Arnold's small turbine

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arnoldb

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I want a small turbine, and the great Mr. Elmer Verburg published plans for one. My build is loosely based on his design, and about the same size, but I'm taking some liberties and doing some things my way - which might just bite me in the back :big:

Having said that, I feel it is also VERY important to stress that turbine builds should not be taken lightly. At high pressures and very high rates of rotation even a small turbine can be a little bomb waiting to disintegrate - it is NOT the type of engine for people who are inclined to want to test engines "to destruction". My aim is to build a small breath-powered turbine for display purposes - nothing more. I really hope I can get it to run on breath power, but therein lies a problem; if it can run on breath power, it will be a dangerous engine if used on high pressure compressed air. From my research, a turbine needs to be built pretty darn accurately; the rotor needs to be as balanced as possible and tolerances should be kept tight.

Last Sunday afternoon I started off with a block of aluminium for the main engine body. This is my first deviation from Elmer's plans - which call for some pieces bolted together. I want to practice some milling techniques, hence the solid block. It was first flycut square on the mill:


Then marked out:


The main "steam port" was drilled out 2mm to the center of the block and then opened up to 4.2mm to be threaded for a 5mm steam connector. Then the block was centered up in the 4-jaw on the lathe. You can see the hole for the steam connector on the side. I'm using a sharp pin in the tailstock drill for alignment; this is accurate enough at this stage and gets me to within 0.02mm. I still can't center punch a hole accurate enough to use a DTI and center finder to beat this ::):


That lot was then center drilled, drilled 7.8mm and reamed through to 8mm:


Then drilled with a 19mm drill to a depth of 12mm at the drill's tip:


And bored out to 32mm diameter 12mm deep:


I then changed chucks - without removing the engine body from the 4-jaw, I fit the 3-jaw.
Elmer specified 2 bushes pressed in from both sides; I went for one bush - turned from some hex brass - turned to 8.02mm OD and drilled to 5.9mm and ready to be parted off:


After parting, it had a 0.2mm thick flange:


I then re-mounted the 4-jaw and pressed in the bush with a bit of aluminium gripped in the tailstock - with a smidge of bearing retainer to make sure it would stay put:


Yesterday (Saturday) was a total loss in the shop. The past week went from a high of watching UB40 live in concert on Thursday evening to a very low on Friday afternoon with the passing of my 15-year companion Chakie the wire-haired terrier. I've been expecting this for a while, but it still hit hard. Yesterday when I tried some shop time, there was an empty spot behind me where he used to make himself comfortable and I just couldn't get anything done.
The day was not entirely lost though; my neighbours are building extensions, and their builders needed access to my property to plaster some border walls. While my property was invaded thusly, I sub-contracted them to finish a long-outstanding job for me as well. The planter on my stoep was filled up and a concrete slab poured on top, so now I can get around to laying out my small "garden" railway:


A new day today, and I started off on the rotor. Some oversize aluminium turned down, and parted down part-way:


With the dividing head mounted in the mill vise, I started whittling away at it - at an angle chosen by eye:

My starting cut was a bit aggressive, and I broke one of the Richon Tools cutters on it. Purely my fault; a 2mm HSS cutter can not take a 2mm depth of cut at a silly feed rate - and 1200RPM is a bit slow for it as well :big: - So I settled back to an acceptable 0.6mm DOC and a sensible feed rate; I can't do anything about the spindle speed; that's max for my mill.

A little while later, and with a new angle on the cutter:

It would look (and maybe function) a lot better if I had a 2mm ball-nose for this. I'll include that on my next order.

On to the rotary table with the chuck, and poked some 5mm holes in the rotor to lighten it up a little:


Finally, back on the lathe, and drill 3.9mm deep enough for the 4mm reamer to ream out the center hole:


Part it off:


A year or so ago, parting off was one of my worst nightmares, and a challenge I set myself to conquer. It's not fully conquered yet, but improving all of the time. This was the result of the above parting - after I used a countersink to clean up the holes:

There's still a lot of rough bits, but a heck of a lot better than what I did in the past, and a lot less brown stuff in the pants!

A quick rub on some 600 emery, and no-one would be any the wiser - except for everyone reading this, that is :big::


It fits nicely in the block as well:


There was a short hiatus on tooling work to mount my tooling plate on the rotary table (which I'll post on my tooling thread), then I started on some mounting holes for a clear perspex cover for the engine - with 2.5mm holes drilled for threading M3:


And a bit of fettling with a 6mm mill:


There's quite a bit of fettling to do, but time caught up, and I made the main shaft to check things out. My collet chuck is pretty accurate, but not good enough, so I clocked a bit of 6mm silver steel up in the 4-jaw - with less than 0.005mm run-out on the end, and turned it down to 4mm to fit the rotor, and then threaded it M4 to take a nut:


Where I ended up for today:

;D - at least, if I blow in the hole, it turns, but it looks like it will need an exhaust passage as well.

Regards, Arnold

 
D

DaveH

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Arnold,

Sorry to hear about Chakie, I'm sure he will be still watching you in your workshop.

Dave
 
D

DaveH

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Arnold,

Very well documented and photographed.

Your normal excellent standard :bow:

Dave
 

lazylathe

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Hi Arnold,

My sincerest condolences on your loss of Chakie.

Another great build log and excellent workmanship as usual!!

Andrew
 

Maryak

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Arnold,

Sorry to read about the loss of your good friend Chakie.

Best Regards
Bob
 

tel

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Geez Arnold, you don't let the grass grow, do you? I'll be watching this one with interests as well.

Sorry to hear about your mate tho' - that's always a bad time.
 

compspecial

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Lovely work Arnold and a change from the good old reciprocators sad news about your old companion, they are like members of the family, but you sure are keeping your mind active!
Stew
 

arnoldb

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Many thanks for the commiserations gents :bow: - the little terror is missed, but will be very fondly remembered.
And thank you for the compliments on the build as well :)

"Geez Arnold, you don't let the grass grow, do you?"
I be going a bit slow Tel; should have had it done this weekend. I need to get cracking on the experimental loco again to see if it will run if built properly, and then there's the matter of some test tubes that I got my hands on as another diversion ::)

Shop time in the evenings after work is non-existent at the moment, so I'll probably only get back to the engine on Saturday.

Kind regards, Arnold
 

njl

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Very nice work Arnold, I bet it would go at a fair old lick with a good blast of air. Sorry to here about Chakie.

Nick
 

Chaffe

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Thats pretty cool, you could exhaust the gas through the centre like a turbo turbine, all you would need to do is drill some holes through from every "fin"
 

arnoldb

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Thanks Nick :) It already goes - but I can't test it properly as there's some things to finish off ;)

Chaffe, Thank you :) - I'd like to keep this build mechanically simple though; it would be a lot of work to accurately re-setup the rotor to drill those holes.

Well, had a bit of shop time today. I was hoping to get the engine done, but time flies when one's having fun :big:

First off, I cleaned some excess off with a 6mm ball nose mill. I've had the bare minimum experience with using ball nose mills, but it cuts surprisingly easy, and leaves a nice smooth finish to boot:

There's a very ugly spot to the left of the groove milled with the ball-nose; that happened last Sunday when the draw-bar on the collet chuck came loose. I was a bit slow hitting the E-stop on the mill... Fortunately it can be fixed; just a bit of effort needed.

Next I very roughly started hogging away some excess aluminium:


Rather than using the tooling plate for the next step, I centered the rotary table to the mill spindle and zeroed the X and Y dials taking care to remember in which direction for each axis I'd taken up backlash. Then I mounted the chuck adapter and 4-jaw on the RT. With a bit of 6mm rod to fit the workpiece bearing, I chucked it up; lightly touching each chuck jaw against the side of the workpiece, and then going round tightening each jaw just a little till things were clamped down properly. Not very accurate, but plenty good enough for the profiling I'm going to do:


Then I started profiling with a 6mm end mill again:


A considerable while later, things looked like this - with a 3mmx3mm step left around the profile:

Not pretty, but OK for now.

Then I used the 6mm ball nose mill to clean up the step - and lightly cut deeper against all the sides with it to clean up the poor finish from the previous step as well:


Bogs kindly gave me some pointers on exhaust holes. I couldn't go exactly to his recommendations, as there is the matter of a screw that's in the way that I had to work around. I drilled the first hole with a center-cutting 4mm 2flute cutter:

The second one was done the same; but nearly in-line with the inlet port - barely missing the screw hole.

On my previous engine builds, I've been very lax about adding oil holes in the bearing blocks, but this one definitely needs it:


Then I spent a couple of hours with files, needle files, riffler files and emery paper to get rid of some of the tool marks:



::) Some latent insanity surfaced and I wondered what it would look like buffed up a bit. I'm not sure if I like it; I'll sleep on that tonight. If I want it buffed, I have to make a plan to get into all the little corners with a buff. That will require some careful work with the Dremel and perhaps lateral thinking. I might just give the whole thing a rub-down with some 600 or 800 emery to get back to the satin-like finish:


So, a lot of faffing around today - but some valuable exercise. I've not done a lot of profiling with the mill, so this is all new to me, but I'm fairly happy with the result. More practice needed though :)

Regards, Arnold
 

zeeprogrammer

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Hi Arnold.

Very sorry to hear about Chakie. I know what having a dog means and how tremendous the loss can be.

I've been out of the country (again) for a week and was very pleased to see your thread. As usual (I keep saying that), I find your work high quality and inspirational.

Sadly for me, I'm going to oil my machines and cover them. No time in the shop for some time and it looks like it will be a while before I do.

Happily, I have this forum to enjoy all of the members' projects.

Looking very much forward to seeing more of your excellent posts.
 

Diy89

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Nice work! I vote for the polished finish. Me likey shinny things!
 

arnoldb

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Dankie Dave :)

Many thanks Carl :). Rats - I was looking forward to your progress on the Spinster. But life intrudes and one have to earn a living. I'm looking forward to your efforts once the interlude is past though. And yes, do keep in touch on the forum - your wit is missed when you're silent ;D

Thanks Diy89 - you should be happy with my decision then :) - This one will remain shiny.

This morning I finished the axle; first I milled a flat for the pulley/retaining ring's grub screw to engage on:


Then I widened the recess on the shaft that I made for oil retention slightly. This also makes the bearing surfaces slightly smaller - hopefully to reduce friction a bit:

The axle was then sawn off to length and the sawn end cleaned up.

To retain the shaft, I decided to turn a pulley instead of just using a plain ring. Some "scrap" aluminium that was used on a previous project was turned down and profiled a bit; I didn't have a suitable radius cutter for the pulley groove, and was not in the mood to grind one up, so just used a largish needle file to profile it:

The pulley was then just center drilled, drilled out to 5.9 and reamed to 6mm to fit the shaft before parting it off. A quick trip to the drill press and a 2.5mm hole was drilled and threaded M3 for a grub screw to engage on the flat on the axle.

Next I turned up an air connector from some 8mm hex brass. All the threading and profiling for the pipe connection was done first, before drilling it out in the center to 3mm. Doing the drilling out last saves a lot of heartache, especially when doing threading!:

That was then just parted off as well.

In yesterday's post I was wondering about how to polish into the nooks and crannies... That was solved with an ear bud cut in half and mounted in the Dremel. The first one broke off very quickly close to the Dremel's chuck, went into orbit, and landed in an inaccessible part of the shop. To prevent this, I used the other end, and just inserted a piece of straight wire in the plastic "handle". Worked a treat at lowish RPMs on the Dremel:


The engine still needs a base. With my aluminium plate stock running low, I didn't want to use any of that for the base, so wood is the only other viable alternative from my stocks. I _really_ was not in the mood for fiddling with wood today, so I'll make that up when I do a bit of woodworking again. Saves on cleaning up as well :big:

All the parts for the engine:


And all assembled:




::) I only noticed now there were some drops of oil I didn't wipe down!

Does it run ?
Well... yes, but not as well as I'd hoped on breath power. It takes a fair bit of blowing power to get it running, and it seems the bearing is a bit tight for breath power. It works OK on its side though. And I learned today just how much air friction there is in 1.5m of aquarium pipe!. With a 30cm piece of pipe I got it to run; but by blowing straight into the pipe connector it goes quite well.
The first part of the video is on breath power (and NO - those are not farts ;D) and the second part off the compressor with 20 psi maximum pressure:
[ame]http://www.youtube.com/watch?v=UWgienOBldk[/ame]

The final result remind me of some women I've met; pretty from far, but up close far from pretty :big:

Regards, Arnold
 

bearcar1

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Hi Arnold,

So is what you are saying is some woman are like a mud fence? At 10 meters they look good but up close it's still just a mud fence? :shrug: Rof}

Liquor helps that a lot you know. *beer*

I have to agree with the rest of the lot that your work is to a very high standard and that your presentations are top notch. That little bugger seems to turn some serious RPMs a treat. How is the torque aspect of that turbine (I suppose that the term engine would truly be a misnomer) :bow:

I as well, like the polished finish, it seems to attract attention rather than appear like just a piece of plate stock. ;D Tally HO!

regards

BC1
Jim
 
D

DaveH

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arnoldb said:
The final result remind me of some women I've met; pretty from far, but up close far from pretty :big:
A real good looking spinner to me ;D

Dave
 
D

DaveH

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Bearcar1

bearcar1 said:
Hi Arnold,

So is what you are saying is some woman are like a mud fence? At 10 meters they look good but up close it's still just a mud fence? :shrug: Rof}
regards

BC1
Jim
If I was a women I would take offence to that. Rof} Rof} Rof}




Do you get it ..fence ...offence. Goodness I'm good Rof}


Dave
 

Foozer

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bearcar1 said:
Hi Arnold,

So is what you are saying is some woman are like a mud fence?

BC1
Jim
With 20/400 vision all them fences look good, trick is to leave the glasses off

Robert
 
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