another cracked spinner

rmorris · #1 03-21-16, 02:39 PM

First - our 337s will fly without a spinner just fine, very low perf hit if any....don't ask me how I know....just know that the FAA guy told me that we can't fly them without the spinner solely because they were certified with them on...

OK, so here's my issue...I've owned the BumbleBee for about 9 years now...think I am now going on my 4th or 5th spinner, and several of the times didn't catch it in time and also had to replace the backplate.

The cost of the spinner and backplate are outrageous, as removed combos run from $600-2k (and good luck finding the $600 sets)....new are in the 4.5-6k range. crazy for a couple of pieces of aluminum.

I was seriously thinking about looking to buy the MT props at sun n fun, but now have to sink a couple of thousand into replacing my spinner and backplate yet again.

no, the front prop has not been balanced since owning the plane, and is the only thing I can think of that would cause these recurring problems. New engine and crankshaft, so prop balancing is the only thing, right?

anyone else have problems with these front spinners and backplates? for sources these past few days I checked:
-Dodson, Preferred, KNR, AZ Aviation Salvage, Texas Aviation Salvage, ASOD
-also sent emails to Owen Bell and Neiser, neither responded as of yet
...other obvious sources I missed?

hharney · #2 03-21-16, 07:26 PM

Robert
Do you have a lot of noticeable vibration? Or maybe you haven't had a chance to compare with another Skymaster. Sure seems odd that you would be cracking those critters all the time. I still have my originals but didn't realize they were so expensive. Not sure I want to sell them, but also not sure why I am keeping them either.

I know my MT's have smoothed out my bird but I never had cracked the original spinners in the 25 or 30 years we had them. Doesn't Aviation Enterprises have some composite spinners that will retro the originals?

rmorris · #3 03-21-16, 08:05 PM

I do not notice any unusual vibration, but you are right that I don't have another Skymaster to compare against.

I am pretty convinced that I need to balance or replace the prop, and was literally near top of my sun n fun shopping list...to likely get the MT props. I say top because I am thinking I might upgrade the engines in the BumbleBee or build a twin velocity...want to go faster. So when I evaluate the 3-bladed MT props, I will need to understand (with that big of cost) whether they will work on a bigger engine in the T337C, or just the TSIO360s.

as for composites from Owen? He has to reply to one of the 2 emails I've sent since last Thursday....neither he or Don have made a peep.

I paid $600 for the front pair of spinner and backplate from a salvage yard in FL on ebay last year. but so far am having a tougher time. Given my desire to potentially upgrade soon, don't want to sink too much into it...just want to get it off the ground so I can fly to sun n fun and shop

hharney · #4 03-21-16, 10:30 PM

The 3 blade MT's will slow you down a tad, maybe two or three knots. The MT's are STC'd for the 337 only, it's really not by engine but they are made for the Cont. 360. Not saying that they won't be the same for another STC but there are no other STC's that MT has that fit Skymaster.

The only choice on engine is the Aviation Enterprises STC for the Cont 550. And I'm not for sure that is a completed STC, I think it is. One good thing about AE mod with the 550 is you can do one engine at a time. But that's the only STC, unless you are thinking field approval. The old Riley STC for the 520's is sold and owned by someone else and they are not doing anything with it.

Even with the bigger engine the cruise speed really a huge increase for the extra fuel you will burn. You have to get real high, like the Super Skyrockets do, to really take advantage of the extra HP without filling the tanks every 3 hours. That Skymaster airframe is only going to go so fast. It's really not very clean.

You need speed, you better look elsewhere. I see these guys around me with their Bonanza's and it make me so mad that they can blow the doors off my push pull and burn 1/3 less fuel. Then there's the guys with the RV-10's and that is one performing machine. Climbs like a maniac and cruises 170 kt burning 12 gals. I'm doing 155 kts burning 20 gals. Oh well a nice Bo or the 10 is $150k - $200k and I can buy a lot of gas for those dollars

You need to just call Don, he not real good on the keyboards. Not sure if Owen is still at the AE shop but call Chris his son.

SteveG · #5 03-22-16, 09:00 AM

Is there some reason you don't just repair the spinner you have? Stop drill, weld, paint, return to service. Done. Just wondering.

Kim Geyer · #6 03-22-16, 10:40 PM

ASEi in Georgia can usually fix them but their price is high @ 1600.00. K&K precision welding in Wisconsin is @400.00. They just did 2 for me.
Their phone number 262-642-5003

SteveG · #7 03-23-16, 09:07 AM

One other thought on cracking spinners. If you don't already know, the spinner needs to be a tight fit on the plastic centering wedge mounted to the prop hub. If you can put the spinner in place and have the screw holes align with no pre-load then it's not tight enough. Shim the wedge out until the screw holes mis-align by about half their diameter, then load the spinner with enough force to insert the screws and you will have a stable spinner centered on its axis of rotation.

rmorris · #8 03-25-16, 05:22 PM

Steve -
msg 1 reply 1) yep, I did that with the spinner, but the backplate was much, much worse off...so needed just that part. In the end, the person selling me the backplate just wanted to sell as a set, so I'm going to use as a set and be done with it.
msg 2 reply 2) good advice. the current mechanic doing the r&r said the exact same thing - good to hear it again, reinforces we are doing right thing. the guy who put on a backplate spinner combo for me last April did not do any load on it, I was there when he mounted, and he just mounted it all and off I flew.

Kim -
good to hear from you as always...should have known you would have a good source for repair. I tried the ATL guys last April when things went awry, and even sent them the stuff for repair. They told me it was beyond repair, so I sourced an as removed set and moved on...but knowing the Wisconsin option is great....since this keeps occurring.
How ofteen do you have cracks in spinners? Do you also have issues with backplates?

Don Nieser · #9 03-31-16, 02:05 PM

Robert, sorry I was out of town when you first contacted me. I was investigating a cracked wing spar. I will post information after we have done the engineering analysis.

I have a number of front and rear prop spinners and spinner bulkheads in stock and will try to beat any other prices.

Instalation of the spinner is critical: We use 2 people, have one person push (at the tip) of the spinner onto the spinner bulkhead, ( you can use up to 4 spacers (1457305-2) inside the plastic support (p/n 1457302-3)). Use enough spacers so that when you push on the spinner you can just get the screws started. It may take a couple of trials to get the proper number of spacers in place. Keep the pressure on the tip of the spinner as the second person start all the screws, then go around the spinner and tighten the screws in an alternating pattern. Also, I wonder some times if the plastic spinner supports have some wear, distortion or that 4 spacers are not enough. It may be that new spinner supports should be used.
Don Nieser
Commodore Aerospace Corp
405-503-4686
nieser.02.337parts@juno.com

hharney · #10 03-31-16, 04:42 PM

Don

I have seen a spinner that has been grooved inside from improper fit. With this issue what do you suggest?

SkyMac · #11 04-05-16, 07:39 AM

Both front and rear spinners on mine had deep internal grooves at the location of the nylon spinner support, when we striped them back to commence polishing we found the groove had almost worn through.

Now I have two polished ornaments, I had managed to obtain two rear spinners sets and a front spinner set. Now polished and fitted, I will be interested to read comments on the cause of the grooves, my thought- not enough washers.

I have a spare rear set just in case, an extra rear backing plate as well and front backing plate. Recently I have been offered another another front and rear set, yet to inspect them.

Dave

hharney · #12 04-06-16, 09:50 AM

I would suspect fitting issues cause the internal abnormal wear. There may be some justification to prop balancing also but the higher percentage of damage is most likely the spinner not properly fitted. More washers would be one concern but I thought I read somewhere that the number of washers is limited. This would indicate that the spinner or the internal support is worn beyond specs. I have seen many units with multiple washers, homemade too. One needs to be careful as the internal support will be compromised on the prop hub if too many washers are stacked up. Remember these things are 50+ years old and have been removed at least 50+ times.