BenHawkins

I had the transmission brake shoe arrangement on another gearbox so I have removed them to use on this one. It all came apart quite easily so I was able to blast and prime some of the parts. Along with the gearbox covers. And the transmission brake hub. I will need to make a pattern for the drum itself but it is fairly simple and I think it is small enough that I can machine it myself.

When I purchased the chassis it had a single silencer bracket so I tidied it up and had a foundry use it as a pattern. For the lower halves I had to cut the mounting arm off and grind it flush. After drilling the holes I was able to blast and paint them and use them to put the silencer in place. The end plates for the silencer were made from a pattern I borrowed from Steve. I need to source some longer bolts to fit it properly.

After quite a bit of tapping the water jacket tops with a hammer they eventually started to move. I poked around in the water jacket with a welding rod whilst having a vacuum cleaner fitted to the water inlet. I think I have all the lumps of rust out. We then started with paint stripper to get the thick silver paint off. The next stage was to clean them up with a selection of wire brushes to get into every area, acid etch and give a coat of engine enamel. It was nice to find the thick silver paint was not covering up any issues.

I spent quite a bit of time cutting threads on lengths of 1/2" EN8 steel rod. The threads were roughed out on the lathe and then finished with a die nut. All the existing rods were either too short or too corroded. So the brake rods are in place as far as the adjuster, but I still need to finish a few parts off. I don't have the original hand brake and gear selector gate etc. The drawings have not survived and there is not another example of this exact model. I do however have a later set for the same model of gearbox, they will not fit this chassis but the forgings for the levers and handbrake ratchet were common to a number of models. These are the parts I intend to recycle fitted to a piece of MDF so I can check all the dimensions and draw the parts I want to have laser cut to get it all to work correctly and look in keeping.

Once the shoulder screw that the reverse arm pivots on was removed it was possible to knock out the taper pins and then give the box a clean. The top of the gearbox also had a good clean inside and out. There are quite a few deep corrosion holes but obviously none of them pass all the way through (probably because the oil contamination protected it). I don't think the holes will be a major issue for the strength of the box and think that trying to repair them by welding would be difficult and risk making things worse. So I gave all the holes a good clean out using scrapers and a fibreglass pencil. Then I cleaned them all out with solvent and mixed up some epoxy resin and mixed in about an equal quantity of aluminium powder and used this to fill in the craters. I will need to add some proper metal back to repair the two bolt holes in the bottom left of the photo.

1st/2nd was no trouble to remove. The taper pins for reverse are more difficult to remove as there is not enough space to swing a hammer in the normal orientation. I might be able to rotate the shaft if I can remove the arm but I need to free off the shoulder bolt and that is being stubborn as well. I need to replace all three selector rods as they are heavily corroded and bent where they protrude from the box. This photo shows the sorry state of the box. One mounting lug is completely broken off, one is missing one flange and the others are heavily corroded. I was thinking of having steel profiles laser cut to run inside the aluminium so they will not be too obvious. Possibly fitting new pieces of aluminium where they are missing but there is not much to stitch to where the lug is completely missing. I want to retain as much of the gearbox as possible but obviously need something that can be driven at the end of the project.

Not wanting to completely give up I removed the bolts from the worn 2nd gear and used a puller to remove it from the hub. Then decided to try removing the selector rods with the detent plungers in place. There are access plugs in the bottom of the box to allow the taper pins that hold the selector forks on to be removed. But when I tried this 3rd/4th selector fork seemed very bouncy. When I looked I could see the side of the split pin hole. The shaft was broken through at the tape pin hole! Pretty sure I didn't manage to do this driving the pin out! So I had to resort to drilling out the other taper pin.

Quite a bit more progress on the gearbox. I removed the main shafts Then the reverse shaft. [ATTACH=CONFIG]107172[/ATTACH] I then thought it would be a good idea to remove the detent plungers and started by turning the gearbox over and removing the dome nuts covering the plungers. The plungers are kept in line by pins that run in a slot in each plunger so I removed these. As you can see the casting is very corroded in this area. I tried to unscrew the brass housings but gave up in the end.

I then turned my thoughts to the engine again and fettled the tappets until I was happy with the fit. Followed by removing the nuts that retain the water jacket tops. I could not get the water jacket tops off so I will continue to spray them with oil and gently hammer them over the next few days until they come off. They have repairs to previous frost damage so I need to be quite careful with them. So all I was able to do was paint strip, wire brush and paint the tappet covers. [ATTACH=CONFIG]107170[/ATTACH]

On that basis I could cast a new shallow clutch so it did not protrude from the flywheel. It would probably be the easiest solution as I am not sure if I can acquire an original clutch of this size and design.

I ruined all the bolts when taking the back axle off as well. These were actually studs with a short thread one end and the thread peined to hold on the nut. So I made eight new ones in the same way. I had just enough Grover spring washers for the job. Then used them to bolt the back axle on after putting the hole for the split pins in the correct place.

On Monday lunchtime I took a trip to the local steel stockholders to pick up my latest order. I used to order from the hobby suppliers and although they offer a good service they are generally quite expensive and then the postage is expensive as well. I was missing a cotter pin from one of the brake cranks (I must have damaged it taking it out). These are 1/2" diameter with a 3/8BSW thread offset at one end. So with a piece of 1/2" EN8 in the four jaw chuck I adjusted it to run out by 0.120" Then turned the diameter down. And finally cut the thread and put the flat on with a file. You do have to wonder if the Dennis designers borrowed this from their bicycle designs!

I have done a quick drawing of the Aster flywheel and standard Dennis cone clutch. Unfortunately it is not going to be quite as simple as just machining a taper in the rim and fitting a boss in the middle. I think the options are: New flywheel to Dennis pattern. New larger (non standard) cone clutch. Fasten a metal ring to the existing flywheel before boring a taper to get the full depth. The standard Dennis flywheel at this point in time was a disc with the cone bolted to it. The original flywheel could be machined back to a disc but by that point it might be more sensible to get a new disc laser cut from a steel plate and make a pattern for a cast iron rim. Any other ideas?

The engine was originally part of a generating set so has no clutch. Drive pegs fitted into the six rubber lined holes. A good friend of mine has leant me his clutch so I can see if the smaller of the Dennis cone clutches could be made to fit. The bore is slightly too large and a bit too shallow so I will need to draw it all out to confirm if the flywheel could be machined to accommodate the standard clutch or whether a non-standard clutch cone or new flywheel will be required.

Now the tappets are finished I decided to remove the pistons from the connecting rods ready for further work including the new retaining rings. Put the camshaft back in. Then placed the crankcase back in the chassis.

The back axle is free to rotate in the journals mounted under the leaf springs. The axle is prevented from rotating under acceleration by torque arms bolted to the front of the axle. These slot into buffer tubes that contain stiff springs. These springs are new as the originals were broken. The torque arms and buffer tubes are loosely fitted to the chassis as I had run out of steel to make the bolts to fix the springs to the axle.

And finally using the rotary table to finish the profile. And finally all the roller follower assemblies are finished!

More work on the tappet plunger shells. With the flange in the vice I used a dial test indicator to find the middle. Then used the correct size slot drill to make the slot using a number of small cuts. Before turning over and putting the bolt hole in.

Glad to hear it was an uneventful trip and that it fitted in the garage! And a photo of the Dennis towing the Hallford at Woburn Abbey after some carburettor issues.

Ok, I had not been able to find much more detail on the Reinecker Stub Tooth form but it is probably fair to assume that the profile stays the same and the dedendum should not make much difference to the strength.

They can only be ordered in batches of 100, and for a 3/8 version that is around 70GBP. There is a minimum order value of 200GBP. I will probably put in an order but then use them only where they are on show as that is over 25x the price of a standard spring washer. It is a real shame they don't manufacture 1/2" any more as there are a lot of those on show.

So I have been measuring the gears and referencing period literature (including a 1918 copy of machinery's handbook). All the drawings that have survived show standard Pitch Circle Diameters. However the ODs are smaller than one might expect. From Machinery's Handbook: "The stub gear tooth was introduced a few years ago and has been applied successfully, particularly to automobile drives. This gear tooth has a shorter addendum and dedendum than the ordinary standard and the pressure angle is 20 degrees instead of 14.5 as is the ordinary standard" Another challenge to overcome as that means a standard cutter or hob cannot be used (unless both the gears are replaced).

Thanks Robert, I have just had a reply from them. They are no longer manufacturing anything bigger than 3/8 but I will order the smaller sizes.

We repeated the process for the other wheel and removed the blocks from under the axle so it could rest on the wheels. The first torque arm required some fettling to get the holes to line up (this is a mix of parts from different axles). Sarah could then use the torque arm to stabilise the axle whilst I pushed the axle into position under the rear springs. There is still quite a lot to do before the axle is actually fitted but it does seem like a big step forward. If nothing else there is a bit of room to move in the garage again! I need to order some more steel including the 5/8 EN8 for the spring bolts. I have come across an anomaly with the Dennis gear drawing. The one I have shows 37 Reinecker teeth, 6Pitch; however it also states an OD of 6.4284". Obviously we would expect it to be 6.5" ((37+2)/6). The pitch diameter is stated at 6.166 as would be normal (37/6). Obviously I now need to get the gear pair out to measure but does anyone know why this smaller OD would be used?

The bronze bearing was then slid over the axle tube and more oil applied. The pallet truck was then used to slide the wheel on. Then the driving star was fitted. This has a square hole in the middle that fits over a square milled on the end of the half shaft. The eight protrusions then mesh with the slots machined in the wheel. So the driving star/half shaft hold the wheel on as well as transmitting torque.