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Member postings for David Senior

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

Thread: how to make it stay in ?
29/03/2022 22:08:55

Turn a groove on the section that fits down the tube, and fit an O-ring. Use a fairly chunky O-ring and play with the groove diameter to get a good grip. We make wheel centre caps using this retention method. The section that fits inside the hex can be cylindrical - no need to make a hex. The O-ring will grip on the flats in the hole

Dave

Thread: Changing my Email client
17/03/2022 19:03:59

I've used Thunderbird for years with no apparent problem, until I became aware that I was not receiving quite a few important emails. It took me a while to realise that I had no Spam folder, whereas on my wife's computer my account did have a Spam folder and that was where the missing emails were ending up. Turns out that I was using POP on my computer, and IMAP on hers. I had to change to IMAP and now I get all the emails. Quite why they end up in the Spam I have no idea.

Dave

Thread: Cross-slide fixture plate considerations
06/03/2022 13:59:40

Can't offer any advice on the main part of your question, but Cutwel do 8.8mm in their aluminium specific range, though I am not sure why you wouldn't use a standard jobber for this, and I wouldn't expect any issues with the life of the drill

Dave

Thread: tapered tap
06/03/2022 13:39:53

Are you sure the female thread needs to be tapered? If you were to try an M4 nut would it start, and would it tighten up the collet as it moved up the thread?

Dave

Thread: Stuart #1 Reverse Drawings
20/02/2022 19:05:03

John

There is no reason that I can think of for having the shaft longer, apart from not wanting it to be shorter than the bearing so that it can't wear a groove in the bearing. So I guess equal or just slightly longer would be best.

I haven't got to making the eccentrics yet, but I am thinking of doing the bore and keyway first, then mounting on a mandrel with both centres in the ends so that I can set between centres to machine. I intend to machine them to the same width as the straps, so there will be a section between them that looks like a woodworking biscuit joint piece, if that makes sense. That way it is not so critical about getting the 'joint' in the middle.

Not sure when I will get round to it. Technically I retired at the end of Jan, which is why I have started on this project. However retirement for me will be going to work everyday as normal (all my equipment is there) and hopefully not having to do any 'proper' work so that I can concentrate on the models. Right now I am still choosing to run cnc machines until a new employee starts in a fortnight, so I am not able to concentrate fully on this.

Dave

Thread: What type of steel
20/02/2022 10:22:29

I buy ground flat stock from Cromwell (cromwell.co.uk). They offer 1/4" x 3/4" x 18" long Order code IND-413-0704E. As for shipping to Italy - who knows!

Dave

Thread: Stuart #1 Reverse Drawings
20/02/2022 10:13:01

John

I think you have missed the fact that the strap is not symmetrical about the locating groove. By my calculation (and as shown visually on the reverse gear drawing - not that that should be taken as gospel!) the straps align with the outer faces of the eccentrics, leaving a gap between the straps.

This doesn't change your conclusion, except that the skimming of the bearing face will only be to give working clearance, rather than to correct a foul. The eccentric pair will definitely need counterboring to clear the crankshaft bearing diameter.

I have yet to attempt to master the joys of tapered gib keys. Clearly here it is going to be important that the key doesn't protrude beyond the eccentrics.

I think we are there now!

Dave

19/02/2022 21:59:31

John

Thanks for taking the trouble to check your drawings

My belief is that the bearings need to be fitted with the thin flange inwards, and the thick one outwards (crank width across webs = 1 7/8", Gap in bed plate = 2 1/4" leaving space for bearing flanges of 3/8" i.e. 2 at 3/16"

So my calculation for bed plate centreline to bearing outer face is 1 1/8" + 3/4" + 5/16" = 2 3/16"

I agree with the 2 9/16" to the centreline of the valve rod

The eccentrics are a total of 3/4" wide, so half of that (3/8" inboard of the valve rod gives 2 9/16" - 3/8" = 2 3/16" so nominally touching the bearing face.

The crank bearing diameter extends to 15/16" + 1 5/16" from the centreline (2 1/4" (i.e. protruding from the bearing by 1/16"

If I am correct I will need to either shorten the bearing diameter on that side of the crank or (more likely) counterbore the eccentric pair to clear the step on the shaft. Skimming a small amount off the main bearing on that side to give a small clearance should be straightforward.

I haven't checked with Stuart Models as to whether the drawings have been changed, so I don't know whether this is a recognised problem (or whether I am somewhere mistaken)

I am impressed with the look and finish of your No1 - I can only hope that my 5A will be somewhere near and that my grandfather would have been proud of it.

Dave

19/02/2022 08:18:01

I've followed this thread with interest - I'm working on a 5A with reversing gear at the moment, and if I've got it right the eccentrics foul the step in the crankshaft. On nominal dimensions the eccentrics will rub on the flange of the crank bearing, but the crank change in diameter is a further 1/16" out. The additional drawing for the reversing gear shows a clearance of about 1/16" between the eccentrics and the bearing flange. (My drawings are dated 1954 and issued in 1965 - the engine was started by my grandfather who died in 1966 and I feel it is about time it was finished!)

Dave

Thread: 1960's Car Steering Wheel Taper Angle
01/04/2021 22:09:33

I have an Automobile Engineer's Reference Book from 1956 which gives the taper as 3-1/2" per foot on dia, or 1 in 3.43, or 16° 35' 41" included angle. So I guess your 8° per side is close enough!

Dave

Thread: Tufnol, Phenolic, SRBP, HPL, CGL, SGL
15/02/2021 22:19:49

Trespa offcuts are available from David Meddings DeSign (or they used to be when he had the unit next door to my work - he has now moved further up the industrial estate so I don't see the piles of material any more). I don't have a contact number handy but I am sure you can find him on Google - he also used to trade as Reel Furniture. He is in Attleborough, Norfolk

Dave

Thread: Marine Engine Flywheel Fixing
18/01/2021 18:51:46

I've had a quick look through some books on marine steam engines and I can't find any that show a flywheel, but they all appear to have a flange as Jason suggested. I doubt if you would get keyways on the bigger stuff.

Dave

Thread: Great Central Atlantic in old ME
17/01/2021 20:29:53

Pages are in reverse order, but hopefully still useful

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17/01/2021 16:55:45

I have the issue you want. I will scan it for you

Dave

Thread: ME 4653
08/12/2020 18:30:27

Mine arrived yesterday, so there is probably still time before it can be considered lost.

Dave

Thread: non delivery of magazine
24/05/2020 15:15:52

My experience of ME mags that don't arrive is that they say they don't have any spares left to send out and they extend your subscription by 1 issue. Then you find that the company that takes all the surplus ones will sell you one but you have to pay the postage. It's a bit of a con! You would have thought they should get a copy back from the surplus company, or at least arranged for that company to supply one FOC

Thread: High Grade Aluminium Supplies
01/05/2014 20:05:53

I also use Metalfast (or ThyssenKrupp as they are now known) but have recently started using Shropshire Stainless & Aluminium www.ssaltd.net . Not sure whether they will deal without an account, but they are very keenly priced on sawn plate.

Dave

Thread: Bridgeport clone quill / knee conversion
11/06/2011 06:32:15
It may be a bit late to add to this thread, but I motorised the knee of my Myford VMF mill (article published in MEW issue 137). I had problems with the weight of the knee assembly, and the conversion had it's limitations. To solve this, I added gas springs, which was very successful. I submitted 2 follow up articles to the editor but unfortunately they have never been published.
I was very pleased with the overall conversion, and it allowed me to dabble with some ideas for products to fit to my classic mini. Things moved on from there when I decided to try and sell those products, such that my company bought a 'proper' cnc mill. Now the VMF gets little or no use, and seems incredibly slow compared to the scary speed of a modern machine!
Let me know if any more details would be useful.
Dave
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