Wanted: A65 Cylinder 0.015 over

[Robert Lees]

Re: Wanted: A65 Cylinder 0.015 over

I have posted the SB on engine balance, its something like 1 or 2 ounces of total mass difference, at 2300 rpm, its not too much of a problem. There is also a difference between the casting numbers and the part numbers of the pistons. If is old piston was good, I would clean, put new rings on and slide it into a new jug. Tim

Tim, the A&P has quoted to me that he needs to weigh the pistons for balance purposes. He seems to know what he's talking about.

Rob

[mikerice]

Re: Wanted: A65 Cylinder 0.015 over

Robert-
Has your IA torn down your engine? Are all pistons the same configuration?

Many A65 engines have been upgraded to A75 over the years by changing pistons and rejetting the carb. A75 can go to 2600rpm while A65 is limited to 2450rpm. The extra 10 HP is only available at max rpm, and the improved pistons were to provide better cooling/lubrication at the 2600rpm redline for the A75. We bought 3 of our cylinders redone at Gibson Aviation in El Reno OK, and now I am wondering if the 4th cylinder we retained had a matching piston/ring setup...

We have an A75 on our BC12D, and went through a mod STC with Terry Bowden years ago to get the engine approved on our BC12D. The Taylorcraft A690 Type Certificate does not allow an A75, and the 10 HP increase is in excess of the 10%HP allowed with a field approval 337. There was also an issue with the correct propeller, as allowed by the Type Certificate.

Just thought I would muddy the water more for you

[astjp2]

Re: Wanted: A65 Cylinder 0.015 over

Speaking of yellow tags, what FAA form is a Yellow tag? I had 4 cylinders that had yellow tags on them and assembled the engine and it seized when it got warmed up. cooled down and it would run. Pulled the jug, tagged .015 and it was only .010. Just because it has a tag does not mean its right. It only means that the cylinder has a piece of paper. TIm

[astjp2]

Re: Wanted: A65 Cylinder 0.015 over

I have posted the SB on engine balance, its something like 1 or 2 ounces of total mass difference, at 2300 rpm, its not too much of a problem. There is also a difference between the casting numbers and the part numbers of the pistons. If is old piston was good, I would clean, put new rings on and slide it into a new jug. Tim

[Robert Lees]

Re: Wanted: A65 Cylinder 0.015 over

I think 3Dreaming is correct. The piston part number reported as being fitted is 4368.

[Edwin Otha]

Re: Wanted: A65 Cylinder 0.015 over

Put in what you want, probably might work.
EO

[3Dreaming]

Re: Wanted: A65 Cylinder 0.015 over

Robert called it a 4 ring piston, but looking at the picture I count 5. I think this would make it a 4638.

[Edwin Otha]

Re: Wanted: A65 Cylinder 0.015 over

A65 uses a 3 ring piston, p/n 40312 or the cam ground 40731 which uses ther .921 pin. The A75 uses a 3 ring p/n 40577 and a 5 ring 4638 both have the small pins. If the engine is an A75 you need a 40577 piston and a 25127 pin.
Since you have a 4 ring piston installed most likely a p/n 4544, I would weigh the parts and make sure you dont take the engine out of balance. TCM has the current weight limits listed in a S/B.
The piston shown would not be an O200 due to the small pin, change in the compression height and the bore.
EO

[Mark Julicher]

Re: Wanted: A65 Cylinder 0.015 over

After looking in the parts and overhaul manual, the A-75 and A-65 use three ring pistons right? The piston in your photo looks like an O-200 with the skirt ring configuration. It seems likely to me that the piston skirt is too long and possibly bumping somewhere.

[Robert Lees]

Re: Wanted: A65 Cylinder 0.015 over

The Tcraft engine is (on paper) an A-75. It certainly didn't wind up to A75 rpm like the Aeronca did, Mark.

But that was most likely due to the prop.

Rob

[Mark Bowden]

Re: Wanted: A65 Cylinder 0.015 over

Question, from the photo of the piston, if the A50, 65 is four rings and the A75, 80 is five rings is that an A75 piston in this rebuild? Wouldn't that require special paperwork on the rebuild to use the A75 pistons? At least a 337?

Do you have the drilled connecting rods too then?

Mark

[Edwin Otha]

Re: Wanted: A65 Cylinder 0.015 over

The .859 pin has a thin wall and a thick wall. Use the thick wall. Also the pin plugs are different use the correct one with the pin you choose. The cam ground pistons use the .912 pins with the pressed in plug. You will need a piston with a small pin or you'll have to re-bush the rod. The 4 ring pistons are a pretty early piston for the A50's&65's, if you can save it, I would.
EO

Re: Wanted: A65 Cylinder 0.015 over

Someone please correct me if I'm wrong but isnt the "big (no AD) piston pin" suppose to meausre 0.90? Not sure what the +/- allowances are for the piston pin but until that's the bad one I think it's worn 0.05.....again, I'm trying to go by memory so please correct me if I'm wrong. The A65 overhaul manual will tell you this under the table of limitations but I don't have mine hue at them moment, it's at the airport.

Hi Kevin,

The caliper and the measurement appear to be for the purpose of showing the approximate pin size so as to identify the pin.

For example the caliber is a plastic 2 digit model. One would use a micrometer for a pin measurement.

Also we would hold the caliper jaws perpendicular to the pin if we wanted an accurate measurement.

Rob's mechanic is doing a good job of showing us that this is the small .859 pin not the big .922 and that it has a 4 ring piston.

I would not make any conclusion about condition based on this.

BTW- I posted the AD above.

Dave

[Mark Bowden]

Re: Wanted: A65 Cylinder 0.015 over

I have a collection of scanned manuals from 1939 thru 2011 and will try and get them uploaded to the ref section. The only one that has a nominal pin diameter is from 1939. All subsequent manuals do not have nominal sizes which is strange.

Pin Dia. = 55/64. (0.8594)

Pin to piston limits from 1939 Continental Manual
Desired 0.0004
Min 0.0001
Max 0.0007
Max 0.0015 (Max allowable after use)

Pin to piston limits from Aug., 2011 Continental Manual
Min 0.0001
Max 0.0007
Max 0.0015 (Serviceable Limit)

Mark

[waltermrich]

Re: Wanted: A65 Cylinder 0.015 over

Rob, this isn't related to the current topic but since its your post I thought I would chime in. When I last saw you at Blakesburg at our lunch you asked me where my Uncle was stationed in WWII in England, at that time I could not remember, but I now remember Him saying it was near the town of Ipswitch on the east coast of England , he was a turret gunner mechanic, and I can remember as a kid during holidays he would always be talking about his time there spending three years in a tent and working on his B17 Rumdum, that B17 went on with some notoriety as it came back with heavy battle damage, I have brought it up on the web and read about it , it went on to complete all its missions. Currently I have a friend named Cliff who sits next to me in our church choir in his mid 90's He trained to be a pilot but wound up being a navigator on a B17 based he said at Ridgeway near Cambridge, early on I think in 43 there b17 was shot down over France, he parachuted safely, but was captured by the Germans and spent the rest of the war at Stalag Luft 3, he said it was where the story of the movie the Great Escape was derived. He is a really nice old fellow and Im trying to get him to record his story, finish his log book I have told him. Thanks for all your stories they were great and I hope you get your Taylorcraft in the States flying