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Post by keith1500 on Apr 10, 2020 14:17:05 GMT
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stevep
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Post by stevep on Apr 10, 2020 14:27:18 GMT
Hi Roger, Whoooppss...I just mis-read that for Spinal Tap !!....... Somehow mate I didn't think that was quite you. eh ??........LoL !! ( en.wikipedia.org/wiki/Spinal_Tap_(band) ) For hand tapping I think Phos. Bronze, Copper and Aluminium are the ones most likely to give the embryo tyro a spot of bother....mainly due to "stiction", especially if not lubricated....Old text books used to quote Paraffin or Tallow at one time but nowadays these can be in short supply....I've found WD40 ( or cheaper equivalents ) to give good results, especially on my mini-lathe.. Just be careful when tapping a copper boiler for stays. I remember, many years ago, one of the members in the Basingstoke club was helping another member with the silver soldering of his boiler. When it got to the stays, he couldn't get the solder to flow. When asked, the builder explained that he had used 3-in-1 oil for the tapping process. Apparently, it took a lot of cleaning before satisfactory joints could be made.
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Post by andyhigham on Apr 10, 2020 14:37:22 GMT
I have seen fluteless taps for copper. They push the metal instead of cutting it so are less likely to tear the threads. They are similar in principle to a "taptite screw"
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jasonb
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Post by jasonb on Apr 10, 2020 15:38:29 GMT
You are not missing anything the slot is too narrow. You will actually have to reduce the dia by at least 3.4mm to clear . Max room needed throw 7mm plus half eccentric strap dia 18mm = 25mm and as per your calculations you only have 23.3mm clearance so that needs to come off all round therefore 3.4mm off dia. Probably easier to enlarge the slot as you will not have so much thread depth unless you reduce the diameter on the rotary table to leave a thicker section where the rod screws in. This is one of the problems with Julius' drawings they are just computer models and have not been built, he also has some dubious methods of getting things to rotate when the linkage geometry would cause binding! simplified sketch
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Post by keith1500 on Apr 10, 2020 16:16:16 GMT
Hi Jason,
Many thanks indeed for doing that for me. Glad I haven’t overlooked something simple.
I am two minds which way to do this. I think modifying the slot would look quite good and is doable for me, though I would have to sharpen up my filing skills!
I have thought as per your suggestion to reduce the brass ring to the same diameter as the eccentric and leave a thicker piece for the rod. I haven’t a rotary table so that would be done by turning down the ring and then silver soldering the bit on. Less work and easy to achieve.
Hmm decision decisions.....
And yes I noted a few potential problems with bits rubbing etc which is why I tweaked a few dimensions, namely the crank and the con rod.
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Post by coniston on Apr 10, 2020 21:13:34 GMT
Hi Keith, if you don't have a rotary table, then you can clamp the eccentric strap to a plate with a pivot in the middle, also clamped with some resistance. attach a suitable bar to the moving plate to act as a handle and rotate slowly against the milling cutter. This is a method Martin Evans, and probably LBSC advocated for rounding coupling and connecting rod ends. I can confirm this does work as that is the method I used for coupling rods before I had a rotary table. Just be careful not to climb mill and keep the cuts light. Or you could just sliver solder the bit on after.
Chris D
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Post by delaplume on Apr 10, 2020 22:19:39 GMT
Hi Roger, Whoooppss...I just mis-read that for Spinal Tap !!....... Somehow mate I didn't think that was quite you. eh ??........LoL !! ( en.wikipedia.org/wiki/Spinal_Tap_(band) ) For hand tapping I think Phos. Bronze, Copper and Aluminium are the ones most likely to give the embryo tyro a spot of bother....mainly due to "stiction", especially if not lubricated....Old text books used to quote Paraffin or Tallow at one time but nowadays these can be in short supply....I've found WD40 ( or cheaper equivalents ) to give good results, especially on my mini-lathe.. Just be careful when tapping a copper boiler for stays. I remember, many years ago, one of the members in the Basingstoke club was helping another member with the silver soldering of his boiler. When it got to the stays, he couldn't get the solder to flow. When asked, the builder explained that he had used 3-in-1 oil for the tapping process. Apparently, it took a lot of cleaning before satisfactory joints could be made. Hi stevep I think the fault lay in the boiler not being cleaning properly rather than the use of 3-in-1 oil as such......... in all case the boiler should be pickled and washed prior to each soldering event.... These days we don't tap the boiler to take a stay... Here is a 30 year old Simplex boiler that I am preparing for Hydraulic test prior to sale.....Notice that all stays are rod type, especially the crown ones which replaced that original girder arrangement.........All are plain drilled holes with a slight countersink to give a viable fillet...It's an early one from the then Bishop - Ellis Company..... Sorry Keith---back to your engine -----------> ---------->
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Post by keith1500 on Apr 14, 2020 21:07:06 GMT
To solve the eccentric problem I chose to opened up the slot in the base. The slot has been made longer by 2.5mm either side to allow the brass ring to pass through. The width is governed by the brass base to the column, hence the step in the corner. Hopefully, if I have the calculations right the eccentric will pass through with 0.5mm clearance either side. The brass ring of the eccentric should now clear without problem. Such is my confidence that I sprayed it up green ! Simple single cylinder steam engine by GL5Keith1500, on Flickr
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Post by keith1500 on Apr 15, 2020 21:46:52 GMT
The eccentric clears the base nicely. Simple single cylinder steam engine by GL5Keith1500, on Flickr Interesting and tricky bit of assembly. Kept me quiet most of this evening. The eccentric was set in the right place on the shaft using a feeler gauge to ensure it clears the brass block and the slot. The flywheel was fitted allowing 0.15mm end float, then the eccentric set to 20 degrees below the horizontal with the crank vertical. I am not sure that’s will give correct timing? It’s a simple steam engine and I was expecting the valve to be set 90 degrees to the crank? The long rod is being used to ensure correct alignment of pivot. Simple single cylinder steam engine by GL5Keith1500, on Flickr The project to date. Mimicking the picture on the drawing. Simple single cylinder steam engine by GL5Keith1500, on Flickr
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jasonb
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Post by jasonb on Apr 16, 2020 6:19:02 GMT
20-30deg will be OK, nearer 20 works better on air and 30 if running on steam as both give smoother running. I would usually say set it to 4 or 8 o'clock if the crank pin is at 12 depending on direction you want it to run. It's looking good.
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Post by keith1500 on Apr 16, 2020 9:23:56 GMT
20-30deg will be OK, nearer 20 works better on air and 30 if running on steam as both give smoother running. I would usually say set it to 4 or 8 o'clock if the crank pin is at 12 depending on direction you want it to run. It's looking good. Thanks for the info. It looks like the eccentric is shown in the wrong position for the direction which is based on the red arrows on the flywheel . I have now reset it and the events look a bit more logical. I’ll now work towards getting it running on air then finish it off to run on steam.
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jasonb
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Post by jasonb on Apr 16, 2020 12:28:04 GMT
Yes it looks like he has his "x angle" in the wrong place that should be 60-70degrees as the max throw of the valve should be 90deg plus the angle of advance (90 + 30 in your case)
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stevep
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Post by stevep on Apr 16, 2020 13:59:20 GMT
The crank would be at 90 degrees if the valve had no lead or lap - i.e. edge-on-edge with the ports.
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Post by keith1500 on Apr 20, 2020 12:17:00 GMT
Here is my cock up.... I have said before there’s something not right about my mill. Well it caught me again. Here I am making the cylinder cover. Turned the boss to fit the cylinder leaving plenty high enough to clock from. Clocked it in the mill using wobbler and centred the boss. From this point set out the holes. Clearly not centred as the centre drill has kissed the boss. Why on the last holes! If it had been the first I would have stopped the job. Simple single cylinder steam engine by GL5Keith1500, on Flickr
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uuu
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Post by uuu on Apr 20, 2020 14:27:34 GMT
Before jumping to blame your mill - have you checked the diameter of your wobbler tip? You seem to be a bit out in X and Y, so it would be a worthwhile first test.
Wilf
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jasonb
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Post by jasonb on Apr 20, 2020 15:16:07 GMT
Before jumping to blame your mill - have you checked the diameter of your wobbler tip? You seem to be a bit out in X and Y, so it would be a worthwhile first test. Wilf That's why it's best to touch either side and half the distance between as dia of end does not matter and you also get an average of two edges. Or stick a dti in the chuck and spin that round the spigot, co-axial ctr finder does the same thing but don't use mine that often as I can't be bothered to wind the head up that far.
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Post by Roger on Apr 20, 2020 15:33:30 GMT
If there's a diameter, and you're trying to set out the holes around it, I'd mount the clock to the spindle and run the clock around the outside of it.
My guess is that the column isn't vertical, and you're drilling the holes with the Z-axis as a different height. This is a problem on most milling machines, it's just a matter of how bad it is.
So picture this....
Imagine the spindle at the lowest position with the spindle not vertical to the Z-axis slide motion. Then imagine the spindle at the highest position. Unless the Z-axis slides precisely true to the axis of the spindle, the spindle centre line will now point at a different point on the job.
This is why it's important to tram the head, in both planes if possible. Sadly, I can only do it on one on mine. Having said that, this still doesn't guarantee that the spindle axis is coaxial to the Z-axis motion, but it's a good starting point.
On mine, I try to drill holes at as close to the same Z-axis height as possible. I get a better result if I put a centre drill in the collet chuck for example, rather than putting it in the drill chuck which forces me to move the Z-axis another 40-50mm higher.
I agree with Jason about the wobbler, I'd always touch both sides and halve it, you'll get a significantly more consistent result that's independent of the diameter of the wobbler tip and will also work if you touch both sides of a round or tapered part if you stay at the same height.
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Post by keith1500 on Apr 20, 2020 15:34:28 GMT
Before jumping to blame your mill - have you checked the diameter of your wobbler tip? You seem to be a bit out in X and Y, so it would be a worthwhile first test. Wilf That's why it's best to touch either side and half the distance between as dia of end does not matter and you also get an average of two edges. Or stick a dti in the chuck and spin that round the spigot, co-axial ctr finder does the same thing but don't use mine that often as I can't be bothered to wind the head up that far. It can not be the wobbler as I am doing as just that; touching both sides to get the centre. Plus I am being thorough by doing one axis then the other, then going to the centre and checking to the edge and I am not happy until I get very close results all around. That is all four values x axis plus and minus and y axis plus and minus I will clock some moments and double check the DRO. I suspect it’s cheapness is beginning to show.
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jasonb
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Post by jasonb on Apr 20, 2020 17:14:47 GMT
Make sure nothing has come loos such a the bracket holding the read head as that will have a similar effect to backlash
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Post by andyhigham on Apr 20, 2020 17:58:58 GMT
Are you using the dials on the machine or a DRO ? If you are using the dials everything has to be done in the same direction. If you have used the wobbler on both sides then you have used 2 directions on each axis
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