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#1
18-01-21, 16:51
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Here are the comparisons of a -46 cam on the left and a C1 cam on the right.You can clearly see the difference in the lobes. The closest lobes are for the intake valves and not surprisingly, the -46 has a lot more air/gas valve inlet time!
cams.jpg 
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#2
18-01-21, 22:45
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Bob,
I know that C4 and C1 had different superchargers to each other but I thought that the cams were different too ? David
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#3
19-01-21, 01:57
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Good question about the cams, David. I had a quick run through the manuals and here is what I found. The M18 (G163) book lists 3 cams;
-G104-7006836 (CO201932) being standard for C4 -G104-0100293 (CO200742) (C66800) bolted for the C1 ( this C1 being replaced/superceded by) -G104-1531497 (CO242347) rivetted for C1 so it seems to suggest that there were both C1 and C4 cams...BUT -my interchange book lists cam 201932 as interchangable in both C1 and C4 engines. Then check out the photos below. I just got these today and they show the damaged engine with sheared off bolts (that restarted this thread a couple of weeks ago) going back together with NOS bolts. Look closely and you can see the number on the cam of this C4 engine. It says 202347 which is supposed to be a C1 cam.(This is the cam in my early Sexton book with C1) Finally, I reread the " Ordnance Development of the Wright-Continental R975 Radial Engine", from the Sherman Site. It makes reference to changing the aircraft cam for ground use. " To obtain the highly variable speeds required in tank operations, the engineers changed the intake and exhaust cams to decrease the valve overlap, to obtain higher torque at lower RPM and to improve idling characteristics...". But there is no mention through the rest of the report (including where changes made to upgrade C1 engines to C4s are listed) about a different cam. the report says that 85 percent of the parts between a C1 and C4 are interchangable. So, without a 201932 C4 cam to examine, I would conclude that the cams are interchangable between the C1 and C4. bcam1.jpeg bcam2.jpeg Last edited by Bob Phillips; 19-01-21 at 02:04.
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#4
27-01-21, 19:08
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R975 cylinders and a story
As I am stuck at home during the continuing covid days I thought I would write abit about cylinders (mostly C1) and an interesting historical story I uncovered during my research.
Much earlier in these pages I included descriptions and photos of both C1 and C4 cylinders. I also compared them to the -46 cylinder off the helicopter engine. I have been rooting through my trailers looking to put together a few sets of cylinders and I thought I would give you a look at what I found. First, most cylinders are available in either steel bores (usually new black cylinders ) or chrome cylinders ( reconditioned with chrome bore to bring them back out to standard dimensions).They are usually painted primer red. These cylinders are choke bored meaning they have a taper of about.007 being bigger at the bore opening.They are very similar to the original aircraft type cylinders made by the Wright Corporation in the prewar years, but probably don't have the nitride hardening of earlier Wright cylinders.. Both the black and red cylinders have spark plug coolers and cast bosses beside the rocker boxes. The aviation cylinders (photos 3&4) are easily identified by the large size of the spark plug coolers and by the fact that the cast bosses along side the rocker boxes are drilled and threaded to accommodate baffles. While some 7 cylinder (760) Wright aircraft engines apparently did not use any spark plug coolers, most did. They were a repair item and could be replaced on C1 engines. Note that C4 engines did not use them. NOScylindersa.JPGcylinder6.jpg cylinder3.jpgcylinder4.jpg C4 cylinders were designed to significantly increase cooling. The increased fin area amounted to 50% on the head and 100% more for the barrel. The barrel no longer was machined with fins but instead an aluminum "muff" was slid over the steel barrel and this design was used on many other large radial aircraft engines of the time. At the bottom of the next post are photos of a steel barrel of the C1 style with machined cooling fins, and a much larger radial cylinder from a bomber, with aluminium muff on the cylinder base. Last edited by Bob Phillips; 27-01-21 at 20:31.
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#5
27-01-21, 20:12
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The steel cylinders that I have were manufactured at the Rock Island Arsenal in the early 1950s. They were built as spares for the 50,000 plus engines that had been built in WW2 and were still widely used around the globe.
The chrome cylinders are used cylinders that were reconditioned for the US government (the RIA) probably also in the 1950s. Unlike chrome cylinder repair jobs done today, they have the complete package; so including new valve guides and valve seats. As I checked the remanufacturing details provided on some of the box labels (see below) I discovered an interesting story. Some of the cylinders were reconditioned by the Van der Horst Corporation. These cylinders were reconditioned by honing the used bores out oversize, and then chroming the bores back to standard size. This technology had been developed through a patented process by a Dutch engineer named Dr Hendrik Van der Horst in 1936. He called his patented process "porous chrome". He improved his chrome plating process again in 1943 and set up a plating company in the USA called Van der Horst Corporation of America ( later United Van der Horst). His challenge had been to create a plating process that was not as hard and smooth as traditional chrome plating. The chrome needed to have the ability to retain oil in it's surface. This was accomplished by chroming the bores in the traditional way but then near the end of the process to reverse the polarity of the electrical charge which attracted the chromium solution onto the bore surface and in so doing, create a series of tiny grooves and furrows which would retain the lubricating oil. The finished bore has a frosted appearance but is still very hard. While Dr Van der Horst was setting up shop in the USA, that nation entered the war against Germany. At home his son Kuno was in hiding with the wider group of people that included Anne Frank, having refused to swear an oath of allegiance with the German occupiers. His wife Catharina provide refuge to a number of displaced Jewish citizens but ended up having the family home (Alexanderlaan 22, Hilversum) seized by German forces for the use of their officers. After the war the family moved to the US. There is much more to this fascinating story and you can find it by googling.. "More Than A Footnote, The VanderHorsts, Anne Frank and World War 2 Resistance" . A final word about cylinders. Steel cylinders are easy to work with, the rings are quickly seated and they have minimal oil consumption. They look great and are often the choice of high end collectors and restorers. Chrome cylinders on the other hand, area little more difficult to deal with. It often takes a much longer time to get rings to seat. One old A&P mechanic I know told me he always uses a ball type glaze breaker to encourage ring seating. Chrome cylinders frequently use more oil than steel though some have reported that this is really most apparent during the first few weeks of break in. Most importantly however, may be the much greater resistance that chrome has to rust and corrosion than steel. If you do not run your vehicle on a regular basis or if you have a cold, damp storage facility, steel cylinders may not be your best choice. I have photos of engines I have dismantled that sat for 25 years, and often it would appear at first glance that with a bit of tidying up maybe the chrome could be used again. Not so with the steel cylinders which are usually badly rusted and pitted.  cylinderbottom.jpg cylinder2.jpg cylinder1.jpg Last edited by Bob Phillips; 27-01-21 at 20:27.
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#6
10-02-21, 12:54
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the good old days...
I wish I had bought a few of these...
allison.jpg
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#7
11-02-21, 02:58
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Quote:
__________________
Terry Warner - 74-????? M151A2 - 70-08876 M38A1 - 53-71233 M100CDN trailer Beware! The Green Disease walks among us!
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#8
13-02-21, 15:04
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A very interesting story about chrome rifle bores,thanks for sharing. Its funny but now days most of us associate chromed barrels with chinese rifles like the SKS. I don't know if any of our modern sport rifles manufacturers use chrome bores. My understanding about SKS bores is that they are highly resistant to corrosion.
On a slighly related topic I found a video on the net showing the use of a non electrical conducting "arbor" or " twisted core" with wires twisted along it. It is inserted in a barrel blank and electricity applied and it erodes the bore beside the twisted(spiral) electrodes to create etched rifling in the barrel. AN interesting idea, ever heard of this before?
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