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Member postings for Brian Oldford

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

Thread: bunging up hole in CI
12/02/2019 15:12:34

What item is it going in to? Does it need to colour match?

Thread: Jason's Firefly .46 Build
11/02/2019 19:45:33
Posted by JasonB on 25/01/2019 07:03:48:

Does depend on the commercial carb, I have Perry and OS ones where the barrel moves the same as the firefly rather than in a helix and no remote adjustment of needle. Also no air bleed to lean off at idle.

I suppose with modern radios you could link a micro servo for the mixture to the throttle so that the mixture is adjusted proportionally to the throttle.

Edited By JasonB on 25/01/2019 07:04:23

A fairly common-place practice by the RC racing power boat fraternity.

Thread: Quorn Castings
11/02/2019 19:30:06

Isn't tackling a Quorn almost a rite of passage?

Thread: One off castings
09/02/2019 21:27:54
Posted by Neil Wyatt on 09/02/2019 21:22:09:

If someone uses a good foundry that will do one-off castings for a reasonable (but not unrealistic) price for hobbyists, it would be great if they could (1) check with them that they are happy to be more widely known (it's not unusual for places to help hobbyists but be reluctant to get swamped) and if so (2) share their details here.

Even better, suggest they advertise in MEW!

Neil

I'll speak to the guys I use.

Thread: Single phase verses 3 phase motor
09/02/2019 21:26:07
Posted by Pete White on 09/02/2019 18:26:22:

I am lucky to have 3 phase in the workshop, never used a VDF, but do you need to ensure your motor is a six ends out so that you can make sure the voltage is correct, or already suitably wired?

There was single phase motor on my wood lathe when I bought it., it was hopeless with all the stopping and starting leading to over heating. Sorted by fitting a readily available cheap three phase option. Maybe the motor had a problem but convinced me that single phase is not for me.

Pete

Actually Pete, so long as the stator windings aren't epoxy potted, on a three post machine (415v only), if you're not afraid of a bit of motor open heart surgery, you can almost always get to the star point and open it up. Carefully noting the phase relationship you can rewire it to delta and they'll invariably run beautifully. Getting the phase relationship is crucial (don't ask!).

Thread: Overload trip
09/02/2019 17:36:33
Posted by SillyOldDuffer on 09/02/2019 10:34:57:
Posted by not done it yet on 09/02/2019 05:08:57:

Check its stall current and fit a slow-blow fuse? ...

Probably not necessary to be that clever. An 240V 8W motor will draw 33mA at full load. We don't know how hard the motor works when winding the clock, but it might be a significant proportion of 8W if it lifts a heavy clock weight in 10 seconds. Even so, the fuse only has to cope with a short burst of current. 32mA is a standard size instrument fuse and I'd use the ordinary fast blow version. It shouldn't blow when presented with 33mA for only 10 seconds and it's more likely to blow quickly if the motor is genuinely in trouble.

A suitable holder and box would also be necessary - this type of fuse won't clip into a mains plug!

When looking at the fuses listed by RS Components I noticed they're using a new-to-me suffix to encode the fuse type. In case the scheme is unfamiliar to anyone else:

FF - very fast blow
F - fast blow (the common type)
M - medium blow
T - slow blow
TT - very slow blow

Dave

Edited By SillyOldDuffer on 09/02/2019 10:37:30

You overlooking the even faster fuses. They have three legs. We usually call them transistors. cheeky

Thread: LBSC 3 1/2 Britannia
09/02/2019 17:24:28
Posted by Jon Lawes on 09/02/2019 13:41:45:
Excellent, thanks Brian. When I got rid of the siphon tubes my intention was to move the inner throat plate back to a sensible place, I guess omitting the combustion chamber.

Whilst there are advantages to your proposed simplification it is possible that the now longer tube/flue sizes may become non-optimal.

I know of two instances where people built combustion chambered boilers then lightly inverse hydraulically tested the assembled firebox and tube nest by blanking off the grate aperture and the smokebox ends of the tubes and flues before moving on to further boiler assembly.

Your choice, of course.

Thread: Single phase verses 3 phase motor
09/02/2019 17:17:30

IMHO good solid 3 phase motors of that capacity can often be picked up S/U for a song. With all the advantages of Soft Start, Infinitely Variable Speed and even Over-speed a VFD is a no-brainer.

I have them fitted to both my mill and lathe and wouldn't go back to single phase machines.

Thread: One off castings
08/02/2019 19:50:54

At the risk of offending some folks;

Even jobbing foundries that make one-offs are sometimes a little cautious about taking on work from hobbyists as occasionally their patterns prove to be difficult to work with. Examples being oversize cores that need additional work to fit into the cavity made by core-prints, insufficient draft making removal from the sand difficult, patterns made with insufficient machining allowance or incorrect contraction allowance.

That's not to say all hobbyists make bad patterns. Even the professionals can turn out the occasional lemon.

Edited By Brian Oldford on 08/02/2019 19:52:03

Thread: LBSC 3 1/2 Britannia
08/02/2019 19:06:09
Posted by Jon Lawes on 08/02/2019 17:37:21:

I DO have the drawings, I just don't know much about boiler terminology. At what point does the gap above the grate start to become the combustion chamber? I am a complete novice, and although I'm picking it up as fast as I can there are still big gaps in my knowledge.

Basically the area of the tube nest of the inner throat-plate is moved into the boiler barrel thus shortening the tubes and increasing the firebox volume. In the case of the Brit and the 9F the extended firebox crown is stayed by means of a number of vertical water tubes passing through the combustion chamber. IYKWIM

08/02/2019 17:06:31
Posted by Martin Johnson 1 on 08/02/2019 13:18:21:

I have just checked the info. I have. The combustion chamber projects 4.5 inches forward of the firebox, and has 6 corss tube thermic siphons in it. I had rather assumed you already had the LBSC drawings.

I have been in correspondence with another gentleman on Brit. boilers, If I can dig out his contact details, I will suggest he contacts you via. this forum.

Martin

LBSC/Martin Evans' 3 1/2" Gauge 9F Evening Star has the same combustion chamber arrangement.

Thread: Clack valve for a model steam boiler.
04/02/2019 21:29:15
Posted by JasonB on 04/02/2019 20:22:50:

don't need a spring, just gravity.

It works first time every time. Try it with buttered toast.laugh

Thread: Is it a drone?
04/02/2019 12:28:13
Posted by Martin W on 04/02/2019 11:50:41:

They are already being used at airports to scare other birds away, not a in seagull form but as a mock peregrine falcon that perfectly mimics the falcon's flight, glide and attack characteristics. A brief clip can be seen here.

Martin W

Were he still flying commercially today I'm sure Chesley Sullenberger would be grateful for its assistance.

Thread: print-offable and laminatable chart
03/02/2019 13:51:24

Or try http://metal.duncanamps.com/software.php

Thread: Myford 33t and 34t gears for metric threads
28/01/2019 16:06:00
Posted by peak4 on 27/01/2019 10:59:37:

Can't see any on ebay at the moment.
Try HPC Gears, who offer 34t 20dp in metal and Delrin.
OK would need modifying to fit, but probably easier than making from scratch.

Bill

Wrong pressure angle.

Thread: Cast Iron Straight Edge
21/01/2019 21:42:26
Deleted
 

Edited By Brian Oldford on 21/01/2019 21:44:06

21/01/2019 08:24:37

PMed

Thread: lathe to cut 26tpi
15/01/2019 18:56:03
Posted by JasonB on 15/01/2019 18:24:14:

There is no reason to stop you buying off the shelf MOD gears to get the tooth numbers required in much the same way a Myford owner may need to buy extra gears.

It may also be a question of what can physically fit on the banjo, I know when I have cut 26tpi on my 280 it was quite a close fit for the train using the supplied gears but I could probably have got round that by adjusting with aftermarket gears.

Also check the pressure angle of any additional change-wheels match too.

Thread: Zyto Gear Comparison Advice ?
12/01/2019 21:30:40

What DP are they? If they are 20DP you could probably use Myford change-wheels.

Thread: Low voltage bulbs
12/01/2019 21:25:16

There are quite a number of sellers on the well know auction site selling 24 v LED lamps with various bases.

50 v may not be quite so easy yet might be do-able using a 24 v LED lamp and a dropper resistor. Since the current will be quite low the power rating of the resistor may be quite modest.

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