Picture of Main Shop Floor MV's

[Cold_War_Collection]

Hello All,

 

here is a picture of our main shop floor, there are a few vehicles not shown, such as the Bv's 202, and 206, but this is the bulk of the collection. The Saracen is hiding in the restoration side

 

Cheers

 

Nick

 

The Cold War Collection (Canada)

[Lauren Child]

Nice to see a Gama Goat with the hard top cab

[g0ozs]

What is the smaller vehicle between the Gama Goat and the Stalwart ?

 

Iain

[Lauren Child]

I think it's a Supacat ATMP with hard cab again.

[Cold_War_Collection]

Nice to see a Gama Goat with the hard top cab

 

Thanks,

 

we felt that it was a seldom seen version. We do have the full kit for the rear, with the heaters and insulated top. That's a project that should wrap up over the next couple of months, we'll post interior pics once completed. The only mod on the vehicle at this point is a turbo system with a stainless exhaust, which tends to boost the power on the 2 stroke Diesel quite nicely. Its a "hidden' change, so most folks don't know it's there.

[Lauren Child]

That will be a really nice (and very unusual) beasty with the insulated back as well - I'll look forward to seeing some pics

 

Does the hard top help with the noise from the engine?

[Cold_War_Collection]

That will be a really nice (and very unusual) beasty with the insulated back as well - I'll look forward to seeing some pics

 

Does the hard top help with the noise from the engine?

 

It is insulated, so a little bit better, but the noise does tend to resonate through the cab section. (still pretty loud, but not as bad as the canvas top) What we do while driving, is to use Helicopter headsets (Sigtronics, model S-20) with a live voice activated mike. We also can run a cable out to our ground guide while backing the Goat, or other vehicles. I used to fly Tactical Helo, years ago, so I'm used to my Flight Engineers outside the CH-47 being able to communicate with me, and find that the system translates to what we do quite nicely

[Cold_War_Collection]

It is insulated, so a little bit better, but the noise does tend to resonate through the cab section. (still pretty loud, but not as bad as the canvas top) What we do while driving, is to use Helicopter headsets (Sigtronics, model S-20) with a live voice activated mike. We also can run a cable out to our ground guide while backing the Goat, or other vehicles. I used to fly Tactical Helo, years ago, so I'm used to my Flight Engineers outside the CH-47 being able to communicate with me, and find that the system translates to what we do quite nicely

 

Here are a couple of pictures, One, the cab inside, and the second, the trubo unit with the S/S header pipe

[Lauren Child]

Cool - the top looks more robust than I'd imagined. You have a very nice vehicle - thanks for sharing!

[David Herbert]

What engine is that? I thought that they had a small two stroke detroit with a supercharger on the side (3-53?). Those sound great untill your brain gets mushed by the noise.

 

David

[FoolsHumor]

What engine is that? I thought that they had a small two stroke detroit with a supercharger on the side (3-53?).

David

 

I believe the Goats did have an aluminum block 3-53 Detroit, but I do not believe it was supercharged. All 2 stroke Detroits had Rootes type mechanical blowers , but they were not used to raise intake pressures. They were only used to purge remaining exhaust gases. Some larger Detroits did have turbo-superchargers along with the blowers. They all howl like a banshee. Regards, Bob

[David Herbert]

Bob,

 

I think that we may have a small misunderstanding due to our alledged common language. In the UK the term 'supercharger' is usually used to mean a mechanicaly driven device that blows air into an engine, the Rootes blower being one of the most well known, and I thought used on all 2 stroke Detroits. The term 'turbo' (short for turbo-supercharger) refers to a centrifugal blower driven at high speed by an exhaust powered turbine. As you say some larger Detroits have these as well as the Rootes blower and got a 'T' designation after the normal no. of cylinders and displacement per cyl.

 

It seems unlikely that you can blow air into a cylinder at all, still less use it to expell exhaust gasses, without it increasing the intake pressure. A Detroit with a worn out blower is very feeble because without the blower there is not enough pressure to get enough air into the cylinder for the fairly short time that the ports are uncovered, and against exhaust pressure which is still there because it is a 2 stroke engine and there is half the amount of time for this all to happen than there would be on a four stroke. The more air you can get in the more diesel you can put in and the more power comes out.

 

My point was that the engine in that Goat had a turbo and did not look to me like a Detroit 3-53 so I wondered what it was and why anyone would change it. Gama Goats had many failings but the engine is usualy regarded as pretty good.

 

David

[FoolsHumor]

David,

 

I will drag this on a bit, not because I believe I am correct, but because my questioning something is the best way I know to prod some other poor soul into unsuspectingly educating me.

 

I understand that the term blower and supercharger are used somewhat interchangeable. As an example, I have heard the phrase Blower Bentley used to refer the early supercharged cars. But in the case of the Detroit’s I am thinly familiar with, 6V-71’s and 8v-71’s, the manuals only refer to them as blowers. I believe the blower cannot raise the cylinder pressure above ambient because the intake ports close before the exhaust valves do. Only then does the pressure rise due to piston compression. Below is an excerpt from a GMC manual on Detroit two-strokes.

 

“The swirling flow of air toward the exhaust valves produces a scavenging effect, leaving the cylinders full of clean air when the piston rises and covers the inlet ports. As the piston continues on upward stroke, exhaust valves close and the charge of fresh air is subjected to the final compression.”

 

I suppose there could be some mild rise in pressure due to resistance in the exhaust system or by trying to push air past the small exhaust valves, but even then the manual claims only 5.5 inches of mercury pressure in the air boxes. The equivalent of 3 PSI. I can only assume the cam and valve timing is much different for the turbo engines.

I agree with you about the feeble blower causing poor power. In the absence of a positive exhaust stroke as in a 4-stroke engine, a healthy blower is the only way to purge the oxygen poor residual exhaust gasses and replace them with fresh air.

 

Nick, So my post is not completely without Gamma Goat content, did the turbo simply replace the mechanical blower, or is it still present as well? Were there any other internal changes made to the engine to accommodate the turbo?

 

I have no doubt that my opinions are flawed and would be happy if someone would take the time to explain why to me.

 

Regards,

 

Bob

[andym]

The correct term here is "scavenge blower". They're used in other two-stroke diesels such as the Rolls-Royce K60 in the FV430 series of vehicles. As has been said, their purpose is to purge exhaust gases, not raise inlet pressure.

 

Andy

[Richard Farrant]

The correct term here is "scavenge blower". They're used in other two-stroke diesels such as the Rolls-Royce K60 in the FV430 series of vehicles. As has been said, their purpose is to purge exhaust gases, not raise inlet pressure.

 

Andy

 

I will have to go back 45 years to my initial training ...... the four stroke cycle, Suck, Squeeze, Bang, Blow. The cylinder fires every second revolution, so has and induction stroke, piston going down, inlet valve closes, piston rises, injection of fuel at top of stroke, piston goes down with the firing pressure and so on.

 

Now to use a two stroke motorcycle engine for an example, that uses the lower crankcase area as a primary compression area to compress the intake before transferring it to the upper cylinder for further compression and firing. With a large diesel such as a Foden or GM Detroit, this is impractical so the supercharger or blower is there solely to compress the intake air, when this is blown in through the lower cylinder ports it does push the waste gases out, but without this blower the engine will never run. Another misconception is people think they run faster, but as the two stroke fires twice as often, this is where they are mislead. To increase power, it can have a turbo charger fitted to the exhaust manifold.

 

Hope that is clear?

 

regards Richard

[Richard Farrant]

So my post is not completely without Gamma Goat content, did the turbo simply replace the mechanical blower, or is it still present as well? Were there any other internal changes made to the engine to accommodate the turbo?

 

 

 

Hi Bob,

You cannot remove a mechanical blower and replace with an exhaust gas driven turbocharger, the engine would never start. It needs positive pressure to compress the intake of air in to the bottom of the cylinder in order to fire.

 

This talk of exhaust scavenging....... it is only really a by product of the compressed intake air entering the lower cylinder and pushing any dirty air out before the exhaust valve closes.

[andym]

Now to use a two stroke motorcycle engine for an example, that uses the lower crankcase area as a primary compression area to compress the intake before transferring it to the upper cylinder for further compression and firing. With a large diesel such as a Foden or GM Detroit, this is impractical so the supercharger or blower is there solely to compress the intake air, when this is blown in through the lower cylinder ports it does push the waste gases out, but without this blower the engine will never run. Another misconception is people think they run faster, but as the two stroke fires twice as often, this is where they are mislead. To increase power, it can have a turbo charger fitted to the exhaust manifold.

 

Hope that is clear?

 

regards Richard

 

I think we're saying the same thing! The difference is that the scavenge blower isn't there to increase the intake charge in the manner of a "conventional" supercharger or turbocharger.

 

Andy

[FoolsHumor]

Could someone please help me understand the turbo versions. My manuals give grand details on repair and rebuild of parts, but little of nothing on theory or operation. All I can make out is the turbo feeds the blower and the air box specs show a 2100 rpm pressure of 5.5 inches of mercury for the non turbo and around 30 inches for the turbo model.

 

As I understand the inlet ports close prior to the exhaust valves closing so that would not allow a pressure rise. On the turbo models do they close the exhaust valves earlier in relation to the inlet ports to allow pressure to build, or is it somehow done on the normal restrictions through the exhaust system?

 

Thank you for whatever help you can offer.

 

Bob

[FoolsHumor]

While we are discussing the curiosities of Detroits I thought these 2 photos might be interesting to someone. They show the exhaust valve train on one head of a 8V-71. Each cylinder has 4 exhaust valves and this one has the infamous Jake Brakes installed. The close up shows a center pushrod and rocker assembly with its own return spring, 4 valves with springs and rockers and the Jake solenoid assemblies. Lots of activity going on under these valve covers.

 

Bob

 

[David Herbert]

I have been away for a couple of days and had not realised that my initial curiosity about the engine in the Gama Goat would develop into quite such a diversion of the thread. Sorry.

 

However.... Andy & Bob seem sure that the blower/supercharger as used on non turbo Detroits, and Chieftain and 430 series engines does not raise the inlet air pressure above atmospheric. If this were true there would be no point in the blower as it would not move any more air than a plain hole in the side of the engine. If you take a deep breath and blow the air out between nearly closed lips you can feel the pressure on the inside of your cheeks despite the fact that you are blowing through a hole with atmospheric pressure outside it.

 

Bob quotes a pressure of 5.5 inches of mercury at 2100rpm. That is ABOVE atmospheric pressure, ie the blower does increase the intake pressure, so that there is fresh air in the cylinder for the fuel to burn in and not exhaust gas. The more that the inlet air is pressurised the more will go in and the more power the engine can be persuaded to make but if you use too big a blower/supercharger it uses a disproportionate amount of power to mechanicaly drive it so to get even more power Detroit added turbochargers which use the otherwise wasted energy in the exhaust to further increase the inlet pressure to the 30 inches of mercury that Bob quotes.

 

Don't forget that a non turbo/supercharged engine runs with a significant vacume (negative pressure) in its inlet manifold. The reasion that the air still moves into the cylinder is only that there is a bigger vacume in the cylinder as the piston moves down. With a 2 stroke engine it is much harder to persuade the exhaust gas to leave first so Detroit and others chose to forceably blow the exhaust out by pressurising the inlet air. This does increase the power as without it the engine will not run. To make a distinction between increasing the pressure enough to make the engine run at all / better / with more power / with even more power seems to me to be pointless, the pressure is still increased above what it would be with no blower.

 

I hope that I haven't upset anyone with this bit of pedantry but I thought it worth writing. I am not going to go on any more about it, or people will get grumpy with me!

 

David