Member postings for Andy_G

This was the Snowdon Railway track in 2015 (you should be able to click for a larger version):

(Please forgive the black and white - I was playing with a new camera)

Edited By Andy_G on 01/12/2022 10:14:42

Edited By Andy_G on 01/12/2022 10:15:34

For a cheap(ish) epoxy with decent temperature resistance, have a look at UHU Endest 300 - the datasheet gives alternative mixing ratios / cure schedules that can be used to tailor the properties to the application.

With a 100:50 (weight/weight) mixing ratio and a 100 or 180°C cure, it has good strength up to 120°C and reasonable strength to 140°C.

Datasheet:

https://media2.supermagnete.de/docs/uhu_plus_endfest_300_eng.pdf

This video on spindle rebuilding might be of interest:

Don't forget that the fairy lights already include a 2.7 ohm resistor, so an additional 33 ohm in series gives the calculated 36 ohm required (close enough, etc...).

I'm with Huub - make R1 (in your sketch) 33 ohms and delete the zener diode.

Note that it will be dissipating about 2.5W so will need to be suitably rated (say 5W minimum) and is likely to get warm even so.

As Malcolm describes - I have also used this method several times (I have some offcuts of beech worktop that work well for this).

For 1mm stainless, you will need some substantial clamping boards, and a couple of G clamps over the ends to stop them spreading where not held in the vice.

Take it steady, a little at a time, working along the full width of the sheet.

If you use metal clamping bars you will get a sharper bend, but also (likely) scuff marks near the bend.

Edited By Andy_G on 28/10/2022 08:55:34

There are courses available via Llandrillo college. Looks like they’re delivered in Llangefni though.

**LINK**

(No idea of costs)

I happened to be in Lidl today and saw that they had the calipers. Out of curiosity, I took one out of its box and slid it open. AAARGH! It felt like it had been on the beach. I quietly boxed it back up and put it back on the shelf.

I got a set of callipers from Lidl something like 10 years ago. They've been great to use - smooth and accurate and are still going strong. No real difference in feel or accuracy to the Mitutoyo ones at work. I saw them come up in Aldi last year, so picked up a set as a backup.

They new ones are absolute *crap*:

Very rough action;
Poorly ground (a rough, rather than a satin surface);
FULL of grinding grit and residue (absolutely black with it inside);
Not really hardened (I know you shouldn't do it, but scribing with the tip of the jaws bends them - I've been getting away with that on the other set for years with no visible effect...)
When you close them fully, the internal jaws catch on each other when you open them again.

The reading varies a lot with jaw pressure,

The new ones remember their setting when "off" which would be handy for poor men's DROs (whereas the old ones reset their zero whenever they're switched on).
Shortly after, I picked up a set of callipers from Lidl and was equally unimpressed  

Full of grit and really badly finished. They're not the same as the Aldi ones, but of an equivalent standard.

My 'good' ones (that I though were Aldi) turn out to be old Lidl ones (circa 2007).

From top to bottom: Old Lidl, current Aldi, current Lidl:

Old (good) Lidl after 10+ years of abuse. If you run a fingernail across the closed jaws, you can barely feel the joint.

Current Aldi (new) - you could trip over the step between the jaws...

Current Lidl (brand new) - likewise, there is a pronounced misalignment of the jaws.

What the pictures don't really show is the difference in the 'ground' surfaces. The old ones are satin smooth with flat surfaces and square corners - not much different from Mitutoyo ones at work. The newer ones (Aldi & Lidl) are rough and uneven - I doubt that they're ground - more like waved past a belt sander.

I took the Aldi ones to pieces to clean the grit out and stone off the burrs - the grey is loose grit (& look at the grinding on the jaws!):

Inside the current Lidl ones (I didn't take the back off, just slid the jaw out). Grit again (this is straight out of the box - they haven't even been in the shed yet).

I cleaned them up as best I could without taking the back off (which means peeling the label on the rear back) as I was thinking of returning them. They still feel like cheap callipers, but at least they don't make your teeth itch every time you move them.

The battery in the old calipers lasts for years; I've had to change the batteries in the newer ones several times in the last year.

Not the bargain that they once were IMHO.

('current' in my description was ~ May last year)

Edited By Andy_G on 03/10/2022 09:43:10

Absolutely fantastic work (and pictures). It deserves to run on looks alone.

Nice to see some engineering on this site!

Posted by Die Hardenedbedway on 31/08/2022 08:38:55:

There are bench top / vice mounted benders for metal strip (used for ornamental metalwork).

This sort of thing (not necessarily these specific machines though):

Micromark Universal Bender

Metalcraft RBR Tool

(Many examples of home made ones on Youtube too).

Edited By Andy_G on 31/08/2022 09:44:33

Yes, indeed, a true stalwart, but Vce max of 60V.

A motor with same part number is shown with a bridge rectifier here:

https://www.cnc.ist/makina-aksesuarlari/mini-torna-motoru-2500-devir.html

(Mini lathe motor 2500 RPM)

(In Turkish!)

FWIW I suspect it's a permanent magnet motor.

Looking at that circuit board, I'm with Peter Cook - it isn't a "real" PWM controller, but a variable phase angle thyristor circuit: basically a dimmer switch. It will operate at 2 x the AC supply frequency, rather than the tens of kHz that a true PWM would use.

To make a true PWM, it would be necessary to rectify and smooth the incoming AC, then design / copy a control circuit running at PWM frequency (with its associated power supply) to drive some power switching semiconductors that are capable of handling ~400V (xx3055 isn't it!) Ideally, there would be an isolating transformer in there somewhere too. Not impossible, but not a trivial task, either.(And there's the business of making sure it doesn't radiate interference to everyrhing around it).

I would be looking for a ready built unit (I build tube amplifiers as a(nother) hobby )

Wow, very impressive!

What sort of size is it? I take it that you didn't cut that lot out with a jeweller's saw!

Thanks.

My crank bearing oilers are plain blass cups with push-fit lids (held in place by a small o-ring). I put a wad of wool inside to hold onto the oil a bit longer (not in the photos).

Maybe not 'prototypical enough' for the job in hand though:

Lid removed from the RH oiler and resting upside down on top of the big end.

Edited By Andy_G on 24/08/2022 12:46:48

I made this one (for my hit & miss engine) using a test-tube for the 'glass'

It all "works" but the nozzle doesn't drip nicely - the whole thing is just too small to allow an oil drop to develop without touching the sides, so once the initial drop has formed, it wets to the side of the sight hole and the oil just wicks down the inside (it serves its purpose though).

The bottom part screws on to hold the glass in place inside lips on the top and bottom covers, and the joint is sealed with Araldite. There's a small hole in the top cover that acts as a vent and is big enough to fill / empty the lubricator using a hypodermic needle.

Gratuitous picture:

Stainless in aluminium is prone to glavanic corroson unless protected.

Using Duralac (barium chromate paste, I think) or Tef-Gel on assembly will prevent this.It is standard practice in the marine rigging world.

Either of these would be close to a lifetime's supply!

Duralac

Tef-Gel

(I use Duralac, but it has to be said, it can be quite messy.

I think Tef-Gel originates in Australia, so may be more readily available to a 'Kiwi'  )

Edited By Andy_G on 31/07/2022 13:15:27

Have you wired the switches to short tip to sleeve when the plug is removed?

This is usually intrinsic to the design of 3.5mm sockets, but needs to be wired in for the 1/4" socket in your picture - There needs to be a wire between the sleeve contact and the *switched* contact on the tip for it to function like the 3.5mm one.

Yes, it looks like a condenser lens. Its function is as per Clive Steer's post above.

Everything will "work" without it, but there will be a lot of stray and scattered light that will reduce contrast, make edges indistinct and probably create other artifacts. (The fins on the inside of the tube are there to try and reduce stray light, so it was clearly a design consideration.)

This sort of application is very common, and I suspect that the lens will be a generic one, rather than something designed specifically for the microscope.

The key parameters are the outside diameter and effective focal length (EFL).

The condenser will probably be aspheric, which makes it difficult to establish the EFL without having the lens in hand. You will be able to get a good idea of EFL by measuring the axial distance from the lamp filament, at ~mid travel on the slider, to the plane of the back of the lens. This will be the back focal length (BFL). EFL will be somewhere between the front edge of the lens (BFL + 1.5mm from your sketch above) and the very front of the lens (BFL + 1.5mm +9mm from your sketch above) - more likely nearer the +1.5mm dimension (especially if the lens is spherical, rather than aspheric).

The good news is that the lamp is on a slider, so it is possible to accomodate some error / differences in EFL here.

With your lens diameter & EFL estimate, you can try and find a suitable replacement, for example from Edmund Optics:

Condenser lenses

If/when you find something that is likely to be suitable, you may be able to find a more convenient source for it.

I doubt that the material is anything special (the application is visible light only, and the power / heat levels are modest).

ETA: Anti reflection coating would be nice to have, but I doubt that it is critical here.

Good luck!

Edited By Andy_G on 18/07/2022 09:41:49

You can definitely get 10mm and 12mm holders for the SCMT / SCGT 09 inserts. (I have a 10mm one, but can't remember where I got it. The shank is ~10mm high x 12mm wide).

12mm holders are listed at RDG: 12mm

They also list a 10mm SCMT06 holder , but appear only to offer the SCMT06 inserts.

Edit to add:

My 10mm thick tool holder came from 'Chesterfield Machine Tools' on ebay. They now seem to have vanished...

Edited By Andy_G on 11/07/2022 10:22:25