Author Topic: Stew's Simple Mill Engine  (Read 28508 times)

Offline NickG

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Re: Stew's Simple Mill Engine
« Reply #75 on: April 27, 2014, 01:46:27 PM »
Why is there always something that gets in the way?! I needed to clock in the vice and tighten it up on the milling table before I did the next operation as is last had the rotary table set up on it - need another milling machine Jo lol! Anyway, it was going surprisingly well, just by chance I got it square within 0.01mm or something, went to tighten it up and the tee but appeared to turn to mozzarella before my

Tried another tee nut and that was the same just felt like getting to between nipped / tight ish and just fell apart - last one was the same. Great, spent next couple of hours making a new one. On first inspection they appeared to be different failure modes:



But had a closer look later and realised what had happened. The stud didn't go to the bottom of the tee nut which meant it was trying to simply pull the rest of the nut away from the wider bottom but shearing it through its weakest point. This definitely wouldn't have happened had the stud gone right to the bottom. I still think they were made of cheese mind you but more like mature cheddar than mozzarella. This still doesn't really explain why it's been ok up to now (maybe fatigue?) and why the other side was and still is ok. Have sorted a new set if studs which go right to the bottom now though. The new nut isn't a proper tee just a flat bit if metal the right size without the top bit but this is much stronger stuff anyway, the thread will probably be the weaker point now but plenty strong enough.

With this sorted I clocked the vice back in.

Next job was to drill and tap the holes for the valve chest. Thought I'd do this by coordinates the old fashioned way counting the turns as no DRO!

 

Seemed to work pretty well, centre drilled first then went back to drill to depth then start the tap off in each hole. Didn't bother with taper tap in small hole like this as it'd prob just pull out. Could have done to grind the point off to get a few more threads but it's ok.



Looks like I'd drilled the ports in between doing this.

Finished tapping off by hand, Jo would say these 2mm taps are massive but small for me and easy to snap!



Back into the mill on its end to drill the ports from end of bores. There was 1mm of meat either side so not too bad. This went well, pretty easy with this straight port design over traditional angled ports. Good simple cylinder design.

Finally mills the 2mm deep pocket to allow steam / air through.



Completed cylinder except for mounting holes.




Offline NickG

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Re: Stew's Simple Mill Engine
« Reply #76 on: April 27, 2014, 01:49:55 PM »
1.5mm either side not 1mm!

Offline arnoldb

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Re: Stew's Simple Mill Engine
« Reply #77 on: May 01, 2014, 09:32:16 AM »
Good going Nick  :ThumbsUp:

Looks like those T-nuts were hardened but not tempered afterwards...

Kind regards, Arnold
Building an engine takes Patience, Planning, Preparation and Machining.
Procrastination is nearly the same, but it precludes machining.
Thus, an engine will only be built once the procrastination stops and the machining begins!

Offline NickG

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Re: Stew's Simple Mill Engine
« Reply #78 on: May 01, 2014, 06:50:30 PM »
Yeah could be Arnold, they had a structure I wouldn't have expected from normal drawn steel inside, looked more like a cracked casting! Chinese junk I think.

Offline NickG

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Re: Stew's Simple Mill Engine
« Reply #79 on: May 10, 2014, 08:35:34 PM »
Hi all, been burning the midnight oil in attempt to make some progress on this engine it seemed like a box with a few bits a couple of weeks ago and it seemed the finish line was miles away.  :headscratch:

Anyway, here are a few pics of progress  ;D

Forgot how convenient using the 4 Jaw was for making small components flat! This is bringing the valve chest Down to size.


Setting up for the offset bore - I centre drilled in the mill then set the centre mark running true using this technique - I was sceptical but it was pretty quick to get it running true within a couple of hundredths of a mm.


I didn't have any hex the right size for glands so thought I'd try something else new and try the rotary table on its side to drill tommy holes. Was planning on doing 6 but duh ... The jaw of the chuck was in the way on 3 of them so 3 it was! Collet chuck would be useful for this sort of thing but I'd need a 2mt one, beginning to think that would be quite useful actually.


This was making one side of the pivot for the valve / eccentric rod - I did this a little differently to stews, decided to make the valve rod shorter and not bother with the guide. It should be ok as it is a piston valve so mainly guides itself and it has the gland - I did that differently too, mine is just a guide as it is inside admission piston valve it isn't absolutely necessary. I can see why Stew did it with the guide though - good practice and the longer rod makes it much easier to set the timing and totally takes the criticality out of the length of the valve and eccentric rods.


No action shots of these parts but thought they came out ok! Not dimensionally perfect but something I could adjust for on assembly and all a nice fit.


Cast iron piston on its rod is hidden inside the cyl for a test fit - good finish and fit, no lapping or anything can,t be bothered with that molarky!


Back to the valve chest, finished off, cap and inlet made.


Pivot finished



Offline NickG

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Re: Stew's Simple Mill Engine
« Reply #80 on: May 10, 2014, 09:06:56 PM »
Was getting towards the home straight at this point thought id do the base then at least I could plonk all the bits on it for Harrogate.

Nothing to fear about the brown stuff if you just treat it like a bit of metal!  :Lol:


Genius ...

Apart from my first attempt had the screws through a softwood button in the middle and the cutting force proceeded to rip the screws through the wood and take a chunk out of the end of the base!



Flycutting cut out for flywheel lol always thought of this but never thought it'd work ... It did. White stuff is glue where the wood has had a joint down it at some point in its life.


This was risky - measured and calculated all the points for holes, marked for sanity check but done by coordinates using dials ... So need a dro!

This was a struggle working out so late at night after a day at work.

Another good reason for drilling base on wood - holes spotted through for clearance for screw heads on underside. Finished base with a bit of teak oil. Oh forgot to say I acquired a new toy for brown stuff from dad ... a router. This was much easier and faster than milling all the way around the edge and getting steps to line up!


Coat of primer on base - this paint vie been using is pants, seems to take weeks to harden, some sort of enamel, maybe need to stove it !


Eccentric - I decided to use a slightly different design here with a plate and a screw, think it was Elmers engines I'd seen it on. Drilling the offset hole in 4 jaw, then I could simply turn a shoulder, part off and part off a 2mm thick piece for the plate.







Offline NickG

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Re: Stew's Simple Mill Engine
« Reply #81 on: May 10, 2014, 09:32:37 PM »
Phew - worked until midnight on Thursday and Friday night - absolutely knackered but finished just in time for the show - that'll teach me to enter an exhibit when it's just a box with a fee bits in it!









I changed the configuration a little, when I made the crankshaft it was to stews prelim drawings which had an error and it ended up too long with a gap between where the bearing and flywheel go. So I spaced the bearings out and decided to put the eccentric between the crank and bearing on the flywheel side to fill the gsp. This meant turning the cylinder around. I also turned the valve chest the other way up as I think before I bored it I realised it was a marginally better fit or lined up better with the ports that way before I bored it. This makes the inlet a problem, I was planning to have a pipe going straight down hen through the side of the base but ran out of time! This made getting a pipe on it v difficult today as the inlet was just a random this'll do sort of size and is a bit long.

It is all a bit stiff but I can confirm as of a few hours ago that it's a runner !  :whoohoo:Took about 15 psi as it's tighter than I would have liked - combination of binding on piston / rod and valve rod. I probably didn't get the machining sequence quite right so as to get no runout. Because I used stock sizes for piston rod and valve I relied on the concentricity of the chuck and collet chuck which with the fits I had wasn't good enough.  It'll loosen off if get chance to run it but sorry no vid for a while as I don't have a compressor  :( it was thrown together in a bit of a hurry in the end, gaskets are poor and really the baseplate is too think - 3mm aluminium which I thought would be ok when screwed down and all bits bolted to it but you can see it flex.

Oh, also, stud police should look away now, some are too short, some are too long but it's just cheap and cheerful fasteners! I found some nice (dare I say it, cap screws) for the con rod which were just the right length.

Enjoyed the project, lots of firsts for me and probably the most complex project I've done so far despite being a beginner's engine. Lots of learning points too - I was a bit down hearted last night when assembling as nothing seemed to be going right but after a bit of fine adjustment this morning I got it to a reasonable level of friction. Hopefully it'll bed in eventually. The flywheel has a bit of  a wobble due to my crankshaft fiasco but not going to dwell or start remaking parts, onwards and upwards and learn lessons for next time.

Thanks to Stew for designing another nice engine and sharing the plans - will have to show Lawrence when am back, I expect he's onto his next project by now!


Cheers  :cheers:

Nick

Offline zeeprogrammer

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Re: Stew's Simple Mill Engine
« Reply #82 on: May 10, 2014, 10:10:18 PM »
Congrats Nick!
Looks good. That's a lot to do in a couple of days.
I'm liking the color and the base.

But...there's just one little thing missing. Just one.

A video!  ;D
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Zee-Another Thread Trasher.

Offline Don1966

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Re: Stew's Simple Mill Engine
« Reply #83 on: May 10, 2014, 10:13:31 PM »
Wow! You have been busy Nick and a fine job of it to bud.  A video would be nice.  :stickpoke:
But I do like.............. :praise2:

Don

Online Jo

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Re: Stew's Simple Mill Engine
« Reply #84 on: May 11, 2014, 08:03:06 AM »
 8) Well done Nick she looks very nice  :ThumbsUp:

I wonder if a set of castings has caught your eye as you next engine :naughty:

Jo

Enjoyment is more important than achievement.

Offline NickG

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Re: Stew's Simple Mill Engine
« Reply #85 on: May 11, 2014, 08:08:22 AM »
Thanks Zee and Don, got there eventually but took nearly a year looking at the start of the post!!! for some reason when I've looked at this on tapatalk this morn there's only my latest post on, I had split it into 2 but there now seems to be a load missing :-( never mind. The paint was annoying because as I was handling components to assemble was getting finger prints and bits running off etc. as I said, I never thought to get a vid on the one run it's done and it will be at the exhibition today but may go to retrieve it from club on tues and try to sort a better inlet to get a vid / run it in a bit.

Ps just checked on website and post is there phew! Zee all that last bit was over a couple of weeks but didn't have time to update!
« Last Edit: May 11, 2014, 08:18:35 AM by NickG »

Offline NickG

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Re: Stew's Simple Mill Engine
« Reply #86 on: May 11, 2014, 08:12:19 AM »
Thanks Jo, just saw your reply. Possibly the DT will be my next engine although they still scare me. At Harrogate yest there was a new set of castings that caught my eye at Blackgates - a horizontal and vertical engine with 1" bore, set of 15 castings and drawings for 69 ... Later find out they only did 5 sets of each to see how they went and the price is bound to go up. They weren't the best, bit rough around the edges but nonetheless a bargain at that price.

Offline fumopuc

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Re: Stew's Simple Mill Engine
« Reply #87 on: May 11, 2014, 08:16:07 AM »
Hi Nick, that is looking very nice. Well done. Have fun at your show.
« Last Edit: May 11, 2014, 08:51:58 AM by fumopuc »
Kind Regards
Achim

Offline NickG

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Re: Stew's Simple Mill Engine
« Reply #88 on: May 11, 2014, 08:20:31 AM »
Thanks Achim, show was good, I went yesterday as you would expect, some incredible stuff there - all the more impressive when I've just struggled to make something so simple!

Offline ths

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Re: Stew's Simple Mill Engine
« Reply #89 on: May 11, 2014, 12:20:39 PM »
Great work Nick, and good to see your take on Stew's design. Hugh.