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Member postings for Mark Rand

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

Thread: The Workshop Progress Thread 2020
15/01/2020 22:28:50

Less hydrogen! Also a triple bond on one of the atoms, which decomposes exothermically, like acetylene does. smiley

Conversely, hydrogen as H2, rather than a part of larger molecules has an incredibly large flammable concentration range. Got to be useful for little engines!

15/01/2020 02:47:41

I spent the productive part of the day making two clean oblongs out of a piece of 15x150x500mm BMS, then cut a Myford sized T-slot in each. With a bit more work and some additional bits, the bandsaw will no longer have problems cutting small bits square and medium/small bits at an angle.

Thread: VFD Question
14/01/2020 16:34:10

Because an eight pole motor will tend to slip more than the same (physically) sized four pole one.

13/01/2020 23:32:24

Basically, a 50Hz 415V motor, without rewiring from star to delta (because the star point is often hidden/internal for older motors) can produce full torque when run at 240V and 29Hz. It will only produce 58% of rated power at that speed, and can produce the same maximum power at all speeds up to full (50Hz) speed when run at 240V. This can be sufficient with a larger machine in a non-production environment.

Edit to add:- Darn it, replying to a post on the last page again...

 

I do have a 1400rpm 2hp delta motor to replace the 1/2hp 3000rpm single phase motor on my dust extractor. Works happily at 100-150Hz (no problem with the fan, that's got some leeway). The batch of motors, from a work location that closed down, were at a suitable price (free) that running one off a VFD was cheaper than buying a replacement for the burned out, crappy original.

 

Edited By Mark Rand on 13/01/2020 23:42:30

13/01/2020 01:44:32
Posted by Steviegtr on 13/01/2020 00:11:46:
Posted by Mark Rand on 13/01/2020 00:02:31:

Simples! There are VFDs which are either originally manufactured or later modified to use a voltage doubler so they can produce 415V output from a 240V input. It's a circuit that was around even before Messrs Cockcroft and Walton used it.

Could you point me to one of those.

These are the prime culprits. Note:- I'd rather use a 240-415V transformer to feed a 415V inverter or better still a 240-415 transformer on the output, so one can earth the star point, which is what I did for my workshop. But if you have star-delta wireable machines, a delta connection is simpler than having to provide 415V if you only start with 240V single phase.

Edited By Mark Rand on 13/01/2020 01:46:34

Edited By Mark Rand on 13/01/2020 01:48:44

13/01/2020 00:02:31

Simples! There are VFDs which are either originally manufactured or later modified to use a voltage doubler so they can produce 415V output from a 240V input. It's a circuit that was around even before Messrs Cockcroft and Walton used it.

Thread: What Did You Do Today 2020
12/01/2020 23:24:02

All steel producers use remelt as much as possible, since it saves a lot of energy compared with reducing virgin ore. It's rather jingoistic/xenophobic to assume that 'foreign' product is likely to be worse than Port Talbot of Scunthorpe product...

Thread: Welder Inrush Current
12/01/2020 22:40:30

If it's an Oxford/Pickhil etc. Bantam or equivalent welder, it really needs a D32 to supply it. Cost me a few breakers to work that out. If you don't want to automate anything, wire up a box with either a 15Ohm 100W resistor or a kettle element and a switch to short it out, in series with the mains lead plug the welder in with the switch open, then short the resistor out before starting to weld. That'll limit the inrush current to no more than 16Amps.

I recently sorted the same problem on my electronic multi process welder that has replaced the oil cooled one. That had the problem that the inrush current to its power supply regularly welded its switch contacts closed angry. Said resistor, coupled up with a time delay relay has tamed the problem.

PS, anyone need an oil cooled welder?

Thread: Bottled Gas Suppliers
11/01/2020 11:21:33

I will admit to moving over to Hobbyweld due to the costs of running a BOC argon bottle. Second the caution about clinging on to the original bottle receipt. I need to add a codicil to my will to tell the kids where they're stored. smiley

Edited By Mark Rand on 11/01/2020 11:21:53

Thread: Biax Power Scraper
11/01/2020 11:14:10
Posted by Raymond Anderson on 11/01/2020 07:07:12:

Mark Rand, Biax scrapers are German, some products are made in Switzerland and Italy aswell as Germany. They are a German company. Schmid &Wezel [ the founders ] Expensive, but the best power scrapers made.

Swiss products from a Swiss division of a German company are still Swiss smiley. My BL40:-

 

 

Edited By Mark Rand on 11/01/2020 11:17:17

10/01/2020 00:44:58

The multi-tool rotates 3.2°. the Biax has a linear stroke adjustable from 0-20mm. So not really convertable.

 

There are two reasons for the price of Biax scrapers. Both apply to the new product and the latter apply to the second hand market.

  1. Swiss.
  2. Small market with high demand.

I'm afraid I off mine via EBay before the world went mad £60 for a BL-10.

I'll probably be finished with it in two or three years time after which I'll pass it along so another poor sod can make his toys better than new.

Edit to add:-
The variable centre swash plate drive that the Biax scrapers use is a fairly simple thing to make.

Edited By Mark Rand on 10/01/2020 00:51:14

Thread: Call for Classified Ads for MEW
10/01/2020 00:24:57

It's a hard life being an illiterate grammar nazi.crying

Thread: Electric motor ratings
09/01/2020 21:10:32

If a 1hp motor happened to consume 1.5kW at full load then either it would be incredibly noisy (from the fans) and hot or it would be a smoking puddle on the floor after a short while. Similarly, describing a 1.5kVA motor as a 1.5kW motor would be a false trades description. The motor may actually be a 2hp motor...

Time to knock up a test rig and maybe, rent a lawyer!

Edited By Mark Rand on 09/01/2020 21:10:59

Thread: Call for Classified Ads for MEW
09/01/2020 17:28:30

Note the errant apostrophe. embarrassed

09/01/2020 12:07:19

On it's way

08/01/2020 23:24:39

What's the cut off date Neil? I'd like to separate the sections of my 10" shaper so that I can indicate what maximum weight the parts are for the aid of any potential victim/buyer

Thread: Anyone with a surface grinder near Leeds?
07/01/2020 01:41:48

Jones & Shipman 1400 grinder (which I have) has approximately 11" of height capacity and 8x24" of area capacity.

My Beaver milling machine can cope with 20" height and 28"x11" area.

The shed's crane can do more than a ton.

 

If you're in reach of Rugby Warwickshire we could make some swarf. Probably blue, especially if you'd hard-face welded the anvil first!

Edited By Mark Rand on 07/01/2020 01:42:11

06/01/2020 21:58:53

Out of curiosity, can you show photos/sizes of the parts?

Thread: Ebay being clogged up by certain sellers
06/01/2020 14:42:21
Posted by Neil Wyatt on 06/01/2020 12:54:03:

The best solution, if you can afford it, is to buy from suppliers who support our hobby rather than saving a few percent by going to random suppliers on eBay...

Neil

Yesterday I was looking to see if I could get some 440C stainless steel flat bar for a kitchen related project. All I could find in the UK was round bar. When I looked on EBay, there were a small number of sellers listing flat bar. All were Chinese. I guess they'll get the order when I get around to the job.

Thread: Case Hardening
06/01/2020 00:49:34

Some, but not all EN1a had lead, tellurium or antimony in it to improve the machineability. These tended to make it no good for case hardening or welding. It also tends to rust if you look at it cross eyed. It's lovely stuff to machine, but pretty useless for anything else (No, I'm not bitter and twisted, far worse than that wink)

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