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#1
26-09-18, 01:09
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Last edited by Matthew Noonan; 26-09-18 at 01:32. 
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#2
26-09-18, 01:39
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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
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#3
26-09-18, 01:39
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975-46
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.
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#4
26-09-18, 02:01
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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
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#5
26-09-18, 02:18
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975-46
Here is a picture of the gear (#9) from the -46 book, hope you can see it.
rearcrank.jpg
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#6
26-09-18, 03:03
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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.
Last edited by Jesse Browning; 26-09-18 at 03:08.
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#7
26-09-18, 04:00
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975-46
So Rob, what do you know about the history of your radial? Was it installed as a govt rebuild or rebuilt by the previous owner? It is safe to assume that if someone stripped off the mags and wiring it had electrical issues ? If it has not suffered a catastrophic failure ( blown cylinder, broken piston, thrown rod, master rod fail etc) it may be a straight forward fix. Look forward to hearing more! Thanks for the comments and great pics Jesse!
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#8
26-09-18, 16:16
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Quote:
I have been warned before about these radials to read the manual twice, and if I think I got it, read it a third time. I am pretty sure it is one of those projects that, when the time comes, I will have to immerse myself in it. In the meantime, there are still many other vehicles, some operable and some not, that change the priorities of work. I have also warned my boss that whatever this engine does need, it will not be cheap. The grizzly sitting next to it is in the same boat....too many years passed form the time it was operating. I heard a story form someone who was apparently visiting the museum almost 30 years ago that the museum was giving rides in it and the front end packed it in. Again, I can't be certain as I have been too busy to start diagnosing it. Summers are extremely full here between public displays and parades, sandblasting and painting, etc. I am hoping that when my day comes to leave the museum, I am not leaving a bunch of torn apart stuff for the next guy.
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#9
02-10-18, 00:26
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Jessie, A tip of the hat for that rebuild. You have shown it can be done. Worked on radials at an aircraft engine shop. Here's a similar P&W R-985 on a test run. For anyone doing a rebuild for their MV..Get yourself a good quality torque wrench and follow the torque setting to the pound. The engine is held together with steel studs threaded into aluminum alloy..Really easy to over-torque and weaken the holding strength. Under-torquing allows bits and pieces to "squirm" into the soft alloy. Aircraft style engines are notorious for shock load damage...If a propellor strikes the ground...the whole engine has to be taken apart and inspected. That's why Dumping the Clutch in a radial powered AFV is a no-no. The engine is not capable of absorbing that sudden impact....
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#10
02-10-18, 00:56
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975-46
So in side that soft, squirmy aluminium case ( as Dennis put it ) there is a big heavy lump of steel rotating. The crankshafts for C1, C4 and -46 are similar the most obvious difference being their length. From the front counterweight a C1 and C4 crank sticks out about 11.5 inches. The -46 aircraft crank sticks out about 16 inches. I do not have an earlier Weight aircraft crankshaft to measure but I think it would about the same length as the -46. There is another important difference. Pleaser look at the (hopefully) attached photos. Two pictures compare a C1 crank to a -46 crank, while the third picture is a C4 crankshaft. There are two bearings on the shaft inside the nose case of these radials.
Note that the shorter C1 crankshaft (like Wright aircraft engines) have both bearings retained by a nut on threads cut into the shaft. If you look closely at the top view you can see the thin nut next to the bearing on the C1 crank. Note that the -46 crankshaft does not have this threaded portion to retain the inner bearing. You can see on the photo of the C4 crankshaft that the inner bearing is held in place by a sleeve which is pushed in place by the outer bearing and held by the outer bearing nut. Now could some of the metal wizards in this forum rework a -46 crankshaft into an ultra rare C4 crankshaft, your comments always appreciated! C1&-46 cs.jpg C1&-46cstop.jpg C4crankshaft.jpg
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#11
29-02-20, 23:04
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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 
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#12
10-03-20, 02:11
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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
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#13
31-03-20, 04:34
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Wright engine manufacture
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 Last edited by Hanno Spoelstra; 31-03-20 at 10:34. Reason: Fixed link
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#14
31-03-20, 10:39
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1942 curtiss wright aircraft engine promotional film "wright builds for supremacy" 85
"A Cyclone 14-cylinder enigne contains over 8,000 separate parts, and more than 50,000 inspection operations are performed on the parts and the assembled engine before it leaves the plant."
Fascinating! The pinnacle of mechanical engineering and manufacturing.
__________________
Regards, Hanno --------------------------
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#15
13-04-20, 23:21
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R975 sparkplugs
Well while everyone is at home with lots of time to read and ponder, let me introduce the topic of sparkplugs in radial engines. Because most radials were designed as aircraft engines it is not surprising that in the early days tanks radials used aircraft sparkplugs. Aircraft plugs were shielded, had 18mm diameter
short reach (.5 inch) threads and had multiple electrodes ( usually 4). The premium manufacturer of aviation sparkplugs in the USA was the BG Corporation of New York. These were not run of the mill disposable spark plugs. They were manufactured in two pieces and a well equipped shop had proper fixtures to adjust both the electrodes and the core. There are a number of BG plugs that were used in the 975 engine( and the 5 & 7 cylinder aircraft versions), 4B2S, 314-GS and 417-S. While the BG manual does not say they were suitable for the W670 Continental, it seems that in practical terms they were. (the finned 314-GS was intended for aircraft, not to build the economy version of a C4 !!) By wars end the Champion 63-S plug was standard in the 975. It was a single electrode conventional plug but retained the shielded connection. See the photos below. The 975-46 also used an aircraft type plug (AC) and it also used multiple electrodes. Perhaps this style was retained because they were used in helicopters. Note the longer threads on the -46 plug have been cut back to .5 inches so the threads don't foul with carbon (check out the Champion HO-14S beside it). So anyone tell me why the change? Are multiple electrodes more prone to fouling and failure? Could it be about the cost of the part? All comments appreciated. There must have been vast quantities of the BG plugs made as they are much easier to find today than the Champion 63S. sparkplugs1.jpg sparkplugs2.jpg sparkplugs5.jpg sparkplugs6.jpg Last edited by Bob Phillips; 13-04-20 at 23:31.
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Hybrid Mode
