Spinner and backing Plate

[Bonanza91K]

Today I discovered that my spinner and backing plate were both cracked beyond repair. My plane is an F21 but I believe that F19 parts will fit as well. Anyone have a source or sources for these parts. Backing plate is 10" diameter, flange out and the spinner is 10" by 7" long

Thank

Jim
F21
Baumann Amphib floats
TrickAir skis.

[LostnSpace]

Re: Spinner and backing Plate

Jim, PM sent, Gary

[PA1195]

Re: Spinner and backing Plate

Maybe check Univair for Piper spinners that fit the O-235 and prop? They're short and fat and found on PA-12-18-20-22's for example.

Gary

[Bonanza91K]

Re: Spinner and backing Plate

Gary,

I think I will just go with a Piper one from Univair. The stock ones are hard to find and will only get damaged again.

Thanks

Jim

[PA1195]

Re: Spinner and backing Plate

I just threw out that Univair suggestion but there may be other new or used sources that would work as well. Any idea why the Taylorcraft spinner is prone to self destruction? I did have a spinner depart a C-185 once in flight but that was probably due to some sort of prior imbalance and structural fatigue.

Is your engine smooth or is it rough at certain rpms? Is your propeller balanced and tracking properly? They can become imbalanced over time via profiling and wear.

If the prop's ok the engine/prop combo can be balanced by adding weights to the spinner bulkhead and I've had that done several times on a variety of planes. They use a balance test unit originally designed for a helicopter and put the G-sensor on a crankcase clamping bolt. Just some thoughts to consider before replacing parts.

Gary

[Bonanza91K]

Re: Spinner and backing Plate

I called Univair and then Sensenich who both said that the Univair spinner won't work since I have different props than what is required for that spinner setup. Looks like I might just have to use a skull cap style.

Jim

[Robert Lees]

Re: Spinner and backing Plate

Is the F21 a Certified aircraft? Surely you just ask the FAA to point you in the direction of the TC holder for spare parts?

Rob

(Awaits incoming)

[Robert Lees]

Re: Spinner and backing Plate

Is the F21 a Certified aircraft? Surely you just ask the FAA to point you in the direction of the TC holder for spare parts?

Rob

(Awaits incoming)

[PA1195]

Re: Spinner and backing Plate

Tim Popp was by for a good visit today in Fairbanks, Ak., and from what he told me they (the FAA) might have to swim the Rio Grande to find the TC. Boom! Boom!

It's hard to believe that the prop hub on the F21 and Pipers with the same engine are that markedly different in size, shape, and bolt pattern. Isn't the crank the same SAE 2 size on O-235's? Wonder where the fitment problem is?

Edit: Answered (?) my question...the 72CK-0-50 prop on the F21 uses a SAE #1 crank flange (TCDS 1A9 and 1P2); the M76AM-3 prop the Univair U13661-A spinner is listed for uses a SAE #2.

From another Forum:

"SAE 1 is 4-3/8" (lug 5/8") => external diameter (out of lug's holes) = 4-3/8" + 5/8" = 5".
SAE 2 is 4-3/4" (lug 5/8") => external diameter (out of lug's holes) = 4-3/4" + 5/8" = 5-3/8".

==> SAE2 is 3/8" larger than SAE 1, with same lugs.
Cont. engines are SAE 1,
Lyc. engines are SAE 2, BUT O-235 can be SAE 1 or SAE 2."

Gary

[Bonanza91K]

Re: Spinner and backing Plate

I use two different props on the plane. Both fit the prop flange although one hub is thinner than the other requiring shorter bolts. The thinner one is not "legal" for the plane but is my seaplane prop and has never been a problem with the same spinner. The flange on the backplate cracked at one mounting hole, separated and tore the spinner beyond repair. Sensenich tells me that the cut outs in Univair's spinner is incorrect for my standard prop because it is thicker at the hub but "could" work. I'd like to find a direct replacement but with so few of that model made, I'm probably out of luck. I may just buy one from Univair and try it.

Jim

[d.grimm]

Re: Spinner and backing Plate

Jim,
I have a short Pacer spinner and back plates you are welcome
To try. If it works, 50% of Univair price. Polished and very nice.
Dave

[Ragwing nut]

Re: Spinner and backing Plate

wag aero makes a pug nose spinner that is identical to what taylorcraft used but it is not listed as a certified spinner. It is what I used when i put our F-21 back together.

[PA1195]

Re: Spinner and backing Plate

If my plane were experiencing metal fatigue in spinners I'd address that issue before simply buying and flying yet another. I'd ask my mechanic or the local prop balancing repair station if available to inspect the crankshaft runout, install the prop and spinner as concentric as possible, then look for any wobble or out of round activity. It can be measured while stationary or visibly noted or measured with a probe marker briefly touched to the unit while rotating. The spinner shouldn't wobble and have the assembly balanced if possible.

Edit: I did a search here and as usual from experience Tim notes the Ercoupe spinner may fit...might be worth a look.

Gary

[Robert Lees]

Re: Spinner and backing Plate

I agree with Gary's post above. Furthermore, these larger diameter spinners make prop balancing easier, because they have the diameter whereby added weight (in the form of washers attached to the back plate) has effect. It's more important on wood props (because they have less inertia) and you will see washers on most aerobatic aeroplane backplates that use MT or Hoffman props. This doesn't apply to most of our Taylorcraft, of course, but the principle still applies

But dynamic prop balancing does need to be done by someone with the kit!

For us with 1940's Taylorcraft with the little skull-cap spinner, I don't think there is enough room (or diameter-> moment of inertia) to be able to add washers...unless anyone can suggest otherwise?

Rob

[PA1195]

Re: Spinner and backing Plate

Here's what was done to my C-85 with dome spinner and bracket to balance the assembly. A piece of chromoly plate steel of the appropriate thickness and weight (about 50 grams) was placed under the head of one of the attaching bolts on the face of the prop hub at the light weight location. It's flat under the bolt, fits inside the spinner, and then is bent forward and mimics the angle of the spinner bracket leaving the hub for a short distance. It can be adjusted by varying the plate thickness, width, and overall length to supply the weight the dynamic balancer calls for at that station.

Washers were initially tried but it became obvious that to get sufficient weight the stacking of the washers required a longer bolt and required trimming to fit under the spinner. As installed it's not going to bend or come loose and we're monitoring it for any signs of stress. So far it's airworthy and I have repair station documentation to substantiate the installation.

I'll take a picture and post.

Edit: I'll add that my plane and newly overhauled prop/engine never shook, rattled, or rolled. The only change noted during the progressive balancing process was the slight tingle felt in the rudder pedals disappeared. Everything else remained the same as far as I could tell.

BTW I've flown other planes with the balance tech onboard to see how airspeed, manifold pressure, rpm, and constant speed prop pitch affected the imbalance. He ran his prop strobe from within the cockpit and monitored the G-load IPS acceleration. It walked all around depending on engine load and airspeed so we ended up setting the balance weight and station location for level normal cruise flight where the plane spent most of it's flying life.

Gary