Old Bill Posted January 27, 2010 Share Posted January 27, 2010 The body will be the later pattern 'Subvention' body with steel hoops and a canvas top. It is quite straightforward and various drawings and diagrams have been published over the years. I think we have an original Dennis drawing in stock too (I must go and look it out!) so I don't anticipate too many problems. It does, however, have quite a few forged iron brackets which I would like to make. To that end, I am in the process of setting myself up with an anvil and hearth and reading up on blacksmithing so I can do it. The most difficult bit will be in bending the steel angles to form the hoops and side brackets. Nowhere can I see how to do it so if there are any experienced blacksmiths out there who can explain how it is done, I should be very glad to hear from you! The body will be of some nice quality pine planks on an ash frame and we are budgeting about £1000 for it. A joiner friend will procure and prepare the timber for us and Tim has been busily importing square nuts from the USA to go on the bolts and hold it all together. As far as the seat box is concerned, we have only overall dimensions. However, an original exists on the Thornycroft J at the East Anglian Transport Museum and I have measured that up and drawn it in detail. It will need tweaking to get the shape right for the Dennis but we will use the same methods of construction. We just need to find the time to do it all! Steve Quote Link to comment Share on other sites More sharing options...
Old Bill Posted January 27, 2010 Share Posted January 27, 2010 This is the early pattern body from a Dennis publication which explained how the 'Subsidy' scheme worked. Ours will be of the later pattern with solid sides and much squarer hoops but you get the general idea. Steve Quote Link to comment Share on other sites More sharing options...
Stormin Posted January 27, 2010 Share Posted January 27, 2010 The most difficult bit will be in bending the steel angles to form the hoops and side brackets. Nowhere can I see how to do it so if there are any experienced blacksmiths out there who can explain how it is done, I should be very glad to hear from you! Steve I believe a ring roller with appropriate formers is the tool to use if the radius is not too tight. Probably better to get them done at a fabricator that is set up for the job. They're used all the time as strengtheners on large silos and tanks. To buy a machine is quite expensive. http://cgi.ebay.co.uk/Power-Section-roller-ring-roller-30mm-shafts_W0QQitemZ120513707746QQcmdZViewItemQQptZLH_DefaultDomain_3?hash=item1c0f2d3ee2 Quote Link to comment Share on other sites More sharing options...
Old Bill Posted January 28, 2010 Share Posted January 28, 2010 Last weekend, we had a family get-together, not only to work on the lorry but to celebrate Tims and my birthdays. A good time was had by all and look what I got! Aren't I lucky! :-D Steve Quote Link to comment Share on other sites More sharing options...
andreadavide Posted January 29, 2010 Share Posted January 29, 2010 If you need a blacksmith, this one, Richard Maynard is a Land Rover fanatic and may have a clue about lorry parts... I know him from the United Kingdom Land Rover Owners mailiang list. Andrea rich@muchhadhamforge.co.uk http://www.muchhadhamforge.co.uk Quote Link to comment Share on other sites More sharing options...
Old Bill Posted January 29, 2010 Share Posted January 29, 2010 Thanks Andrea. A sympathetic blacksmith is a very good find. I also see that he does short introductory courses which seem like an excellent idea. There is nothing like learning a new skill! Steve Quote Link to comment Share on other sites More sharing options...
Old Bill Posted January 29, 2010 Share Posted January 29, 2010 Thanks for the suggestion Norman. What sort of radius could they cope with? The pictures below show the rear of the headboard on the original Thornycroft J which are, I think, about 8-10" radius and what we want to achieve. The other pic shows the rear of the IWM, FWD model B. You can see that the angles on the sides are bent very tightly indeed and I am sure that must have been a blacksmithing job. Of course, I could just cut and weld them but that would be giving in! The FWD pic also shows a lot of other ironwork around the tailboard quite a bit of which has been hot worked. I think these items are going to keep me amused for quite a while! Steve Quote Link to comment Share on other sites More sharing options...
Stormin Posted January 30, 2010 Share Posted January 30, 2010 Radius capability will vary with machine and material but I see no problem ring rolling that front headboard hoop. It's the best way to get a nice even curve. The angles on the sides look far too tight a radius to be rolled and will have to be hot worked. Cheap forge on Ebay at the moment. http://cgi.ebay.co.uk/Gas-forge_W0QQitemZ330398175881QQcmdZViewItemQQptZLH_DefaultDomain_3?hash=item4ced441289 Quote Link to comment Share on other sites More sharing options...
Great War truck Posted January 30, 2010 Author Share Posted January 30, 2010 The remainder of the Water Pump castings are not back from the Foundry yet, but we have pushed on with other bits of the Pump. Steve had already made up the shaft, and the Gland Nut and Gland have now been machined up from Bronze Bar. Quote Link to comment Share on other sites More sharing options...
Asciidv Posted January 30, 2010 Share Posted January 30, 2010 Steve, Have you ever seen a Dennis spanner for tightening up this type of gland nut? I have never seen one, although it does seem a bit rudimentary if the expectation is to tap it round with a hammer and a screwdriver. Quote Link to comment Share on other sites More sharing options...
Old Bill Posted January 31, 2010 Share Posted January 31, 2010 No, I never have seen one or even a picture in the parts book. I was planning to make a sort of 'C' spanner with two buttons riveted on to engage in opposite slots. Even with that, looking after the gland will be difficult as the only access is through the hole in the side of the mounting casting. I think that re-packing will require the pump to be removed and partially stripped each time which will be quite a pain. With a bit of luck, the long bearing and pressure lubrication will extend this process to long intervals. Steve Quote Link to comment Share on other sites More sharing options...
Great War truck Posted February 1, 2010 Author Share Posted February 1, 2010 Most of the constituent parts of the Universal Coupling have now been made up to the original drawings - some by us in the home workshop - but the EN24 parts - a very tough steel, were farmed out to the "Professionals" to machine for us, and the final part, the actual Drive Shaft (pictured) has just come back from them. This just leaves the Coupling Flanges to be finished with a "Square" for the coupling wire cut in one and a Spline in the other one, after which final assembly of the unit can take place, and it can be installed into the Truck. Quote Link to comment Share on other sites More sharing options...
phil munga Posted February 1, 2010 Share Posted February 1, 2010 Hi , you say the " Most of the constituent parts of the Universal Coupling have now been made up to the original drawings" on the drawings does it specify the type of material strength or if case hardened ( if they did that sort of treatment ? ) I know you've used other materials for some jobs for the better just wondered what detail is on the drawings No, I never have seen one or even a picture in the parts book. I was planning to make a sort of 'C' spanner with two buttons riveted on to engage in opposite slots. Steve Would an angle grinder spanner do this job ? Quote Link to comment Share on other sites More sharing options...
Stormin Posted February 2, 2010 Share Posted February 2, 2010 I'm surprised that those cross drilled holes for pins in the dumbell shaft are not at right angles to each other. I'm sure it would allow greater articulation and misalignment of the drive. Quote Link to comment Share on other sites More sharing options...
Gordon_M Posted February 2, 2010 Share Posted February 2, 2010 I'm surprised that those cross drilled holes for pins in the dumbell shaft are not at right angles to each other. I'm sure it would allow greater articulation and misalignment of the drive. Ouch, he could be right - that might be why you can see one pin in the drawing and just the dotted line in the other end? Drawing should have specified though, and thinking about it you would see a dotted hole, rather than two dotted lines, if the other end was indexed 90o Quote Link to comment Share on other sites More sharing options...
radiomike7 Posted February 2, 2010 Share Posted February 2, 2010 I'm surprised that those cross drilled holes for pins in the dumbell shaft are not at right angles to each other. I'm sure it would allow greater articulation and misalignment of the drive. If you consider each joint as a complicated universal joint the pins have to be in line to give an overall constant velocity. I assume these joints are filled with a thick oil, but how are they sealed, the end caps look like they are in 2 halves for a start? Were conventional Hooke joints not in favour at the time? Quote Link to comment Share on other sites More sharing options...
Stormin Posted February 2, 2010 Share Posted February 2, 2010 If you consider each joint as a complicated universal joint the pins have to be in line to give an overall constant velocity. Of course you're right. I hadn't considered the constant velocity issue :blush: Quote Link to comment Share on other sites More sharing options...
Damian GT Posted February 2, 2010 Share Posted February 2, 2010 Sorry to ask what might be a silly question, but this is my first post! What, in simple terms, is the constant velocity issue? Thanks in anticipation.. Quote Link to comment Share on other sites More sharing options...
Old Bill Posted February 2, 2010 Share Posted February 2, 2010 Sorry to ask what might be a silly question, but this is my first post! What, in simple terms, is the constant velocity issue? Hello Damian. Good question and one that took me a while to convince myself I understood! Here goes: The classic universal joint is a Hooks Joint with two forks facing each other at 90° and a block between them. A pin goes crossways through each fork and through the block as well. The forks can therefore move around the block. If each fork has a shaft connected to it, then if one shaft is turned, the other must follow and you can take the drive around a corner. This arrangement is commonly seen at both ends of a prop shaft. (see picture below). So far so good. The point that is often missed is that the output shaft does not turn at exactly the same speed as the input shaft throughout the revolution. If the input shaft is running at a smooth constant speed, then through one revolution, the output shaft goes a little quicker, then a little slower, a little quicker and then a little slower until the revolution is complete and the shafts are in exactly the same position as when they started. Thiis effect gets worse the greater the angle of the joint. Now if you have two joints and the first (input) shaft is parallel to the third (output shaft) the joints can be arranged such that they cancel each other out. In that case, both pins in the middle shaft must be in line and the output shaft runs smoothly even if the centre shaft keeps speeding up and slowing down. If the pins are arranged at 90° then the effect of the two joints is added and the output shaft will be very rough. If the pins are worn, then the centre shaft will rattle and you will hear this in a vehicle, particularly when you ease off the power and coast. Does that help? To convince yourself that it happens, take a prop shaft and put a bit of tape both sides of the joint exactly in line. Then bend the joint as far as it will go and turn it slowly in your hands looking along the joint. You will see that the second piece of tape moves first one side and then to the other of the first. I had to use meccano to prove it to myself! Steve Quote Link to comment Share on other sites More sharing options...
Runflat Posted February 2, 2010 Share Posted February 2, 2010 And if your maths is up to it, have a look here: http://en.wikipedia.org/wiki/Universal_joint Quote Link to comment Share on other sites More sharing options...
Cel Posted February 2, 2010 Share Posted February 2, 2010 That is a very good explanation Steve, thank you! So actually it is a homokinetic joint which has the same properties as a propshaft with two universal joints. Marcel Quote Link to comment Share on other sites More sharing options...
Old Bill Posted February 2, 2010 Share Posted February 2, 2010 Hi on the drawings does it specify the type of material strength or if case hardened ( if they did that sort of treatment ? ) I know you've used other materials for some jobs for the better just wondered what detail is on the drawings Would an angle grinder spanner do this job ? Yes, the drawings do quote materials but this is before the days of En numbers and standardised specifications. The clutch bearing housing is described as 'Steel V.7 (HT) Brinell 217/269'. There is another specification which has been crossed out and I can't read it. It finishes up saying 'Harden and Grind'. The clutch bearing nut says 'V.4 H&T Steel' which I take to be 'Harden and temper' and again finshes up with a Brinell hardness specification. I must admit that we have not hardened any of this but I think we will get away with it. The sockets for the flexible joints use '40 ton mild steel' which we took to be something like En24. We have no drawings for the short prop shaft so I sketched it from the GA drawing and used En 24 again as we could get it and it is good tough stuff. Time will tell! An angle grinder spanner is the right sort of idea but I think I will need to make one exactly the right angle and with pins both sides to get it to work on the pump gland. Access is very tight indeed as we will find out very shortly! Steve Quote Link to comment Share on other sites More sharing options...
Old Bill Posted February 2, 2010 Share Posted February 2, 2010 That is a very good explanation Steve, thank you! So actually it is a homokinetic joint which has the same properties as a propshaft with two universal joints. Hi Marcel. I had to look up 'homokinetic'! I think that means 'constant velocity' so that the output shaft is always at exactly the same speed as the input throughout its whole revolution. Looking at it, I don't think these joints are. They appear to me to have the same action as a Hooks joint but to include some telescoping ability as well. If the engine and gearbox are correctly aligned, then there is no articulation of the joint at all and the constant velocity issue does not arise. Our shaft will not be perfectly in line but close enough not to cause a problem. Also, as the pins are directly in line with each other, the gearbox won't see any vibration anyway. Gosh, we are getting technical tonight! I think we may just have set some questions for the clubhouse Christmas Quiz! Steve Quote Link to comment Share on other sites More sharing options...
Old Bill Posted February 2, 2010 Share Posted February 2, 2010 I assume these joints are filled with a thick oil, but how are they sealed, the end caps look like they are in 2 halves for a start? Were conventional Hooke joints not in favour at the time? Hi Mike. Yes, they seem just to have a thick oil poured in and rely on centrifugal force to keep it there. The end plates are split but are cunningly made as a single piece and broken in two across the centre so there is no gap between them. I doubt that they will be oil tight though. One thing about the se old lorries, if they are not dripping, you haven't got enough oil in them! Dennis had some funny ideas about flexible joints. Many of their early vehicles had 'box' joints where the end of the shaft had a large square lump machined on it with curved faces. This ran in a square hole on the end of the next shaft and had bronze wear pads in between. They are horrible things and gave endless problems to the Royal College of Science students fire engine. I expect Barry might make some comment about them in a moment, as used on his fire engine. Steve Quote Link to comment Share on other sites More sharing options...
Asciidv Posted February 2, 2010 Share Posted February 2, 2010 (edited) It is strange that the 'box joints that Steve has just referred too were used on fire engines but not on his subsidy lorry. Here are the essentials of a box joint The bronze 'slippers' wear or in the worst case the actual box splits apart. Making sure that they are full of graphite grease before any journey ensures a longer life. Jezebel the RCS Dennis 'N' Type has had a fair share of box joint trouble but this probably because it is driven by students who have yet to hone their mechanical empathy. (Steve, didn't you use to drive Jezebel....?) By the end of the 20's where the 'T' headed White and Poppe engines were being phased out and unit construction was being introduced the box joints had gone too, to be replaced by a flexible cotton disk coupling. The last picture shows this type of coupling on my 1930 Dennis Low Load fire engine. Barry. This last picture also shows the 'drip tray' which is fitted to early Dennis Fire Engines. It runs from the flyweel to the back of the gearbox. It means that all the oil seals and couplings can dribble oil or spray grease without leaving it all over appliance room floor in the fire station. Edited February 2, 2010 by Asciidv Addition of drip tray note. Quote Link to comment Share on other sites More sharing options...
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