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Post by Roger on Aug 28, 2020 22:43:51 GMT
Hi yeah I used the worm/wheel setup I ended up getting a bigger servo so I could tighten up the worm into the gear. I have noticed that closed loop stepper servo systems are getting much cheaper so that would be an excellent way to do it if you were using steppers. Definitely think you have the right idea Roger going with direct drive, much better if you have the torque in your drive system. Thanks for the reminder Doug, I thought that was how you'd done it. Closed loop is definitely preferable, and the AC Servo has a lot of torque, so I'm confident it will all work ok. I've been fleshing out the drive mount as best I can without the dividing head being here. It looks like it's being shipped though, so hopefully it will be here soon so I can model it.
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Post by David on Aug 28, 2020 23:36:23 GMT
The ball is being held up to the seat on the upper part of the injector by the plunger, there's no seal against the plunger. Yes, I get that. But I'm wondering if you could just do away with the ball and have the plunger with an o-ring around it forming the seal. That would mean you could make that part shorter by the dia of the ball. It means you need a way for the water to get around the head of the plunger though. I've been thinking about this scheme for non-return valves recently after seeing Chris Tolhurst use it in G1 to make small and reliable non-return valves. Plus, the injectors we buy down here use this scheme. The plunger/o-ring assembly is in the usual place on the top.
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Post by KennLindeman on Aug 29, 2020 5:35:45 GMT
Hi Roger been following your build for couple years like it seems and love your ideas and the way you have tackle this project. I love steam but the knowledge of understanding needs more input. I am looking forward to following this injector project of yours as this is a area of knowledge I would like to improve on. Great work so far with you engine and looking forward to see it running soon Ken
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Post by Roger on Aug 29, 2020 8:04:20 GMT
The ball is being held up to the seat on the upper part of the injector by the plunger, there's no seal against the plunger. Yes, I get that. But I'm wondering if you could just do away with the ball and have the plunger with an o-ring around it forming the seal. That would mean you could make that part shorter by the dia of the ball. It means you need a way for the water to get around the head of the plunger though. I've been thinking about this scheme for non-return valves recently after seeing Chris Tolhurst use it in G1 to make small and reliable non-return valves. Plus, the injectors we buy down here use this scheme. The plunger/o-ring assembly is in the usual place on the top. Ah, I see what you mean now. The answer is yes, I think that would be a viable solution. Whether it would be a better one is debatable. I do like the hard seat and a ceramic ball for the valve element if that will work.
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Post by Roger on Aug 29, 2020 8:08:04 GMT
Hi Roger been following your build for couple years like it seems and love your ideas and the way you have tackle this project. I love steam but the knowledge of understanding needs more input. I am looking forward to following this injector project of yours as this is a area of knowledge I would like to improve on. Great work so far with you engine and looking forward to see it running soon Ken Hi Ken, It's good to hear from you, I hope you're keeping safe and well. A while back I started a thread dedicated to injector design and how they work in which I add my musings about possible changes to their design. I don't know if you saw that, but here's a link to it in case it's of interest. Roger
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Post by 92220 on Aug 29, 2020 8:12:36 GMT
Hi Roger.
It's an interesting idea, to use a belt drive for your dividing head, but you will have to retain the locking mechanism to eliminate movement due to stretch in the belt while cutting, and not rely on the belt drive to hold the workpiece tight. Even toothed belts have some degree of stretch, even if it is only a few thou. You work to microns and I can't see how a belt drive could allow you to work to that close tolerance. Will you just lock it mechanically like the original dividing head lock?
Bob.
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Post by Roger on Aug 29, 2020 8:48:01 GMT
Hi Roger. It's an interesting idea, to use a belt drive for your dividing head, but you will have to retain the locking mechanism to eliminate movement due to stretch in the belt while cutting, and not rely on the belt drive to hold the workpiece tight. Even toothed belts have some degree of stretch, even if it is only a few thou. You work to microns and I can't see how a belt drive could allow you to work to that close tolerance. Will you just lock it mechanically like the original dividing head lock? Bob. Hi Bob, I don't think the belt stretch issue is as much of a problem as you think, especially if it's a wide one. The AC Servo has a lot of torque, and with about 1:6 ratio that's massive at the dividing head. If you look at some of the offerings on eBay, they're using small components and stepper motors in this way, and they seem to take useful loads even with those. I bought an AC Servo with an integral 24DC mechanical brake, so it's locked when the drive isn't energised. I might contrive a way to use that so it can be locked while in use, but I honestly don't think it will be necessary. I plan on removing the mechanical locks altogether.
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Post by 92220 on Aug 29, 2020 9:58:03 GMT
Hi Roger.
I hadn't realised there was a reduction involved. In that case, that would make all the difference as it would reduce the 'stretch' by the same ratio, so not a problem. Now makes sense. It's going to be quite a complex project, and a real mixture of mechanics and electronics (!), though I am sure you will achieve what you want. I will follow it with interest
Bob.
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Post by Roger on Aug 29, 2020 11:33:52 GMT
Hi Roger. I hadn't realised there was a reduction involved. In that case, that would make all the difference as it would reduce the 'stretch' by the same ratio, so not a problem. Now makes sense. It's going to be quite a complex project, and a real mixture of mechanics and electronics (!), though I am sure you will achieve what you want. I will follow it with interest Bob. Hi Bob, Here's a teaser of what might be coming on the Servo mount. I've just eyeballed the photo on the web site and thought this arrangement might work. So picture this sticking out the side of the dividing head with the axis of the motor parallel to the chuck. The motor will be standing out in the same direction as the chuck, but far enough away that it doesn't foul the spindle. The two blue cylinders are each a pair of needle roller bearings running on Shoulder Bolts. The belt runs on the inside of those and then goes round the body of the dividing head. The motor is mounted via slotted holes in the mounting plate so the tension can be adjusted. As shown, the belt is 25mm wide, but that might be too wide to fit. I'll fit the biggest one I can. The pulley around the dividing head would be horrendously expensive, so I'll probably make that one. It's the sort of job you need a 4th axis for! Possible motor mount by Roger Froud, on Flickr
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Post by andyhigham on Aug 29, 2020 11:38:22 GMT
Where did you get the nice quick release fittings from, and what size are they? Hi Ed, If you search eBay for 'Rectus type 21' you'll find loads of them. Mine came from Context Pneumatics, but you can also get them from any mainstream supplier. They're designed for water systems, but they work just as well for pneumatics. I use Context Pneumatics. They are based just across the park from my front door www.contextpneumatics-catalogue.co.uk/default.aspx
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Post by 92220 on Aug 29, 2020 16:46:22 GMT
Hi Roger.
It's going to be a very interesting, and challenging project, but it should work out. Will this mount on the front or back of the casting? If it is on the front, behind the chuck, that might allow you to make use of the rotating facility to enable you to use it at any angle between 0 and 90 degrees, though I suppose you may not need the facility with CNC. I don't know enough about CNC to guess if it is even possible.
Bob.
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Post by Roger on Aug 29, 2020 18:36:35 GMT
Hi Roger. It's going to be a very interesting, and challenging project, but it should work out. Will this mount on the front or back of the casting? If it is on the front, behind the chuck, that might allow you to make use of the rotating facility to enable you to use it at any angle between 0 and 90 degrees, though I suppose you may not need the facility with CNC. I don't know enough about CNC to guess if it is even possible. Bob. Hi Bob, The idea is to be able to use it at any angle. It's bolted to either face, ie the one with the clamping levers or the dividing plates. It will be used such that the motor is sticking out to the front of the machine, well clear of the chuck and the spindle. When the tilt is adjusted, the bracket goes with the body, so everything is still in tension. The motor sticks out in the same direction as the chuck so that it doesn't hit the table. You can't mount it the other way round because it would hit the table. As you say, you don't need the rotary table to be vertical to be used as a rotary table, since the CNC can do all of those operations. However, when you're performing multiple operations on the workpiece on both sides and the end, you need to be able to get it vertical to access the end. It's also handy to be able to orientate the rotary table to suit the way the path has been programmed. I think this is going to be a really useful piece of kit, so it's worth designing it to do as many things as possible.
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Post by 92220 on Aug 30, 2020 7:46:38 GMT
Hi Roger.
Yes. That does sound really useful! I hope it works out as expected. It certainly looks as if you have it well sewn up!!
Bob.
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Post by doubletop on Aug 30, 2020 7:58:28 GMT
Thanks for clearing that up Alan, I'll use the Head Lamp drawing from 1946 then for mine. It looks like there was some variation though. I took some pictures of the one that's in the museum at Kidderminster and it's constructed slightly differently. At least I've got the Works Drawing to go from, that makes life a lot easier. This part of the thread got me to contact Roger to see if he had the drawing 123877, he had more than that, having modelled the lamp in CAD, to the level of detail expected from Roger. I've been tinkering on my 3D printer over the weekend. Attempt #7 is getting close. Thanks Roger Pete
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Post by Roger on Aug 30, 2020 9:08:18 GMT
Thanks for clearing that up Alan, I'll use the Head Lamp drawing from 1946 then for mine. It looks like there was some variation though. I took some pictures of the one that's in the museum at Kidderminster and it's constructed slightly differently. At least I've got the Works Drawing to go from, that makes life a lot easier. This part of the thread got me to contact Roger to see if he had the drawing 123877, he had more than that, having modelled the lamp in CAD, to the level of detail expected from Roger. I've been tinkering on my 3D printer over the weekend. Attempt #7 is getting close. Thanks Roger Pete Hi Pete, I'm glad that was of some use to you, they've come out really well, especially considering how detailed and fine the model is.
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Post by uuu on Aug 30, 2020 13:46:24 GMT
Very good looking. I happened to visit the Pump House today, so took a quick shot of John's 4th axis (knowing that it's not what Roger is aiming for): FourthAxis by Wilf, on Flickr Wilf
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Post by Roger on Aug 30, 2020 21:20:59 GMT
Very good looking. I happened to visit the Pump House today, so took a quick shot of John's 4th axis (knowing that it's not what Roger is aiming for): FourthAxis by Wilf, on Flickr Wilf Hi Wilf, That's a neat little unit, thanks for sharing. I'm sure it's plenty good enough for most jobs. I presume you can set it up on its back too.
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Post by uuu on Aug 31, 2020 6:29:23 GMT
I suppose you can, although I've only seen it used stood up.
Wilf
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Post by Roger on Aug 31, 2020 6:49:50 GMT
I suppose you can, although I've only seen it used stood up. Wilf In reality, turning it through 90 degrees is only useful for retaining the angular position of the part if you're doing operations on the end as well as the side. You've seen me do that quite a lot. Obviously, if you have CNC then you don't need the table to turn when it's in that orientation.
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Post by uuu on Aug 31, 2020 6:59:52 GMT
Oh no! Now I can see you devising a way to motorise the top-to-side change.
Wilf
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