R975 Radial engines

[David Herbert]

Thanks Perry,
It also says it in the operating section of the manuals for the various radial engined Sherman variants and of course private owners are really good at reading manuals and doing what they are told.....

David

[rob love]

So if a guy needs to overhaul one of these, is it doable, or does it need to be sent somewhere that specializes in the radials? The boss keeps talking about wanting to get the Sexton going. I's hard at this point to even know what the problems with the engine are....something initially caused it to be parked, and about 6 years back a volunteer tore out the magneto and all the ignition wiring. We just got back the magneto (untouched) after about 5 years of it sitting at the local air museum.

Any recommendations for rebuilders? We had company in Winnipeg (standard aero) who used to do all the Dakota engines a few decades back, until the air force retired them in 1989. Or are the C1 radials too oddball for a regular commercial rebuilder?

I think I saw in the US a company that said they do them for around the $30K mark. They warned that they were often fixing other rebuilder's mistakes.

[Matthew Noonan]

Speaking of R975 mods

https://imgur.com/a/cnnMRnk

Are these towers? with the repositioned exhaust?

[David Herbert]

There are other photos of Rams with this same modification. The engine is completely standard but the exhaust is routed out through the engine decks instead of the standard arrangement as built with two mufflers side by side just bellow the engine deck discharging through fishtails that are hidden behind the rear upper hull and discharge downwards.

The other photos that I have seen were gun tower conversions for towing 17pdrs and I had assumed that the relocation was to make hooking up easier but the photos Matthew has found appear to be ordinary Kangaroos so it may be related to the fact that all these Rams are equipped for the fitting of wading trunking. However the standard wading trunking did not require the relocation of the exhaust and was very similar to the radial engine Sherman design which never had the exhaust relocated.

David

[Bob Phillips]

Hi Rob,
I think your question about overhauling a radial might best be directed to Jesse as I recall he tackled the overhaul himself. Would welcome your comments Jesse. On a related note I think that with care and patience the overhaul might be much easier to do using the TM manuals as they are very detailed compared to aircraft OH books. There are a number of engine companies that specialize in radial overhauls. The price quoted (30K US) is not out of line. Last year I talked to a large company overhauling a pair of C4s, they needed a lot of work (including salvaging badly smashed up cylinders) and the offhand comments about cost put it much higher than the 30k number.

[David Herbert]

Going back to Bob's question in his post #21 about common failures in R975s, another one that I have come across more than once is that the eight small high tensile screws, that bolt the gear onto the rear section of the crank, fail and there is then no drive to anything on the back of the engine. This usually does not result in any seccondary damage, just a dead engine. It is a huge amount of work to replace them but doable by a competent person who reads the TM and can work very carefully.

This failure is easy to check for as nothing on the back of the engine goes round when the engine is turned by the fan. Also of course the starter does not turn the engine either.

David

[Bob Phillips]

Here is a picture of the gear (#9) from the -46 book, hope you can see it.
rearcrank.jpg

[Jesse Browning]

Rebuilding an R975 is not for the faint of heart, nor is it for one with little mechanical ability. Even though I was novice in radial engines, I had 30 plus years of mechanical, electronics training and experience. Using that experience, I CAUTIOUSLY undertook the project. I spent hundreds of hours reading every bit of information about the engine I could find. Read the manuals until you completely understand everything BEFORE you start the project; almost to the point you have them memorized. Measure EVERY part. Make sure EVERY part is serviceable, and clean. That includes every part of the accessories. The work area has to be spotless and dustless. Does that seem like a lot? It is. I would say a successful conclusion to a project like that requires a passion. No weekend warriors are going to do it. It was a privilege for me to be able to take on a radial rebuild. A once in a lifetime event.

[Stew Robertson]

Hi Rob
the sexton engine we rebuilt after Bill got it. It sat in the shop for almost a year before we got all the parts to finish it
It was not a hard job just took time . At the time I had and mechanic that worded for CP AIR help me with it
After the rebuild and break in of about 10 hrs we reinstalled it and put 400 or 500 gallons of fuel through it and it run flawless in the sesquicentennial parade in Kingston in I believe 1985
the biggest problem the engine had to be cranked by hand 52 revolutions of the crank handle before starting with the starter
That is what happened to the engines in the sexton and the grizzly in Shilo
oil compression or hydraulic locks and they scattered or bent a few rods
WHO NEEDS TO READ A MANUAL
lots of luck with the rebuild, Levy's are not around anymore

[Bob Phillips]

Thanks for your comments Stew.
In my earlier post (#73) I put up some pictures of the rear main bearing as used in the C1/C4 engine. I also floated the idea that even though the bearing is separately identified (by part number) for either C1 or C4 engine -perhaps they are/were interchangable. I have not yet pulled a bearing out of a crankcase to check, but I did find a sealed box labelled Continental Motors Corp, with intriguing and slightly contradictory labels, the outside indicating a C4 bearing the inside wrapping indicating a C1 bearing. See the photos.
A case of messed up packaging or strong indication about bearing interchanbability??
rrbring1.jpg

rrbring2.jpg

[Bob Phillips]

Check out this video of WW2 engine production in the Wright factory. Of particular interest is the detail shown in the manufacture of engine cylinders.
Amazing!


https://youtu.be/sBfFpcdyd5Q