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Member postings for Cornish Jack

Here is a list of all the postings Cornish Jack has made in our forums. Click on a thread name to jump to the thread.

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Thread: Unmitigated Woe
20/11/2011 21:11:34
Neil
Can you confirm that you are in Spixworth, Norfolk?
If so, and it is of any use, I have a spare Hobbymat which you are welcome to borrow. It all works as advertised and would only require collection from Bacton.
PM me if of any use
Rgds
Bill
Thread: UNregulated DC??
20/11/2011 14:09:47
Thank you very much, Steve.
That explanation managed to make sense to me as regards the no load/high voltage situation. In practical terms, I shall stick with regulated supplies, however it does seem to me that making an UNregulated supply with SELECTABLE output voltages which are meaningless, is a pathway to disaster for electrical thickheads like me!!
Rgds
Bill
 
20/11/2011 11:00:21
Thank you gentlemen, one and all.
What I think I understand is that I COULD use regulated or unregulated and the units will sort out what's needed??
Still can't get my limited brain cells around why THREE Unregulated supplies metered out at 17 volts with each one selected to the 6 volt selection
I have some voltage selectable regulated units lying around so will try those.
The DROs are the BW MPS versions - nicely basic, no confusing 'bells and whistles' and they MIGHT just improve my machining tolerances out of the present 'Oh well, nobody will notice that!' level
Rgds
Bill
19/11/2011 11:12:50
Possibly one for Les Jones or one of the other wiggly amp gurus.
I've just got some DROs which should be powered by a 9 volt supply. The makers stipulate an UNregulated supply. My only previous experience with such things resulted in nadgering an FM radio (6 volt selected on a variable output 'wall wart' ) Checking the output (later) with 6 volt still selected showed 17 volts on the meter. The vendor of the supply confirmed that this was what one should expect. I am not the sharpest tool in the box re 'lectrics and I cannot see the point of having - a) variable selections on an UNregulated supply (if the output is always maximum) or
b) why would such a supply be stipulated.
Would much appreciate an explanation ... in simpleton terms , please?
Rgds
Bill
 
 

Thread: Steel castings?
19/11/2011 11:00:40
Thank you, Ian. I'll see what's available on line here and give it a whirl.
Rgds
Bill
18/11/2011 11:19:01
Thank you Ian.
Agree about the ali castings but have now (more or less) got them sorted Your crankshaft idea sounds better than the kit version - 'glued together'?? Loctite ?? or epoxy resin?? or?? 'cos I haven't used glue in engineering context. If I knew a bit more about these things, I suspect that I would be mightily impressed with your latest.
Rgds
Bill
17/11/2011 11:14:12
Interesting comments and suggestions, thank you.
Neil - could be; only previous experience of laser cutting was a batch of Minnie wheel spokes and the finish on those was very smooth; these are much more like casting finish. Ian - yes, had considered that but persevered on the mill and now have reasonable surfaces (close enough for Government work!!) so will struggle on.
The main crank looks worryingly fiddly - built up from brass webs and steel shafts and (with no instructions) presumably press fits. Definitely a case for my 'Good Lord, that was lucky' tolerance machining

Edited By Cornish Jack on 17/11/2011 11:15:12

16/11/2011 17:11:52
Thank you Jason.
No, not at all sure what it is. The external and internal surfaces were 'as rough as guts' and the first cuts were like getting under the skin of iron castings. However the brackets support the crankshaft which is made up from quite thin section brass strip webs and insubstantial pins in brass bearings - overkill and underkill??
Rgds
Bill
16/11/2011 14:39:30
G'day all.
No doubt rthis will seem somewhat odd, but how common are STEEL castings?
I'm in the middle of making a mess of a Sieg Hot Air Engine kit and machining the 'A' bracket supports. They looked like (the expected) alumimium castings when first seen but machining generated blue chips and some sparks!! Can't think of any particular advantage of steel in this area and it certainly makes life somewhat more challenging. Any thoughts as to why Sieg went down this route, anyone?
Rgds
Bill
Thread: HAE03-1 Hot Air Engine
11/11/2011 11:31:44
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
10/11/2011 14:16:17
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
10/11/2011 11:03:30
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
09/11/2011 22:05:40
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
09/11/2011 18:45:36
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
09/11/2011 18:40:47
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
09/11/2011 14:51:12
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
Thread: A good 'Model Engineers Day Out'
03/10/2011 11:42:51
Bill, Ramon et al ... let me add my thanks and congratulations also! Super day, exceptional models, both in variety and quality. The full size engines were awe-inspiring - I did a 'by eye' calculation of the size of just one of the crank webs on the big beam - about 2'6" x 2'.0" x 9"!!! ...that is serious metal!! Steam and hot oil ... Aaaah! lovely! Couldn't manage the whole day - knackered back and knee past its 'sell-by' date saw to that - but hugely enjoyable. Last, but not least, special thanks to Ramon for his patient explanations, particularly of the anodising process - model engineering expanded to encompass chemical experiments and the results truly superb.
Rgds
Bill
Thread: electronics
26/09/2011 16:41:57
John - thank you so much! Looks like the very thing and some interesting potential other bits as well. Much appreciated.
Rgds
Bill
26/09/2011 11:38:36

I'm similarly interested in an area which has always left me a bit 'mind-boggled' - pretty easy to bring about!! Most electronics treatises leave me wondering whether we're using a common language, although I've managed to do the basic practical things like wiring up workshops etc.
I would like to 'fiddle' with simple circuitry and integrated circuits etc., to which end I've got a couple of beginner's breadboard kits plus a more interesting device shown in the photo. Purchased secondhand, it came with no instructions and 'Net' searches have produced nothing. Does anyone, a) recognise it or b) have any thoughts as to where I might find any useful info, about it, please?
Rgds
Bill
Thread: A good 'Model Engineers Day Out'
23/09/2011 16:46:59
Thank you, Bill
That sounds much better! Looks like a good day out, indeed - looking forward to it.
Rgds
Bill
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