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How to install a safety aluminium spinner nut on a OS-95V

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How to install a safety aluminium spinner nut on a OS-95V

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Old 08-18-2017, 12:02 AM
  #1  
alarconpiperj3
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Default How to install a safety aluminium spinner nut on a OS-95V

I almost finish my piper .60 great planes. Is looking good!

I bought a 5/16-24 Aluminium spinner nut to my O.S. FS-95V engine.

My question is to install the aluminium safety spinner nut i have to put first the prop nut, then the special tapered and slotted locknut? i have to use both and the the safety spinner?

The spinner nut just enter to the shaft about a 1/4.

This is the way to do it? or is there any other options.

Thank for your help.
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Last edited by alarconpiperj3; 08-18-2017 at 01:02 AM. Reason: word error
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Old 08-18-2017, 04:40 AM
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I've installed prop hubs in a similar fashion to yours. I like the factory double nut set up. The prop hub allows the use of an electric starter.
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Old 08-18-2017, 07:47 AM
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alarconpiperj3
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Thanks Thom. I appreciate your help.

Does the spinner nut is safe at about 1/4 on the engine shaft?

Do you think the aluminium spinner nut is the best option? Do you recommend something else?
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Old 08-18-2017, 09:01 AM
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Looks like you have a Cub. That prop hub, along with the stock prop nuts, is a good option.
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Old 08-19-2017, 03:57 AM
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I would use the spinner nut by itself.
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Old 08-20-2017, 03:51 AM
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As a Toolmaker by trade, the word of thumb is full strength is achieved by the threads contact at the same depth as the diameter. So a 1/4 inch nut would be 1/4 in depth. For you it's 5/16. After that little appreciable strength is gained assuming the threads are in good condition which yours obviously are.
You state 1/4 inch thread engagement. By looking at your photos it appears as though your prop nuts are on finger tight. Somebody correct me if I am wrong but I usually end up with some crush on the prop when tightened to what I feel is proper torque. Perhaps that will give you the needed engagement for full strength.

My two cents.
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Old 08-20-2017, 12:07 PM
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Originally Posted by Therapy View Post
As a Toolmaker by trade, the word of thumb is full strength is achieved by the threads contact at the same depth as the diameter. So a 1/4 inch nut would be 1/4 in depth. For you it's 5/16. After that little appreciable strength is gained assuming the threads are in good condition which yours obviously are.
You state 1/4 inch thread engagement. By looking at your photos it appears as though your prop nuts are on finger tight. Somebody correct me if I am wrong but I usually end up with some crush on the prop when tightened to what I feel is proper torque. Perhaps that will give you the needed engagement for full strength.

My two cents.
If the engine's prop nuts are being used, would the "spinner" then become purely cosmetic ? If so, the question would be "Is it threaded on well enough to stay in place?"
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Old 08-20-2017, 02:35 PM
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I myself like the OS split nut jam nut a lot also. But I took the split nut off since the spinner attachment nut acts as a jam nut. Myself, I consider it double nutted and it stays put.
So If I was him, I would remove the split nut and use the aluminum spinner nut as a jam nut thus solving all the issues. But if he feels more comfortable with the split jam nut AND the spinner nut, (thus 3 nuts) go for it as long as you can get 5/16 depth of thread. Which I feel he can once the prop wood starts to crush and engage the face knurl flange of the prop shaft. Just doesn't have the same cosmetic appeal.

Last edited by Therapy; 08-20-2017 at 02:37 PM.
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Old 08-21-2017, 02:48 AM
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Originally Posted by Therapy View Post
I myself like the OS split nut jam nut a lot also. But I took the split nut off since the spinner attachment nut acts as a jam nut. Myself, I consider it double nutted and it stays put.
So If I was him, I would remove the split nut and use the aluminum spinner nut as a jam nut thus solving all the issues. But if he feels more comfortable with the split jam nut AND the spinner nut, (thus 3 nuts) go for it as long as you can get 5/16 depth of thread. Which I feel he can once the prop wood starts to crush and engage the face knurl flange of the prop shaft. Just doesn't have the same cosmetic appeal.
I never thought of it, in that manner.It makes sense to me.
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Old 08-21-2017, 11:11 AM
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Hi!
Use only the aluminium spinner nut ! There is no need for a "safety nut" on any glow engine!
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Old 08-21-2017, 11:20 AM
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Agree totally with jaka. That's what I said in Post #5. I've never used another nut with all the spinner nuts I've used and have had no problems. Looks better and is safe, the two reasons for using one.
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Old 08-21-2017, 12:48 PM
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I totally disagree. I've seen 4 strokes throw props. The added safety is well worth the extra minute it takes to install the second nut.
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Old 08-21-2017, 01:12 PM
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I've never seen one thrown.
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Old 08-21-2017, 04:11 PM
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Sorry, totally bad advice. I threw a prop on my very first run of my brand new OS 62 FS. Besides, How is it bad? I double nut engine mount bolts too. Is it crazy unneeded? My first flight the engine bolts loosened and the freakin engine fell right off! Hanging there by the throttle cable for a dead stick landing. IF it fell all the way off the center of gravity would be blown and amount to pile of sticks!

Anyone in this hobby knows to be double careful and sure. At least the ones with experience.

If there is no need for a safety nut, Why does OS include one with a new engine? Boom!
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Old 08-21-2017, 04:26 PM
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Engine bolts should be tight. I've never had an engine come loose.
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Old 08-21-2017, 04:47 PM
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They were tight. But it was a fiber mount that was threaded. Now they are through holes with dbl nuts.

I am happy for you that this has never happened to you. Truly. At my club 6 different people with boucou experience stated that is has happened to them.

Can we please keep this on topic and not a personal squabble? This takes away from the original poster asking advice.
On a 2 stroke, backfires have "never" happened to me and I often went with a single nut. 4 stroke a different story.

The original poster here can take whatever advice he wishes. Play it safe or resort to "I heard it on the internet, it must be true".
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Old 08-21-2017, 05:07 PM
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So, only you are correct? Who is squabbling? You? I've only stated that I have used propnuts since the 70's, just a propnut, and it has worked just fine for me. Sorry if my opinion doesn't count. If I use a propnut, put it on tight, really tight, I'm not going to have a problem. Period.
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Old 08-21-2017, 06:00 PM
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Great! All I'm saying....is that I'm not incorrect.

Last edited by Therapy; 08-21-2017 at 06:03 PM.
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Old 08-22-2017, 09:13 PM
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Default Thanks to all for your time.

Thanks to all for your time.

TomCrump answer to post number 7: If the engine's prop nuts are being used, would the "spinner" then become purely cosmetic ?
Yes on one side is cosmetic but also the engine instruction manual says that the engine is intended for use with an electric starter. The aluminium safety spinner nut that i bought on tower hobbies was the one with the closer look that i could found to give the plane a piper j3 a clasic look and to be able to use the electric starter.

Therapy your post number 8 also make sense to me. And I think is the best combination between cosmect appeal and safety.
Just to double check is going to be like the new photos, right?
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Old 08-23-2017, 03:50 AM
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Perfect.
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Old 08-23-2017, 11:33 AM
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I won't get into the need for double nutting motor mount bolts, I like to use a nylock nut if I can get it in. Yes I have heard motors run very rough in the air, and land with the screws way out. Seen motors fall off, usually from ARFs with the hot glue. Our combat planes need a tether on the bellcrank to a motor mount, and boats and floatplanes often have a tether to the muffler or pipe, all for good reason. I just thought I should add that a few guys have had the acorn nut on top of the prop nut and washer, and the starter would spin it right off immediately. I have never had a prop come loose with acorn nuts, and have used them exclusively for decades. I just hate being at the field and needing to file slots in spinners and forgot the file, the starter shaking on the prop nut, bumbling a pit stop....I will admit that I only have one fourstroke, and have seen others backfire and loosen the prop. At work we were told 6 turns on a thread is fine. Aluminum or plastic I would go a bit more if possible. I have been proven wrong in the past, but question the judges. :-)
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Old 08-23-2017, 05:10 PM
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a few guys have had the acorn nut on top of the prop nut and washer, and the starter would spin it right off immediately
I don't see how this is different from a lone prop nut. Not tightened enough to jam it in place.

At work we were told 6 turns on a thread is fine.
As a toolmaker it is my job to use the correct nut/bolt thread engagement for proper strength. As such, engagement of the thread equal to the diameter gives full strength with like materials. As in, the bolt thread would fail (shear) without the nut failing. That's what I do and is backed up by years of worldwide research by the "Machinery Handbook" which is a collection of facts based by physics throughout the years. (Widely available anywhere) Not anecdotal evidence about what is good enough. Not being argumentative, just stating the facts backed by research. Hope this clears this up.

Last edited by Therapy; 08-23-2017 at 05:22 PM.
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Old 08-23-2017, 05:36 PM
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I am still going for the story that the acorn nut can unscrew with the starter spinning it off. I have seen it many times. Even tightening it pretty hard. I guess the guys I saw just did it over the nut, and there was not enough friction to hold it tight. The prop will likely not spin it off on it's own I doubt. Hopefully the OP will have good luck with his, and I would like to welcome him to the forum. I am a retired toolmaker/machinist too, and have read a fair bit of that book looking for oddball thread specs that we always seemed to need. Pretty thick and expensive book, pretty dry read but informative.
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Old 09-07-2017, 05:00 AM
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"...full strength with like materials..." That's the problem, isn't it? They are not like materials. The spinner nut is aluminum and the prop shaft is steel. I wouldn't trust just an aluminum nut on a a steel shaft.

I had this problem on my RCV 60 SP. It comes with the split jam nut. I wanted a spinner nut, partly for looks and partly for the starter. I might have tried the spinner nut over the steel nut, and not used the split nut, but thread space was marginal, so I used the stock set up.

The starter works fine without the spinner nut (RCV provides a separate shaft for converting the start to a heli-like starter, but for the 60 SP starting from the front is fine).

Jim
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Old 09-09-2017, 07:49 AM
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I have a Cub with a Saito .72 on it. Great combination. Like you, I thought I needed the jam nut since the manufacturer had included it and 4 strokes are more prone to kicking backwards than 2 strokes are. I hated the appearance though, and so have run the plane for 5 years with only the spinner nut and washer. But I do something that few modelers have figured out (from what I can tell anyway).

The issue with nuts coming unscrewed from backfires is a lack of friction between the prop hub and drive washer. Sometimes it's not an issue if the prop hub fits the textured part of the drive washer, but they often don't. The same problem occurs with plastic backplate spinners too. I bought a roll of open mesh plumber's sandcloth several years ago. I cut a washer out of it and put it between the prop hub and drive washer. Open mesh sandcloth is rough on both sides, so it bites into both surfaces and greatly increases the friction. You'll never kick a prop off of an engine using the stuff. Yes, you might unscrew a spinner nut if you put your starter on a flooded engine, but double nutting doesn't help with that anyway.
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