Thompson Class B1 Springbok

[springcrocus]

Apr 4, 2017 21:17:02 GMT John Baguley said:

Does anyone know what happened to Bob (Springbok)? He seemed to just disappear. He was a regular poster on the Model Engineer forum as well but disappeared from that.

John

A check of his profile shows that it has been over three years since his last visit. It also shows that he is, or would be, seventy seven years old so it's possible that he now spends time in that great workshop in the sky that we all end up in eventually. Do any Bristol members know anything?

Regards, Steve

[cnc..... not for me]

does it really matter a hoot if a loco uses 1/2 a pint of water more per two laps or a shovel full of coal, or the valve event diagram doesn't match. we do this for fun not efficiency or major passenger hauling. this is why the model engineer and engineering in miniature are pants now to be frank. people who build nothing dictating what is right and wrong. martin evans did not claim to build miniature masterpieces but engines that worked just like lbsc. after all building an engine to perfect scale and then putting a guy on the back twelve times bigger doesn't really work? just have fun

[jinks82]

Does anyone have any pictures of a completed valve liner? I am confused by the drawing

[don9f]

Hi, do you follow MrCrispin on Youtube? He is building a B1 and just covered valve bobbins a few days ago, but 
I think he’s already done his liners.....I’ll search back.

Cheers Don

[don9f]

He starts the liners in this episode, so it may help you....

Cheers   Don

[Roger]

Jul 4, 2018 23:28:02 GMT cnc..... not for me said:

does it really matter a hoot if a loco uses 1/2 a pint of water more per two laps or a shovel full of coal, or the valve event diagram doesn't match. we do this for fun not efficiency or major passenger hauling. this is why the model engineer and engineering in miniature are pants now to be frank. people who build nothing dictating what is right and wrong. martin evans did not claim to build miniature masterpieces but engines that worked just like lbsc. after all building an engine to perfect scale and then putting a guy on the back twelve times bigger doesn't really work? just have fun

I know this is an old post, but it's worthy of a reply, albeit a rather late one...

I think you're missing the point that many of us get our fun from the very challenges you mention as not mattering. What you do it for is entirely up to you, but you can't assume what motivates others.  The spectrum of interest and ability is vast, with some only building, never running, and the reverse. Some build to exquisite detail, and it would give them little pleasure to copy a simple design with no creative input of their own. Some try to tell others the 'right' way to do things, others just show how they do things. There's no right or wrong, we are all involved in ME for our own reasons.

I've never bothered with the Model Engineer or any other magazine but for different reasons to yours. They either re-iterate ancient techniques that have been published ad nauseum, or don't do justice to modern methods. This is why stagnation rules in ME and why I do my own thing. A hobby that only looks to the past is a hobby that's doomed to shrinking and eventual extinction.

[jinks82]

Many thanks for the info chaps

[jinks82]

I have started machining my first valve liner. I am using phospher bronze. I tend to follow Martin Evans design rather faithfully being a first time builder of a loco. Will this be ok? What material should I make the valve bobbin out of? Also the cylinder casting is CI and no liner is shown. Will the piston run ok without a liner? I am honing these bores. What material should the piston be made of as I believe it is best not to use the same materials acting upon each. other.
Thanks

[uuu]

I've no experience of piston valves. But cast iron cylinders would typically have cast iron pistons and rings. This is an exception to the rule about different metals: cast iron is fine. There have been differences of opinion on this forum about rusting of the bores. If you go the all iron route, it makes sense to arrange for some post-run lubrication as a rust preventative. Some users favour PTFE or other soft rings - although one IWMES member got fed up replacing the o-rings on his B1, and we made him some iron rings. As with all things here, there's no single right answer.

Wilf

[jinks82]

Many thanks for the advice. Where can I get piston rings for this engine?

[uuu]

If you want to go the cast iron route, I would make them. It's not really that difficult. 1 - turn a ring to fit. 2 - snap it in one place. 3 - dangle it from a small rod held in a vice (with the broken ends squeezing the rod) and heat until it drops off. You can add extra steps into the process (like making jigs to hold the part-made ring for closer-tolerance machining). There are videos on youtube if you search for "making cast iron piston rings". As with all things in this hobby, it's much cheaper (and more fun) to make parts than to buy them.

Here's one supplier: A J Reeves - I don't know what size you need. There must be several other suppliers.

Wilf

[don9f]

May 16, 2020 10:08:33 GMT jinks82 said:

Also the cylinder casting is CI and no liner is shown. Will the piston run ok without a liner?

Hi, a liner isn’t really needed for the main bore....a liner is used for the valves because of having to machine the valve ports, which would be extremely difficult otherwise. The ports in the main bore can be done from the ends.

Am I right that the pistons are 1 11/16” dia?
Cheers   Don

[KennLindeman]

Has anybody looked at the alternate valve gear arrangement offer on the website

www.sarikhobbies.com/product/alternative-valve-gear-for-5-gauge-4-6-0-b1-lner-locomotive-plan/

[jinks82]

I have another conundrum I am facing. It concerns the steam passage between the piston bore and the valve liner. As you will know the valve is offset from the piston. Do I grill this passage vertically so that it intercepts the valve liner between around 7 o'clock to 9 o'clock or do I make this passage 'slanted' to intercept the liner between 5 o'clock and 7 o'clock? Obviously the liner steam passage would have to be fitted to suit. Or does it even matter?

[pault]

May 14, 2020 11:55:46 GMT Roger said:

Jul 4, 2018 23:28:02 GMT cnc..... not for me said:

does it really matter a hoot if a loco uses 1/2 a pint of water more per two laps or a shovel full of coal, or the valve event diagram doesn't match. we do this for fun not efficiency or major passenger hauling. this is why the model engineer and engineering in miniature are pants now to be frank. people who build nothing dictating what is right and wrong. martin evans did not claim to build miniature masterpieces but engines that worked just like lbsc. after all building an engine to perfect scale and then putting a guy on the back twelve times bigger doesn't really work? just have fun

I know this is an old post, but it's worthy of a reply, albeit a rather late one...

I think you're missing the point that many of us get our fun from the very challenges you mention as not mattering. What you do it for is entirely up to you, but you can't assume what motivates others.  The spectrum of interest and ability is vast, with some only building, never running, and the reverse. Some build to exquisite detail, and it would give them little pleasure to copy a simple design with no creative input of their own. Some try to tell others the 'right' way to do things, others just show how they do things. There's no right or wrong, we are all involved in ME for our own reasons.

I've never bothered with the Model Engineer or any other magazine but for different reasons to yours. They either re-iterate ancient techniques that have been published ad nauseum, or don't do justice to modern methods. This is why stagnation rules in ME and why I do my own thing. A hobby that only looks to the past is a hobby that's doomed to shrinking and eventual extinction.

Firstly there is no right or wrong about the locos people build, maintain and run. We all do it for our own reasons and as long as we are happy then it’s job done.

However as far as it doesn’t matter about valve events, water and coal consumption and the like, you are totally correct or totally wrong.
If you are going to build a loco to trundle up and down ten metres of track in your garden then as long as it can move it will make you happy.
If on the other hand you want to get into some serious passenger hauling on a challenging track (and many do), a loco that performs in a mediocre manner can make an afternoon hard work and frustrating.

There are probably a large number of people who have given up ME due to building a loco that does not live up to their expectations. This all becomes more relivant the small an engine gets. A 7 ¼”, 9F that is a little down on power will still pull a good load. A 3 ½” 0-6-0 has very little power to start with so can ill afford to lose any power.

I would agree with Roger about needing to look to the future, and it doesn’t need to spoil anything. At the Romney there is stacks of modern high tech stuff on the locos and the line side, it’s just that we hide it so things look pretty much like they have done for the last 90 years.

[jinks82]

If a hole is drilled in a CI casting incorrectly (yes, I have done this...) what is the best way to fill this before re-drilling? This is in the cylinder casting and will be subjected to steam. I was considering soft solder but I don't think it will stand the heat.

I want to minimise and rework to the piston bore (for obvious reasons) and was looking for a way to mask the exit so that I can silver solder.

Any ideas chaps?

[uuu]

Thread the hole and screw in a plug?

Wilf

[jinks82]

The trouble is that I have chain drilled 3 of these and they connect

[ettingtonliam]

A photo would help. If the holes just touch but don't overlap much, its possible sometimes to tap and plug alternate holes, then go back and tap the missed holes. Its how one method of metal stitching cracks in casting works.

[don9f]

Hi, is there any way you can post a picture so we can see what has happened? Maybe it’s possible to temporarily “bung” an adjacent hole whilst you tap the next one for a threaded brass plug that can be loctited in place.....I have had to do this myself in the past when things have gone wrong.

Cheers Don