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Old 07-16-2014, 10:00 AM
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OldScaleGuy
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Default Spinners

I would like to start a discussion regarding spinners. I have a DLE-111 in an Extra 330. I have installed an MPI 4-1/2" aluminum spinner. This spinner is very good looking, the finish is as good as you could ask for. The problem i am running into is when the cone is tightened the back plate warps. It not only looks bad, it creates a condition that brings a portion of the back plate very close to touching the cowl. The question, is there a way to avoid this and still be confident the cone is secure? I wouldn't mind replacing it with another brand of spinner but not crazy about spending $100 plus to do that.
Any thoughts, ideas, suggestions will be appreciated.
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Old 07-16-2014, 01:02 PM
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da Rock
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Simply stop tightening the cone before the backplate starts to warp. Large spinners are not what binds the prop to the drive shafts. They don't have the leverage to do so.

The cone should not contact the prop anywhere. It should not even touch it. So it has absolutely no leverage to hold the prop to the engine. That's what the engine bolt(s) and washer are for.

I'm sure you already know all that but there are lots of members who probably don't.

Last edited by da Rock; 07-16-2014 at 01:25 PM.
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Old 07-16-2014, 01:07 PM
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da Rock
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When a cone continually loosens in use, the problem is with the surfaces on the cone that contact the cone. Rough them up to introduce significant friction to resist spinning.

If your backplate isn't robust enough to stand sensible tightening of the cone, you've either bought a poorly designed spinner or gotten a spinner that doesn't belong on an engine like the one on which you've put it. There isn't much cure for that.

Gas engines with multiple prop bolts for example don't play well with friction held spinners.

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Old 07-16-2014, 01:35 PM
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The backplate shown in the ad for the MPI 4.5" spinner ($40) doesn't look very thick. A Johnson Stunt Supreme I once had would throw spinners regularly. One night, I used some brass wire and a drill bit the size of the wire to put some teeth into a backplate. Drilling holes around the spinner, half the hole in the cone and half in the backplate, made some places to epoxy short pieces of the wire. They gave the backplate teeth that fit into the cone.

Clamp the cone to the backplate and drill along the seam.
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Old 07-17-2014, 02:36 AM
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Originally Posted by da Rock View Post
When a cone continually loosens in use, the problem is with the surfaces on the cone that contact the cone. Rough them up to introduce significant friction to resist spinning.

If your backplate isn't robust enough to stand sensible tightening of the cone, you've either bought a poorly designed spinner or gotten a spinner that doesn't belong on an engine like the one on which you've put it. There isn't much cure for that.

Gas engines with multiple prop bolts for example don't play well with friction held spinners.
I have been flying with nothing but large gas engines with multiple prop bolts, and True-Turn or carbon fiber center bolt spinner's for decades and literally thousands of flights, never had an issue with them playing well together so far. The back plate on the MPI is just too thin. personally I would just toss it in the trash, it's like most things I guess, you get what you pay for. Have you ever seen how fast an engine comes off the front of an airplane when the spinner ejects and brakes one blade off at full power? I have seen it actually a few times, it does an excellent job of destroying the engine cowling and airplane during its exit, all while blowing the canopy off from all that new found pressure inside the fuselage, then for the grand finale was the airplanes impacting the ground after several falling leaf oscillation maneuvers, seem like they always hit tail first tearing up the other end as well. Just food for thought.....

Bob

Last edited by sensei; 07-17-2014 at 03:06 AM.
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Old 07-17-2014, 03:25 AM
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Thanks fella's. Sounds like it is time to "bite the bullet" and buy a good spinner. I really like the plane it is on and certainly don't want to loose it due to a spinner failure.
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Old 07-17-2014, 03:42 AM
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Great decision, I don't want you to lose an airplane either.

Bob
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Old 07-17-2014, 03:45 AM
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Thanks! Now it is a matter of deciding which one.
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Old 07-17-2014, 05:45 AM
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Originally Posted by OldScaleGuy View Post
Thanks! Now it is a matter of deciding which one.
Can't go wrong with Tru-Turn Spinners
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Old 07-17-2014, 06:38 AM
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Originally Posted by OldScaleGuy View Post
Thanks! Now it is a matter of deciding which one.
In addition to Tru-Turns and a carbon, I'm using a Dave Brown spinner with good results. I preferred the Dave Brown shape to Tru-Turn, and the price was a bit better also.
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Old 07-17-2014, 07:12 AM
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Interesting. I have heard that Dave Brown makes the MPI spinners.
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Old 07-17-2014, 09:34 AM
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Originally Posted by OldScaleGuy View Post
Interesting. I have heard that Dave Brown makes the MPI spinners.
Not sure.

Pricewise DB is between MPI and TT.

Does that mean DB is better than MPI?

I like my DB, and my TTs, never used MPI.
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Old 07-17-2014, 10:44 AM
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Originally Posted by dasintex View Post
Can't go wrong with Tru-Turn Spinners
Ditto !
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Old 07-17-2014, 11:03 AM
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Good question Don. I have used several MPI's with no issues but they were all smaller than this one. Perhaps i just got one with a thinner/softer back plate than normal.
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Old 07-17-2014, 01:15 PM
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I like tru turns.
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Old 07-17-2014, 01:46 PM
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I like the fact that True Turn will cut where the blade is. If you tell them what prop your using they will cut it. And it's also balanced.
Very important !
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Old 07-18-2014, 03:09 AM
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Dave Brown will cut spinners, too.

The one MPI spinner that I have appears to be cast, not spun. It's quality is far inferior to Tru Turn, or even Dave Brown.
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Old 07-18-2014, 03:29 AM
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It is good to know Dave Brown will cut spinners.
The MPI's i have are all spun. I am asking a local machine shop about turning just a new back plate. We shall see how that works out.
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Old 07-18-2014, 03:33 AM
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My MPI is probably 10+ years old..

I feel that DB spinners are a viable choice when we are on a Buick budget, and can't afford a Caddilac (Tru Turn.).
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Old 07-23-2014, 09:53 AM
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Had to share this with you in this thread, i just happened to stumble across looking for another item.

Can this possibly be worth a darn?

http://www.abellhobby.com/XOAR-4-5-A...er-p/xs4.5.htm
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Old 07-23-2014, 12:07 PM
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Looks like a Chinese copy of Tru Turn. Buy one, and let us know:-)))))))))))

Les
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Old 07-25-2014, 09:57 AM
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Received the new plate from the machine shop today. It looks much more robust than the original.
I have to drill the prop bolt holes then will be trying the fit and function this weekend.
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