Member postings for Brian Fisher 1

Thanks.

Brian

Hi. Yes domed ends and a stay is not a problem if we are looking at say .064 or .08 thick material, it was my original thought of having to flange .16 thick 2in diameter ends that felt was a bit extreme.

Cheers Brian

Hi br.

Your tank dimensions give a safety factor of around 7 which sounds pretty sensible to me.

Cheers

Brian.

I have just realised that I have been making a silly mistake in that I have been applying the safety factor to the proof test pressure and not the max working pressure.

The pressure regulation document published by the UK boiler test group stipulates that all miniature gas tanks shall be designed to be able to use 60/40 butane/propane and must not be heated to more than 60deg C.

At this temp the tank pressure will be 219 psi, so if the tank is designed for this pressure a 2in dia copper tube of .080in wall thickness will have a safety factor of 9 which seems much more sensible.

Cheers. Brian.

Hello. I am thinking of making a butane/propane tank for a small steam plant I have made?

I have a number of steam boilers in the past and am familiar with the design and stressing of them as well as the silver soldering etc.

I know that the safety factor generally accepted in copper boilers is 8 with a uts of 25000 psi and various additional factors for temperature, lap joints etc.

Now to my question. Can anybody give me the acceptable safety factor used in the design of miniature gas tanks as I cannot believe that the safety factor is as much as 8 after having looked at the thickness of the material in the tanks of some of the garden railway locos in our club.

I am quite happy to do the stress calcs before making the tank but would appreciate advice regarding the safety factor.

Regards.

Brian.

Hi.

Thanks for all your responses to date. I have not been ignoring you all but have been inwardly digesting all the comments. I am learning a lot from it all.

One thought which has come to mind is that if a 20amp led power supply objected to the high inrush current of a motor would it improve things if a variable resistance was wired in series with the motor to give it a soft start. So long as I always remember to use max resistance at start-up.

Or alternatively one of Geoff's suggested speed control devices.

Cheers. Brian

Hello.

I have been interested in model engineering since buying my first m.e. in 1950.

I have just made a high speed drilling spindle for spot drilling holes on a pcd on my super 7 lathe. It runs in ball bearings and uses an er11 collet.

It is driven by a 12v dc motor out of my come in handy stuff and works ok on a 12v battery but I would like to make a 12v power supply to overcome the need to charge the battery.

I was going to buy one of the dc power supplies advertised on the net for powering led lighting but am advised that it would not like the inrush current.

Can anyone advise me please as to whether this is true?

If it would not be suitable I would be happy to build a suitable power supply but am a retired mechanical engineer and am not experienced in electronic design.

I would be very pleased if someone knows where I can find one

Thanks.

Brian.

PS the motor draws 10amps according to the makers plate.