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| arnoldb:
Good going Nick I like your write-up - good couple of bits in there put a smile on my dial :thumbup: Cheers, Arnold |
| NickG:
Cheers guys, thanks for the support. Bogs, I usually use the soft fuel type tubing too, didn't think of it tearing, I was trying to make it so it wouldn't come off. May need to round those off with a file. I think i've made the taper too steep anyway to be honest. Well I should be telling you about what bit I made today. Originally, I was going to get some time in the workshop today during the day, the wife and kids were supposed to be going to meet up with the mother in law on their own. But this morning she started moaning and asking me to go too, I wasn't going to but thought that would come back to bite me, so I did! I was supposed to get a bit of 'shop time' when we returned but we decided that seeing as it was such nice weather, we'd have a bbq. This meant I was in the workshop but was fixing the bbq! :bang: It's very fragile cast iron and my son kept knockin it over in the old house. He'd snapped one of the brackets off for the thing you rest the grill on. So I had to cut a bit off that, drill and tap 1BA and add a little bracket of my own. I found a bit with 2 holes drilled in the right place from an old project and even a csk screw with it! Just shows never to chuck stuff out! :lol: I think this material was ali bronze, the colour is sort of, well, somewhere between aluminium and bronze, like a very pale shade of brass. Will take a pic later. I think I might even give the crankshaft a go later. I just remembered I have some steel much nearer the size, so getting a sweat on cutting that 1 1/4" chromium steel could have been for nothing! Although this other stuff has previously been forged so it might be a bit tough ... when it's machined on the cnc's at work it squeels like mad! :dremel: Hopefully will update you all later. NIck |
| NickG:
Right, Back onto this ... i've missed two nights installations as had a bit of a nightmare over the last couple of days, well not as such, just things didn't really go to plan. It seems there's been a hive of activity on the forum, I almost couldn't find my thread after replying to all the new / updated stuff! Looks like it's going well. I think Bogs thread a couple of months ago really kicked things into life. On Sat night I started on the crankshaft. Didn't get in the garage until 10pm, and didn't get out until 2am - hence no write up! The crankshaft didn't really pose too many problems, just took a lot longer than I thought. There was a lot of material to remove. Luckily I found this whacking great tool that was probably sharpened by my grandad god knows how many years ago. But because of that, it worked well! The swarf was a bit scary though, didn't really like this task. The thing started to shape up, I was taking pretty large cuts, probably around 1/8" at first but ended up taking 10 and 5 thou cuts as the diameter reduced. I thought I'd left it a couple of thou oversize but did a test fit in the bearing, at which point it slid merrily in. Probably marginally looser fit than I would have liked but once it's got a film of oil in there it's good, I want as little friction as possible really. As long as the flywheel doesn't wobble and I don't think it will. I later found out (when making a different component) that the problem was my cheap digi verniers. There is some error between the internal measuring bit and the external. I should use the starret ones my grandad gave me, they'll be a damn sight more accurate, just so fiddley to use and hard to see. Maybe I need to get another pair of digi ones as they are so convenient. Anyway, marginally happy with that so part off a couple of thou over, I like taking a facing cut after to ensure better finish, get to spot on length and to get rid of the pip. Found a bit of aluminium for the split bush...I said I'd do it this way instead of messing around with the 4 jaw. I'm not experienced enough with that yet and it would have taken me hours. Face to length Mark where to drill hole: I missed the pic of drilling but did it in the mill with a V block to keep it vertical. More trusty hacksawing, I didn't go right through, just left a couple of mm holding it together - glad I did that or it would have been fiddley. Crankshaft was a nice tight fit in bush: In the lathe ready for the offset turning. Note different cutting tool below, I managed to mess up that big one by trying to sharpen it! Don't know what it was but I put a steeper rake angle on it ... normaly about 20 deg for steel, where as before it was pretty flat. The tool below is the one I use for brass so only a couple of degrees rake angle, this forged steel likes that for some reason, maybe more rigid? Finished crankshaft. It just took ages, I didn't like turning along the spindle axis so I did it by taking facing cuts across the piece until it left a pin of about 3/16" dia, then took the pin down to size. It still took a long time but there wasn't all that chatter etc. Pretty pleased with it, although I can see that part of the disc is thicker, it won't affect performance as it's on the back face, not sure why though, must have got the hole in the bush wonky somehow. I did the same thing on my hot air engine and that was straight in the 4 jaw though ... not sure why! Assembled with rest of engine: I'll post last nights component as another reply as this may crash! NIck |
| raynerd:
I can`t wait to see this one running, it is looking great!! Chris |
| NickG:
:jaw: Brass turning nicely with that same tool as the crank! Took a big enough cut to get past the hex bit ... no problem. Lot of material to come off here too ... had to double the longitudinal feed speed otherwise I'd still have been there! I must be getting lazy, don't like turning the handwheel now! All going pretty well, couple of finishing cuts on the rod. The middle was to be wasted down further still. Started parting off, then filed the radius in situe. A test fit on the cylinder resulted in lots of swearing as it was already quite a bit undersize ... good rattling fit which wouldn't have worked. I put this down to getting different measurements between the internal and external jaws of my digi caliper .. piece of cheap cr@p! 'Buy cheap, buy twice' as someone always said to me at work ... not always the case, but in this case buy cheap, make twice, buy twice! :lol: actually, don't know whether to :lol: or :( ! So: No, I didn't do that in my temper, although I felt like it :bang: ! I had a cunning plan, it was a good job I stopped there, I could turn that down to rod size and part off a bit further along then cut a thread on the end, make a disc from the remaining bit, tap it to suit and screw em together. By this time it was about 11:45 ... again, hence no post last night! Disc drilled & tapped, parting off. Rod in collet chuck again ready to turn down and thread end. Disc screwed on, faced to length and profiled with needle file. This time checking fit in cylinder. It's still not spot on though, very easy to go a tincy bit too far with the file. Missed the step of drilling the hole in, the pin was quite a tight fit in the big end but waggled it about a bit with some oil and it's loosened off. Still might be a tad tight, no it should be ok, spins quite freely. The good news is, when I blow into the cylinder it gives a decent power stroke, but on the exaust stroke I can feel a bit of a power stroke too if you know what I mean. I mentioned this before, it was my fear that the piston doesn't rock sufficiently to vent the air pressure. I have a 4" dia cast flywheel which just happens to have the right bore, so I tried that ... i could get it to turn over a few times on lung power until I ran out of puff. So, I think it will run, at certain pressures, but I think it's a marginal design. I might have to experiment a bit with the flywheel, the one I've designed might not have the inertia required to counter act pressure forces on the piston. Also, the best configuration to run these in is probably vertically with the power stroke upwards. Then you also have gravity helping on the exhaust stroke. Will have to see. I want to do the 2 pedestals next then the wooden base, so when I've done the flywheel it is properly finished and ready to run! This should, all being well, be Sunday night. I'm away in South wales for the next couple of days so the plan is Thurs night: Pedestals Fri Night: Base, Sat & Sun night, Flywheel, Polish, Assemble, Run! Nick |
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