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

[James P]

Happy new happy Big D. Small baby steps but each and every one brings you closer to seeing a new and complete M8 in time. Breathtaking amount of in depth work you are putting into this project.

[Big D]

Happy New Year to you to James P.

Thanks for that. I have to admit that I wasn't holding my breath about getting all the radio gear going but it looks like I am getting there. I've made more progress in the last couple of days so will post another update soon.

[Big D]

Hi all,

I have had some limited success with the interphone system in the BC-604 transmitter. I had to do some more fault-finding and with the assistance of a radio forum I worked out that one of the vacuum tubes in the set was faulty. I replaced this and the audio stages in the set started to work.

The BC-604 mounted in the FT-237 does allow you to test sidetone, which is a test on the interphone circuit. The BC-604 now works but it has a wee problem which I may or may not be able to resolve in the short term. I am told that in the Interphone mode, the dynamotor in the BC-604 should run continuously (can anyone confirm this?). This makes sense as the dynamotor powers up the audio stages in the set which are required for the interphone audio to operate.

On my set however, I seem to have an intermittent problem which is likely to be caused by the S104 radio/interphone relay. I had the BC-604 in the FT-237 radio tray and for a short time the dynamotor was running continuously in the interphone position (which I’m told is correct). However, then the dynamotor stopped running continuously and now it won’t run in interphone mode unless I key the microphone. I figure that one of the contacts in the radio/interphone relay is the cause of the problem but there seems to be no easy way to get at the contacts to clean them. It is a complicated relay with lots of connections and I don’t really fancy the idea of trying to replace it, even if I could source a replacement!

As it stands, when using the interphone, one has to key the microphone and pause for a second or two before talking to allow the dynamotor to fire up the audio. At this stage, I’ve found the audio is a bit noisy and there is some dynamotor whine in the audio so I intend replacing the capacitors on the dynamotor to see if that helps. I have also ordered some replacement vacuum tubes for the audio stages, just in case one of the existing ones is not quite right. Not an ideal situation, but when it does work, it does work! If I’m not happy with the performance, I do have a NOS BC-605 that I could fit instead of one of the BC-603’s and this will provide interphone capability.

I have tidied up the BC-604 and the two BC-603’s. I didn’t do a complete strip down and paint of all the panels on the sets. There was just too much involved in removing all the control panels and besides, the appearance of these was not too bad as it was, and I may replace the French sets with US ones at some point anyway. The new paint on the exterior panels has freshened up the appearance of the three sets though.

I am still having some issues with the DM-34D dynamotor that I needed to work on to get it to run and I am ready to admit defeat on this one. More often than not it won’t start. The resistance measurements I’ve done on it suggest that there are some open windings on the armature, so I will keep an eye out for a replacement. If anyone has a good spare they want to part with, I’d be interested.

In the meantime, a few other bits and pieces have arrived in the post (thanks to Brent and Jean-Marc).

Next week I hope to have some progress photos on the hull sandblasting.

[Big D]

More photos.

[Big D]

Hi all,

The sandblasters have started on the M8 so I took the opportunity to check for serial numbers before they put any paint on it, to see if I could learn a bit more about the hull.

As I previously mentioned, the ordnance serial numbers ‘7373’ are in each lower corner of the front hull. These were nice and clear. I was hoping to locate the other number on the front armour plate in the centre below the front hatches. The metal on the hull here is quite rough and I could not make out a lot out with any certainty. I thought I could see a ‘6’ but then again it could have been a ‘C’. I took some pictures of this area but even blowing the photos up didn’t reveal anything. Whatever was there was very hard to see and nothing like as clear as the ordnance serial numbers on the lower front corners.

There are a range of other numbers on the hull in various places. There is a series of numbers on the top of the hull at the rear above where the radiator is. There are other numbers in the front armour which I figure are plate drawing numbers. All in all, not a lot more learnt!

I’ll send through some more photos once they’ve got some paint on the hull.

Along with cleaning up a few other parts, I’ve just about reassembled the generator. I had to fit a new electrical stud and make up a new insulating plate and insulating sleeves for the two studs. The repair appears to be okay. I’ve made up some new gaskets, replaced one of the bearings and have some new brushes coming, so hopefully not a bad repair cost overall, excluding all the hours I put in! Everything seems to check out so far but we’ll see what the auto electrician says. He’ll tell me how good (or bad) I am!

I’ve also had some other radio/interphone parts arrive. It seems a shame to open these boxes up.

That's it for today.....

[Big D]

More photos.

[colin jones]

Hi Darryl, fantastic . The rewards will be great after you get the hull back and start bolting things back on. Your radio and generator look like new.
Great job.