# Going round the bend - an Elbow Engine



## arnoldb (Oct 23, 2010)

I've been spending a lot of shop time on experimental work, and reached a point where I first need to build a bending roll to continue - GH Thomas's design is perfect for my needs. Checking my stock inventory this morning, I could not find some of the material I thought I had... 

I've not built an engine for a while, so decided to divert from my experiments and the bending roll for a while and build an engine. I've had my eye on the elbow engine for quite a while, so I decided now's the time. I think I can keep to the required accuracy, and there's some great tips here on HMEM from Bogs, Stew, Rick and others on getting the thing going; it is by all accounts a finicky, difficult and frustrating engine to get to run, but I'm up for the challenge.

I'm working from Stew's plans - He incorporated a lot of nice features, and the plans are in metric, saving me some calculations 

Scratching around for stock, I found this lot:





12mm aluminium plate for the base and flywheel post, 100mm bronze with a hole through it hidden by the 4mm brass plate I'll use to make a built-up flywheel, a bit of 35mm brass rod to make the valve ports from, some 30mm cast iron to make the cylinders from - I dont have brass for this, but the CI should be OK as the coefficient of friction with steel when moving and lubricated is pretty much the same as that of brass to steel, and some 6mm silver steel to make the pistons from.

The base and flywheel post was roughly band-sawn from the bit of plate, then I started cleaning up the edges. Here I've finished getting the base square and to size; a block of wood serves as a parallel to lift the workpiece far enough in the mill vise for the chuck to clear, and a toolmaker's clamp with a bit of scrap as a vise stop:





The flywheel post needs to have its base perfectly - as near as perfect as one can get it - square, so I milled it standing upright in the vise. A good angle plate would be a boon here, but I used what I have, and my vise is pretty square:




I _could_ have turned up a couple of cylindrical squares to substitute for an angle plate, but that's an exercise for another day 

A check with my "best" machinist square, and things look good to go:




 ??? I wonder if I can remove the rust from it and still maintain a semblance of accuracy on it ?

Next up was an exercise in mill-dial calculations, x handwheel spinning and deep-hole-drilling in aluminium... I don't have long series drills, and this project really requires it, so I had to go for some carefully thought out modifications bodges. Fortunately there is a load of room between the needed holes, so going for bigger drills for the deep holes is not a problem. For the flywheel column, I went for a 4mm drill instead of the 3mm required. Here you can see the two together; the 3mm drill pushed against the chuck jaws, the silver mark on the 4mm showing the depth I drilled to (just above my thumb), and there is just 5mm of that 4mm drill chucked up:




It is not ideal to chuck such a short bit of a drill, and will cause chuck damage. I first chucked the drill bit normally, and drilled as deep as I could get; lot's of cutting fluid (methylated spirits for me in ali), peck-drill 2-3mm at a time till the chuck jaws are close to the workpiece, then extend the drill a bit & repeat.

The deep port holes in the base, the best I could come up with was drilling with a 6.8mm drill... There's barely enough space, but it will do:




That drill bit is actually black; the gray on it is from the deep drilling. Why 6.8 ? - well, it reaches far enough, and I can tap the port ends for M8 for the steam/air connectors 

The lot assembled so far; everything aligns very well ;D - even if it looks crude so far. The counter bores on the base are 0.8mm deep, to take 4mm ID x 1mm thick O-rings and allow for compression; I had to change Stew's dimensions a bit there as that is what I have.





Next up - after a diversion to my day-job office to attend to some servers, the alarm system, and taking some photos for the company's web-site-under-development - work on the valve ports. This is the bottom one partly done:




I don't have a 5mm slot mill, so I used a 4mm one for this; if needed, I might have to increase the rotary angles of the milled ports later - as using the smaller milling bit leaves them "shorter" in circumference than designed, but that is better than having them too long, as there is a point at which the milled slots would connect incoming steam/air directly to the exhaust if overdone. IMO the bits between is basically a top/bottom "deadish" bit, where the addition of steam/air, or the resistance to exhaust does not have too much of an affect.

The flywheel valve port needs a close-fitting "stem" to fit in its column. My parting tool is thinner than any of the measuring calipers I have, so getting it to size puzzled me a bit... Measuring in the parting slot was a challenge - none of my digital or dial calipers fit in there :, and then I remembered my little-used little OD spring calipers. Works a treat ;D - With the lathe STOPPED!:





I stopped work today with the base, flywheel post, and both valve ports done:





There is one glitch though... Stew's plans show the M3 tapped mounting holes for the base valve port from the top. They should be from the bottom. Working from the plans, I fell in this hole - literally :big:. To recover, I had to drill and tap the holes right through the valve port instead of having blind holes. If needed, I'll make a couple of threaded plugs to seal the holes on the cylinder side of the port, but that might not be necessary.

Regards, Arnold


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## zeeprogrammer (Oct 23, 2010)

Geesh Arnold, I'd have called it a day after finding the bits and pieces!
You're moving right along as you do with all your projects.
I've seen a few elbow engines...I have no confidence of building one at this time.
Looking forward to more of your work! er...play!


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## SBWHART (Oct 24, 2010)

That's the way to go Arnold :big:

Quote:- Stew's plans show the M3 tapped mounting holes for the base valve port from the top. They should be from the bottom. Working from the plans, I fell in this hole - literally . To recover, I had to drill and tap the holes right through the valve port instead of having blind holes. If needed, I'll make a couple of threaded plugs to seal the holes on the cylinder side of the port, but that might not be necessary.

Sorry about that, :-[ but you wont need to plug them.

You,ll enjoy this build, Elbows Engines give a great deal of satisfaction when you get them running, with a great wow factor.

Getting things square is the secret to success.

When you come to the cylinders drill both together then part them off this way they will align spot on.

Stew


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## Blogwitch (Oct 24, 2010)

Arnold,

I didn't realise you were into self flagellation.

But in all honesty, if you take your time, and make sure EVERYTHING is PERFECTLY square as you travel on your journey, you just might end up not being totally bald from pulling your hair out.

They are a very satisfying build, and at the very end, you can baffle almost anyone when you show them it running.

The hints and tips you have seen will really help.


Good luck


Bogs


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## Omnimill (Oct 24, 2010)

This looks like an interesting build Arnold and nice pictures, good luck with it.

Vic.


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## arnoldb (Oct 24, 2010)

Carl, Stew, Bogs & Vic, thanks for checking in 

Stew, no worries mate; I thought it would not be necessary to plug the holes. I have some others to plug now though :-[

Bogs, I do wonder what got into me to try this one... Fortunately I'm pretty much bald already ;D

Shop time for this afternoon - things were a bit frustrating at one point...

Started on the cylinder blocks; some cast iron turned down to size and a bit of work with emery to make it shine:





Then chuck and all onto the rotary table on the mill. I didn't even need to do any setup; yesterday when I finished the valve blocks, the last operation was to mill those half-moon slots, and that was at the same circle diameter as the cylinders must go. Just started to center drill, drill 5.9mm and ream out to 6mm for each hole:




I love machining cast iron, even if it is so "dirty" 

After some more lathe work - parting off, adding some very simple cosmetic turning and cleaning up - I ended up with these:





The pistons followed; a very quick turning job in the collet chuck to thin out the middles for the bend areas, and then I took a smudge off the diameter with emery to make for a slightly looser fit in the reamed cylinder holes:





Things were going too good up to this point :. When I tried to assemble all three pistons into the cylinders, the lot didn't want to go together. Closer checking on the cylinders revealed that the holes had wandered off badly... I trammed my mill last weekend, so that's not the cause.

I decided to make new cylinders - this time using the 4-jaw chuck on the lathe for the offsets, and after part-way drilling the 5.9mm center hole, I could see the drill bit starting to flex around :wall:. This does not happen on my lathe often, so I took a good look at the drill bit, and the cutting tip was damaged on one web; most likely the cause for the failure in the mill as well. I only have this one 5.9 mm drill bit, and store it together with the reamer; one of my "matched pairs" Time for a new one - make that a couple.

I nearly gave up shop time for today in disgust then, but then an idea hit me; seeing as the original cylinders was basically bust after a fair bit of work has gone into them, I decided to try a recovery. Their center holes were OK, so that's not a problem. I carefully chucked up each one in turn on the RT again - picking up a reference from the old holes, and drilled and reamed new cylinder holes in between the old ones. Instead of just center drilling and running through with the damaged 5.9mm drill bit, I center drilled, drilled 5mm and then 5.9mm. I didn't ream the holes on the mill though - after finishing both cylinders, I put a piece of 6mm silver steel through the center holes, and lined up one set of the new holes by jamming the 5.9mm drill into them. Then I hand-reamed the two open cylinders out to 6mm, and shoved a piston into each; these still went in a bit stiffly. Then I removed the drill bit, and manually reamed out that hole as well. Then I chucked the reamer in the collet chuck on the lathe, and ran trough all the holes each in turn again to open up the cylinder bores a whisker more - keeping pistons in all the holes not being reamed. I did this reaming by holding the assembly by hand, as I felt it safe enough to do so once the initial hand reaming had opened up things. 




It seems to have worked ;D - the pistons slide easily through the bores, and nothing looks like it wants to jam up any more. 

I'm in two minds whether I want to make a new set of cylinder blocks or use these - a bit of brass loctited into each of the stuffed holes might just do the job of plugging the holes and adding some visual appeal, otherwise I'll drill out the holes in the cylinder blocks to make desk pen-stands from and make new cylinder blocks 

Regards, Arnold


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## SBWHART (Oct 25, 2010)

I'd give the cylinders a try, if you have a problem it's not a big job to remake when you've got a new drill.

I think you'll have a runner.

Stew


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## Deanofid (Oct 25, 2010)

I'll be watching, Arnold, and sticking around for moral support!


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## arnoldb (Oct 26, 2010)

Thanks Stew; I'll give the cylinders a go as-is with plugs in the extra holes. It WILL be a runner - even if I have to re-make or bodge some things and go more insane than I am in the process :big:

Thank you Dean ;D ; by all accounts this one needs moral support!

I stole 30 minutes after work for some shop time & turned up the axle pins from some 8mm hex brass. 

I didn't follow the plans here; just turned them up as single pieces - chucked up the rod, turned down an 8mm length on the end to 4mm and threaded M4 with the tailstock die holder, then turned down a section "just" longer than the cylinder to 5.98mm to give a free-running fit in the cylinder hub, and used a 0.02mm feeler gauge (one of the ones I don't mind damaging a bit) to set the parting tool to give a bit of clearance to maintain a free-running fit once the pin is used to mount the cylinder to the valve block, and then parted down to the minor diameter of the 4mm thread to give a good shoulder and thread run-out at the end:





While doing the first pin I made mental notes of all the cross-slide settings to hit the correct sizes, so the second one went quickly - I ended up with this for today:





Regards, Arnold


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## don-tucker (Oct 26, 2010)

Been searching for Stews plans for this engine,found sheets 1 & 2 are there any more,please I would like to have a go.
Don


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## arnoldb (Oct 26, 2010)

Hi Don

You can find the full plans here - that's just a few posts above the single sheets you have on which Stew made a couple of corrections 

Enjoy ;D


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## SBWHART (Oct 27, 2010)

Hi Don

The drawings are where Arnold said all 6 sheets on the post I made on 26th Feb, I thought I'd added them in the download section but like you I can't fine them ???, any way Arnold has already uncovered one mistake I'll wait until you guys have finished your builds to see if any others are uncovered then I'll correct the drawing and add them to the download section.

Its a real satisfying engine to build it can be a ***** to get running but if you concentrate on getting things nice and square and aligned you should have no problems,

Good luck with your build

Sorry for the high jack Arnold

Stew


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## don-tucker (Oct 27, 2010)

Thanks boys I must be going blind in my old age.
Don


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## NickG (Oct 28, 2010)

Nice work Arnold, I'd missed this. I've seen Stew's engine running and it is mesmorising to watch!


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## arnoldb (Oct 30, 2010)

Pleasure Don.

Thanks Nick 

Today's shop time - some ups and downs, but mostly very satisfactory 

First thing this morning I made up a washer and screw to retain the top valve block on the upright:





Then I got set up to bend the cylinders. One of the second set of failed cylinders with a bit jammed in the bottom of a hole to act as the bottom bending bit, a bit of 12mm HRS rod from the scrap pile with a 6mm hole drilled in one end to make the top bending arm, the oxy-butane torch ready to make some heat, and a leather welding glove at the ready in case things got a bit hot to handle. The steel plate lying on top of the vise jaws is a reference to eyeball a 90 degree bend as close as possible:





Cylinder bending done and lying on a firebrick to cool down:





While those were cooling, I turned up the plugs for the "Extra" holes in the cylinders. I left the parting pips on, as that would be convenient to handle them with a pair of sharp-nosed pliers:





Then I popped the plugs in the cylinders with a bit of high-strength retainer, and set the cylinders in the sun to cure; it was 34C at this point, so curing would be quick . Attention was turned back to the cylinders; I got them close to square; in fact one was spot-on, but the other two needed a tiny bit of adjustment. Adjustment results :-[:




There was not even a tiny hint at bending - both literally shattered like glass when I tried. A test with a file followed; it didn't even mark those bends.
My silver steel supplier has never been able to tell me if the stuff he supplies to me is oil or water hardening... From the results, I'm thinking it's air-hardening silver steel... At least I'll be able to grind up some boring bars from that lot now.

So - the cylinders were stuffed... How now brown cow ?
I had a look around. I know bronze brazing rod bends easily without breaking, and I have a good supply of that. I also had enough 7mm brass rod to turn down to make pistons, but I was not about to go try bending it... A quick test with a bit of 3.2mm bronze rod showed that it bends easily and sharp enough, but then breaks if one fiddles. After an initial bend, and then annealing it, it easily bends a bit more, so this plan was hatched:




Turned cylinders with a 3.2mm hole drilled in one side to solder a pre-bent and annealed bit of bronze brazing rod into. Electronics solder would do the job, and an advantage was that I could turn the cylinders to correct length as everything could be pre-measured 
I thought I took a photo of the finished cylinders - I didn't :-[

Attention then turned to the flywheel; first a slice sawn off the bronze:





My thoughts on the flywheel construction had changed a bit during the week. I cleaned the bronze slice up on the lathe, and then turned a bit of aluminium I had down to a press fit in the bronze core, and pressed it in with the big vise. I forgot the other side of the aluminium had some protrusions, so the last bit of "pressing" was done with a BFH with the rim supported on a piece of wood; hence the hammer marks on the ali:





Time for some cosmetic work... Off to the mill, and a hole saw made a 25mm hole on the column:





Followed by the boring head to open the hole to 26mm and get a better finish:




The other side of the column received the same treatment.

The flywheel was cleaned up some more and I drilled a couple of 10mm holes in the bronze part:





The column was screwed to a block of wood through some holes drilled through bits that will be removed, and two strips of Meccano I conveniently found while digging around for something to clamp with was used as clamps. The rotary table centered on the mill, and then the 4-jaw chuck mounted and the big hole in the column centered on that, with the aid of an 8mm drill mounted upside-down in the collet chuck:




Somewhere some poor kid is going "Bwhaaaaaa - I wish I had those strips of Meccano !!!" - or then maybe not; it's not a PS3 game :-X

A bit of offset fed in on the mill X, and then doing the roundy-round with the rotary table:




This is where I stopped for the day, as a very insistent swarf magnet came and shoved a wet nose against my leg and dropped a beer-bottle top at my feet... I don't know where Zorro got the bottle top, but he knows "daddy" gives a lot more attention to doggies when he's having a beer than when he's running the machines :big:

There was another good bit in todays episode ;D - after I made the new cylinders I put things together for a look-see. there were a couple of slightly tight spots, and I lavishly applied some metal polish mixed with engine oil for a diesel engine. After turning things a bit manually it smoothed out, and at 40 psi of air, this is what I got - oil, polish and all woohoo1:
[ame]http://www.youtube.com/watch?v=9ARrZk7xqaY[/ame]
The roar is not the engine; it's my poor little compressor trying to keep up... Air leaks all over the show - so some work required to cure as many of those as possible. At least though, I can say I've seen an elbow engine running ;D

Regards, Arnold


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## GailInNM (Oct 30, 2010)

Congratulations, Arnold. Another runner. All work from here on can be considered as refinements.
Gail in NM


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## Blogwitch (Oct 30, 2010)

Congratulations Arnold.

Now you are ready to baffle all your friends when you show it to them running.

You seem to have made one of the worst engines to get running into an easy project.

Very well done indeed.

BTW, the engine will never run clean.


John


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## zeeprogrammer (Oct 30, 2010)

Less than two pages Arnold. Gee.
But packed with awesome stuff.
Congratulations!


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## bearcar1 (Oct 30, 2010)

Bravo! Arnold, Bravo! I tuned into this post just before the dreaded 'message of impending doom' appeared on HMEM and was not able to follow along. Now, in just a very short time you got a "weiner". I really do enjoy watching your progress and I especially like the method you used for making the piston assemblies in three pieces. Much, much easier in my mind than to have to fiddle around with bending first too much and then not enough and so on and so forth. Make the pieces, line them up, solder them and you're more or less done with the lot Thm: And your "roundy round" base is a big hit as well. :bow:

BC1
Jim


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## cidrontmg (Oct 30, 2010)

Congrats Arnold, that´s a fine piece of work! Good idea about the 3-piece pistons. I guess you could also have Loctited them together, even less chance of them not being "square". You certainly put that together fast and neat. Mighty fine!


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## SBWHART (Oct 31, 2010)

Great Job Arnold

Another baffle machine running, a great bit of work. :big: :big: :big:

Stew

PS

Whats makes it an even more satifying engine for you is that you used tools:- Rotary Table, and boring head that you have made your self:- very well done indeed, you should justly feal proud.

Stew


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## NickG (Oct 31, 2010)

Well done Arnold, I thought that video was going to be you running it in with a motor or on the lathe but to my surprise I clicked it and you had a runner!

Great project, cheers

Nick


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## arnoldb (Oct 31, 2010)

Thanks Gail  - The refinements are done as well now.

John, thank you  - building it was relatively easy, but it wasn't easy to get running - especially today after final assembly. I've got the oil splatters to prove it ;D

Thanks Carl - I'll try to stretch my next project a little longer ;D - now, what will it be ???

Jim, thanks  - I'd actually recommend the multi-part piston assemblies now 

Thanks Olli - Loctite would work as well - but somehow I don't yet entirely trust the local equivalents I get :big:

Stew, thank you  - and another thank you for your revised plans for the engine. I do enjoy my home-made tools; somehow it just feels more special to use them rather than bought items ;D

Thanks Nick   - as an aside, I wouldn't recommend running this engine in using external power, as it will not run in properly due to it's "peculiar" design...


This morning I finished the column:






Then I finished the flywheel; I felt it was too heavy, so I drilled out more holes in the circumference, and thinned it out a bit; it's still too heavy, but should work. The flywheel center was bored out for a light press fit on the cylinder, and the lot pressed together. Then followed quite a bit of elbow grease with files, emery and scotch-brite to get the parts presentable.

Finally assembled, and now complete, this is what it looks like:











I had a bear of a time getting it running again - I suspect mostly because of the heavy flywheel. But run it does ;D - although it requires a bit more air than my little compressor is capable to constantly supply, so the run is not very long before it stops at about 15psi:
[ame]http://www.youtube.com/watch?v=1bD_QPQwd7E[/ame]

While this was a fairly simple engine to build, it required extreme accuracy - and as such was a big challenge. Seeing it run makes the effort worthwhile though ;D

Once again, many thanks to Stew, Bogs, and others who shared their own experiences and recommendations for getting this engine to run.

Regards, Arnold


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## Metal Butcher (Oct 31, 2010)

Hi Arnold. Beautiful! Congratulations on your successful build. :bow:

Someday.... I will build one too. Too many planed projects, and not enough time! :shrug:

-MB


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## don-tucker (Oct 31, 2010)

That's brill Arnold,be having a go myself soon,it looks like fun.
Don


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## Maryak (Oct 31, 2010)

Congratulations Arnold - Yet another great build. :bow: :bow:

Best Regards
Bob


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## tel (Oct 31, 2010)

Congats from here as well Arnold - I've had photocopies of the original Popular Mechanics blueprints & article for at least 30 years, but never got around to attempting one!


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## nfk (Nov 1, 2010)

Very nice engine!
Congratulations!


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## NickG (Nov 1, 2010)

> Then followed quite a bit of elbow grease



Was I the only one that spotted this pun?! 

Nice work Arnold, looks really impressive.

Nick


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## Omnimill (Nov 1, 2010)

Good job Arnold, nice looking and a runner!

Vic.


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## arnoldb (Nov 1, 2010)

MB, Don, Bob, Tel, nfk, Nick & Vic - thank you very much 

MB, Don & Tel - it's a fun engine to build - but just a tad frustrating to get going; but definitely worth a go. I also had this one in my sights for a project for much later; it was a purely impulsive decision that got me started on it so soon :big:

Good catch Nick 

Kind regards, Arnold


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## Deanofid (Nov 16, 2010)

Gee Arnold, you got this one done so fast I nearly missed the whole thing. You did a very
nice job on it, and it's turned out to be one of the best looking of its type. Nice work, man!


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## arnoldb (Nov 17, 2010)

;D Thank you Dean.



> it's turned out to be one of the best looking of its type


Well, thank you ;D - but I'm not too sure of that - I feel it's a little bit too "chunky". Makes a great paper-weight and conversation piece in my office for now though  

Kind regards, Arnold


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## cfellows (Nov 17, 2010)

Looks great, Arnold. Wouldn't change a thing!

Chuck


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## Fingers (Dec 10, 2010)

Congratulations I'm new to posting here, I have been reading for a while engine looks class I never saw one before.


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## arnoldb (Dec 11, 2010)

Thanks Chuck 

Welcome Fingers - and thanks  - Theres been quite a few of these built by members; in fact I greatly benefited from their shared wisdom while building it. I've found a lot of gold in older posts on HMEM; the Search option is invaluable!

Kind regards, Arnold


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