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Member postings for duncan webster

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

Thread: Motorcycle General Discussion
21/05/2022 21:48:20

I remember the suzuki super 6, lightening fast in a straight line, but dodgy on corners, especially with the original tyres, which seemed to be a bit short on grip to put it mildly

Edited By duncan webster on 21/05/2022 21:50:44

Thread: Fkesxispeed...what is the back gear for and how to use it
19/05/2022 23:23:52

Before I fitted the 3 phase motor and vfd my lathe had a speed range 50-2000 rpm. My 3 phase set up can deliver constant torque up to 50hz,constant power from there to 100hz. If I set the belt ratio to give 2000 rpm at 100 hz I get full power 1000-2000 rpm, but only 1/20 full power at 50 rpm. I'll stick to having back gear for slow jobs where I want a decent cut, but I usually leave it in middle belt ratio and use the control pot. I've got max frequency set at 75 hz

No way would I go back to single phase motor, I've also got a vfd on my milling machine, and had one on my little cowells 

Edited By duncan webster on 19/05/2022 23:25:18

19/05/2022 15:01:46

To be pedantic (who me) reducing speed doesn't necessarily reduce torque, it does reduce power. The normal reason to reduce speed is bigger workpiece, so the cutting load is at a larger radius, so for constant torque you need smaller depth of cut. I have a vfd, but still use backgear as running motor too slowly means the cooling fan is ineffective. I have seen industrial variable speed motors with separate cooling fans, a bit ott for a little lathe

Thread: threading delrin - alternative method
16/05/2022 19:15:07

Winding in reverse but with the tool the right way up but at the far side works as well. Then with a bigger thread you can see what's going on. I usually cut internal going the right way (my last lathe had a screw on chuck) but with the tool inverted at the far side, then feeds were the same as external, and the chips fall away from the tool

Thread: Wyvern crankshaft question
14/05/2022 18:13:16

The crankpin holes on old British bikes were tapered so you Coul push them nearly home but still adjust by putting between centres and hitting with a lead hammer. Having broken a hydraulic jack trying to dissemble a loctite joint I have great respect for it

Thread: A mandrel for long narrow tubes
13/05/2022 23:11:12

I used an expanding oring to grip the bore of a 22mm I'd bronze sleeve whilst I machined the OD. No need for tapers, just squeeze it endways and it expands sideways, or tries to. However in this case if you can have the tube a tad overlength just slide a 12mm bar up it, grip one end in the three jaw, (4 jaw would be better), support the outer end of the 12mm bar on the tailstock and away you go

Thread: Drone advice needed, please
13/05/2022 14:21:53

Helium balloon (perhaps several), a long string and a camera with radio control shutter

Thread: A tyro desoldering question.
10/05/2022 17:06:24

I think this works, but it would be good if someone checked it, we don't want to release the magic smoke on something difficult to replace. The switch is this, break before make. If you need make before break you'll fond one easy enough. I'm not sure which you need (see Nicholas above) you might be able to tell by connecting a resistance meter between pins 1 and 3 and very slowly sliding the switch across. If it is MBB you will get momentary connection, but it might be hard to spot with a digital meter. If you'r edestroying the switch you might be able to see what's going on. I must admit I'm always wary of prodding about with a resistance meter in a circuit like this, could you reverse bias something and kill it? Someone who knows what he's talking about will advise.screenshot 2022-05-10 165455.jpg

10/05/2022 00:27:21

I think you could do it with a rotary wafer switch, not sure how many poles. If you're interested I'll think some more. Something like this. Certainly easier to mount

09/05/2022 01:05:39

What I do in a situation like this is use a big iron with a wide tip, hold the board in the vice in a suitable orientation and apply some force trying to tip it and pull out the 4 pins on one side. Apply the iron to the 4 pins under load, run it back and to if it's not wide enough and you will feel a click as it moves. Then go to the other side, and back and to until it is out. Don't remove the solder first you need something to melt, in fact adding extra solder sometimes helps

Edited By duncan webster on 09/05/2022 01:06:33

Thread: Gearbox splines internal and external
09/05/2022 00:54:14

If a new one would have to be hardened after machining, so would a built up one. At least with new material you know what it is, what it's current state is, and how to harden/temper it

Thread: Davy Tandem Blowing Vertical Steam Engine
09/05/2022 00:05:11

There is a very large Davy engine in Kelham Island museum in Sheffield. 3 cylinder simple expansion, used to drive an armour plate rolling mill. Might be worth contacting them. I had a big contract with Davy McKee, very competent and a pleasure to work with, but I think they've gone now

Thread: electrolytic derusting
08/05/2022 10:44:30

The bubbles form on the cathode, the paint was on the anode

07/05/2022 22:49:43

I've just tried this for the first time with excellent results. No surprise there, it has been widely reported. What did surprise me was the effect on the anode, which was a bit of scabby old plate, some covered in paint. All the paint very quickly fell off. Anyone know what's going on? The only thing I can postulate is that the electrolysis turns the washing soda into caustic soda, but I never was all that good at chemistry. I once answered a question in an organic chemistry exam with 'under the right conditions of temperature and pressure, anything can happen'

Thread: Almost 4BA but not quite
07/05/2022 22:17:20

No doubt someone with a fascination for working out change gears will be along with a suitable setup, not me, life's too short!

However, I'm confused, you say you have a drawbar which fits the collets "A 4BA nut threads easily onto the drawbar", so what do you need to make?

Thread: Myford Super 7 at SRS for only 395
06/05/2022 15:14:55

Just realised nvr won't work with an on/off switch, but contactor will

Thread: Tools needed to build a 3 1/2in gauge Tich
06/05/2022 13:52:36

I'd build a Juliett, slightly bigger, not much more expensive, but much easier to drive when it's finished

Thread: Myford Super 7 at SRS for only 395
06/05/2022 12:27:44
Posted by Bob Mc on 02/05/2022 20:08:37:

You may notice my on-off switch housing which I thought would complement the rounded change wheel casing, the one thing I am looking for is a 'snubber' circuit since there is a definite electrical flash when the switch is turned off.....anyone point me in the right direction..? it has to switch off the induction motor.


cleaning up.



No-one else has got back on this so here's my 2 pennyworth. I'd use that switch to control a proper NVR contactor hidden elsewhere.

Thread: Emergency Radio Format
04/05/2022 16:01:47
Posted by pgk pgk on 04/05/2022 12:39:49:
Posted by blowlamp on 04/05/2022 11:22:55:
Posted by John Haine on 04/0........

A cording to Wikipedia the barracuda anti-torpedo missile can do 800kph 430knots. Stingray needs a turbo.

Ah but according to Google it won't be in service until 3056, might still beat CrossRail

03/05/2022 22:38:35
Posted by Peter Greene 🇨🇦 on 03/05/2022 18:51:32:
Posted by blowlamp on 03/05/2022 18:43:10:

Just something else to keep us on edge.

... Not for long. I figure all this means that the super-beings that are running this universe feel that the experiment has failed in this corner of it and is about to be terminated.


Edited By Peter Greene 🇨🇦 on 03/05/2022 18:52:47

So have the mice sent for the Vogons?

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