Chaindrive Posted April 1, 2013 Share Posted April 1, 2013 I see that the bits sold - were you the successful bidder, Robert? Tony I managed to secure the parts,so they are now safe from the scrapmans grasp. Now to organise freight as they are about 2000km from where I live. i should add that I am enjoying this thread very much. Very inspiring as to what can be achieved with a few tools and a lot of passion for restoration. Keep up the great work. Dale Quote Link to comment Share on other sites More sharing options...
Minesweeper Posted April 1, 2013 Share Posted April 1, 2013 I managed to secure the parts,so they are now safe from the scrapmans grasp. Now to organise freight as they are about 2000km from where I live.i should add that I am enjoying this thread very much. Very inspiring as to what can be achieved with a few tools and a lot of passion for restoration. Keep up the great work. Dale Well done, Dale - very pleased to know that the parts have been saved! Glad to know that you are enjoying the story - Tim has quite a bit more to post yet relating to the weekend's efforts! Tony Quote Link to comment Share on other sites More sharing options...
Redherring Posted April 2, 2013 Share Posted April 2, 2013 I see that the bits sold - were you the successful bidder, Robert? Tony Chaindrive put his hand up. Did he win? Quote Link to comment Share on other sites More sharing options...
Redherring Posted April 2, 2013 Share Posted April 2, 2013 Whoops. Clearly should have read ahead...... Quote Link to comment Share on other sites More sharing options...
Great War truck Posted April 2, 2013 Author Share Posted April 2, 2013 After more hitting and levering, one of the sides eventually lifted off, revealing a nice oily and greasy interior. It was a job that had to be done very carefully as the body castings are quite thin and could easily be broken. Again, so far, so good but still some way to go. Removing the second half of the outer cover again proved to be very difficult as it had to be removed over the end of the swinging lever shaft. A gentle heat did no good and eventually we got it out by supporting it on the anvil and the swage block and then hitting it with a good hammer. That did the trick. These two pictures show some of the bits after removal and before cleaning. Everything well covered in lubricants – so hopefully well protected against corrosion. Quote Link to comment Share on other sites More sharing options...
Great War truck Posted April 2, 2013 Author Share Posted April 2, 2013 And after a preliminary quick wash in paraffin. Notice the big “silver” spots on the steering nut shell. They are of white metal and the whole of the big thread inside the shell is white metal. Goodness knows how this is done but there are “ silver spots” like this on the four sides of the shell. Presumably the white metal is poured in through these holes and the outside of the casing is then cleaned up afterwards. But how is the thread inside made? More parts after the preliminary “wash”! One half of the casing after a quick preliminary clean – the job remains to be completed satisfactorily. The worm after a quick clean – the bend in it is quite obvious – and finally the white metal thread inside the casing. The last bearing is proving stubborn to remove – and that is now taking a trip to Leicester for the benefit of the Press! Quote Link to comment Share on other sites More sharing options...
Hoseman Posted April 2, 2013 Share Posted April 2, 2013 With careful pressure you will be able to straighten that shaft out in a Fly press. we use them to straighten some hydraulic cylinders with a bend in the middle! Quote Link to comment Share on other sites More sharing options...
Redherring Posted April 2, 2013 Share Posted April 2, 2013 Fascinating. You can see the logic behind the mechanism... and it is so completely different to, for example, contemporary Leyland's. Have you assessed the wear in the white metal, the rotating insert and the parallel finger thingies? Quote Link to comment Share on other sites More sharing options...
mattinker Posted April 3, 2013 Share Posted April 3, 2013 (edited) Notice the big “silver” spots on the steering nut shell. They are of white metal and the whole of the big thread inside the shell is white metal. Goodness knows how this is done but there are “ silver spots” like this on the four sides of the shell. Presumably the white metal is poured in through these holes and the outside of the casing is then cleaned up afterwards. But how is the thread inside made? The threads would "smoked" with lamp black (acetylene torch burning without Oxygen, or a candle) to stop the white metal sticking. Dams would be made to stop the babbit leaking out and they would be poured in the same way as a smooth babbit bearing. This is a method that is sometimes used to refurbish worn half nuts on old lathes. Regards, Matthew Edited April 3, 2013 by mattinker Quote Link to comment Share on other sites More sharing options...
8_10 Brass Cleaner Posted April 3, 2013 Share Posted April 3, 2013 Notice the big “silver” spots on the steering nut shell. They are of white metal and the whole of the big thread inside the shell is white metal. Goodness knows how this is done but there are “ silver spots” like this on the four sides of the shell. Presumably the white metal is poured in through these holes and the outside of the casing is then cleaned up afterwards. But how is the thread inside made? The threads would "smoked" with lamp black (acetylene torch burning without Oxygen, or a candle) to stop the white metal sticking. Dams would be made to stop the babbit leaking out and they would be poured in the same way as a smooth babbit bearing. This is a method that is sometimes used to refurbish worn half nuts on old lathes. Regards, Matthew Alternatively, and a method I have used to make a new brake 'nut' for my steam roller which is also either an ACME thread or square thread is to bore the material out to the core diameter plus some clearance, work out the TPI, and grind up a tool to the thread profile, then fit it to an ajustable boring bar, taking out 2-3 thou of the 'thread' a time, turning it all backwards, and taking another cut etc untill you are there. I did a practice piece first and noted the settings before tackling the job. I have also seen special taps made for the purpose. I expect this is how Thornycroft will have done it. Quote Link to comment Share on other sites More sharing options...
GeePig Posted April 3, 2013 Share Posted April 3, 2013 ...I have also seen special taps made for the purpose. I expect this is how Thornycroft will have done it. Looking at the end of the white metal thread, it looks like there are some imprints from some kind of mould. Could they have used some kind of mould core during manufacture instead? Quote Link to comment Share on other sites More sharing options...
David Herbert Posted April 3, 2013 Share Posted April 3, 2013 Looks to me like the idea was that the nut was bound to wear so lets make it easy to remake it with primative facilities and no machining. Briliantly simple to just block up anywhere the white metal could run out and heat up the nut housing till the old thread melted, add a bit more to make up for the wear, let it cool, clean it and put it all back together. The one problem is stopping it sticking to the screw but if lamp black works, great. "My steering has too much slack in it, I must find a plumber!" David Quote Link to comment Share on other sites More sharing options...
Great War truck Posted April 3, 2013 Author Share Posted April 3, 2013 Steve put the steering worm in the press and at about eight tons, it gave a mighty bang and the bearing let go. It is nice to have the right tool for the job! Quote Link to comment Share on other sites More sharing options...
Hoseman Posted April 3, 2013 Share Posted April 3, 2013 use the same press to straighten it also! Quote Link to comment Share on other sites More sharing options...
Asciidv Posted April 4, 2013 Share Posted April 4, 2013 (edited) Well, I feel a bit more relaxed about keeping fire engine Breathing Apparatus in our dining room, knowing that Steve has a hydraulic press in his lounge! Barry. Edited April 4, 2013 by Asciidv Quote Link to comment Share on other sites More sharing options...
Minesweeper Posted April 4, 2013 Share Posted April 4, 2013 Sorry, Barry - that's not his lounge! You will have to think of another excuse to keep it there! Tony Quote Link to comment Share on other sites More sharing options...
Old Bill Posted April 4, 2013 Share Posted April 4, 2013 Well, I feel a bit more relaxed about keeping fire engine Breathing Apparatus in our dining room, knowing that Steve has a hydraulic press in his lounge! Barry. As Dad says, that is not my lounge. I keep my railway wagons in the lounge along with an air horn from a ship! The back-lash in the arms and bearings is negligible but in the white metal, it is about 1/16". I'm not sure whether I want to do anything with that for the moment. It depends on how brave I am feeling! I must admit that once you get more than 90° of slop at the wheel, keeping the machine on the road becomes a bit of a challenge. This will give us about 30° I think which is pretty borderline. I think I will make up all of the other bits first and then see how it feels. Do you think that the metal was simply poured in to fill the space between the worm and nut? Assuming it doesn't stick to the worm (smoking is a good idea) would not the wear in the middle of the worm prevent the nut from moving to the ends? Have any of you chaps ever done this as I am finding the thought of it a bit daunting! Straightening the worm will be fun too. it is straight between the bearings and runs OK. Therefore, I need to unbend it at the point where it bent in the first place. Currently, I am thinking of making a split block which I can use to clamp the worm in the vice at the bearing seat. Then I will heat it with oxy-acetylene (borrowed) and lean on it with a piece of pipe. Does anyone have any thoughts about this? More challenges! I will think about them further whilst making my piston pattern. Cheers! Steve :-) Quote Link to comment Share on other sites More sharing options...
David Herbert Posted April 4, 2013 Share Posted April 4, 2013 Steve, I think that I would try to exactly reverse the forces that bent the shaft in the first place: make a sleive/bending handle for the part of the shaft that was protected by being clamped inside the bit that drives it, and support it only where the bearings supported it. If you heat it it will only bend where the heat is, instead of gradually between the end of the sleive and the bearing. Fortunatly it is not very bent and is probably fairly soft steel so you are very unlikely to crack it. I think you will be suprised how easy it is to get it right. Mind you that press does look tempting... David Quote Link to comment Share on other sites More sharing options...
gritineye Posted April 4, 2013 Share Posted April 4, 2013 (edited) Just an idea you might like to consider, although I'm not sure weather you could live with the intrusion of plastic into your lorry, so feel free to dismiss this idea if it doesn't appeal to you, I won't mind :-D I have recently made a new Acme lead screw nut for my lathe using Acetal, the screw is a little worn in the middle, the Acetal is formed by heating and pressing it around the screw thread so it makes a perfect copy. Because the Acetal has a minute bit of flexibility it can tolerate the screw wear more that a metal nut would, and it will have zero backlash. It should be strong enough for purpose, Delrin/Acetal is used widely for similar applications in industry. Wear rate is said to be minimal. A link to some more info here: http://bbs.homeshopmachinist.net/threads/43645-Making-Acetal-leadscrew-nuts-the-easy-way?highlight=acetal Edited April 10, 2013 by gritineye De-cluttering thread Quote Link to comment Share on other sites More sharing options...
Hoseman Posted April 5, 2013 Share Posted April 5, 2013 This is a good idea and I can vouch for the wear properties of Acertal. They use it for slide guides on the masts of Fork Trucks and inside the boom of Hiab (grab) cranes etc. Only seem to wear if not lubricated tho. Quote Link to comment Share on other sites More sharing options...
GeePig Posted April 5, 2013 Share Posted April 5, 2013 As good as Acertal is, I am sure there are many of us waiting to see the team tackle the white metal approach... Quote Link to comment Share on other sites More sharing options...
mattinker Posted April 5, 2013 Share Posted April 5, 2013 Using the whitemetal approach, I would start y looking at the actual wear. If your good enough with the lath to take the wear out then your in. Have you done a file test on the thread? When making leadscrews for a lathe, you use an unworn part of the lead screw. It would be possible to turn up a dummy shaft. Youtube film on making babit. Is there a "split line? Babit is usually poured with shims toi to allow for adjustment. Regards, Matthew Quote Link to comment Share on other sites More sharing options...
Redherring Posted April 5, 2013 Share Posted April 5, 2013 Could you use Delrin to replace bronze bushings which weren't likely to get too hot i.e. > the 175 degrees C melting point e.g. brake pivots? Quote Link to comment Share on other sites More sharing options...
8_10 Brass Cleaner Posted April 5, 2013 Share Posted April 5, 2013 As Dad says, that is not my lounge. I keep my railway wagons in the lounge along with an air horn from a ship! The back-lash in the arms and bearings is negligible but in the white metal, it is about 1/16". I'm not sure whether I want to do anything with that for the moment. It depends on how brave I am feeling! I must admit that once you get more than 90° of slop at the wheel, keeping the machine on the road becomes a bit of a challenge. This will give us about 30° I think which is pretty borderline. I think I will make up all of the other bits first and then see how it feels. Do you think that the metal was simply poured in to fill the space between the worm and nut? Assuming it doesn't stick to the worm (smoking is a good idea) would not the wear in the middle of the worm prevent the nut from moving to the ends? Have any of you chaps ever done this as I am finding the thought of it a bit daunting! Straightening the worm will be fun too. it is straight between the bearings and runs OK. Therefore, I need to unbend it at the point where it bent in the first place. Currently, I am thinking of making a split block which I can use to clamp the worm in the vice at the bearing seat. Then I will heat it with oxy-acetylene (borrowed) and lean on it with a piece of pipe. Does anyone have any thoughts about this? More challenges! I will think about them further whilst making my piston pattern. Cheers! Steve :-) Steve, before trying remetalling using the male thread as the pattern I would have a look at the male, if it is worn anywhere (and I would expect it to be so in the middle), then if you did cast it, you wouldn't be able to unscrew it even if it hadnt stuck to the metal. The boring bar method I described does work, the clearance and accuracy depends on the machinist! I get the impression you and your dad are pretty good. I would certainly try to straighten the shaft, but check the harndess of the material before heating it to make sure you do not loose any temper with heating. I would be tempted to make a clamp that holts the bearings true, whilst also giving support to the worm, then having a go with your press cold. Once it is within 20thou or so, you could easily clock it up to find the new centre and turn the shaft down round, or grind if it is hard. (A bench grinder on the toolpost is ace if it is not your lathe!). I cant see a little bit of lost section will hurt. The other option is to butter up the bent side of the shaft with weld oversize then turn true. Quote Link to comment Share on other sites More sharing options...
hbtoday98 Posted April 8, 2013 Share Posted April 8, 2013 (edited) Hi Steve I would use two vee blocks and line them with a bronze bush cut in half and I would use a fly press screw type then cheak it between centres in the lathe. if you had an old lath you could split a bush to hold it where it is bent and tap the end true in an old chuck with a large hammer and a brass drift. running the white metal ,smoke the shaft and clay round the holes, tin the housing with solder a jig to hold it in the centre . regards Mal Edited April 8, 2013 by hbtoday98 add mor words Quote Link to comment Share on other sites More sharing options...
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