[Big D]

Hi all,

With Covid19 here, I haven’t been able to do much to the M8, but prior to the lockdown I got a few things done.

I fitted all the bits and pieces back onto the engine after I had stripped it back for the installation. Ed and I fired up the engine again and it went well. It looks like my tweak with the starter motor brush springs has done the job. I note though that I have got coolant seeping from the water pump elbow and the thermostat housing where it bolts to the head so It looks like I will have to drain the radiator and fix those up. Bugger.

Thanks to Michael for his tips on my generator problems. You will recall I didn’t think the generator was charging. I had previously read about polarising the generator but just assumed that the auto electrician would have done this when he tested it. Anyway, Michael suggested I check on this and sure enough it was the problem. I did a whole lot more reading again about generator polarising and confirmed I needed to establish what type of grounding my generator had before trying to polarise it. I had read that if you have a non-insulated Field terminal on the generator case, then it was likely you had a Type B grounded generator which is one which is internally grounded. The generator on the M8 was certainly one with a non-insulated field terminal but just to be sure I checked the resistance between the field terminal on the generator and the generator case, while I lifted the brushes. The continuity remained the same which confirmed a Type B internally grounded generator. Once I confirmed that, I removed the Field wire from the Regulator and flashed that field wire to the positive terminal on the battery. Once connected back up to the regulator, that did the trick and I then had a generator that was charging the battery.

I fitted the lower engine covers around the battery side of the engine. I have to say, it does make the engine area look really smart. I need to modify the brake line going into the hydrovac though as the way I have folded it, it won’t allow me to fit the lower engine cover on that side.

I made up a rod for activating the carburettor arm from the throttle slave cylinder. I made it straight although I have seen a number of variations; straight and with several bends in it. The straight one works well in my setup though and the hydraulic throttle works well.

You might recall I had a Voltmeter and Ammeter that weren’t working. I figured I would have a crack at seeing what the problem was with the voltmeter. This is a Stewart Warner voltmeter and not sure if you have ever tried fixing one of these but for starters you have to get the bezel off. I used a small screwdriver with a bent tip on it, to pry the edges of the bezel up. It takes some time so you have to be patient.

Once you have the bezel off, you need to remove the assembly from the outer housing. There are two insulators holding the positive and negative terminals and you have to remove these first. Once they are off, you can push the assembly out of the housing. There are two small rivets holding the faceplate on. I couldn’t see a way to easily remove them without damaging the gauge so I filed the ends of the rivets off and just pushed them out.

Once inside you can see the bi-metal strip that is connected to the pointer. When this is connected to a power supply, the bi-metal strip bends and the pointer moves. In testing, I found the circuit on the voltmeter was open. I couldn’t quite work out why as everything appeared to be connected, albeit through glue holding the wires onto the terminal posts. I eventually found that the wire from one end of the bi-metal strip was not connected to the positive post, despite it being glued down to the terminal along with the other wire. I’m not sure how this would have ever worked but it looked like it had been glued in place, but had never ever made contact with the terminal post.

I’m not used to dealing with wires that are the thickness of cotton but I removed that wire from the glue, wrapped it around the other wire and then tried to connect it to the positive terminal. I couldn’t get solder to take to the terminal so in the end, I left a blob of solder on the wire and using a drop of super glue, connected it to the terminal post. I fitted it to the instrument panel and tested it and it worked. I couldn’t reuse the rivets so I put a small droplet of glue on each side of the wee panel. I then cleaned up the bezel, fitted it and folded over the edges of the bezel. Job done. Haha.

Back to the engine, and all you clutch gurus…..

I’m having some clutch issues and would be keen to get some ideas from you all. I was a bit suspicious about the clutch before we put the engine in, but we did appear to get some pressure so I ran with it. After bleeding the clutch though, there is a problem.

The issue seems to be that the fingers on the clutch pressure plate are compressed too much during assembly of the pressure plate and clutch disc. When you activate the clutch using the arm on the side of the housing, there is about 10mm free play in the arm, and then about 25 mm of ‘soft’ throw in the arm. I say soft, as it appears that it is just the release bearing movement on the shaft I can feel, and only finger strength is required to move it. The arm ends up in roughly just past the vertical position at the end of its travel. As a result, the disc is not released. I’ve had the clutch and gearbox in and out now a couple of times and it is still not right.

Here’s what I’ve done/checked:

• The clutch release bearing assembly looks correct. The yoke and arm are as I received them and were already wired. They match the configuration in the manual.

• The clutch release bearing is a recommended replacement model. It is about 90mm in diameter while the inside diameter of the fingers is 70mm. The clutch release bearing has about 25mm of travel on the retainer on the main shaft.

• I’ve put the clutch disc in the right way, with the long end of the hub toward the flywheel. This puts the raised portion of the hub inside the circular opening in the pressure plate. Note that the 1943 TM 9-743 manual suggests fitting the clutch with the short end of the hub to the flywheel. This error was corrected in the 1944 TM 9-743 manual and described in an issue of Army Motors. The disc will go in the other way around but I imagine the springs on the hub would clash with the crankshaft bolts.

• The clutch disc fits neatly and flat on the flywheel face. The end of the hub on the clutch disc is clear of the pilot bearing so it is not bottoming out on that.

• I have examined the pressure plate and the clutch disc alongside a spare pressure plate and clutch disc. They are the same diameters and thicknesses, to within a couple of millimetres. The height of the pressure plate face and fingers within its housing is the same as the spare pressure plate, again to within a couple of millimetres. The pressure plates are as I received them and they have not been professionally set up.

• I wrote a while ago about the differences between the White Scout car and M8 clutches. The Scout car pressure plate is bigger so won’t fit, so the clutch pressure plate on this is correct.

• From what I’ve seen, the M8 hub setup on the clutch disc is different to the White Scout Car, with the short end of the splined shaft on the raised portion of the hub on the M8. The White Scout car hub has the long end of the splined shaft on the raised portion of the hub. I think I have this right, but thinking about it, I don’t think it would matter. Interestingly, I saw a picture of someone restoring a Scout Car clutch and the clutch disc in that was the same as these M8 (?) ones.

• Each time I have fitted the disc and pressure plate I have ensured the disc is central on the flywheel and under the pressure plate. The raised portion of the hub sits neatly in the middle of the pressure plate with about 10mm of clearance around the circumference of the circular opening.

• I’ve been using an old output shaft to align the clutch disc during the tightening of the pressure plate. The output shaft doesn’t go fully into the pilot bearing because of the threaded section on the end, but it is enough to align the disc. The gearbox fits into the bellhousing and engages with the pilot bearing without any problems. It bolts up neatly, so I believe I have everything aligned, otherwise the gearbox wouldn’t slot into place.

• The flywheel is an original one with new ring gear fitted. It appears to be seated on the crankshaft and in the bell housing correctly, but I have nothing else here that I can compare the depth to.

• When the pressure plate and clutch disc assembly is tightened down on the flywheel, the fingers on the pressure plate drop around 20-22mm from their neutral position. This seems excessive to me and I think this is the problem. The fingers end up so low that the release bearing is not making contact with them.

What have I missed? Any ideas would be appreciated.

Thanks.