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Member postings for Capstan Speaking

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

Thread: Make your own 'Air Rifle'
15/07/2015 17:11:28

Controls were introduced by The Firearms (Dangerous Air Weapons) Rules 1969.

Sub 12flb pellets will not cope with much more energy. PCP guns are tamper-proof now. In any event a chronograph cannot be fooled.

No animal may be shot lawfully unless it is on the list of pest species and is actually being a pest. The land occupier's permission is required.

Gun crime in the UK has been falling steadily for the past ten years. We don't need any misinformation.

15/07/2015 09:43:08

Years ago I saw a poachers gun on Antiques Roadshow. It had a hollow butt made from soldered sheet metal. It ran at a relatively low pressure and needed a stirrup pump. It's amazing what can be done. The barrel is the hardest part to make.

Amateur gun making even when legal totally freaks the police out. It would be unwise to do so without consulting the local firearms licensing department.

Thread: Stress Fracture
15/07/2015 09:25:07

All of the torsion from the cutting forces is passed through to the two pins. The leverage must be enormous. If they are used for clamping the compound slide too then that will add to it. I'll bet it suffers from poor rigidity too.

I think the replacement plate will fail under heavy load. There is scope to improve the mechanism though.

Thread: Metal spinning on a mini-lathe
14/07/2015 21:00:38
Posted by murrmac on 14/07/2015 20:42:09:
Posted by Capstan Speaking on 14/07/2015 20:31:37:

How about a 100mm blank chuck back plate?

It will fit easily to the spindle flange and you could put holes in it in for wood screws to fasten the former on.

I'm thinking there might be problems with registration if I took it off and put it back on again ... ?

A metal bush driven into the former and a spigot made from a dowel in the back plate?

14/07/2015 20:31:37

How about a 100mm blank chuck back plate?

It will fit easily to the spindle flange and you could put holes in it in for wood screws to fasten the former on.

Thread: Make your own 'Air Rifle'
14/07/2015 16:55:19

Quite so Stuart.

If the police see a home made "firearm" they will take it to chronograph it.

Thread: What did you do today (2015)
14/07/2015 16:28:19

Using castings from College Engineering Supply I finished making a fixed steady for my mini lathe. It's meant for something the size of a Myford but I have managed to modify it to fit.


Thread: Make your own 'Air Rifle'
14/07/2015 16:13:35

For over 18's only in the UK.

Thread: Idea for Beginners - experiment with plastic
14/07/2015 14:17:54

If there is a risk to the machine or user then maybe but plastic is more expensive than mild steel by volume.

Thread: Non hardening high tensile steel
14/07/2015 07:21:02

High temperature connections are usually flanged or clamped. A thread will never be the best choice.

13/07/2015 21:11:05

EN 8 is only about 0.4% carbon. It shouldn't harden much. However if being red hot means it is exposed to exhaust gasses then carbon monoxide is an excellent carburising agent. That means that any low carbon steel will be a problem.

Titanium would do but is phenomenally expensive. Could you redesign it to cope with lower strength stainless steel? The chromium should prevent hardening.

Thread: What did you do today (2015)
09/07/2015 16:37:27
Posted by Bob Rodgerson on 09/07/2015 12:03:19:

Hi Capstan,

This taught me thereafter to treat all model engines irrespective of their size with the utmost respect. Even a little .1CC model aero engine can cut rour hands to shreds if you make contact with the prop. Cuts from them can result in severe damage to tendons and bones.

I salute your approach Bob.

I'm not recommending this but I have seen some tricky old full size rotaries started by bouncing them off reverse compression.

Modern magnetos have a "flick" mechanism to spin them up to sparking speed. They are naturally always on and the key switch actually earths them. That's why an aircraft prop is treated as "always live" just as a gun is "always loaded."

09/07/2015 16:31:42
Posted by richardandtracy on 09/07/2015 11:00:26:
Posted by Capstan Speaking on 09/07/2015 09:25:51:
Over the years many people have lost hands or died from hand swinging props. It is a serious business.


However, with care and attention, and a full appreciation that something is potentially dangerous, the user can make it very safe. Not sure about you, but I have never had an injury on my lathe. I know it's dangerous, so I'm careful. Screwdrivers, on the other hand, cause me quite a few injuries, and everyone knows they're not dangerous. embarrassed



It can never be safe but it can be managed to a satisfactory level. Even as a qualified Group A flying instructor I'd never have gone near one without someone to show me.

09/07/2015 09:25:51
Posted by richardandtracy on 09/07/2015 08:58:56:

On my 602cc flat twin I've been known to use a starting handle to get it going - it works quite well. You already have a lever permanently attached (the prop), could you not use it? As a brat I often watched my father start his motor falk (well the one the gliding club loaned him) that way.

Oh, my 602cc flat twin? That's in the front of my 2CV, and if the battery has enough life for a sidelight, but not the starter, then the starting handle needs two flicks to get the engine going. Never more, never less.



Over the years many people have lost hands or died from hand swinging props. It is a serious business.

Thread: Struggling to understand a drawing.
08/07/2015 12:20:16
Posted by Peter Nichols on 08/07/2015 10:09:57:

Hi all,

Can someone please help me understand a small detail in this drawing please.

I'm not from an engineering background and struggling to understand the measurements to make the eccentric on this little engine I've almost completed.

In the bottom right drawing it says the eccentric is 3/16 stroke am I right in saying that 3/16 is the total movement of the eccentric rod but the throw is to be 3/32 ?I don't know what you think but to me the drawing seems a tad misleading and any help would be greatly appreciated

Many thanks


It's not you Peter, that "sketch" is amateurish. Given that the stroke is more likely to be an important dimension, I think it is supposed to be as below.


However that is insanely close to the edge. I would increase the o/d and modify the con rod to suit

Thread: Locking nut
06/07/2015 06:46:46
Posted by Mick Berrisford on 05/07/2015 23:26:31:

Are these classed as a one shot use or are you "allowed" to crush/close up the slitted area so it grips the thread again?, it just spins on and off loosely like a normal nut at the moment.

As a last resort you could put a tube over the end and knock it to close the "petals." Unlike Nyloc they aren't deformed when fitted.
Failing that, if there is enough thread you could add a spring washer to it.

Thread: NG10 blow gun Thread- any idea?
06/07/2015 06:39:11

NPT is not unheard of in British pipework. Now I could roll a grenade in the room by mentioning Enots standard fittings too. They even have their own spanner sizes. sad

05/07/2015 22:48:18

If it's not 1/8 BSP then it's probably American NPT.

Thread: oil pads
02/07/2015 17:45:54
Posted by Black Cat2 on 02/07/2015 16:46:45:
I find it gets so tight the last inch towards the chuck is almost impossible..Removing it afew times has made any difference! I m not so newto gib strips I cant do this..But I cant!!

It's little out of parallel. So is mine. You get what you pay for.

You might need to keep re-adjusting it if using the full travel.

Thread: Price of aluminium
01/07/2015 12:49:12

It's not a bad price but it's not great.


It would weigh just under 8 kilos (17lbs)

Oh and don't forget VAT

Edited By Capstan Speaking on 01/07/2015 12:55:55

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