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Member postings for Nigel Bennett

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

Thread: Boiler build abandoned !
27/09/2019 17:20:26

Sorry to hear of your woes!

If you can find a fellow club member who is well versed in boiler-building, and who has access to oxy-acetylene or oxy-propane, the boiler may be rescuable. See what your boiler inspector says!

One thought; you've not been dumping the boiler when it's still very hot into the pickle, are you? That can easily cause massive thermal stresses which result in leaks.

Also, if the boiler is generally sound but just has the odd weep, then don't discount Comsol to caulk it up - but you won't be able to do any silver-soldering on it afterwards!

Thread: To Pin or Not To Pin
11/09/2019 11:31:01

I had the wheels come off (well not absolutely off, you understand) my 5"G Edward Thomas a few years ago. The Loctite gave way as a result of some over-large stresses caused (I think) by a hydraulic lock and as a result, the motion ended up in an interesting arrangement of angles and unsurprisingly it Wouldn't Go. I removed the coupling rods and ran it as a 2-2-2 for a few laps, rather than waste the nice bright fire, but it sounded a bit off-beat.

Later investigation showed the quartering on the driving wheels was about 120 deg not 90. I fitted some axial pins once I'd got it all back together.

The load on the Loctite had obviously gone far beyond expectations - but I've never relied solely on Loctite after that for sticking wheels on to axles. Crankshafts would, I imagine, be prone to similar unexpected stresses when in use.

I suppose it's down to where you want the weak point to be - did the Loctite failure on my ET wheels save me knocking a cylinder cover off or bending a rod or two?

Thread: Just bought an ML7, what should i do first?
07/09/2019 10:18:27

Whereabouts in the world are you, Shaun? If you're anywhere near me in Leeds I could pop over and have a look at it and perhaps offer some advice. For instance, engaging backgear on an ML7 is not obvious and requires a specially-shortened Allen key to slacken and move a little gear segment fitted to the bullwheel. Good luck with the restoration, anyway!

Thread: Steel axleboxes
06/09/2019 12:51:41

No problem at all with steel axleboxes with either gunmetal or cast iron horns, but they need to have a proper bearing for the axles. This could be with needle roller bearings or pressed-in bronze bushes.

You could even use steel horns with steel axleboxes, as the movement is slight, but you need to pay more attention to the lubrication.

Steel-on-steel does not work well as a rotating bearing as it's prone to "pick up" and seize.

Thread: Long tender means the controls need extending
04/09/2019 15:16:04

I could lend you a hacksaw to shorten your tender...

I've seen quite a few contrivances to operate loco valves from the rear of the tender. It usually involves a number of controls attached to a cross-plate secured to the tender. The controls are usually rotary (for steam valves) and generally involve a long operating rod provided with a couple of universal joints. The "loco end" of the long operating rods also need some kind of bearing/support.

There needs to be some provision for changing the effective length of the rods as the tender and loco negotiate curves. This could be a pin through one part of the rod and a slotted tubular section on the other. Water valves can be sited at the rear of the tender so that their operating valves can be sited where it suits you.

It depends on how you feel about your loco; if you want it to look realistic when you aren't using it, then it would be an idea to have all the jiggery-pokery removable - but that will add to the complexity of the design.

It does need very careful thought to make the regulator control safe; you don't want to be faced with the loco running away and you being unable to shut the regulator. Hence give a bit of thought to fail-safe design of the linkages so that if the loco-tender coupling parts, then the loco will coast to a halt.

You've got a big task to operate a pole reverser remotely, but a screw reverser might be susceptible of remote control.

My advice is to stay away from electronic/radio operating devices and use something mechanical.

Thread: Jim Al Kahlili : Revolutions
01/08/2019 13:41:01

I think you're just trotting out the tired old cliche of "parasitic cyclists" again. Why do you say cyclists are "parasitic"? Is it because they don't have to pay vehicle excise duty? Well work it out for yourself. VED is based on the amount of pollution caused by the vehicle. Electric cars pay no duty - but the carbon effect of generating the power in the first place is hardly negligible, and the road damage caused by them is no less than an IC vehicle. So as cyclists cause less pollution than electric cars, then surely then they should be paid to use the roads?

So let us assume that cyclists have to pay a proportion of that paid by petrol or diesel cars - £145 currently for a typical car. The only fair way to do that is to base it on vehicle weight as the effect of damage by the vehicle to the roads. Bikes weigh say 10kg. Cars typically weigh 1500kg. So that's 96p a year. Then you have to consider that the cyclist is barred from all motorways, so to be fair, that would further reduce it to about 60p.

Are you going to be able to instigate a viable tax system whereby you can ask cyclists for 60p a year? No, I didn't think you could.

Cyclists, pedestrians and horses have a RIGHT to be on a public highway. Cars do not - they only have permission.

I forget the exact figure, but I think it was in the 90% or so of adult cyclists who also tax and own motor vehicles.

Personally, I use my bike to keep myself fit and reduce my need for the overstressed NHS. I commuted to work when I was working because I hated being in long queues of cars when I did have to use it. And it was often quicker, and taking the canal towpath occasionally kept me off the roads altogether, thus freeing it up for nincompoops in cars.

I often find that people who moan about cyclists do because they're just too fat and idle to ride a bicycle.

Parasitic? Don't talk rubbish.

Rant over.

Thread: What lathes have you had?
22/07/2019 16:28:37

Got a bank loan at 18 to buy a Zyto lathe for £45. I recall making some cardboard dials for the cross slide.

Sold it and got an ML7. Sold that for £750 to buy a Super 7 for the same price! Still have it; I went to Nottingham to buy a gearbox and QC tooling several years ago.

Unimat 3, which seldom gets used other than mounting the head on a post on the Myford cross slide.

Boxford 280, which is a lovely machine, very under-rated. Designed by the same chap who designed the Harrison M300, I understand. Plan was to sell the S7 to pay for it, but a windfall meant that I could keep them both; it’s just a bit of a squeeze in the shed now. Great to have an Imperial and a metric lathe.

Thread: Dangerous 2" Scale BB1 Boiler
19/07/2019 14:30:56

Some years ago I bought a part-built 2" scale Fowler BB1 ploughing engine to John Haining's design from the estate of a deceased model engineer. He'd bought it from somebody else. The workmanship wasn't brilliant, but the boiler had been commercially built in about 1975 and came with a certificate, saying it had withstood 175psi without leakage or distortion. The boiler itself looked lovely, so I was quite happy with the purchase. It was always going to be a long-term project, so I was in no hurry to get on with it. (Ignore the bloody great hole in it in the picture below!)

After about twenty years, I thought I'd get the boiler certificated. So before taking it to the club, I pumped it up. Only I couldn't pump it up. As soon as the water level rose far enough, it poured out of the firebox from around all the tubes, none of which were actually soldered to the firebox tubeplate. So for the builder to claim it had hadn't leaked was an out-and-out lie. But by now it was far too late to complain - even if he was still alive to complain to.
I had a conversation with our chief boiler tester, and he suggested that I expand the tubes and then run round them with Comsol. So I did that, and pumped it up again.

There were a lot of further leaks from stays (screwed and silver-soldered) so I applied more Comsol. A couple of days ago I pumped it up again, and it withstood 150psi with only some very slight weeps from the odd stay. One or two responded to a bit of gentle caulking with a hammer and punch. Then a small leak manifested itself in what was apparently a plain section of boiler barrel, just in front of the firebox. Curious... I lightly tapped the area with a hammer and the leak became a torrent. I filed the area and a brass colour became exposed. The barrel had been brazed to the firebox, and then smoothed over before copper-plating the boiler to disguise it.
That was it. The boiler was scrap. I got out a hole saw and drilled out the area of leakage. When I got deep enough, a semicircular section of barrel became dislodged, leaving its mating half still riveted to an internal piston ring joint. I couldn't finish drilling through the piston ring because there was no fastening of the piston ring to the boiler other than where it was riveted in places to the firebox and it was pushing away from the hole saw. All that had been holding the barrel to the firebox was a manky brazed butt joint, which had locally come apart with the stresses of hole-sawing.

That piston ring was only serving as a location for brazing the two halves together!


These are the two sections of barrel/firebox wrapper removed by hole-sawing - and the braze had given way during the operation.


The whole thing had been a potential bomb. The scary thing is that if the joint had been only a few percent better than it had been, it wouldn't have leaked and I would have been blissfully ignorant of the potential. And it's a ploughing engine - it's not just pressure stresses on the boiler, but driving it over rough ground imparts who knows what additional loads on the joint?
Further investigation showed that the barrel was only 2mm thick - it should have been at least 3/32" (13SWG) and if I had been making the boiler it would have been at least 3mm thick. The backhead had been brazed in place too - and the section through it shows that the penetration of the braze wasn't all that good. And what kind of brazing rod was it anyway? How long would it have taken to de-zincify?


There were other concerns as well, such as very thin fire tubes - they'd have worn through very quickly - and the internal pad under the cylinders was not in the right place (or too small) so the front ring of cylinder bolts were only tapped into 2mm of copper.

I'm not prepared to disclose the name of the maker. Technically I can't prove anything because there is no marking on the boiler or certificate. Suffice it to say that he was later bankrupted. And I hope he had a really miserable time of it.

At least there's no chance of it being used - it's well cut now and I shall weigh it in for scrap.

Moral: Take care when dealing with older boilers built by unknown "professionals", and look at them very carefully before parting with your money. If a boiler has been copper-plated, walk away from it. It's hiding something. And always, always test a boiler you wish to use.

Thread: Forging brass; how easy would it be?
10/07/2019 10:14:46

If it's brass bar, then it's probably CZ121, in which case you've little chance of forming it as you want to do. It just doesn't anneal like brass sheet and stays hard after you've heated it. You can usually anneal the generally-supplied grades of sheet. Mostly due to the zinc content!

Just try it out on a small piece of brass rod first - so you don't waste both gas and brass - and after bopping it cold, try battering it hot, to see what Guy Lamb means about it being "hot short". Phosphor bronze rod can behave similarly.

Thread: Bespoke bicycle making
02/07/2019 11:41:50

I built a bike frame in Reynolds 531 back in 1978 - and I won a road race on it! I used a 5-pint paraffin blowlamp to silver-solder the frame - before I acquired a Sievert outfit. The frame is a rather sad-looking rusty affair hanging up in the garage now, because it needs a new down tube and a new bottom bracket shell and it isn't worth the effort - but I can't bring myself to throw it away!

Thread: Is it bad practice to lock my Myford lathe using the slow speed lever
25/06/2019 12:03:59

On my S7 I have marked one of the two possible engagements of the little flick lever which gives the solid drive rather than back gear, so I always ensure it is only engaged in this one position. Hence when the spindle lock is engaged, my headstock spindle is always in a certain orientation. Having engaged the spindle lock, and properly fitted a chuck, I have then drilled a little dimple in each and every headstock spindle-mounted chuck such that the dimple points upwards. These dimples are painted black. Hence I can easily spin the chuck to rotate the headstock spindle more or less the correct orientation to engage the spindle lock.

Having engaged the spindle lock, each chuck was unscrewed very carefully until it just disengaged with the thread. Another dimple was drilled in each chuck at the vertical position at the point of disengagement and the dimple filled with red paint. Hence I know when the chuck is about to unscrew - or it has one more full turn to make - so I can take hold of it before it unexpectedly releases and smashes down on to the lathe bed. Also I can orient the chuck correctly to start it on the spindle threads (with the spindle lock engaged) so that again, it engages immediately and doesn't fall off when I release my grip on it.

I did the same thing with my ML7 years ago but I dimpled the spindle so I could orientate that correctly for chuck-changing as above.

I did this because I did something similar with M42 screw-mount lenses many years ago when I dropped a 400mm lens on to some concrete due to it not being in the correct orientation to start engaging the threads.

The spindle lock is provided for a purpose - use it and don't end up with a dentally-challenged lathe and a stupid expression on your face.

Thread: Historic Frogs
20/06/2019 14:32:38

Boggy the Frog in Into the Happy Glade and By A Silver Stream. Written by Trevor Dudley-Smith, aka Elleston Trevor, who is more well-known for his "The Flight of the Phoenix".

Bit obscure, but true!

Thread: Making High Speed Steel Injector D Bits
17/06/2019 11:38:15

Hardening D-bit reamers usually resulted in banana-shaped curiosities for me. So having been inspired by an article about injectors by Basil Palmer, I ground some HSS injector reamers using his idea of triangular section. (Would be likely to give more even results in silver steel as the section is more uniform and symmetrical, so less prone to distort.)

I mounted a Quorn head on my Boxford 280 to grind some HSS and it worked out quite well. Note that if you want a 9 degree included angle, you DON'T grind the faces with the top slide at 4.5 degrees but at about 2.2 degrees - it depends on the diameter of the grinding wheel.

I made the mistake of grinding some Chinese-sourced HSS 6mm dia, only to find out when I tried to use one for reaming an injector cone that the stuff wasn't hardened. After trying it, the pointy end of the reamer came out looking like an oliver off a Showman's engine! I then dug out an old HSS tap and ground that instead. I did get a working injector, but it needs more time and attention than I have at present to get the working pressure range I want.

Despite covering up all of the lathe I could with newspaper, it still took ages to clear up all the horrid mess after grinding - so take care!

Thread: Noise Cameras
12/06/2019 12:01:25

Posted by Mike Poole on 12/06/2019 11:18:38:

Before the ignition was part of the steering lock or keyless a decent backfire could be obtained by turning off the ignition and then back on ( of course this is just what I have heard).


When I was a child of about two, my uncle showed me how you turned the ignition off and back on again to create a very satisfying bang. It was perhaps predictable that I thought I would see if I could make it go bang, too. It was perhaps unfortunate that Uncle was doing about 70mph when I tried it. It went bang, all right - blew the bloody exhaust system to bits! And it was his own damned silly fault for teaching me how it was done...

Thread: Internal grooving help required.
08/06/2019 09:57:49

For reasons that escape me now, I once did a small job where I bored the groove OD into the bore with a slot drill, and then pressed in a little turned slug to create the groove. It depends on how much load you will have on a pressed in slug if you go that way.

Thread: Boiler issues juliet
05/06/2019 13:59:57

Silver-soldering studs into a boiler with any sort of soft solder in it is a Very Bad Plan. Don't do it!

Fitting studs into your boiler should be possible if there's a reasonable thickness of material and the studs aren't too big in diameter. You need good threads in both boiler and stud, and some Loctite 542 will provide an excellent seal.

Once you've fixed it, do a hydraulic test on the boiler to one-and-a-half times working pressure by pumping it up with the hand pump to check all is well before lighting the fire.

I'm sorry to hear about your health issues - I hope you can sort the Juliet out and get it running again.

Thread: Minnie 1"
28/05/2019 17:03:24

Check the bar litres of the boiler. A Minnie is very small and likely to fall within the “smaller boilers” category specified in section 11.7 of the regs, where only one water feed is required.

Thread: Cast Iron For Boxford Change Gears?
21/05/2019 14:20:06

If you've set yourself the task of doing it, fair enough, but this chap advertises plastic ones on eBay and I had a couple off him for my Boxford 280. Usual disclaimer; I've been very happy with them.

I can't find exactly what you're looking for, but here's a sample:


Suggest you contact him and ask for a price for what you need.

Thread: Servicing a Myford 254
03/05/2019 11:17:09

I've no knowledge of the Myford 254, but in the Boxford 280 manual I have it suggests very strongly that you don't faff about with the bearings, but leave it to their service department.

However, they say - if you must...

"Pre-load condition may be checked using the cord & 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 disconnected from the drive."

I imagine the two arrangements are very similar - adjustment by fine-pitched collars to set the preload.

I changed my spindle bearings on my Boxford, and it's not a task to be undertaken lightly.

Thread: 2" Clayton Wagon help
26/04/2019 17:32:20

Quite a few folk (including me) have omitted the feed-water heater as it causes more problems than it solves. My steering wheel is fine relative to the regulator. Are your boiler feet set too low? Or is the steering column a tad short?

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