Author Topic: NickG's Mine Engine  (Read 8570 times)

Offline NickG

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NickG's Mine Engine
« on: January 20, 2013, 09:27:41 AM »
Hi All,

Just thought I'd post some of the work I've done in the new year, unfortunately so far it's only in the 'virtual world' of CAD!

I've been studying and mulling over lots of drawings and my list of ME projects has changed and changed back many times.

I've been thinking about buying castings, then thought about doing one of Elmers engines from bar stock, then I considered doing my own design of a Corliss, then a beam engine from some French plans, then doing one of Stews engines as I know they look and run really well.

You get the picture, some might say this is just an excuse for not getting in the shop and getting on with something!  :slap: However, I think it's because there's either some machining process in there that I'm uncomfortable doing and the engineer in me thinks I could make that easier for me to make and maybe suit materials / sizes I know I have.

Anyway, at some point (not sure why) I settled on designing my own Mine or Table Engine. Anybody who has used CAD will know it's fairly easy to come up with beautiful works of art that are extremely difficult to make, so I try to design my components with manufacture in mind, using methods I know I can do. Try to reduce the number of components, no or little fabrication, standardise components and sizes. Unfortunately I picked an engine that has quite a few components! I also get a bit bored sometimes when embarking on a large project so I tend to design simple components. I've tried though to put a few frills on here and there but nothing complicated!

Before Jo starts talking about studs  :naughty:, the chances are (if I can be bothered) the steam chest and top cover will have studs and nuts rather than bolts - I just haven't got around to modelling them yet.

I've got enough 8ba nuts / washers but I think they might have 9ba heads and look too small here - is this normal? I think the 8ba bolts I got had 9ba heads too  :shrug:

Still quite a few parts to model yet, then all the working drawings to create so it could be a few weeks before I cut metal on this.

To give an idea of scale, the flywheel is 4" which it is largely based around  - I thought I'd use the RDG casting the wife got me for xmas, then I can't be accused of just leaving her xmas present on the shelf for years!

The cylinder is only 5/8" bore and 1.25" stroke despite looking like it should be bigger, this is due to the method of manufacture I've chosen.

One thing I've been struggling to make a decision on is the valve linkages  :-\. I've got an idea which I think I'll get cracking on as my sheet of A4 with scribbles on looks just like that now  :facepalm: Need to get them modelled to see if they fit with the rest of the design.

Any comments / improvements / criticism welcome!

Here is the progress so far:


Offline NickG

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Re: NickG's Mine Engine
« Reply #1 on: January 20, 2013, 09:41:12 AM »
One thing to ask already is, if I do use studs, how do people go about it? I thought 3/32 rod would be about the right size for 8ba - but I would need to open up the clearance holes a bit. If I used 3/32 rod, would I cut the threads straight onto the end or would it need turning down by 7 thou on each end prior to threading?

Or, for this, seeing as there will only be about 14 studs, could I simply buy 8ba studding - I know it's not as good etc but for this it would give the desired effect?

Thanks,

Nick

Offline Jo

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Re: NickG's Mine Engine
« Reply #2 on: January 20, 2013, 10:12:50 AM »
Nick,

When you make studs don't use anything less than 1/8" it flexes too much, then turn it down 8). Looking at the size of your model I would opt for 10BA studs & nuts not 8BA with 9BA nuts. You will struggle to get spanners and nut runners the right size. 10BA is 3mm ish (2.97mm) so you can get then anywhere.

Depending on the lengths you are talking about having the plain piece in the centre may be too much like hard work (I gave up on my 12BA studs :ShakeHead:)

Jo
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Offline stevehuckss396

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Re: NickG's Mine Engine
« Reply #3 on: January 20, 2013, 10:20:09 AM »
One thing to ask already is, if I do use studs, how do people go about it? I thought 3/32 rod would be about the right size for 8ba - but I would need to open up the clearance holes a bit. If I used 3/32 rod, would I cut the threads straight onto the end or would it need turning down by 7 thou on each end prior to threading?

Or, for this, seeing as there will only be about 14 studs, could I simply buy 8ba studding - I know it's not as good etc but for this it would give the desired effect?

Thanks,

Nick

The correct rod is available. If it's worth it to you you can get it.

http://www.ba-bolts.co.uk/threadedbar.html


8 BA is almost exactly the same size as #2-56. That is also available in rod for sure because I have a foot or so out in the shop. The 2 are so close I doubt anybody could tell.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline NickG

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NickG's Mine Engine
« Reply #4 on: January 20, 2013, 10:54:55 AM »
Hi Jo, thanks for that, so you turn all yours down from 1/8th? argh! this stud business sounds harder than i thought! thats why i thought could you just put 8ba straight onto the 3/32 rod without touching in lathe? its 7 thou oversize but guess thats quite a lot when talking about this scale. when I put 10ba on, it looked too small to me.  The size ive drawn us 8ba but when ive looked at the 9ba headed ones i on my smaller models i think they look too small fir this (by my standards) larger one. I was debating whether to use 6ba! The spanners arent a prob, my grandad left me a box of them that have 0-12 and 0-10 in box spanners! 10 maybe more realistic scale wise if that's what you mean? There prob should be a lot more than 6 too I guess? I don't like tapping that small though, let alone 12ba! Using 10 there would mean I couldn't use any smaller elsewhere on the model.

Thanks for the link Steve will have a look. I don't have any taps / dies the sizes you mentioned but I do have a set if small metric ones so will look into that too.


Offline Jo

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Re: NickG's Mine Engine
« Reply #5 on: January 20, 2013, 11:02:42 AM »
Ok so go for 8BA they are easy to make, but stick with the 8BA nuts.

The other advantage of using 1/8" (or 3mm) is it is cheaper than the 3/32".

Jo
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Offline ths

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NickG's Mine Engine
« Reply #6 on: January 20, 2013, 11:39:21 AM »
Hi Nick,

I think you'll find that 7BA is a fairly natural fit for 3/32". That's about 2.5mm, 8BA is 2.2mm (+/-)

Cheers, Hugh.

Offline NickG

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NickG's Mine Engine
« Reply #7 on: January 20, 2013, 12:16:46 PM »
Ah really - didn't know that Jo, thanks. Ok will go and check the size of my nuts so to speak and get new if necessary. At least nuts are a lot cheaper than bolts.

Hugh, thanks for that, do you think 7ba are harder to get? I'll have a look on computer later, too fiddley on the phone!

Offline ths

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NickG's Mine Engine
« Reply #8 on: January 20, 2013, 12:30:17 PM »
I think Jo is referring to nut size, which really sets the scale of the whole thing, and is in the end a bit more relevant to the visual effect. 7BA and 5BA do screw very nicely on to the stock imperial sizes of 3/32" and1/8" respectively. Probably one of the reasons they have always been popular in model engineering, even though the odd numbered BA sizes have been non-standard for some time (I have read somewhere).

Hugh

Offline sbwhart

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Re: NickG's Mine Engine
« Reply #9 on: January 20, 2013, 01:36:48 PM »
looking good Nick

As you know I tend to stick with meteric threads, M3, M2.5 and M2 the taps and dies are cheep to buy, and being industrial standard you can get the nuts and washers by the 1000 for less than a ?10, and you can get lengths of pre threaded studding easily through ebay.

As for the valve linkage keep it as simple as you can eccentric/eccentric arm up to the entabulator, then bell cranks, to lifting rods,to cross arm, connected to the valve ro.

The cold weather has driven me onto the CAD board, started on this see attachemt

Its just a simple mill engine but I wanted to design something that could be made just using a lathe and a drill, it uses a piston valve and standard stock sizes.

Stew
« Last Edit: January 20, 2013, 01:41:54 PM by sbwhart »
A little bit of clearance never got in the way

Offline NickG

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NickG's Mine Engine
« Reply #10 on: January 20, 2013, 01:55:25 PM »
That's good to know Hugh. Well just been to check / measure my nuts and bolts. I've got a few of those 8ba ones but the heads def look too small for this. They measure 0.125" across flats where as normal 8ba nuts measure at 0.152 - that's how I've drawn it, looks ok I think? And I've got plenty of nuts and washers for this and a couple more projects!

My 10ba ones measure at 0.0975, not sure whether that is standard. Then I've got 4ba which are 0.214 and 6ba with smaller heads that measure 0.173. Will have to check the 4ba and 10 BA.

Cheers Stew- I got a set of small and large metric taps and dies last Xmas and you saying that's made me realise I've hardly used them yet - except to repair a screw from a wall socket 2.5mm I think! You're right about the price too , my 10ba were 3.85 for 25 I think!! I'll have to look for some metric ones. Some of the grub screws and csk socket screws you can't see may be metric as I've got those.

I'm logging onto the computer as we speak to see your engine.


Offline NickG

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Re: NickG's Mine Engine
« Reply #11 on: January 20, 2013, 02:12:56 PM »
It looks smart that Stew, I was tempted to do a mill engine, still like the simplicity of them but keep adding projects to my list  :hammerbash:

How does the piston valve exhaust? Out of each end of the valve bore?

Have you started a post yet? I'll be watching out for it  :ThumbsUp:

I have a mental picture of how it will look, as you say eccentric up to a rocker shaft with bell cranks, rods and cross arm. It's just how I will do the links - currently thinking a  fork on the end of the eccentric rod then an arm coming off the rocking shaft and two forks between the bearings on that shaft, up to the valve cross arm.

I think I want to do it out of 1/16" and 3/32" rod with little brass bearing bits loctited to the ends, or should I mill them from solid or could they even just be little strips of flat 1/16" thick with holes drilled in them? Think round rods will look better - milled ones in a size I could manage may look to chunky to go with the rest of the engine.

Attached is PDF version so people can zoom in/ twirl it around etc.


Offline Captain Jerry

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Re: NickG's Mine Engine
« Reply #12 on: January 20, 2013, 02:14:18 PM »
Nick

It looks good to me.  I agree with your design philosophy completely.  I try not to design the un-make-able but sometimes it happens.  I like your choice of bore and stroke.  Its big enough to work with and small enough to run with a small compressor.

Jerry
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There are things that you can do and some things you can't do. Don't worry about it. try it anyway.

Offline NickG

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Re: NickG's Mine Engine
« Reply #13 on: January 20, 2013, 02:50:22 PM »
Thanks Jerry. Yeah, it's difficult sometimes - I've ended up with a bit of a dodgy cut out in the cyl and top cover which looks like i've made a mistake but it makes other things easier so I'll accept it.

The bore / stroke were picked for those reasons and also so there's enough meat on the cylinder to just start with 1 1/4" round, mill the flat for the valve face and have straight drilled holes and ports rather than any angled holes.

I've just measured the flywheel casting and I'll be lucky to get 3.875" out of it  :wallbang: so I'll have to adjust the model, it still should look just about OK, I hope!   :facepalm:


Offline sbwhart

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Re: NickG's Mine Engine
« Reply #14 on: January 20, 2013, 04:31:44 PM »
It looks smart that Stew, I was tempted to do a mill engine, still like the simplicity of them but keep adding projects to my list  :hammerbash:

How does the piston valve exhaust? Out of each end of the valve bore?

It exhaust at each end, all you need for the ports is to be able to drill resonably accurate

Have you started a post yet? I'll be watching out for it  :ThumbsUp:

I wont be posting for some time I'm intent on getting my loco on the rails, I also intend to draw up a vertical and a grasshopper all using the same common cylinder and hopfully being capable of being made only using a lathe and  a drill

I have a mental picture of how it will look, as you say eccentric up to a rocker shaft with bell cranks, rods and cross arm. It's just how I will do the links - currently thinking a  fork on the end of the eccentric rod then an arm coming off the rocking shaft and two forks between the bearings on that shaft, up to the valve cross arm.

I think I want to do it out of 1/16" and 3/32" rod with little brass bearing bits loctited to the ends, or should I mill them from solid or could they even just be little strips of flat 1/16" thick with holes drilled in them? Think round rods will look better - milled ones in a size I could manage may look to chunky to go with the rest of the engine.

Round rods with couplings is the easyest way to go

Attached is PDF version so people can zoom in/ twirl it around etc.

Stew
A little bit of clearance never got in the way

 

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