Sunday, March 13, 2011

Historic Commercial Vehicle Club of Australia

I am a member of the discussion forum of the Historic Commercial Vehicle Club of Australia, and have set up a post pertaining to the restoration of the Dennis F1. The HCVC forum supplements this blog with comment and advice, and tips and tricks from other members. Have a peep at the discussion thread of the 1949 Dennis F1 Fire Truck Restoration on the HCVC discussion forum.

Monday, March 7, 2011

Flushing out the block

I removed the water jacket side cover this evening, and Murphy's Law said that I would snap off a bolt or two. In fact out of fourteen bolts, seven sheared off. So looks like I will have to drill the broken end out, and re-tap the holes for new bolts They were originally Whitworth, but may be able to change to BS with the tap. The cover plate looked great from the outside, but after cleaning it with a wire brush it was found that there was quite severe pitting on the inside, with two holes. So it looks like I need to make another cover plate. Apparently the earlier engines had a brass plate, whereas this one is pressed steel. Brian (Museum of Fire) suggested that a temperature gauge sender unit be fitted into this plate. Great idea, and I'll do exactly that.


Looking inside the water jacket ... my gawd, what a build-up of scale and crud! The drain tap was blocked solid, so I removed that and cleaned it out. I also had to sharpen up a welding electrode to act as a long bit to get up inside and clean out the drain. A lot of probing and scraping with bent lengths of fencing wire, and I managed to vaccuum up most of the scale from inside. Then set up a 25 litre bucket under the drain tap, dragged in the garden hose, and flushed through with three bucketfuls of water before I got rid of the sediment and the discolouration.

It's for sure I'll be using Penrite Coolant Conditioner in this truck from Day One!

Saturday, March 5, 2011

More on the water pump

Brian from the NSWFB Fire Museum confirmed what I suspected ... the plug on the front of the water pump housing was in fact threaded into the engine block through the casing. He also said that there was a second plug, directly behind this one on the rear of the block. Sure is! I'll have to drop that one out as well to allow for a good clean.

The front plug finally came out, helped along by a pipe over the ring spanner for added length. I was happy with the state of cleanliness once the water pump was removed ... there appears to be very little rust scale in the block or the pump.


The impellor had very little wear on the vanes, but it was a bit noisy (and grabbing slightly) on turning the shaft.


Unfortunately two things turned pear-shaped when removing the impellor. Firstly, one leg of the dog driving the impellor shaft broke. As there are three dogs, I will be able to have this welded, but it is grey cast iron so it will need to be done professionally.


The second thing that happened was that the phosphor-bronze bush at the front end of the impellor shaft moved back down the hub during the shaft removal, and I can't get it back to the front without risk of damage to either the bush, or to the carbon ring water seal behind the impellor. Probably the best way of overcoming this is to have another bush made up and inserted at the front end, leaving the displaced one where it is.

I still want to strip down the fan hub further, to check the two ball races and clean out the oil feed galleries, but I still have to figure out how to get in. It looks like this is a removable plate on front, but I've yet to find the key to get in!

Wednesday, March 2, 2011

The Dennis F1 water pump

Before I start the engine for the first time, I want to make sure that all of the engine systems are working effectively, so from the oil filter I moved on to the water pump. I have lubricated with oil the pump shaft through the oiler on top. Before it would take oil, I had to remove the grease that somebody had pumped into it, even though the tag underneath said "USE OIL NOT GREASE". It now spins quite freely.

I want to remove the water pump to check the impellor and bushes, and have undone all of the nuts and washers, until I got to what looks like a 7/8"W plug on the right side of the water pump casing. The following picture shows my spanner on the plug:


This plug appears to be stopping the removal of the water pump casing from off the front of the block. Does this plug (if that is what it is) thread directly into the block, holding the casing against the block? If so, does this provide access to a water gallery around the valves/valve seats? If this threads directly into the block, this will be stopping me removing the casing without first removing the plug.

I tried to undo the plug, but it is TIGHT!!! The only way it will budge is if I place a hydraulic jack between the ring spanner and the chassis and jack it undone. I cannot think of any other way to remove it. Can anybody please confirm that (a) it is a threaded plug, and (b) that it threads directly into the block and not the cast casing? I don't want to damage anything in undoing it, so gently gently is the key I think!

Looking forward to any comment anyone may be able to provide. From what I gather, this engine may be similar to the Dennis Ace or Dennis Light Four engines.

Friday, February 25, 2011

The Amal fuel pump

I cleaned up the Amal fuel pump tonight. It had a clean screen inside, but there was a lot of sediment in the pump bowl. The truck had a Ryco in-line fuel filter between the fuel pump and the carby, but I guess the dirt in the pump is a good reason to stick an in-line filter between the tank and the pump.

Thursday, February 24, 2011

Dennis's oil filtration

The original filter was a compressed-felt type, and the one I removed from the engine may well have been there since new, although washed while servicing. Time for a new filter methinks! After much measuring, and some tricky stuff with a spring, I have finally got the oil filtration sorted out. Here's how I did it.

The felt filter was 155mm long, so I initially hunted for a filter of around this length. Brian from the NSW Fire Museum recommended the Ryco R205P, which the museum fits to their Dennis Ace fire trucks. At 153mm it was close, but even at this length there was a possibility of the unfiltered oil bypassing the ends of the filter. I really needed one about 10mm longer, but it appeared that to suit the diameter of 75mm or so, the longest filter available was 153mm.

Time for some lateral thinking ... what if instead of going longer, I went shorter? Bingo! Two Ryco R2053P filters at 73mm outside diameter and 83mm long end-to-end gave me 166mm, and at 33mm ID they were perfect!


Next task was to source a compression spring to tension down on the top filter. The spring removed with the felt filter I was convinced was not correct, as the internal diameter seemed too small. Internet shopping came to the party with a 60mm long 33mm I.D. spring, but when received it seemed to be about 10-20mm too long and a bit strong. I tied the spring with wire so that it was compressed to 25mm high, and popped it into Mum's gas oven when she was out shopping.


After baking at 250 degrees Celcius for 90 minutes, I allowed it to cool naturally and then removed the wire ties. Beautiful! It ended up 45mm long, and about half the original spring tension. I was happy with that!


The filters sitting nicely in the cooling chamber, and the tension spring perched on top ready to fit back onto the engine. I just need to make a gasket to fit between the cooling chamber and the filter mount. Four inch OD and three and a half inches ID, so this will be fairly easy.


The sump screen sits above a removable plate at the bottom of the sump. Here's what it looks like:


And here's a peep inside the bowels of the engine, viewed throiugh the sump screen hole:

Sunday, February 6, 2011

Back to the F1

Gee, 14 weeks since the last post!

This weekend I dropped the engine, clutch and gearbox oils. They haven't been changed for some time, and I knew that I wouldn't start the engine until I had new lube oil and filters in the truck.

I also removed the sump screen, a metal screen about six inches in diameter into which the engine oil drops on the return journey. The screen acts as a "pre-filter", and had quite a lot of sludge in the screen. Once the oil passes through the screen the oil is picked up by the pump and passed through the felt oil filter contained within the external filter housing/cooling chamber, before passing to the various parts of the engine.

The felt filter is designed to be cleaned and re-used, however this just could be the original filter, and I'm sure that a more modern paper element filter would provide better filtration. For this reason, I will be looking at what options are available to change to a disposable paper element type filter. If I can get one at about the same size as the felt filter, it should still fit within the original external filter housing/cooling chamber on the side of the block.

The original recommendation by Dennis Brothers for F1 engine oil was Shell X-100 S.A.E.50 where the vehicle was exported overseas to an ambient temperature of 90 degrees Fahrenheit. This temperature equates to about 32 degrees Celsius, which is the ambient temperature in Darwin. Therefore the oil chosen for the engine is Penrite Shelsley Heavy, which is recommended for 1920-1950s era petrol and diesel engines where the original recommendation was for SAE 50 oil.

So that I can clean down the block more easily, I also started to remove the bolted-on items like the generator, fuel pump, oil filter housing, magneto and starter motor. Once everything has been cleaned up I can paint the block and the bolt-ons and reassemble.