Author Topic: Burrell Single Crank Compound Traction Engines - 4" Scale  (Read 44395 times)

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #135 on: April 28, 2018, 07:52:58 PM »
Thanks for the kind words; I really appreciate them.  :ThumbsUp:

As an antidote to riveting I've been machining the chimney base and perch bracket castings, details to follow soon.

Andrew

Offline Steamer5

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #136 on: April 28, 2018, 11:13:42 PM »
Hi Andrew,
 The wheels came out very nice indeed!
The rivets look the business to. How did you form the hollow in the snaps please? Ive had a play using ball end mills which do a nice job, take the hole to a little deeper than required then turn back so the rivet is flush to just proud, seems to work ok, but your rivets look way better.

Cheers Kerrin
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Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #137 on: April 29, 2018, 09:45:39 PM »
The rivets look the business to. How did you form the hollow in the snaps please? Ive had a play using ball end mills which do a nice job, take the hole to a little deeper than required then turn back so the rivet is flush to just proud, seems to work ok, but your rivets look way better.

Same way, with a ballnose endmill. For the preformed head I set the depth so the rivet head was slightly proud, about 5 thou give or take. For the snap that forms the head I ended up grinding a few thou off the depth, and also tapered the bottom edge away from the rivet. That is so that even if the snap for the formed head hits the spoke it doesn't leave an annular mark, just a slight rim around the rivet. I found that rivet length was pretty important to within a few thou. Too short and you end up with a dome on a cylinder as there isn't enough metal to fully form the head before the snap contacts the spoke. Too long and you end up the with the same as although the metal fills the snap the snap is still proud of the spoke. It takes a lot more force to extrude the metal sideways and outwards from the snap through the gap between spoke and rivet. If that doesn't make sense I'm happy to take some pictures of my rivet experiments to try and clarify what I mean.

Andrew

Offline Steamer5

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #138 on: April 30, 2018, 05:36:52 AM »
Hi Andrew,
 Many thanks for the explanation. Think I follow what you did.....a couple more coffees will help the thought process. And yes please more photos will definantly help!
I have a bunch of 3/16 rivets for the main frames of the loco build to put in, so any helpful hints & tips will be most welcome.

Cheers Kerrin
Get excited and make something!

Offline scc

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #139 on: April 30, 2018, 10:56:52 AM »
Looking good Andrew.............Terry

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #140 on: May 01, 2018, 08:50:55 PM »
Thanks Terry, I've got quite a way to go to catch up with you!

Andrew

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #141 on: May 01, 2018, 09:08:53 PM »
And yes please more photos will definantly help!

Here's a picture of the last set of riveting (in one sense) experiments I did:



Starting at the front from the right:

The first rivet is the wrong way round, commercial head at the top  :embarassed:

Next left is a full length rivet, it's not too clear but the formed head is a dome on a cylinder, the cylinder being about 20 thou high. The rivets are nominally " but measure 0.885" overall

Left again is a rivet filed to be 0.875" long, again a dome on a cylinder, but the cylinder is slightly lower

Left again is a rivet filed to be 0.860" long, but it's the wrong way round too  :embarassed:

Front row on the left is a rivet filed to be 0.855" long, the head is a dome on a cylinder with the cylinder about 12 thou high

Rear row on the left  is a rivet filed to be 0.850" long, the head is a dome on a cylinder with the cylinder about 8 thou high

Rear next right is a rivet filed to be 0.840" long, the head is still a dome on a cylinder but the cylinder is almost imperceptable, less than a few thou

Next right is a rivet filed to be 0.830" long, the head is a dome on a cylinder but the cylinder about 8 thou high, so is getting higher

This gave me good indication of what length to make the rivets. After fine tuning on the wheels proper I settled for 0.845" (possibly slightly long) and a few good final swings of the flypress to ensure proper closure. It's probably better to be slightly too long than too short.

BF & BI wins out every time.  :)

Andrew

Offline Steamer5

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #142 on: May 02, 2018, 05:03:30 AM »
Hi Andrew,
 Many thanks for the picture & explanation, just goes to show how very small differences make a reasonable difference to the shape / height of the shop formed head.

Cheers Kerrin
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Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #143 on: May 13, 2018, 09:29:43 PM »
As well as the front wheels I've also been working on other parts for the front end of the traction engines. One of these is the perch bracket which is bolted to the smokebox and holds the pivoting bracket on the front axle. The perch bracket is a casting, which is fairly simple to machine. The first operation is to drill and bore the hole in which the pivoting bracket will sit. The boss on the casting is set "true" by eye ready for drilling, the drill shown is 15/16":



Once drilled, bored and faced, the boss and bottom of the bracket can be machined. The drawings are wrong in respect of the length of the boss. Generally traction engines sit slightly nose up in an attempt to keep the top of the firebox covered with water as the road undulates. Although unspecified on the drawing the length of the boss is shown as about 3/16". I made mine a bit over 7/8", which is nearer what it should be for the front axle being " higher than the rear. In fact it's about 11 thou out, but I'm not going to worry about that:



At the same time as the inner face of the boss was machined the rear face of the casting was also skimmed flat to act as a reference face for subsequent machining operations. I also drilled a small hole in the rear face so I can access the grub screws in the collar that holds the pivoting bracket in place. On the front of the perch bracket is a towing eye. Having drilled the hole for the towing pin the bottom of the slot is formed by drilling:



Turning the casting through right angles the slot can then be machined with a 12mm slot drill. The 0.5" gauge block is used for sizing the slot; not really necessary but I like things just so:



To machine the curved surface on the perch bracket that mates with the smokebox I needed to make a flycutter, which is hogged out of a lump of hot rolled steel:



The diameter across the flycutter is precisely 8" and was turned at the same setting as the arbor hole was drilled and bored so concentric is assured. Since the picture was taken I've added a keyway slot in the bore and a plate to help locate and clamp the tool. Since I know the diameter of the flycutter body gauge blocks can be used to set an angle plate at the correct distance for tool setting, so the correct radius is generated. In this case I need a radius of 4", so the gauge block is 0.75":



After some tentative cuts I ended up using a depth of cut of 80 thou and 8 thou feed per rev, easy to hand feed on my metric mill as it is about 0.2mm; the flycutter was rotating at 41rpm. The flycutter didn't even cough and left a really nice smooth finish with no tool marks:



That's one of the plusses of a horizontal mill, they make a brick built s**t house look flimsy!

Andrew

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #144 on: June 03, 2018, 10:22:37 PM »
Slow progress on the engines at the moment. Now the nice weather, relatively speaking, after all this is England, is here every man and his dog wants his glider signed off so it's legal to fly. Thus I've been bogged down in surveying gliders and checking paperwork over the past few weeks.

On the theory side of the engine I've been reading the original Pickering governor patents. I now have a clearer idea of the proper operation of the Pickering governor, and it's also clear that there are some major boo-boos in the design as drawn, over and above the use of a non-balanced valve. So I'll need to re-design the valve spindle drive in due course.

On a practical note I've been preparing for riveting the spokes on the rear wheels. The formed rivet heads on the rear wheels are on the outside, and therefore in full view. They need to be right! A new fixture has been designed, and checked that it fits all four rivet positions per spoke in CAD:



Annoyingly one thing that came out of the CAD model was that I couldn't use the 20mm diameter rivet snaps I used for the front wheels. Due to some idiot  :embarassed: choosing to use a zig-zag rivet pattern as per full size rather than on a circle as drawn no way no how would the 20mm snaps fit. So I had to make a new set that are 16mm diameter. Here is the new riveting fixture and snaps ready for action on the flypress:



The "rust" is a trick of the camera; that's my excuse and I'm sticking to it. When I riveted the front wheels I used a lump of " thick steel plate to cover the hole in the flypress base. For the rear wheels this raised the riveting fixture too high to fit under the press. I tried a " plate but it just folded. A piece of " plate was passable but I think the fixture was flexing slightly, and the handle was in an awkward place to get a good swing on it. So I reverted to plan A which was to fill the hole with a " thick slug of steel, as seen in the picture. The slug was hogged out of some 25mm thick hot rolled steel, as I have a lot of it in stock. Knocking the corners off the as cut square in the lathe at 540rpm and 4 thou per rev feed made the floor vibrate.  :o  But the carbide insert seemed to survive.

Having made new snaps I had to revisit my riveting trials. After a few tweaks to the rivet length, and the snaps, I've closed a number of test rivets that look acceptable:



Next job is to weld up some 50mm square steel tube to make a T-piece the same height as the flypress base to support the outer edge of the rear wheel. Then let riveting commence!

Andrew

Offline zeeprogrammer

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #145 on: June 03, 2018, 10:59:09 PM »
What are those 4 objects within the spokes?

I have to admit, at first I thought I was looking at a paddle wheel.  ;D
But that's me.
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Offline crueby

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #146 on: June 03, 2018, 11:36:54 PM »
What are those 4 objects within the spokes?

I have to admit, at first I thought I was looking at a paddle wheel.  ;D
But that's me.
Thats the rivet fixture he was describing, checking clearance at the four rivet locations.
Gotta stop just reading the pictures Zee!   :ROFL:

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #147 on: June 03, 2018, 11:38:42 PM »
What are those 4 objects within the spokes?

Sorry, I didn't explain it very well. The four objects are copies of the riveting jig to check that I could reach all four rivet positions while clearing the spoke, having clearance for the lower T-ring and enough vertical movement to slip the preformed rivet head into the lower snap.

Andrew

PS: I see I've been beaten to the explanation! Too slow on the typing; I blame the third glass of wine.

Offline zeeprogrammer

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #148 on: June 04, 2018, 12:51:03 AM »
Too slow on the typing; I blame the third glass of wine.

When you get to the fourth...you don't care.  ;D
With my stinking hoppies...I don't have to work to the fourth. The second one is sufficient.  :Lol:

Thanks for the explanation Chris and Andrew.
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Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #149 on: June 19, 2018, 09:10:08 PM »
Riveting the rear wheels has been ruddy hard work. And there are a lot of rivets, 64 per wheel. Everything is heavy and nowt is square with anything else. So it's been two steps forward and one back a lot of the time. Due to boo-boos, or I wasn't satisfied with the result, I've had to drill out and replace a few rivets. It's taken quite a while to get a working system. I've even dropped the wheel a couple of times. Darn glad I recently bought some steel toecap slip on shoes for use in the workshop. Saved a potential trip to A&E. Here's the general setup:



The height of the rim is on the limit of my #3 flypress, so I can't use the bar support as per the front wheels. I thought of using a transmission style jack, but they're quite expensive for something that will only be used once. So I welded up the stand to the left from 50mm square ERW tube. It was intended to use the stand at right-angles to the position shown, but that didn't work as nothing was square and it meant I couldn't easily tilt the wheel slightly. Here's the riveting fixture in close up:



I had to make a few adjustments to the rivet snap heights. I made the snaps in a bit of a rush and rather over tempered them during heat treatment, somewhat over 300C rather than the intended 270C. They worked, but the top snap got a bit expanded at the top. Here are some of the closed rivet heads, acceptable and I plan on using thick paint when the times comes:



As before I pinned the spokes into the hubs with dowels and put a smear of araldite on each spoke before finally screwing the hub covers down. Shown here are the two finished wheels. Note the zig-zag rivet pattern, as per full size, rather than in a line as shown on the drawings:



One of the problems I had was the riveting jig bending at the bottom toe:



First time I noticed this I machined the base flat and then machined a 1 taper so the jig leant slightly back to account for the T-rings not being exactly square with the rims. It didn't make any difference. So before I rivet the next two rear wheels I'll strengthen the base so it doesn't bend so easily.

I've now got a complete set of wheels that I can send away to have proper rubber tyres fitted. But I've still got two more wheels to build. It's mostly going to be tedious. The only problem to solve is how to form the strakes so that they are a nice fit on the anything but straight rim. I've tried the usual methods of twisting them in a vice and putting them through rolls. Neither worked to my satisfaction. The current plan is to make some curved press tooling that replicates the shape of the rim and press the strakes red hot before fitting.

Andrew

Edit: Dunno why almost everything was doubled up? I blame cut 'n' paste finger trouble and red wine.
« Last Edit: June 20, 2018, 04:18:39 PM by jadge »