Adapter plate rest of the story

[ERicter]

So The craft is up and running etc and we're all wondering what was the cause.
The last prop installer (not my mechanic) put the prop on the adapter while it was still on the crankshaft. My mechanic put the prop on the replacement adapter first, then installed the assembly on the engine. Is the method critical enough to maybe cause the part failure I experienced???
The instructions says to attach it to the adapter first.

[Guest]

Re: Adapter plate rest of the story

So The craft is up and running etc and we're all wondering what was the cause.
The last prop installer (not my mechanic) put the prop on the adapter while it was still on the crankshaft. My mechanic put the replacement adapter not the prop first, then installed the assembly on the engine. Is the method critical enough to maybe cause the part failure I experienced???
The instructions says to attach it to the adapter first.

I have done it both ways.

I doubt it makes any difference.

The instruction to install prop on the "adapter" first could lead you into re-doing the job.

I say this because you may end up installing it (by mistake) on the adapter such that when you put the assembly on the engine the prop is not in the correct position for hand propping the engine.

FYI - I gave a nearly new tapershaft hub (a.k.a. as adapter) this evening to another mechanical engineer that I know that is going to model it in ANSYS with some loads/speeds... and with a ring gear plate installed. We spent a long time talking about the problem. I plan to send him the pictures that you posted as well. He agrees at least for now with my initial assessment of what may have happened, I am an ME also. What can you say about the prop that was on it before you purchased it? Can you say what the i.d. is of the hole in the center of the starter's ring gear? Ring gear plate thickness?

Dave

[ERicter]

Re: Adapter plate rest of the story

Hi Dave

I will bring it is and get these measurements.. I'm a carpenter, only have a tape. 2-21/32 is i.d. And if I'm remembering correctly the thickness is 1/8. The machinist said it was out of true 15 thousands..(quick estimate) He did not chuck it up to get that is what he said he would have to do to be sure.
It was suggested to send ring gear out to you for further testing??? Whatcha think??

[Guest]

Re: Adapter plate rest of the story

I would not do any additional testing on the ring.

Is there any info about the prior prop?

Dave

[Ragwing nut]

Re: Adapter plate rest of the story

Your failure was caused by the sketchy starter system that never should have been stc'd. I'd bet if that hub was turned over to the FAA there would be an immediate grounding of every airplane that had that starter setup on it. Those hubs just don't fail in that manner.

[ERicter]

Re: Adapter plate rest of the story

Here are the three pieces that went with that hub.
First that one at the top was against the hub and that is .502 thick with I.d. 2.658

Then skinny one is .120 thick with I.d 2.666

Then ring gear .120 thick with I.d 2.662

That spacer against the hub has a slight bevel to it, and one can see where the hub was gouging it with the broken edges.

Anything else, planning on going airplane camping on some river bottom in the mountains this weekend so if I don't answer I'm away for a bit, doing my first bush landing.

[Guest]

Re: Adapter plate rest of the story

Thanks Eddie,

Tell me something is there any evidence that the spacer was installed upside down when the old prop was on?

Dave.

[PA1195]

Re: Adapter plate rest of the story

I see three hub pieces in Eddie's picture when the normal tapered hub adapter lists two...the main hub #3745 and the outboard flange #3991. What's the stacking order of assembly and where does the third spacer go? Can I assume the thick spacer at the top is a starter ring gear inner spacer to allow the outboard ring to clear the cowl?

Gary

(PS- saw Eddie today and he survived his bush trip and big fish)

[Guest]

Re: Adapter plate rest of the story

I think that the spacer goes on first because Eddie said "First that one at the top was against the hub and that is .502 thick with I.d. 2.658" in his last post.

You have a good question Gary.

For my purposes of modeling I need to know (assuming the spacer goes against the hub) if the spacer was installed upside down with the prior prop.

However your question makes me think of another thing to ask Eddie and that is what was the assembly sequenced used with the prior prop?

Dave

[PA1195]

Re: Adapter plate rest of the story

Eddie's probably enjoying the fine Alaska weather this weekend flying again. If I see him today I'll ask re the sequence but likely he'll have an answer soon. I also wonder what the prop position was relative to the starter gear that's apparently warped? I gathered from a discussion yesterday with Eddie and Fred that there's not much info on the longer prop that was installed prior to sale. The former owner would have to be asked.

That whole assembly puts the prop further forward on the hub than normal (via the combined thickness of the spacer and ring gear)...maybe the resulting longer arm could magnify any inherent imbalance in the components and stress the base that cracked?

Edit: We may have walked this around before, but it appears there's two systems...one for flanged cranks and one for tapered. The tapered model uses the spacer likely between the adapter hub and the ring gear. The flanged crank apparently does not based upon these pics: https://www.facebook.com/SafestartStarterSystems/ That's why there are two sets of holes in the ring gear...smaller to fit the adapter and bolt size on the tapered, larger to fit the flanged crank's forward bushings that engage the recess in the prop.

Gary

[Guest]

Re: Adapter plate rest of the story

I guess now I have third inquiry, does the spacer have chamfer on both sides of that hole in its middle?

[ERicter]

Re: Adapter plate rest of the story

I guess now I have third inquiry, does the spacer have chamfer on both sides of that hole in its middle?

The order when we took it off was the thick spacer up against the hub, then the thin one then the ring gear.
Yes the spacer has the chamfer on both sides.
We cannot find any info on what prop was on there before, I will try to get this answer.
Thanks