AdrianGER

Following up earlier posts concerning the boiler explosion, Brunton was examined by Parliamentary committee in 1817 investigating a steam boat explosion in Norwich. Amazingly, he did not mention the Newbottle /Philadelphia explosion in this evidence at all! But he did say that he had tested wrought iron boiler plate material to 650 psi and hydraulically his boilers to 150 psi, working them at 50 psi. This quite sensible and good practice. What he did not know was that riveted joints were much weaker than the plate. Only in the 1850's did Fairbairn discover that a single line of rivets was only 30% as strong as the plate and even a double line of rivets was only 70% as strong as the original plate. Interestingly, William Chapman's evidence to the steam boat accident committee advocated double lines of rivets. This was ignored. Brunton's safety margins were in line with those advocated by other engineers such as Woolfe. the committee recommended 2 safety valves, one locked and a mercurial gauge. The mercurial gauge arguably also acted as a safety valve as it was open at one end. The press reports of the Philadelphia explosion suggested that a section of the boiler nine feet square was blown off. The boiler plates available at this time would have been much smaller than this. Trevithick quotes the largest available plate in 1813 as being 8.5" x 4'. So a failure at or of the seams appears likely.

What, no inside motion? What would the Fat Controller say? I enjoy following your various P4/S4 blogs.

Hi All, Great to see this thread. I'm the guy the built the 1/32nd Brunton style model on U-tube. I will be exhibiting it at Sawston 31A railway show on 14th April 2018 if anyone is interested. For you other mad folks wanting to build one of these things, the following may be of assistance. 1/ OO gauge version - bear in mind that my model on 32mm gauge track uses mostly 14BA and quite alot of 16BA screws. I model Scalefour normally, so I thought I was building it plenty large enough but it seriously tried my patience, expecially the feet. You will have fun with the feet; they are really critical to good operation. I recommend Airstick for the soles. 2/ My model is actually about 9.2mm = 1ft scale, only approximating to 1/32. Using 32mm track, and the 3' 6" plateway gauge of the Crich loco, but using converting to edge rails. I used Ambis fish belly rail 7mm version now sold by hobby holidays. This is based on Buttlerley Mansfield and Pinxton 1819 iron rail so is just about perfect for the job. 3/ I made mine 2 cylinder to make it easier to drive the pistons internally. To do this I enlarged the boiler so the 'cylinders' were totally enclosed so I could drive the piston rods from inside the body and then reduced the wheel size and drawbar height to keep the piston thrust line as per the original. It's a pot bellied Brunton! 4/ Back in 1922 L S Pendred suggested a modification to the 'scissors' mechanism between the legs which turns the leg mechanics into Scott-Russell motion by addition of a bracket. I adopted this as from a previous plasticard model I could not see any other way for the thing to work. See also in Dendy-Marshall. 5/ It is vital to get to grips with the foot lifting straps. Some later drawings, Nicholas Wood, Clement E Stretton for example, show the leg strap attached to the protrusion at the top of the same leg. It was only when I read the text of Brunton's patent, I found that this was incorrect. He specifically crosses over the straps so that each foot is raised by the action of the opposite leg. Also, there are counter weights, shown in the patent that I made from solid lead for my model. Even using lead, at this scale the frictional resistance of straps was too much so I had to resort to chains which work quite well. 6/ At the top of each rear protrusion from the hip joint is a ratchet. I'm no clockmaker and my very crude ratchets - for 1/32nd scale not OO - are made from 10BA nuts. If I wasn't insane before I made them, I sure was by the time I finished! 7/ Weight. This thing lifts the back wheels at the slightest opportunity. You will need as much weight as possible on the rear (leg end) axle to keep it on the track. The problem would be reduced by shifting the front (chimney end) axle as far forward on the frame as possible. Like the CAD above, I blindly followed the patent and other drawings with evenly spaced axles. I have written an article on construction of my model but I'm pretty lousy with a camera and have not go around to submitting it to any of the magazines yet. Given where this thread appears, I guess RM should get first refusal. Other useful stuff: Why not join the Railway and Canal historical society and ask Andy Guy for a copy of his paper OP232 on the Newbottle waggonway map and my musings on Brunton's loco in OP231? The Polish railway museum has a large scale possibly working model of a sort of Brunton like loco. I'ts none too accurate, but worth seeking out. Walk on!