How To: Restoration of Ford M8 armoured car US Ordnance number 7373

[Big D]

Hi Petr,

Thanks for that.

[Big D]

Hi all,

Here is the last bit of work I’ll be doing before I skip over to France for a couple of weeks. I’ll be hitting the military fairs in Normandy so fingers crossed I pick up some of those hard to find parts.

The front axle is now complete, minus the nuts for the brake lines, which are coming. Brakes shoes, slaves cylinders, lines etc are all fitted. As I said last time, those rubber axle boots were dogs to put on. I thought the inner part of the boot was hard to put on, but the outer part was even worse. The boots I used were NOS halftrack ones and they were very stiff. I had to remove one that I had already half fitted and clamp it in a vice with some bits of wood and heat it up with a heat gun to stretch it. That got it on. I left the other side on and heated that up with a heat gun as well. I was then able to stretch the rubber enough on that to get the outer part of the boot on the steering knuckle. I’m told (thanks to Willy) that the best boots to use are the ones for the REO trucks. I don’t think it will be an easy job to ever replace these in situ, but if I ever have to I’ll be using the REO ones.

You’ll see that one of the slave cylinders is marked with a nylon tie The guy who put the stainless steel sleeves in the cylinders said that this cylinder has a split in the body. It shouldn’t affect the operation with it being sleeved, but I will keep an eye on that. The axle is sitting on a dolly now and I’ll slide it under the hull and fit it all when I get back.

I hooked up a 12 volt battery to the wiring to test the driver and co-driver interphones. The BC-604 transmitter and BC-603 receiver both started up as expected, but I noticed that the dynamotor on the transmitter was running all the time. I tried the driver and co-driver interphones with T-30 microphones, SW-141 chest rigs and HS-30 headphones fitted and neither worked. Bugger...I then plugged a T-17 microphone into the transmitter and that gave me audio at the two interphone stations. Okay, some progress, I thought….

I went back to the wiring diagrams I had. As you can see there are three slightly different versions of the wiring for the BC-606’s on these diagrams. I was just about to try rewiring them to one of the other versions when I noted the jumper on pins 6 and 10 on the connector on the FT-237. Two of the diagrams had the jumper on the FT-237, with corresponding differences at the BC-606’s. The diagram I had used though was the one out of TM 11-2702 and this did not have the jumper. I removed the jumper off the FT-237 terminal and straight away, I could transmit from the T-30 microphone on the co-driver side and hear it on the driver side. I noticed to that the dynamotor on the BC-604 was only running when the microphone was keyed which is correct. I tried transmitting from the driver’s side next but couldn’t hear audio at the co-driver’s side, so I obviously still have something amiss there. Whether it is a fault with the headphones I tried, or something internal in the BC-606, I’m not sure. I was out of time then so when I get back to the workshop I’ll work on that some more.

The T-30 microphone, by the way, seems to work really good. Much better than the T-17 microphone I thought.

Anyway, progress, but more work to do.

[Big D]

The rest of the photos.

[David Dunlop]

Hi Darryl.

Your nice work continues!

The issue with your wireless gear does not surprise me. A chum of mine (retired commercial radio engineer) currently volunteers at the local RCAF Museum, restoring their wireless equipment. This past Winter he was having a heck of a time getting a late war American piece of kit to behave properly, inspite of several triple checks of the service manuals and circuit diagrams he had available. One circuit in particular was giving him grief and seemed odd to him, even though it was in agreement with his available information.

He was lamenting to me about it one afternoon over a coffee, wishing he had an earlier version of the manual to refer to. When he mentioned the manual reference he was looking for, it rang a bell and it turned up in one of my odds and sods drawers. When I dropped it off for him a couple of days later, it confirmed his suspicions. The later version he was working with had an error in the drafting of the circuit diagram that had been missed. He restored the circuit to the original diagram and the set popped back to life perfectly.

Makes one wonder just how many such errors are out there waiting to make our lives challenging!

David

[Big D]

Hi David,

Thanks for that. Yes, the radio stuff has been an education, but fun. Not so complicated that one feels they have the confidence to have a go, but damn satisfying when the thing works like it should!

[Big D]

Hi all,

I’m back on the M8 again after returning from France, albeit briefly, as I have an operation on my hand today so will be out of action for a few weeks.

I picked up a few things I needed while in France: NOS throttle master cylinder, return springs for the clutch and brake, NOS turret support bearing and an A62 dummy antenna. I saw a few M8 parts at the various swap meets there, but not a heck of a lot.

I had another tinker with the interphone system for the driver and co-driver. It turns out that the microphone I was using on the co-driver side was not working. I tested it again with a NOS T-30 microphone and it works fine, so that is good news.

I noticed that the NOS T-30 microphones straight out of the box were really sensitive and clear. They were much better than the T-17 microphones I had tried. I have a few older T-30 microphones that don’t appear to work though. Has anyone tried to repair these? I gather they work on vibrations from the throat. I prised one apart but it doesn’t look like there is a lot that is serviceable, short of replacing the microphone element.

I have the front axle under the hull now and springs fitted. When my hand comes right I will bolt the axle to the front springs. I had quite a battle lining up the mounting holes on the front spring mount on the co-driver side. It is a chunky piece of steel but must have a very small twist on it, and I had to open up a couple of the mounting holes by a mm.

[Big D]

More photos.