C/R engine alternators

[Michael Bryant]

Did you see the following?



This is the same link you will find at the top of the box for 12 Volt Twin Engine Aircraft, Lycoming Engines on the Aircraft Model Eligibility List for Generator to Alternator Conversion on the Plane Power Website.

We had to replace the belt on my 180 because it had the 7 1/2" pulley on the ring gear (singles have the same note).

Michael

[Robert L Markle]

[Charles Schefer]

Just catching back up on this thread and I'm now wondering if I did something wrong on my install... I did the TAL-70 but I did NOT change the belt. The belt is snug right at the minimum point on the mounting bracket (i.e. can't go less snug) but my IA who is a very particular guy felt the belt tension was correct. We are not seeing any issues with interference with the prop governor lines or anything else so thought it was all fine. I've now read the referenced SB from Plane Power. I will check that gear on mine tomorrow and see. Maybe I should replace my belts also... If so not looking forward to that since it requires removal of the prop (unless the rest of you know some other magical way)...

- Charles

[Robert L Markle]

[Charles Schefer]

[Robert L Markle]

[N3322G]

Thanks for sharing all the detail.

Perhaps the difference for my Twin is it always had alternators and didn't have to do the generator/alternator conversion.

[Charles Schefer]

I measured my ring gear support pulley today and it is indeed the 7&1/2" pulley referenced in that Plane & Power note. I'll call them tomorrow and see what more they can tell me.

Bob, my belts also say Lycoming 80668 Dayco 5-7013 and I'm pretty sure they were new when the engines were overhauled 500hrs ago. I did not have to modify my arm bracket as you describe - for me they worked as-is but I have no adjustment in terms of making the alternator belts looser. That said the tension I currently have also does not seem too tight.

Oh by the way... On that Pane & Power page it references a Piper belt P/N 452-541. However under the TAL-12-70 page it then says: "The required Piper belt number 452-541 has been superceded by the belt number 73965-15."

I'll call Plane & Power tomorrow to see what more I can learn.

- Charles

[Charles Schefer]

I just spoke to Dick at Plane-Power and even though I have the original 7.5" pulley he said that the note is on their website in the event it applies. He said some installations require a belt change and others don't but the kit is actually designed to work with the belts already there. He said "if it ain't broke don't fix it". He said a belt change is not necessary unless the existing belt won't fit (without improper belt tension of course). He also referenced this page regarding proper belt tension -> http://www.plane-power.com/images/ALTER ... IONING.pdf

- Charles

[steen]

Small print footnote in the Plane Power instructions designates a different v-belt to be used.
I pre-ordered the belts and they fit perfectly.
The stock belts are too short and will not fit.
Steen

[Charles Schefer]

[Charles Schefer]

Looks like I'll be replacing my belts as well. I did the slip torque tests that Plane Power suggests and sure enough... my belts slip at higher torque than the spec so my belts are too tight. Steen I'd be curious which belts you purchased that work... Plane Power says use "Piper belt number 452-541" but another place on their site says it "has been superceded by the belt number 73965-15". I assume you got 73965-15...

- Charles

[Charles Schefer]

Update on this issue. I called Plane Power again to verify numbers and Dick from Plane Power said they really should not be advising customers on which alternator belt to use since that is an airframe item and their STC does not give them the ability to mandate or suggest a non-Piper approved belt for the particular airframe. He said he was going to talk to his web site and engineer guys about this. I pointed out that if they are going to sell an STC kit and it does not work with the factory belt then they are really not providing a "complete" solution without the proper belt. I sent him pics of my install with data on the belt tension being too tight given the stock belt. They are going to look at this. But in the mean time...

I called Webco and spoke to John who was extremely helpful as Webco always is. John asked what belts I currently have and the answer is Lycoming 60886 belts. John told me that the 60886 is the correct P/N belt for a PA-30 with generators but for alternators I would need a longer belt. John said the 60886 is a 1/2" belt with an overall circumference of 32 & 5/8". John recommended I install Lycoming belt 37B19774-341 which is a 1/2" alternator belt that is 34 & 1/8" in circumference (just 1 & 1/2" longer which should in theory be perfect). For reference the "4" at the end of 37B19774 indicates 4/8" or 1/2" wide belt. The "-341" is similar to AN numbering in bolts.... the "34" is 34 inches and the "1" is 1/8 inches. So -341 = 34 & 1/8".

John checked and said that 37B19774-341 cross-checks to another number which then cross-references to the Piper P/N 452-541 referenced on Plane Power's website (pic below). Note that based on my conversation with Dick this morning it would not surprise me if the web page shown in the pic below soon disappears from Plane Power's web site...

I should have the belts tomorrow. I'll pull the props off and switch the belts. BTW the only other part needed in this process is a new o-ring for the seal between where the prop hub mates up to the engine. I have 2 new o-rings for this. I'll post the results after I get the new belts on.

- Charles

[steen]

On my recent conversion to Plane Power alts.(PA-30B) the specs said a different belt might be required (longer) and I ordered it prior to the work.
Worked out perfectly.
I am very happy with the conversion.
Steen

[Charles Schefer]

Well I did remove the props and install the new Lycoming 37B19774-341 Alternator belts. Pretty easy process just took a few hours and only a new prop hub seal for each prop was needed parts-wise. Also be advised that on the props the torque spec on the studs vs nuts is different (42 vs 50 ft-lbs as I recall but it's in the book). I used the belt tension guidance from Plane-Power (posted earlier in this thread) and both belt tensions are in spec. With this new set-up here's a new pic of my alternator. Now I am no longer at the max loose setting on the adjustment arm slot - much better!

- Charles