Stormin Posted October 6, 2009 Share Posted October 6, 2009 Looks like the castings will not be cheap either. Guessing there's a fair weight of bronze involved. Have you any idea of the total weight? Have you a source of old castings to recycle or are you having to purchase new material? Quote Link to comment Share on other sites More sharing options...
Old Bill Posted October 6, 2009 Share Posted October 6, 2009 Do you soak the leather washers in anything before fitting? Mineral oil is the kiss of death for leather. I always soak the washers for Tilley in Nikwak conditioner. Keeps the stuff supple and also seals the leather. I soaked them in water overnight to be able to shape them and planned to soak them in engine oil before fitting. You reckon oil isn't good for them? They are oil seals and will run in a bath so I wonder how they will last. Will have to wait and see I guess. Certainly, the originals were pretty hard after 90 years! Steve Quote Link to comment Share on other sites More sharing options...
Cel Posted October 6, 2009 Share Posted October 6, 2009 A good product for making leather smooth is whale oil. Marcel Quote Link to comment Share on other sites More sharing options...
Old Bill Posted October 6, 2009 Share Posted October 6, 2009 Looks like the castings will not be cheap either. Guessing there's a fair weight of bronze involved.Have you any idea of the total weight? Have you a source of old castings to recycle or are you having to purchase new material? I don't have a weight but I am estimating at least £50- per casting so the whole set will be of the order of £300-. Then we have to machine them! Never mind. Fortunately, one advantage of taking so long on a project like this is that the spend rate is liveable! Whale oil, Marcel. Now there is an interesting thought. Where would one get it these days? 'Nikwak' is a new one on me too. Where might one get that? Do you think it would prevent the mineral oil from damaging the leather? What a wonderful source of information you chaps are! Steve Quote Link to comment Share on other sites More sharing options...
gritineye Posted October 6, 2009 Share Posted October 6, 2009 Leather seals have been used for ever on mineral oil filled components, and in some cases are superior to modern ones, like taking up wear on worn shafts. I have no fears about using them, where the original seals in my explorer were leather and I have replaced them with the same. We were taught to soak them in oil overnight before fitting, just my opinion. Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 7, 2009 Author Share Posted October 7, 2009 We have no Headlamp Brackets and are now going to have to make two. Mick has very kindly loaned us the ones from his Dennis Charabanc, and whilst they are not completely identical to the Subsidy Lorry ones, they do give us some idea of the size and the tapers of the "U" part of the bracket. From Mick's we can measure the tapers and lengths of that section for ours. Mick's pair are handed but the "Subsidy" pair are not. Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 7, 2009 Author Share Posted October 7, 2009 Some of you may not know, but i am also updating our WW1 Thornycroft restoration project blog at the same time. This project was started some years ago but got overtaken by more complete projects which were less challenging (at the time). I am catching up with scanning the photos. It can be found on this link. http://hmvf.co.uk/forumvb/showthread.php?t=13514 Tim (too) Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 10, 2009 Author Share Posted October 10, 2009 Tony has completed another mundane job - 12 studs made up and fitted to the back of the Brake Drum which hold the main cover over the coupling to the prop shaft. Still another 12 studs to do which hold the smaller cover to the main cover. Quote Link to comment Share on other sites More sharing options...
Tony B Posted October 10, 2009 Share Posted October 10, 2009 I soaked them in water overnight to be able to shape them and planned to soak them in engine oil before fitting. You reckon oil isn't good for them? They are oil seals and will run in a bath so I wonder how they will last. Will have to wait and see I guess. Certainly, the originals were pretty hard after 90 years! Steve Well worth sealing them with a stuff like Nixwak, also are the originals chrome tan? Easy to tell look at the side of the leather. You will see three distinct bands. Dark top and bottom lighter middle. like a sandwich. The diffrence is that heavy duty, white/bluey looking leather such as used on Dodge tilt straps is a mineral tan, waterproof. The leather used in shoes and clothes is a vegtable tan, this won't stand the wear. Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted October 10, 2009 Share Posted October 10, 2009 Well worth sealing them with a stuff like Nixwak, also are the originals chrome tan? Tony, I can see you have not had much to do with leather oil seals, they have to be soaked in the oil that the will be used with, before fitting. Any wax used would stop the oil soaking in, this is what stops them from burning when in use, for instance in a hub seal situation where oil level may not cover all the seal whilst stationary. This has been the procedure since time began. Quote Link to comment Share on other sites More sharing options...
Stormin Posted October 10, 2009 Share Posted October 10, 2009 I assume the oil soaking into the seal causes it swell slightly and tighten it's grip on the running face, hence improving the seal. Something that doesn't happen with modern neoperene types. Quote Link to comment Share on other sites More sharing options...
Tony B Posted October 11, 2009 Share Posted October 11, 2009 'Oak Tanned Leather' That's the best you can get! Most definitley 'English Quality' The tan= Tannin got from Oak bark. Used for best quality saddle and harness work. Normally , a bit like Harris Tweed, such leather is always marked. Leather is a subject in itself but I'd recommend a coat of Neats (Cow) foot oil or Coachaline, a type of preserving grease for leather before fitting. The oil will darken the leather as well as make it supple. If you are laying up anything leather either on a vehicle of on kit Coachaline is great for preserving it. Quote Link to comment Share on other sites More sharing options...
Old Bill Posted October 11, 2009 Share Posted October 11, 2009 Sorry, had to remove my last post for possible copyright reasons. However, I can report that I have now seen the original oil seal drawing and it specifies 'Oak tanned leather' as the material to use. Thanks for your advice Tony. Steve Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 11, 2009 Author Share Posted October 11, 2009 Steve started on the water pump patterns at last and has completed the simplest which is the cover. The material of choice for pattern making is MDF which has no grain, is readily available and takes glue very well. This is good as the first job was to laminate a block from which to turn the pattern. I screwed the block to the face plate and turned the outer face. There is a flange on this face to take the suction elbow so he cut this from a thin piece and then glued it on. The gaps under the edges, he filled with Isopon. Then it was a case of turn it around and bore the underside. Once this had been done, he fitted some blocks underneath to provide material for the elbow bolts to be tapped into. Then turned up a simple block to be used when first ramming the mould to support the pattern. This block will be removed before ramming the other side. The final job now is to paint both pieces. MDF has a rather furry finish after turning and doesn't rub down very well. However, the first coat of primer will seal the surface and allow it to be rubbed down to a very good finish before applying the second. Next pattern is going to be the pump rotor. It will be MDF again but this time with a core box. After that, there are four more, each progressively more complex. Surprisingly, the most difficult will be the suction elbow for which, at the moment, he still has no solution. Watch this space! Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 11, 2009 Author Share Posted October 11, 2009 Tony has made the final 12 studs (out of the 24) for the Universal Coupling Case on the rear of the Brake Drum today. These all fitted - so that's the end of that mundane job! There is Felt Seal to be replaced on the front of the small cover - the old one is visible in the photographs. Quote Link to comment Share on other sites More sharing options...
Tony B Posted October 11, 2009 Share Posted October 11, 2009 Can we just add for those who may follow, ALWAYS wear a dust mask, a good one, when machinging MDF, the dust can be nasty stuff. Quote Link to comment Share on other sites More sharing options...
trinconig Posted October 18, 2009 Share Posted October 18, 2009 With the diff just needing to be put back together (and all three of us in the same location at the same time to do it), Steve has been having a look at the carb. Now, we took this off the inlet manifold and it all looked very good. But on examining it further we see that it is actually a Zenith 36UY and not a bit like the one in the manual: which Ben confirms is a Claudel Hobson. We could probably make it run on the Zenith but probably not very well - as the engine was used of course to run a fire pump and not a lorry. So if anyone comes across a 36 Claudel Hobson, do please let me know. Thanks Tim (too) Hi I have just joined the forum and noticed your carb. I have a zenith 36UY on my 1933 Dennis fire engine, the engine is a Dennis G type, at the moment the carb is giving me some problems i.ie. stopping under load and then it will start again straight away. Anyhow I believe this carb is to modern for your truck as you may be aware. I know the "claudel hobson" was fitted on some Dennis engines as late as 1930 and then i believe was superceded by the Zenith. If you decide you dont want the Zenith i would be interested in it. Nig Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 19, 2009 Author Share Posted October 19, 2009 (edited) Thanks Nig. It is the only carb we have at the moment, but if we get the correct CH one and can get it working with that then we will let you know about the Zenith. We wont of course let it go until we have something to make our Dennis run. Tony has cleaned the nine nuts and bolts that hold the Diff together - so they are now ready to fit. He then cleaned up the Coupling between the Brake Drum and the first part of the Prop Shaft. The first three photos show it after coming out of the paraffin Bath and the second two after scraping and wire brushing. It fits the spline OK now. It is all just a little bit worn but we think that we can live with it. If needs be, he can easily turn up new bronze bearings if they are deemed too slack. He has cleared all the oil passage ways and have squirted oil through them to make sure that they are clear.. Finally, he has started on the Steel Ring to go on the end of the Prop Shaft. It is all coming together. Edited October 19, 2009 by Great War truck Quote Link to comment Share on other sites More sharing options...
Great War truck Posted October 21, 2009 Author Share Posted October 21, 2009 When we got the Prop Shaft, the front end flange was missing so one had to be made up. Just a simple turning job, but here is how it was done! A bit of bar end of mild steel was scrounged from a local Engineer - put in the three-jaw - a 1" hole pushed through it first of all and then bored out to the finished internal diameter. And then faced off. The steel was then turned around in the chuck and held by the internal bore, and machined to finished diameter, thickness and shape. The PCD was marked out in this position for the four 9/32 holes for the fixing bolts or studs. Job done. Quote Link to comment Share on other sites More sharing options...
Asciidv Posted October 26, 2009 Share Posted October 26, 2009 Steve, Returning to your patterns, do you use a contraction ruler when marking out and measuring? Barry. Quote Link to comment Share on other sites More sharing options...
Old Bill Posted October 26, 2009 Share Posted October 26, 2009 Hello Barry. Welcome to the forum! Yes, I do use a contraction rule but I must admit that as most of my patterns are really quite small, the contraction is very close to my woodworking tolerances! Under about 3" it makes little difference. I have been pressing on with my pattern making recently and hope to post some more pics (or Tim will) by the end of the week. There really is an awful lot of work for just one set of castings! Steve Quote Link to comment Share on other sites More sharing options...
Gordon_M Posted October 27, 2009 Share Posted October 27, 2009 1/8" contraction per 12" would be about right. There are various considerations to contraction like this, mostly to do with avoiding cracking and warping of the finished castings. Cast wheels are good examples. Rims and hubs solidify, but the spokes tend to crack as contraction sets in, but there are various ways of dealing with it; Curved spokes; which allow the rim and hub to rotate slightly, relative to each other, when contraction sets in. Odd-numbers of spokes; having three, five, or seven spokes means that there are no two spokes directly across from each other, minimising the tendancy to crack. Gordon (who had a career doing this before he discovered oil rigs) Quote Link to comment Share on other sites More sharing options...
Old Bill Posted October 27, 2009 Share Posted October 27, 2009 A true professional at last! Pattern makers are a rare breed these days and difficult to find to ask advice. I am just making this up as I go along but I do have a puzzle I would like to ask about shortly please! My rule says 1:70 for brass which is the scale I have been using. I plan to get the pump cast in gunmetal which I suspect shrinks a little less, as you have stated. Just for interest, here is a pic of the front face of my rule. The upper scale is true and the lower for steel castings. Brass is on the back. One must really concentrate when using one of these! Steve Quote Link to comment Share on other sites More sharing options...
Old Bill Posted October 27, 2009 Share Posted October 27, 2009 Please Gordon, may I have some advice? The question is, how should I split the pattern for the suction elbow? The fly in the ointment is the flange on the side as I just cannot see how to get the pattern out of the sand. Without it, it would be a simple split along the centreline and a single core but with it, I just don't know. It must be possible as they built at least 5000 of the things. Any advice would be most welcome! Cheers! Steve PS The pipe is 1 1/2" diameter to give you some idea of scale. Quote Link to comment Share on other sites More sharing options...
Johnny Posted October 28, 2009 Share Posted October 28, 2009 Could you use the lost wax method for casting this? I think that is the process used for more intricate shapes that cannot easily be halved. http://en.wikipedia.org/wiki/Lost_wax Quote Link to comment Share on other sites More sharing options...
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