HAE03-1 Hot Air Engine

[Cornish JackParticipant @cornishjack]

G’day all.

Just having a break from grinding and honing the EIGHTH (!!) parting off tool for the main cylinder of the above kit … the previous seven have snapped(6) and bent. To paraphrase Lady Bracknell – “To break one tool is unfortunate to break seven seems like carelessness!!” Mebbe so but I’m doing my best. The problem is the requirement to produce eight fins 25mm deep 3mm wide at 5mm centres in aluminium. To avoid over widening the gaps, I’ve ground the tools to slightly less than 3mm and for a length of 27-ish mm. The ali stock is approx 75mm diameter and I’m using bottom normal speed on a Trileva ML7 (200ish rpm). I’ve so far managed to get 7 slots to approx. 18mm deep and one to about 12. The material is ex RAF Workshop scrap bin but seems reasonable except for the occasional ‘inclusion’ (?)

At last to the questions – a)Any suggestions as to improvements to the above techniques and

b) Anyone with hot air engine experience care to opine as to whether the 25mm depth is ESSENTIAL or just a nice round figure plucked from the air? – If the latter, would the present 18mm serve the (presumably cooling) purpose?

TIA

Rgds

Bill

[Cornish JackParticipant @cornishjack]

[JasonBModerator @jasonb]

What sort of tool are you using? its quite hard to snap a HSS parting blade or one of the insert type parting tools. If grinding from a square toolbit you are likely to have problems.

 

J

[Clive HartlandParticipant @clivehartland94829]

25mm is not an unreasonable depth, the best method is to cut it with a narrower tool and cut a mm or so and then traverse and cut another mm or so and then back to the other side again.

You can do a clean up cut after.

Use plenty of WD40 as a lube and maybe a bit faster speed, like 400rpm.

Try one slot and see how it goes.

I recommend a deep parting tool as well.

Also clamp the saddle.

Regards the Alu. most extruded Alu has hard spots usually just about a third of the way into the Dia. You could have annealed it first though which might have helped.

 

Clive

[Ramon WilsonParticipant @ramonwilson3]

Hi Bill, Jason, Clive – just a word on the ‘cutting fluid’ . I began to use WD 40 at my last place of work where it was bought by the gallon container and decanted in to spray bottles. It did not take long – for me – to find that it was causing me severe respiratory problems when used as a cutting lubricant on the lathe. It makes some pretty acrid fumes when it gets hot. I still use it as its meant at home but am still sensitive to it if I get a good whiff!

 

Paraffin makes a good lube for ally but for years I have found the best of all is Plus Gas – it is still available I believe.

 

25 mm is quite a deep slot but as Clive says moving from side to side should see you through and a fair degree of back rake on the tool will improve things too.

 

Hope you are well Bill, it was nice to meet you at Forncett.

 

Regards for now – Ramon

[Cornish JackParticipant @cornishjack]

Thank you J and Clive.

Re. type of tool, 4 x ground square bits and 3 reground thin parting tools. The most recent is another square HSS ground to width. I have a few clamped blade parting tools but they are 1.5mm width and seemed to flex and jam up rather readily. WD 40 helps a little but I try to feed with the left hand and use the longitudinal feed to widen the slot so a bit short of hands!!

Any thoughts re. the finning depth as regards effect on running/performance, anyone?

Rgds

Bill

[JasonBModerator @jasonb]

Yep I never use WD40 as a cutting fluid, if it just a small job a bit of my usual soluable oil doe sthe job but if I’m doing anything more then Paraffin works for me.

 

Plus if you leave WD40 on anything for a time it dries to a stick film

 

J

[Cornish JackParticipant @cornishjack]

Thank you Ramon – our posts crossed.

Yes, WD40 does seem to get in the ‘tubes’ a bit!! Will try paraffin for a change.

Looking for ward to next year’s Forncett

Rgds

Bill

[JasonBModerator @jasonb]

How square were the tools to start with, for 3mm width you would ant something like a 15mm or deeper section, if you were grinding it from 1/4″ blanks then I can quite understand it failing.

 

Yes a 1.5mm is likely too narrow and they are also not that deep, try something like 3/32″ wide and 5/8″ deep, thats my usual weapon of choice. Go say 1/4″ in, wind back out them move 1/32″ to the side go 1/2″ in, back to first position and go another 1/2″ in etc.

 

Also ensure the blade is perfectly at right angles to the lathe axis and ground square across anny angled end grinding can push the blade sideways

Edited By JasonB on 09/11/2011 18:51:13

[Cornish JackParticipant @cornishjack]

Thank you Jason.

Yes, the tool section is probably a lot of the problem. The ground-to-size versions were from quarter and three eighths square stock and even at that size, it was taking over an hour to get them to size before honing – being done on a bench grinder, off hand. The cuts were taken with the tip just below centre height and as square to the work as I could make it. Considerable variation in swarf produced from one tool to another – some produced a nice gleaming almost continuous ‘slice’, while others, the latest one included, produce a sort of fine powder with occasional ‘blobs’ of fine curls. The noise is enough to wake the neighbours!! Onwards and inwards!!

Rgds

Bill

[adyParticipant @ady]

Would you not be better off using a horizontal rotary table on a shaper.

 

This gives you loads more control over the process, especially once you get to depth.

 

I’ve found making vertical slots up to 12mm in aluminium a doddle on a converted hand shaper.

 

A shaper has zero vibration, I believe that vibration is a serious handicap when things get to the sort of depths you are suggesting.

The vibration energy is being transferred into sound, which is why the process is making such a racket.

 

A shaper is almost silent because it’s only cutting metal and the energy transference is only creating heat.

Edited By ady on 10/11/2011 01:30:21

[Gordon WParticipant @gordonw]

I doubt if the sizes are at all critical. I gave up trying deep narrow slots , even with an insert type parting tool. Would suggest making the cooling fins from plate and shrinking them on, if the sizes are important.

[Cornish JackParticipant @cornishjack]

Thank you Ady and Gordon.

Re. the shaper, I can see the advantages but I haven’t yet got my shaper operational There’s also quite a difference between 12mm and 25mm!! Maybe if (when) the present setup turns to worms I’ll rig the shaper.

The shrink fit fins sound ideal from the accuracy point of view – but “there’s the rub” – my accuracy tolerances range from ‘close enough for Government work’ via ‘a smidgen’ to ‘Good Lord, that was lucky!!!’

Might have to make an executive decision that 18mm is deep enough

Rgds

Bill

[adyParticipant @ady]

Another system would be with a good hacksaw blade on a shaper type automatic hacksaw.

Again, use with a rotary table.

 

Then you could cut extremely deep slots with almost no risk.

Edited By ady on 10/11/2011 11:21:27

[Ian S CParticipant @iansc]

With the bore less than 25 mm, I would think that 25 mm fins are deeper than really needed. I have a formula here from James G. Rizzo’s book ” Modeling Stirling and Hot Air Engines: Area of fin = 8 x area of cross section of cylinder

 

No of fins (1/16″ thick) = stroke of displacer divided by 3.

 

I’m afraid that my method is cut, and if it looks OK thats it, the motors that I build that I want performance from I water cool them. Latest motor (still building has a displacer about 1/2″ bore, the cold end is a 1 1/2″ diameter aluminium door stop, the hot end is the steel casing from a AA size Ni Cad battery. Got to go to town next week and get two more ball races, 7 mm OD x 3 mm ID , for the crankshaft. This is proberbly as small as I will go. ian S C

[Cornish JackParticipant @cornishjack]

Ah Ha! Bingo – thank you very much, Ian.

Nicely timed advice. The final parting tool has survived to produce 20mm deep fins and the executive decision has been made – no deeper!

With a hot air engine experience level of zilch, I am very much fumbling my way through this one. The kit is of materials and two ready made cylinders and pistons – no written instructions at all. A book of drawings of individual parts and an exploded view is what I have to work to. One of the more ‘challenging’ bits still to do is a transfer passage across the central plate – appears to be about an eighth diameter and angled through the quarter inch plate at about 170 degrees (if that makes sense?) Haven’t yet worked out how to do that

Rgds

Bill

[Richard ParsonsParticipant @richardparsons61721]

Re shapers:- have a look at this one http://www.scribd.com/doc/52308512/small-shaping-machine

It was first published in the ME Oct 9 1952. I would make it have a little more tool height and fit it with an Auto cross feed, but not much else. The beauty of shapers and box planer is that you can do very good flat surfaces with them. This one would not take up much space and not ask for lunch!

If (and it is a BIG IF) I can get a piece of 3/8” (10mm) plate and some 5/16” strip I will re draw the thing and modify it. My box planer project is ‘on hold’ problem is the MOQ on epoxy 50 litres (in packs of 24 X 1 litre cans) The supplier’s excuse is he does not want to break bulk!.

 

I do not change the case size the postng bot does this.

Rgds

Dick

[Ian S CParticipant @iansc]

Bill, last night I had a look on google at a Utube clip of the HAE 03-1, a nice wee motor. I have a similar motor with a 35 mm bore x 13 mm stroke, the motor is designed for sitting on a log burner. It has no cooling fins, and the top end stays cool enough to be able to handle it. The idea is to have the fan blowing back over the motor, its suprising how much air a motor that size will move.

The root of the fins should be as near to the bore as possible, in other words you don’t want too much bulk of metal. Ian S C

 

 

PS:  the parting tool I use for cutting the fins on motors is ground up from a broken 12″ power hacksaw blade.

Edited By Ian S C on 11/11/2011 01:38:12

[Cornish JackParticipant @cornishjack]

Ian, thank you again – useful information. The Utube clip sounds interesting but I’ve only found one reference to this kit so far (the kit producers) on a Google search. Will try another search. Will also dig out some power hacksaw blades for future reference.

Rgds

Bill

[Ian S CParticipant @iansc]

Bill, I just typed in HAE 13-1 stirling engine, and went hunting, I’m on dail up so it took a while to load, usually for these vidios I go to the local library, and use the computor there, but I’v just got a new computor, and I wanted to try it out, the old computor was on IE 6, and did not like U Tube.

With the hacksaw blades I grind off the teeth (just), then use this edge as the cutting edge, it’s a bi-metal blade, so that bit is HSS. I think an all hard blade could be risky. I have used ordenary hand hacksaw blades for cutting grooves for circlips. Ian S C

[Sub MandrelParticipant @submandrel]

If you want to make narow, deep parting cuts why not make a vertical brace for beneath the tool out of 2.5mm steel plate. This would stop the flexing that will fatigue the tool, and prevent a big deflection if it digs in.

 

Also, parting aluminium you are almost certainly going to get some metal welding itself on to the cutting edge, even if using a cutting fluid of some sort. Clear the tool regularly and make sure the cutting edge is clean.

 

Neil

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