Member postings for Robin Dufton

On the low end one 3kw VFD is £300, for a sort of trusted brand, and I buy Eaton ones for ~£500. Eaton 550w VFDs cost me £110 a piece. So across 10 machines of varying power requirements you're well over half way to the British made 20hp phase converter. Add in enclosures, switches, cable and time, you're well down.

In 2019 the cost for three phase for us was £1400. £900 of that was the permits and permissions required to dig up a 300mm square bit of pavement at the edge of the property. I know it is now triple that as more and more people want it for EV charging.

Why would you need a 20hp phase convertor if your largest machine is 4hp? The single phase supply you would need to run 20hp would likely raise more questions from the electricity board than what you would be doing with three phase. We recommend a 40A supply for when we supply machines running 5.5kw VFDs on single phase, and 20hp is pretty much three times that.

I know my house has a 100A supply, but I know new builds are lower, something like 63A rings a bell, so they would probably like to know why you would want a 100A supply. I'd go with the diesel generator suggestion if I needed that much beef and couldn't get three phase.

If you're going to do that you might as well put an M4 tap in the hole and use M4 screws. Having had a 1/4 die head I can't see why the body would be hardened and prevent doing it.

Edited By Robin Dufton on 03/08/2023 19:33:30

To drag up an old thread although it might help anyone searching for the same info.

I've rebuilt a few Meddings over the years and have found the spindle pulley from the generic Chinese 16 speed drills to be a close match to the LT and M2 pulleys. The bore is 24mm, so needs taking out, and a keyway needs cutting. Also the smallest step is the same size as the 2nd step on the Meddings and the top step is exactly the same, so the highest or lowest speed is a few percent out while the opposite end speed stays the same. They're also £8 from Machine Mart for the Clarke version and £15 for the Draper, depending on who has them in stock.

The generic type A pulleys don't fit under the cover as they're 80+mm. The 16 speed pulleys are a lot closer to the originals and just fit.

Edited By Robin Dufton on 30/07/2023 00:07:16

Ok. I guessed there would have been more interest in this, especially the steel boiler to our design, as we must be doing something wrong. I guess we'll go back to building it behind closed doors.

I've always liked the look of the Sunbeam S7 Deluxe for the American styling although they're over budget. £5k is a bit tight for a decent classic bike as even Noddy bikes are £2k. I have my well used RGV250 up for sale at the moment for £6k, and mint bikes are over £9k, as classic bikes prices are through the roof at the moment.

We've been a bit light on progress recently as we've had a fair bit of work to get through. The last of the riveting. 700 rivets in total between the tender and belly tank.

We've used Matt in the past to shift stuff and been very happy. https://www.1tonne.com/

You say it's 15' x 8' and have ruled out a large knee mill. The manual machine space in our workshop is that size and has two lathes, drill and a Bridgeport type mill. If the small lathe were gone you have bench space and our walkway is free space to put something like a saw. The mill cost considerably less than £2000 and is like new. It came from a company who repaired weaving looms that had shut down, and had spent it's life making small brass parts. Two of us moved it in our Transit van with an engine crane.

There seems to be a lot of pearl clutching when it comes to steel boilers. I've seen it in old model engineering books that a steel boiler should be 1/4" thick with no evidence to back it up other than best guess or rule of thumb. Our boiler could be 0.27mm thick and take it's working pressure, plus 1mm for waisting, so 1.27mm total. 3mm is plenty. The ASME regs, which I found after doing my calcs and sending them to the boiler inspector, backed up my calcs.

The only thing the boiler inspector questioned was using 3mm thick steel for the firebox and he requested 4mm. I'm happy that 3mm would be fine, although it is 4mm as we're not going to argue or upset anyone, especially someone that experienced and helpful.

When I did the calculations for the Ransomes boiler I also worked out the yield stress for Haining's copper design and it was below the 2x test pressure, something like 11bar without looking at my notes, vs 12 or so. The yield stress for my steel design is at 40bar and it would reach it's UTS at 70bar. At working pressure the sides between the stays moves outwards by 5 microns, it could have just about passed a 16bar 2x pressure test with no stays.

We settled on 8bar, even though it could have been run at 15-20bar, as we made the pump to his design so it seemed like a reasonable compromise and it is 30% higher than the copper design anyway. We could have redesigned the pump although we've changed enough of the design already.

Edited By Robin Dufton on 27/06/2021 15:35:58

Tony Baldwin of AJB has retired and he was also Bell Boilers, as when I rang him the caller id said Bell Boilers. What scale is it?

Rather than worrying about leaks you should really focus on getting started. Things like that can be solved when it's finished. If you're doing it odd evenings and weekends you're a couple of years away from it being finished.

Edited By Robin Dufton on 26/06/2021 20:23:51

I wouldn't bother without a spindle speeder and they do occasionally come up second hand. 3mm is pushing it on a manual mill, trying to cut with a 1mm cutter would be pissing in to the wind, but then people use face mills in little Chinese mill drills.

I guess you want to know the minor diameter. If it's metric just subtract the pitch. Pocket Ref

I've never understood this idea that top slides lack rigidity. There will be a screw to lock it against the gib strip. Take it out and replace it with a handle.

Potting compound wouldn't be ideal as it's often a hard setting epoxy.

We use this stuff for reproducing NLA rubber parts on vintage bikes, just pick a suitable hardness and make a mould. Give it a few days to cure and you're good to go. Link

One piece of advice with castable PU. To reduce the chance of getting bubbles when you mix the two parts, put the bottles in warm water before pouring it out.

Edited By Robin Dufton on 09/06/2021 21:44:01

I remember reading something like the worms on small dividing heads and rotary tables are peened in the factory to reduce backlash, as they're too small to fit in any other way of eliminating it. Even with a new worm gear it may be more hassle than it's worth getting it set up correctly because of that.

If it's a well made unit from a decent company that has a few parts missing, and worth saving, there is the option of buying a foreign copy and stripping it for parts.

Edited By Robin Dufton on 08/06/2021 21:52:26

More progress. Finished the rear wheels and crankshaft, just some tidying up to do on the counterweights from being laser cut. We also managed to work out a system for building the wheels and them ending up straight, unfortunately we only worked it out on the last one, so if the others don't look so brilliant when it's running we may redo them although they're all within 0.25mm in all directions.

Edited By Robin Dufton on 07/06/2021 16:19:18

Edited By Robin Dufton on 07/06/2021 16:19:37

I can't see 4 inch steel tube in anything other than 1/2" wall thickness on there.

Didn't think to ask one of the model suppliers. The fire tube material is coming from them so we should have asked about tube, although the only stuff I can see on there is 1/2" thick.

Finally got all the bits together for the boiler. Getting 4 inch tube was an absolute nightmare.