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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: Diesel fuel
17/08/2018 11:27:12

Did it at school a bit over 40 years ago, but don't need to now because I've still got a good part of a winchester left from when it was simpler to buy stuff.

The scary thing was that as a child, one of my uncles had severe epilepsy and used to live with us. It was quite common for dad to have to knock him out with a handkerchief loaded with the stuff when he had a fit!

Thread: What did you do Today 2018
16/08/2018 21:21:39

Cleaned up the Hardinge HLV yesterday, much swarf of various types had been allowed to accumulate in the back of the chip tray. Also cleaned out and refilled the coolant tank, with kerosene! Makes a good wash down system laugh. While I'd got the lathe clean, I tried to work out where the oil/ATF leak in the apron gearbox was. I didn't think it could be any of the obvious joint faces, since I'd been careful to make sure they were flat and well anointed with Hylomar when I rebuilt it four years ago.

I think I found it. Where the apron motor and worm drive bolts to the apron there is a joint that could have been sealed with a gasket or an O-ring, but doesn't have either. It allows ATF to bypass the shaft oil seals and drip out of a drain hole. Loctite 222 seems to have stopped the leak.

Wasn't a big leak, but the gearbox doesn't hold a lot of oil, so it'd still empty itself over a week or two.

Thread: Diesel fuel
16/08/2018 20:46:20

I think the world might be going too paranoid for its own good. It's not as if it's difficult to make diethyl ether by dehydrating ethanol with sulphuric acid. angry

Or is it just that so few people actually run model aero Diesels these days?

Thread: Are Model Engineering Exhibitions The Same
15/08/2018 18:43:01

The odour problem may be caused by the modern lack of model engineers smoking pipes. There's no way you can detect a bit of sweat over a cloud of Exmoor Hunt from a well pulling briar...

Thread: The Workshop Progress thread 2018
15/08/2018 18:38:29

Sorry, I had thought they were the high density fire bricks used in the back of fireplaces. Didn't notice the shiny spots on the surface until I expanded the picture.blush

Edited By Mark Rand on 15/08/2018 18:38:56

15/08/2018 11:57:22

Is it worth looking for some insulating fire bricks instead of the solid ones? They tend to heat up far more rapidly.

Thread: Are Model Engineering Exhibitions The Same
15/08/2018 11:54:55

Right to left is clockwise on a stall.

As to why it's obvious, it's because that's what I do. Obviously! laugh

14/08/2018 23:52:36

The major problem I have an the shows is all of the folk that seem to progress around the trade stalls from left to right, instead of the obvious right to left progression that they should make. At some shows, it seems that everyone is going the wrong way except me...

Thread: The Workshop Progress thread 2018
14/08/2018 20:50:07

Slapped some rather stale Hammerite on the milling machine riser that I've just finished welding up. Ugly welds, ugly paint, built like the proverbial out-house.

The lugs on the side will be for brackets to hold the milling vices, rotary table and its chuck when not in use. Next thing is to do the machining on it.

 

 

Edited By Mark Rand on 14/08/2018 21:17:17

Thread: Welding issue for a newbie
11/08/2018 23:26:57

Thermal switch could have degraded to the point where it's cutting out at too low a temperature. Farnell will probably have a replacement. Look for the approx 1/2" round device with two spade connectors stuck/clamped to the transformer. It's still worth checking all of the contacts. I assume it's been transported, most of the contacts will be spade connectors or nuts and bolts around bent copper/aluminium. It's surprising how intermittent they can get.

Thread: Eclipse magnetic chuck/baseplate
11/08/2018 23:07:54

I regularly use magnetic welding clamps as well as the Mole Wrench variety when gravity doesn't cooperate.

Having had to disassemble an Eclipse mag-chuck for maintenance/rebuilding, I wouldn't think twice before using one as a welding clamp, with one proviso:- The chuck will come to no harm whatsoever from welding currents. It'll conduct far more current than any welding set you can buy, without any issues at all. However, if welding thinner stock, you may find that the arc wanders about a bit due to excessive magnetic field close to the arc. if this happens, wind the mag-chuck handle back a bit to reduce the force/field.

If the mag-chuck seems at all stiff in operation, drill a couple of holes in the opposite end castings, flush it through with clean oil, then plug the holes. The major cause of failure with the older Eclipse chucks is the casting failing due to excessive force from the eccentric moving the magnets once it gets dried out/contaminated with coolant.

Thread: Welding issue for a newbie
11/08/2018 22:55:46

It won't hurt to take the cover off and check all the connections. Some of them tend to be pretty crude in the low end MIG welders. DAMHIKT!

Thread: Are you a Man or a Mouse When Milling?
10/08/2018 22:55:35

A common guideline for HSS cutters is half the diameter in width of cut and the full diameter in depth of cut or the full diameter in width of cut with half the diameter as depth of cut.

 

Generally speaking, the more depth you can use, the longer the life of the tool befire resharpening, since the corners tend to blow out first.

 

YMMV smiley

Edited By Mark Rand on 10/08/2018 22:55:50

Thread: Latest issue - thread indicators
09/08/2018 22:36:49

Nah, just cut some slots in the far end of the leadscrew and use it to free hob a worm wheel. cheeky

Thread: Gear Hobber : Design ideas please ...
09/08/2018 22:32:03
Posted by Bazyle on 09/08/2018 20:59:10:

We have discussed encoders to provide pulses but, especially in a stand alone machine, at what point doe it become a better idea to drive the hob spindle from a stepper as well? This also enables the system to ramp up to speed in a controlled way which may help.
What direction are the forces in both mechanical and electronic versions. As we know you can 'free hob' with the hob running a freewheeling blank does this mean in a Jacobs or electronic machine the blank is being pulled round and the gears/stepper is acting as a brake to keep it in step, rather than forcing it round?
Any ideas about detecting missing steps - not the electronics failing to command the step but the motor stalling and not making the move due to power/friction problems?

If there were going to be missing steps, they would occur on a stepper driving the hob, that has an intermittent load. The gear drive itself should only have friction to deal with, since the gear PD is going to be moving at exactly the same speed that the hob pitch is moving at, so there should be no torque imposed on the blank by the hob. On that basis, it's probably simpler to use a conventional drive and a rotary encoder for the hob and divide that down for a stepper to drive the blank.

Another advantage of the electronic solution is that there are no universal couplings, bevel drives needed, just spur gears (or straight helical gears, once they've been made) to turn the 200 steps/rev of the stepper motor into enough to give smooth rotation of the blank . Also the gears can be whatever changewheels are to hand initially.

 

Again, the reason for the electronics is to avoid the need for any specific collection of gears in order to create the gears you want to make.

Edited By Mark Rand on 09/08/2018 22:34:32

09/08/2018 20:12:35

Only problem with that approach is similar to the problem with a conventional hobber:- you need a supply of sprockets/gears with the right number of teeth or which can be arranged to have the right ratios to generate all the gears that you want to make, including any prime numbers that might crop up. The electron shuffling approach allows you to get those ratios via the magic of arithmetic. smiley

09/08/2018 11:53:03

Quite a few years ago, I wrote the programs for some racing motorcycle (and car) combined rev-indicator lights and rev limiters. With a 4MHz PIC controller, I could accurately measure frequencies up to 200kHz (had calibrated correction factors to allow for the time taken to service interrupt routined etc). We even made a modified version to indicate the speed of steam turbines on barring gear down to 10 rpm, with an RS232 interface!

Anyhow:- I've got some ideas along the divider route to work as a modification to the recent lathe based gear hobbing setup described in MEW. I've got all the ingredients in various caches around the house and shed, just need to find the time to do it!

Thread: What did you do Today 2018
08/08/2018 21:21:04

Got to try the improved dust extractor today. Laid down three dozen 3.2x400mm 7018 rods on the milling machine raiser project. There was a slight haze in the shed (30m^2), but nowhere near what it had been during previous welding episodes that were far less intensive. Also no discomfort at all. I did open the door for ten minutes at the end of the work, but I don't like working with the door open because it lets Planet Rock escape into the environment!

07/08/2018 22:45:24

Finished adding a secondary filter to the dust extractor. Hopefully it can cope with the majority of cutting and welding smoke now. The dust extractor is now bolted to the crane rail and column via anti-vibration mounts, rather than standing on its original legs. and the whole housing is on top of the computer and VFD cupboard that I built earlier in the year. It's noticably quieter now than it was. 25mm MDF is wonderful stuff for dampening noise!

Thread: Squealing motor
07/08/2018 09:43:20

The problem is almost certainly the oil seal and not the bearings. Motor seals run dry.

 

Rub a little grease into it. Replace when convenient.

Edited By Mark Rand on 07/08/2018 09:44:41

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