is Cox's 2nd generation design and does NOT hook-around the propeller blade root, like the 1st generation does. It was designed to work with the hex drive-plate by "keying-into it".. with a plastic cam piece which the spring automatically engages when the propeller is wound backward.

Here's a photo of the cam-style assy. that I used on a model..

Prop hub nut 3-27-110

note the hex-shaped drive-plate (like yours..)

Prop hub nut 3-27-111

... installed on the engine..

Prop hub nut 3-13-110

The spring-coil is of a larger diameter on this (cam-style) type.. in order to fit-over the larger hex drive-plate. This design also induces a slight "drag" on the crankshaft.. because of the "ratchet" effect that allows automatic-operation when winding backwards for starting the engine. It's handy on an engine that has a cowling.

The 1st generation (1-piece) spring however is a referred to as a "zero-drag" type.. that hooks around the propeller and has a smaller diameter to fit-over the smaller/round drive-plate. It must be manually hooked-over the propeller each time an attempt is made to start the engine. It then retracts back out of the way when released.
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Post  944_Jim on Sun Nov 10, 2019 9:23 pm

Roddie,
I love your tanks...mine look like they are hand-formed with a brick!


Last edited by 944_Jim on Mon Nov 11, 2019 7:16 am; edited 1 time in total
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Post  Levent Suberk on Sun Nov 10, 2019 11:41 pm

Most members in this forum are master craftsmen and working like Cox engineers. Here is a thread to make masterful metal fuel tanks:

https://www.coxengineforum.com/t9455-wedge-tank-build
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Post  roddie on Mon Nov 11, 2019 6:44 pm

Cox did make prop hub nuts for some of their engines/models that used spinners. I'll site some examples of my own.. which fit the .049 engine's 5-40 threaded prop-screw (actually a stub-screw)

This more common type came stock with my PT-19 Flight Trainer..

Prop hub nut Cox_0418

Those are 5-40 stub-screws that thread-into those hub-nuts.. through the propeller hub-hole and into the crankshaft. Notice the "slot" across the face of the hub nut. The edge of a Cox .049 engine wrench fits into that slot for installing/removing the propeller.

I sourced a couple of NOS Cox "Super Stunter" hub nuts from a local hobby shop that closed a few years ago.

Prop hub nut Cox_su14
Prop hub nut Cox_su15

They're solid and heavy. Much heavier than the common type shown above. They're actually a nice flight-trimming tool for that certain model that needs just a tad more nose-weight.. Smile

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Post  jbanes1961 on Mon Nov 11, 2019 10:16 pm

Thanks Roddy, that's what I saw in the original instructions for my engine..
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