Gustaf Posted July 22, 2010 Share Posted July 22, 2010 Another note on oil quality, it was not uncommon to use crude oil in the crankcase of farm tractors in the early years, the heat of the engine would cause the oil to crack, and the lighter distilate could be drained off the top before starting and used as fuel. Best Gus Quote Link to comment Share on other sites More sharing options...
Old Bill Posted July 27, 2010 Share Posted July 27, 2010 Changing the subject: has the Dennis got a water cooler for the transmission brake? I don't recall ever seeing one on a preserved lorry. That's a good question, Roy. I have never seen one on a vehicle. However, the GA drawing does show a water tank on the scuttle above the driver's knees and a photo in the manual on an early pattern scuttle, also shows it. (see below).We have found no evidence of one having been fitted to any of the bits and pieces we have obtained, though, and the holes are not shown on the scuttle drawing so it is my belief that they were probably discontinued early on. We have, therefore, decided not to try to fit one. Actually, I haven't been able to see how it worked either as there is no obvious place to put it on the brake drum. Does anyone have any experience of transmission brake coolers? Steve Quote Link to comment Share on other sites More sharing options...
Asciidv Posted July 27, 2010 Share Posted July 27, 2010 (edited) The transmission brake originally did not have friction material. It was just metal to metal contact like the rear brakes. Does hot metal have a diffferent coefficient of friction compared with cold metal? Also the brake drum and shoes have so much mass that I would have thought that a dribble of water would make negligible difference in lowering the temperature. Perhaps that is why cooling of the transmision brake was not favoured? Edited July 27, 2010 by Asciidv Quote Link to comment Share on other sites More sharing options...
gritineye Posted July 27, 2010 Share Posted July 27, 2010 Just a thought but could the water be for lubrication rather than cooling? I would imagine a metal to metal brake would emit a pretty annoying squeal! A small amount of water dribbling between the parts might prevent this and may stop grabbing as well. Quote Link to comment Share on other sites More sharing options...
Old Bill Posted July 27, 2010 Share Posted July 27, 2010 You might have it there. Certainly, that little tank of water will either run out in no short order or do very little in terms of cooling unless the water could be contained within the drum. Our drum has no provision for that and is full of oil for the UJ. I have driven a car with a metal to metal (cast iron on bronze) drum brake and it was quiet, smooth and effective. Railway equipment was always metal to metal until relatively recent years and that only tended to squeal at the lowest speeds just before stopping. The bottom line is that I don't know why they troubled with the system! Steve Quote Link to comment Share on other sites More sharing options...
Asciidv Posted July 27, 2010 Share Posted July 27, 2010 I just love the metal to metal squeel! Barry. Quote Link to comment Share on other sites More sharing options...
gritineye Posted July 27, 2010 Share Posted July 27, 2010 I just love the metal to metal squeel! Barry. Whatever turns you on Barry I mean whatever slows you down :-D Quote Link to comment Share on other sites More sharing options...
Stormin Posted July 27, 2010 Share Posted July 27, 2010 The transmission brake originally did not have friction material. It was just metal to metal contact like the rear brakes. Does hot metal have a diffferent coefficient of friction compared with cold metal? Also the brake drum and shoes have so much mass that I would have thought that a dribble of water would make negligible difference in lowering the temperature. Perhaps that is why cooling of the transmision brake was not favoured? [ATTACH=CONFIG]31810[/ATTACH] Again another analogy with modern machinery. Modern racing trucks use an almost constant supply of water onto the brakes to cool them. Just a dribble is all that's probably needed. Too much water would reduce the coefficient of friction and reduce braking effect. Just the right amount should burn straight off as steam and take quite an amount of heat away Quote Link to comment Share on other sites More sharing options...
Stormin Posted July 27, 2010 Share Posted July 27, 2010 Maybe the brake cooling was an option on were higher speed use was likely. The single transmission brake would then have come under significant strain. I imagine the engine compression ratio is quite low, coupled with crash gears would mean engine braking is not so good. Subsidy trucks were probably never likely to see the higher speeds necessitating the brake cooling so it was left off. Quote Link to comment Share on other sites More sharing options...
Charawacky Posted July 27, 2010 Share Posted July 27, 2010 (edited) In my experience bacon slicer brakes work well and will tolerate some oil contamination from which they can recover with out permanent damage, this is important if the transmission brake is located close to the grearbox output and torque tube UJ. I would be grateful if any one has any technical info on what grade of cast iron to use as I must cast new shoes this winter, they appear to be cast shoes on steel drums. I will also be interested to know how the wonderful metal to metal noise will be affected by water? No doubt we know in the not to distant future. Tom Edited July 27, 2010 by Charawacky Quote Link to comment Share on other sites More sharing options...
Roy Larkin Posted July 28, 2010 Share Posted July 28, 2010 The War Office subsidy specification states that a 1 gallon water tank be fitted and that a drip feed to the transmission brake be automatically operated from the brake pedal. I'm not sure that a drip feed of water would be sufficient to comfort me if descending a long steep hill, or that a drip feed would do much for cooling. I'm also not sure what effect mixing water with dust would have over a period of time either - probably create a right mess as there was plenty of dust at times. Like many things in those early days, what seemed a good idea on paper didn't always work in reality, so might well have been abandoned from an early date. At least the War Office continued trials right up to August 1914, which were mainly to establish the viability and reliability of new ideas. Would the transmission brake have been used much? My recollections of the Leyland Chivers was that it was a waste of time and the handbrake was the primary braking. Quote Link to comment Share on other sites More sharing options...
Asciidv Posted July 28, 2010 Share Posted July 28, 2010 I doubted the cooling power of a dribble of water, however a 3KW (~ 4 Horse Power ) kettle takes 4 minutes (240 seconds) to boil 3 pints of water, which equates to 40 Horsepower being absorbed for 24 seconds by 3 pints of water. This does not take into consideration the latent heat of vapourisation of water which will give you an extra margin. A gallon of water would therefore absorb the energy of 40HP for at least a minute. However, I am still not convinced that a rise in temperature of this type of transmission brake would lead to reduced braking performance so the water seems unnecessary Roy is correct in saying that the transmission brake is rarely used, with the handbrake being the primary source of braking. On the Dennis the transmission brake is considered to be too fragile for continuous use and is used as an emergency brake only. With the metal to metal contact of the rear brakes activated by the handbrake lever the rear drums do get hot but braking performance is not diminished by the temperature rise. I couldn't help but smile at the small quantities of oil which Tony showed in one of the recent photographs. In particular the Dennis gearbox has a self changing oil facility where the oil constantly drips out and you just keep topping it up with fresh... Quote Link to comment Share on other sites More sharing options...
Old Bill Posted July 28, 2010 Share Posted July 28, 2010 I couldn't help but smile at the small quantities of oil which Tony showed in one of the recent photographs. In particular the Dennis gearbox has a self changing oil facility where the oil constantly drips out and you just keep topping it up with fresh... Quite right. That is one of the reasons why we have not put any in yet! Steve :-D Quote Link to comment Share on other sites More sharing options...
Richard Peskett Posted July 28, 2010 Share Posted July 28, 2010 The handbrake is of course the service brake on all these early vehicles, the foot ( transmission) brake should be effective providing in good working order, cast iron shoes and a cast steel drum. Only for use in an emergency or bringing the vehicle to a final stand. There would be a problem with overheating if use continuously hence the water cooling, my Fiat 15 TER was fitted with such facilities, I always thought for use on the Italian passes where it no doubt would be use as a retarder. Also remember the speeds the vehicles were travelling at required very little use of the brakes anyway except on long downgrades and even then if the gears are used properly brakes are virtually not required. As an aside, all these Fiats were right hand drive, again for use on the passes so the driver was nearest the edge all the time. Richard Peskett. Quote Link to comment Share on other sites More sharing options...
nz2 Posted July 28, 2010 Share Posted July 28, 2010 While from a differing period of time, the use of water on brakes was used in NZ on some trucks through the 1950's and into the early 60's as a means cooling brake drums on long descents. In particular trucks carting logs out of step back country using a jinker type axle supporting the tail end of the load. The water supply was a 44 gallon drum fitted in behind the cab with hoses running off to the brake drums. A stop at the top of the hill , turn on the taps and a slow descent. An addition to trucks that would cause a vehicle inspecting officer now to be horrified as its not in his little book!! But it worked successfully. Doug Quote Link to comment Share on other sites More sharing options...
Great War truck Posted July 28, 2010 Author Share Posted July 28, 2010 Steve has just had a pleasant hour stripping down our latest 30mm carburettor. Everything was solid, of course, but a little heat from the propane torch and everything let go with no breakages at all. The hole pitches in the mounting flange are incorrect for us so Steve tried to remove it but without success. It is screwed on and soldered but even though the solder was running, it wouldn't shift. He has therefore decided to use all of the components to resurrect the 28mm carburettor body we have and make a new flange of the correct size for that. Actually, this will be a perfect solution as 28mm is the size specified for the lorry anyway! Quote Link to comment Share on other sites More sharing options...
Great War truck Posted July 29, 2010 Author Share Posted July 29, 2010 Sorry. I managed to upload the wrong photos. here are the correct ones: Quote Link to comment Share on other sites More sharing options...
Great War truck Posted August 1, 2010 Author Share Posted August 1, 2010 Had a remarkable piece of news today. Look which original part we will shortly have to reunite with the Dennis. Fantastic, and many thanks Mick. Have you all guessed what it is yet? Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted August 1, 2010 Share Posted August 1, 2010 A petrol filter? Quote Link to comment Share on other sites More sharing options...
Great War truck Posted August 1, 2010 Author Share Posted August 1, 2010 Crikey Richard. That was quick off the mark: Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted August 1, 2010 Share Posted August 1, 2010 Crikey Richard. That was quick off the mark: Tim, It looks remarkably like one I came across on a Morris Commercial C4 once. Quote Link to comment Share on other sites More sharing options...
Great War truck Posted August 1, 2010 Author Share Posted August 1, 2010 Could be the same type. manufactured by Enots? Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted August 1, 2010 Share Posted August 1, 2010 Could be the same type. manufactured by Enots? Tim, I think you are correct, Enots springs to mind. I recollect the bowl part has a very fine thread where it screws on to the upper body. Quote Link to comment Share on other sites More sharing options...
Great War truck Posted August 1, 2010 Author Share Posted August 1, 2010 Enots made allsorts of accessories - fuel filters, door handles, buttons, filler cap, radiator caps etc. Here is a page from a catalogue of theirs at the time (with thanks to Ben for bringing it tour attention) : Quote Link to comment Share on other sites More sharing options...
Great War truck Posted August 3, 2010 Author Share Posted August 3, 2010 Dennis vehicles of this period guide the HT leads within a moulded cardboard tube mounted on top of the blocks and we are very fortunate that the one for our engine has survived. As you can see, it has suffered some damage in that one of the grommets was loose and two more were missing as was the reinforcing ring from the magneto end. Steve spent some time puzzling over how to repair it and eventually decided that replacement parts could be made by laminating thin card and then sanding it to shape. He started off by turning up a plug the diameter of the magneto end and then wrapped it with greaseproof paper to prevent the card from sticking. He then cut strips of card from a cereal packet, across the grain so that they wouldn't kink, and wrapped them around the plug in layers using a houshold adhesive to stick them together. The resulting assembly was then left with a rubber band around for 24 hours to harden off. A few minutes with some glasspaper and this was the result which was quite pleasing Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.