g741.org

Hi Guys,

So I'm putting together a VRC-10 set for my M. Does anyone know how much electrical power this set needs to operate? I've seen the 100 amp setups for the M37 with the rectifier mounted in front of the radiator and the bigger generator, but when do you need that much power? Looking at the wiring diagrams for the radio power connection it appears the radio pulls power right from the batteries, not from the regulator. So can I operate a VCR-10 setup with the stock 25 amp electrical system or do I need to upgrade? Would I need to keep the engine running while using the radio to keep the batteries from running down?

thanks,
bob

The radios run at around 5 to 7 amps, if I'm remembering correctly. They do have a start up "surge" of about 12 to 15 amps, once again if my memory is correct.

The reason some radio trucks went to 100 amp alternator systems is because they had radio shelters added to them (S-89 & S-144) which had telex systems in them that needed a lot more power. Also, if you are running more than one radio system ( for example, GRC-3, -5 & -7) you would be facing a start up surge of 36 to 45 amps plus whatever the truck might be using - headlights, engine, slaving another vehicle, spotlight, etc. It can add up quickly.

Adding the 100 amp system is a pretty big project. You'll need to cut holes in your left front radiator support panel and your engine fan shroud. You'll need to change your crankshaft and water pump pulleys. You will need a set of 3 or 4 matched drive belts. Then you install a big alternator, a rectifier assembly goes in front of your radiator, and you need a new regulator. Your batteries also need to be replaced with 100 amp batteries. Of course you need new cables from the rectifier, alternator and regulator.

After all that (and getting it working properly), if you start to seriously put the new system under load, you will really slow down your engine and your gas mileage and road speed gets way, way worse (bet you didn't think that was possible - ). Well, the ARMY wasn't really that concerned about fuel consumption and speed on a day-to-day, mission level (company and below); that was something the majors and above had to worry about.

So, I guess the long and short of it is, that with one radio system, you probably don't have to worry too much about power consumption. You'll need to read the manuals about usage and procedure to insure that you don't run your batteries down or spike the radio by starting or stopping your engine with the radios on, but other than that, you should be fine with a 25 amp system.

I'm running a lot more accessories in my truck with radios and I'm still sticking with the 25 amp system. I just don't try to run everything at once.

I have the complete 100 amp set up (in a nice wooden case I've built for it), which I'm postponing installing because it is such a big job and not really needed (yet). I'll probably get to the installation in a couple more years. A nice big winter project about 2016 or 2017, when I have EVERYTHING else done.

It's something I'm avoiding.

The stock 25 amp system will work fine with a single VRC-10.

The 100 amp system was for the big radio systems & radio shelters, and also for multiple radios all of which required more power to operate, especially when everything was powered up at the same time.

Here are a couple examples:

UZIS9MM,

Do you have any more M-37 Radio Truck photos you could post? Or any more pictures of the S-89 / S-144 Radio Shelters?

Thanks!

As a matter of fact I do.

And even more. Please don't consider this a hi-jack.





M37's in Vietnam.

Thank You!!

It is ALWAYS nice to have MORE PHOTOS. It is always amazing how many little bits of information you can pick up off of photos.

So as not to hijack this thread, just PM me and I'll send you my direct email if you have any more.

Also, do you happen to know of a S-89 (or worst case, S-144) that is for sale? I'd really like to buy / restore one to put all my radios in.

Thanks,

52 M-42

Great bunch of Comm Box photos, keep them coming.

Bert

Yeah, not a hi-jack....just great info. Like 52, I'm always looking for period pics for the details.

Awesome.

thanks,
bob