Member postings for Nigel Bennett

LOL, as they say. Still; you've got the possibility of mounting your Centec on the wall as a vertical milling machine. And it could have been even more amusing - you might have only had a Unimat 3...

Brian's comment is spot on. Building a loco is like a love affair; you really have to love the loco you intend to make, otherwise you lose interest and you start making excuses not to continue with it. Another "Part-finished loco for sale..."

What about "Sweet Violet" - a 3.1/2"G version of Sweet Pea? Not too complex, and it should fit the bill. And the boot.

Good luck with whatever you choose!

It's a simple error with the CAD model; the thread Vee section has been sketched such that it starts the helical cut a little way after the end of the part.

I've personally struggled to assemble a rogue screw exactly like the original illustration - i.e. with a series of grooves in it - before I realised and flung it into the deepest recesses of the workshop with a bellow of rage!.

Unless you really need to 3D print the threads in, I wouldn't bother. Why can't you use a real screw? We often produced 3D parts at work with tapping-sized holes in and tapped them out to fit later. We certainly never 3D printed fasteners unless they were an obtainable special.

As David Jupp says, the processing power needed to create true 3D threads is huge. You'd probably take as long doing it on the CAD as you would tapping out a plain hole!

Edited By Nigel Bennett on 04/10/2017 10:49:18

I read the report in the latest ME on the Midlands Federation Rally 2017 with interest. Well-titled photos of a variety of locos, including the unusual aluminium Sweet Pea Alicat. I couldn't get there, so it was great to read what I'd missed.

I have just opened the October Engineering in Miniature magazine - to find exactly the same report, with exactly the same photos and photo titles. What's going on? Is it just unfortunate for EiM that they've published after ME so it looks as though they've blagged the article, rather than the other way round?

Isn't there some kind of exclusivity clause written into the Author Agreement?

Purley Grange in 2½"G?

Molybdenum disulphide, surely? My S7 ran hot in this way a while back, but I just kept topping up the oil cup with steam oil and that seems to have cured the problem.

Has anybody found a simple way of curing leaks in taper-cock gauge glass blowdown/cylinder drain valves? I'm referring to the conventional bronze bodies and stainless cocks.

It seems that grit gets in and creates grooves in either or both tapered parts, and dribbling commences.

"Grinding in" a leaky fitting only seems to move the grooves to new positions, and excessive metal removal will move the cock axially, so the cross-hole no longer lines up with the fitting.

A PTFE insert might work (either tapered or as a conversion to a parallel cock) but it would be a bit twee and I've no confidence in such an insert not rotating when it shouldn't. - it needs to be fixed to either the cock or the valve body.

Other than making a new cock to suit the reamed-out hole in the fitting (You did remember where you put the reamer you used to make it, didn't you?) does anybody have any bright ideas?

This thread is certainly wandering about a bit! Regarding your cylinders, Steve, you could do worse than fabricate them either from several bits of mild steel (or brass) silver-soldered together, and fit either cast iron or bronze liners - your choice. With a bit of forethought you can make all (or at least some of) the bits to self-jig together, or else knock up some kind of fixture to hold them all in place when brazing up.

Having said that, printing a pattern can allow you to include all sorts of detail that would be tedious and tricky to machine from solid or fabricate. Cast-in passages? Let us know how you get on!

Ah, yes, the Archers - or dah-de-dah-de-dah <CLICK!> as we know it.

What have I done in my workshop today? I've drilled a 2.8mm hole.

Unfortunately it was in the middle of (and through) my finger nail... Ooyah! as they used to say in the Beano.

'Twas a while ago; I've just delved into my old photo album to find it...

I skimmed the bolting face flat with a 12mm carbide cutter in the milling machine (Rishton VM60; same sort of size as yours). The cylinder was then mounted on the lathe cross-slide, sitting on the bolting face with a packer underneath of the correct thickness. A between-centres boring bar then brought the bore to size. I used a lathe tool held in a four-jaw chuck as a fly-cutter and skimmed the end face. The casting was then swung round and carefully angled (NB mine is for "Edward Thomas" but uses the same castings) and the port face fly-cut using the lathe tool again. Then back on to the milling machine to do the ports.

If you need, PM me your email address, and I'll photograph the photos (good old silver halide technology then!) and email them to you. There are just five photos.

Cheers

Nigel

To use a 25mm insert-tool cutter like you show, the milling machine needs to be good and rigid, and the job well clamped down. Your Senior milling machine isn't above suspicion in that regard. I think I'd probably use something like a 12mm solid carbide cutter. You'll need an ER collet or similar to hold it.

One ray of hope. I have one spare unmachined Sweet Pea cylinder so if it goes all pear-shaped for you on one of yours, then you can have it for the cost of the postage.

Good luck!

My Boxford 280 motor is rated at 4.9A for 3-phase 220/240V. It's run from an IMO Jaguar Cub 5A inverter, and I've no problem at all feeding it from a 13A socket. One of the beauties of an inverter is that it ramps up the motor speed relatively slowly - you can adjust it - so that there's no massive inrush current like you get with single phase motors.

Suggest you speak to Pete Moss at Transwave. Very helpful and knowledgeable bloke.

Yeah, done that on my 3.1/2"G Tom Rolt. (Ian Screeton on the KLR was very helpful about it!) It was always intended as a testbed to ascertain whether it would work in a small firebox. Unfortunately, it's still too early to tell if it works or not, as I'm still having great difficulty with other aspects of the loco. I need it to work conventionally at first, and then try it on GPCS. (Having said that, I have tried it briefly when running on the "home trainer", and it didn't appear to have any significant adverse effects, but it was far too quick a test to be significant.)

I fitted hollow stays to admit secondary air above the firebox; it's got a "brick" arch made from titanium, and the exhaust steam feed to the ashpan is controlled from the cab, as well as having an additional live steam feed as well. Making the boiler superheated, whilst maintaining an external regulator like big brother was interesting; I ended up making it a screw-down valve but with a 5-start thread to allow it to pass enough steam.

Instrumentation and measurement of the changes is likely to be an interesting exercise. A Lempor exhaust is also part of the experimentation; I've made several chimney chokes and even more four-nozzle blastpipes with differing hole sizes to try out. So when I've got the blasted steam-operated draincocks to work, I might get somewhere. (Then if I'm happy with the results, I can decide how I'm going to make the boiler for my 9F when I get around to that.)

Anyway, when I eventually get some results one way or another, I'll write it up for ME, but it won't be this year.

I have found that Hammerite Smooth in Cream is as near as dammit to the Boxford colour. The yellow is a bit different, but if you repaint all the yellow bits, then nobody will know...

Clare collets were specifically for Clare milling cutters. They were unthreaded in the area where Clarkson cutters are, but they had a special tongue instead. The idea was that you inserted the cutter into an appropriately-sized collet, twisted it a few degrees to engage the tongue with the collet and then tightened the closing nut.

You can sometimes get Clare collets second-hand, but otherwise the collets are pretty well useless. They'll probably grip a Clarkson or plain cutter reasonably well, but the grip won't guarantee it being pulled out.

We used them back in the 1970s in the apprentice school!

"This is the sort of bloody nonsense up with which I will not put." - Winston Churchill.

I recently got some of the 6mm round HSS from China; I needed them for making some taper reamers for making injectors. I was quite surprised when one of them twisted in use, ending up looking like those olivers they put on showman's engines. So having realised they were unhardened, I simply heated the end of one of them up to cherry red and dunked it in some water. A gentle tap with a hammer had the hard end pinging off into the recesses of the shed, so at least it confirmed they were hardenable!

**LINK** gives some useful information about hardening & tempering HSS. I shall have a go and see what I can do with the Chinese HSS and then make some more reamers!

Doesn't help the OP - using "easy outs" - surely the most mis-named tool that ever was - is useless as John S has said. However, Michael's mention of hexagon socket screws reminds me that it's often possible to batter in a Torx bit into a rounded-off hexagon socket to get it out. Recalcitrant countersunk screws can also benefit from a good crack with a hammer before removing.

Joseph, the Boxford manual says "Pre-load condition may be checked using the cord and spring balance method, when a steady pull in the region of 0,68kg (1.5lb) for new bearings or 0,34kg (0.75lb) for used bearings should be obtained, with the cord wrapped round the spindle nose and all gearing disengaged from the spindle." Tests must be undertaken at room temperature.

A tiny difference in the length of your spacer tube will make huge differences to the amount of preload on your bearings. We're talking tenths of thous here. Ideally you should have some kind of adjustment (think lathe spindle bearing adjustments) and be able to lock it all up once you've got the preload you want. It's usual to specify some kind of torque value when the bearings are adjusted correctly - on my Boxford 280, for example, you wrap some string around the spindle nose and measure the load needed to rotate the spindle, which should be of the order of one pound.

I think you will be in for a lot of mantling and dismantling to skim bits off your sleeve if you go that route, and if the bearings then take up a bit in their housings, you'll have a sloppy assembly and all the weary work to repeat but with a longer sleeve... hence the adjustable bit is a better idea if it's at all possible.

With regard to your original question about how much preload, Timken or SKF websites should give you a clue.

Good luck!