Asciidv

Ben, What is the little cut present on some louvres and not on others. The louvres look absolutely super. It is interesting that it wasn't necessary to make the female part of the press tool to have the the same surface profile as the male part. Barry. P.S. I know you said your bonnet was painted but I have now found a company still with a tank of boiling cyanide/caustic soda/arsenic to do the original chemical blue'ing. My Big Four bonnet is now heading in that direction.

M0XXY, Primarily on 4m, where you might guess was where Fire Engine communications lived until the switch to Airwave. Barry.

Whilst we are completely off topic and talking about castings, I would like to describe a route which I would now always follow. My wood working skills are limited and my time is even more limited, hence the following approach when I needed a new two into one exhaust manifold for one of my Dennis's. I drew the manifold first in Solidworks, and then produced the models for the pattern and core box. I then had them 3D printed at a cost of around £25 each. I tried out the core box making a C02 core. This was perfect. I need two core halves to glue together to make a complete core I tried out the pattern in some greensand and this pulled out easily too. The advantage of doing it like this is that you can define the draft angle easily for easy extraction from the sand and achieve absolutely consistent wall thickness. Also things like scaling to allow for contraction is just a mouse click away. Barry.

Earlier I think you said that the actual rod was just brazed into the end fittings. Are you going to repeat this process or use a more mechanically robust method? If you do braze the fittings on, will it truly be braze or your well loved silver solder? Is there any data which shows the comparative strengths between a silver soldered joint and a true brazed joint? Barry.

Andy, What are the approximate dimensions of this box? Barry.

If you are seeking genuine grover washers I don't think 'bodging' is on the menu, be it edam or not. New casting please. We like to see it done right! Barry.

Ben, Did you roll the silencer tube yourself? How is the seam joined? Barry.

"Any other ideas?" Do you actually need the full depth of engagement as the original Dennis on the cone clutch? The Aster engine probably has significantly less power than the Dennis equivalent so that clutch slip would not be a problem. I know it would look awful and not right though! So if you are doing properly then cast a whole new flywheel. Barry.

Tony, How did you retain the new threaded section in the old pin body? Do you believe in 'Loctite' or do you always prefer a mechanical solution more matching the period of the vehicle? Barry.

When you see the size of the axle casting and the flanges, you would wonder if the tie bar would possibly ever make any difference? Barry.

Doug, Yes, there is a similar range of blacking solutions for aluminium. However the normal way of colouring aluminium is through anodising. An aluminium oxide film is created on the surface of the aluminium by an electrolysis process. This film can then be dyed any colour that you like. The film also provides corrosion protection. Home anodising kits are readily available on ebay and they do work very well. I can see us veering off on another tangent now so we better wait for the boys from Devon to provide new content! Barry.

Just to add the final piece of information to what David has just said, commercially made name plates do not use black paint for the infill. There are a number of chemical blacking solutions available for brass some of which are described here; http://www.modelboatyard.com/blackening.html Barry

I ground off the remains of the thread and then drilled a shortened 5/16" UNF bolt to take the remains of the pin. This was silver soldered in place so all was as good as new. However a couple of weeks later a new cylinder arrived and all was revealed about how the pin was fixed in place. As you can see there is across drilling with what looks like a 3/64" pin inserted which prevents the larger diameter of the anti-rotation pin from moving past. The pin is obvious on this cylinder as the stake marks can clearly be seen. 60 years of rust seem to have obliterated these marks on the original cylinders - if they every existed! Finally, Sean, if you do have two spare transverse cylinders I would love to buy them off you. Perhaps you could drop me a PM if you can lay your hands on them. Best wishes, Barry.

Most British lorries of the 50s and 60's were fitted with tranverse brake cylinders at the rear. These are external to the brake drum and are therefore easy to remove if the seals have to be replaced. The cylinder pulls on a rod which has a wedge at the other end to expand the brake shoes. The same rod is extended and linked to the handbrake. The actual hydraulic piston acts on a coupling cylinder for the handbrake rod. The handbrake rod screws into the coupling cylinder. The coupling cylinder has to be prevented from rotating so there is a 'flat' in it and a pin runs through the casting of the cylinder which acts as the anti-rotation key. In this picture you can see the pin cutting through the inside wall of the cylinder. (The actual hydraulic part of the brake cylinder is below this). This picture shows the pin unscrewed. The pin will not pull out as it has two diameters. The end which does the 'keying' is a larger diameter than the shaft of the pin. So the question that I wanting to ask is HOW IS THE PIN ASSEMBLED and HOW DO YOU REMOVE IT? You may wonder why I would want to remove it. Well today after a brake re-build I was stupid. I gave the pin a little nip up during assembly which was a little too hard and sheared the hex head of the pin. I should be able to unscrew the remains out but of course only as far as is shown in the photo above. This shows the sheared off hex head which looks almost as if it is hollow to take the shaft of the pin, but how would the two be fastened together if this was the case? Any suggestions gratefully received. Thanks, Barry.

Mammoth suggested getting a MIG welder, however the true answer is buy a TIG set. TIG is just so incredibly flexible being able to produce superb welds in steel, aluminium and even metals such as copper. Although relatively expensive and with the need for argon at all times having used one once you would never go back to anything else. Barry.

Tonight I made the vacuum piston seal. As I wanted more than one, I first milled a template. I used this to drill the leather (3mm thick from ebay). I then bolted through the template and leather onto a bed plate. I then profiled the inner and outer diameters ..and within a few minutes I had a lifetime supply of 7" CD vacuum piston seals. Here is one fitted to the piston assembly. It has already been soaked in water ready for fitting to the vacuum cylinder. After an hour in the cylinder it came out looking like this, exactly as it should. It is now being left to dry out and despite Richard saying any old oil will do, I am first going to give it a good soaking in Neatsfoot oil. After it is all assembled I am going to test out the unit before fitting. I hope a 'Henry' type vacuum cleaner is going to give enough suck to prove the correct operation. Barry.

This is the vacuum tank in which the piston operates. This machine had stood unused for almost 8 years and quite possibly brake fluid had sat in the bottom of the tank for all of this period which has resulted in corrosion of the aluminium. I hope that this will not result in a significant loss of vacuum although once the brakes are activated the piston moves further down the tank where there is no corrosion. I suppose my main concern is that the engine could be sucking air in and weakening off the mixture to the B80. I wonder if this is a valid concern when you compare the possible size of the air leak here compared to the big open hole on the Solex? Barry.

My plan was to use neatsfoot oil to keep the leather supple and durable and then red rubber grease for the lubrication. This was prompted by seeing Clayton Dewandre rebuild kits on ebay which included a tube of 'special' grease. However if engine oil has proved successful in the past as Richard has described then this is perhaps the approach that I should take. My vacuum tank is 7" in diameter and is a deep drawn aluminium cylinder. There is no auxiliary port for lubrication injection. Barry

When the piston came out of the vacuum housing, the damage caused by the brake fluid being in the chamber could be seen. It appears that some of the brake fluid had dried out to hard crystalline 'lumps' and these 'lumps' dragging past the seal had damaged the lip of the seal. The leather seal is backed by a spring steel disk with curved 'fingers' which help to keep the seal in contract with the vacuum housing. The seal is a simple leather disk of 4mm thickness. I intend to make a new one and wet mold the leather into the basic shape. Has anyone made such seals before and can you offer any advice? Thanks, Barry.

This weekend the servo came off and this short video tells all! [video=youtube_share;mhgh0vyJF8A] Barry.

Richard, Thank you for your reply. It is re-assuring that someone has come across this problem before. I looked at the bottom of the servo today and you can see quite clearly where brake fluid has leaked out of the bottom section of the servo. I'll take off the servo next weekend, but in the meantime can anyone suggest where I should go to for a rebuild kit. Although there are some on ebay only the kit number is given and not the servo to which they are applicable. I rebuilt the Solex carburettor for the B80 engine and it didn't seem right to put a sparkling carburettor on a dirty engine so it was given a clean and re-paint too. Although I say it myself, I do think it looks very smart! Barry.

I have a mid-50's Dennis fitted with a Rolls B80 engine with a vacuum hydraulic Clayton Dewandre servo. I am in the process of bringing this back to life after it has stood for 8 years. I had to fit new brake hoses and brake cylinder repair kits but I have been puzzled how one week the brake fluid reservoir can be full only to find it empty the next time I looked, but with no trace of fluid on the floor. I have kept refilling and then bleeding the system without understanding what the true cause is. Today I think I have found the cause. It appears that the fluid is being sucked into the engine and burnt in the engine via the Clayton Dewandre servo. With the engine running and the fluid reservoir empty I can put brake fluid into the reservoir and hear and immediate change in engine note with black oily smoke coming out of the exhaust. Looking at the servo diagram it seems a very tortuous route for the brake fluid to reach the vacuum pipe. The seals on the master cylinder would have to be worn and the vacuum diaphragm on the servo piston would have to leaking too. Has anyone ever experienced this before, or can offer me any other explanation of how the brake fluid can just vanish. Over the past few months I have been through quite a few litres! Any suggestions gratefully received, Thanks, Barry.

I had completely mis-understood the operation of the cold start chamber. I had thought that it was the linkage from the thermostat which was enrichening the mixture through the cold start chamber, rather than the cold start chamber modifiying the position of the choke (strangler) butterfly. This picture shows the access point on the carburettor for the injection of the 10psi of air to test the cold operation. Here we see the air gun conencted to this point. I simply used a samller rubber (Hellermann) sleeve over the nozzle of the gun to make an air tight connection. The operation of the cold start linkage could now be adjusted according to the manual. Incidentally does anyone have an ORIGINAL copy of the TSD702 Rolls engine manual that they might like to sell to me? Barry.

Thanks Clive, really useful! I will set up my carburettor like this in the morning and bolt it back on in the afternoon. Hopefully I will be back on the road on Sunday.:-) Barry.

I have a solex 40 NNIP/3 carburetter for a B80. This differs from the normal NNIP as it has an automatic choke rather than a manual choke. This is the picture of the cold start chamber between the two accelarator pumps. The lever arm which acts on the central pin of the diaphragm is operated by a linkage which goes to the choke butterfly. The arm can only seem to pull the pin forwards into the body of the carburettor but as on the other side of the diaphragm ther is a spring pushing the pin forwards too I cannot see how it ever moves from this fully forward position. So just how does it work? Could I have mis-assembled somthing when putting it all back together? Does anyone have a manual showing this variant of the carburettor? Thanks for any possible advice, Barry.