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MarkHolloway · Posted: Sun Apr 09, 2006 11:36 am Post subject: M47 Question

The first tank I ever got on was an M47. Happened at the Motor Pool at the then Selfridge AFB near Detroit where my dad was the NCOIC. Was probably around 1957 or 1958. I assume it was there for some sort of USAF compatability testing. Anyway, I have, what I think, is a pretty vivid memory of the occasion even though I was probably 4 years old. I remember getting in the turret and my dad going to the driver's compartment and starting the engine. After he shut it down he said,"I only started one of the engines". Was there ever a twin-engined M47? Even a prototype? Or do I remember this wrong? Neutral

Maple_Leaf_Eh · ***Power User*** Offline Joined: Jan 24, 2006 Posts: 517

'weed:

I'm wondering if he ran the auxilliary generator instead of the main engine. Tanks have big engines with a lot of mass to spin and get started. The story about the M3 Grant was the motor had to be turned for x seconds to spread the lube oil throughout before firing the cylinders. That kind of draw on the electrical system would need either a whole lot of heavy big wet cell batteries or some sort of chorehorse to generate the current.

Any M48 dogs on the list to help out?

Doug_Kibbey · Posted: Sun Apr 09, 2006 6:49 pm Post subject: Re: M47 Question

I did my AIT on 48's...we'd just git it and go...no fancy procedures. Used to idle in for maybe 20 seconds before going anywhere, other than that, nuthin' special.

M47's only had one main engine (this is what Jay Leno has in his "Blastolene Special" car...though seriously modified). I don't recall an aux engine on any of the Patton series of tanks.

oldtop · ***Power User*** Offline Joined: Mar 17, 2006 Posts: 70

The reason you turned the M3 med tank engine over was because it was powered by a "radial engine" you kicked the engine over with the mag switch on off to pump out the built up oil in the lower cylinders and pervent "hydrostatic lock", if you fired-up the engine with the oil in the cylinders you will break the crankshaft and/or rip the cyliners/"jugs" from the crankcase and get what mechs called a "dancing jug"..remember you can't compress a liquid.
..Ever seen picture of aircraft crews turning over their aircraft's engines over by pulling through the props by hand before starting them...same reason. You did the same test on the old 1790 "gaser V-12s.."hydrostatic test"
1. master switch on.
2. mag switch to "off".
3. squeeze start switch lever to on, kick over for 5-6 sec.
4. mag switch to "both"
5. squeeze both start and "boost" levers together
6. pump "wobble pump" like crazy and hope for a cough and roar, if it was a 1790AVSI you pumped even harder.

oldtop · ***Power User*** Offline Joined: Mar 17, 2006 Posts: 70

The M47 had a 2 cyliner (A41) auxiliary generator (located on the right side of the engine compartment ) as did the M48s up till they were dieselized M48A3, that where the space for the over sized fuel tanks came from in the M48A3s engine compartments. The aux gen was called the "little joe", its cooling airstrem from the engine housing was equipped with a baffle that you engage to devert the heated air to the main engine compartment to heat up the engine before starting. the a41 generator could be started from the drivers compartment or you can "pull start" that bitch by hand. Oh ya the M103 and A1 also had the same thing.

Maple_Leaf_Eh · ***Power User*** Offline Joined: Jan 24, 2006 Posts: 517

- oldtop

The reason you turned the M3 med tank engine over was because it was powered by a "radial engine" .... Ever seen picture of aircraft crews turning over their aircraft's engines over by pulling through the props by hand before starting them...

That is what I was getting around to saying, without getting off topic on the particular post.

As for auxilliary engines, does anyone recognize the nickname, 'chorehorse' in connection to AFVs, or am I thinking about little generators?

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