# Decauville/Couliet 2.75T build



## Kovacjr (Jan 2, 2008)

So I never started a thread on this way back 2 year ago so I am doing an opening post with a bit of history shown. Its been 2.5 years in the making so far. Just never get time for myself.


Dec 2016
For at least a year I have been designing a 2.75t version in 7/8ths, the smallest model they made. Being I had a set of RH Darjeeling cylinders I wanted to use those but with some difficulties. Of course the cylinders are larger so I had to stretch the front of the frame and raise it to clear the chest too. With that its a very short wheelbase and the front driver is smack up to the cylinder. Actually had to cut down the crank bolt to clear. Its a small step but a large one with live steam to get a operating chassis. The buffers are complete and I will move onto the deck plate and some other troubles I've come up to with the valve gear being wider than the buffers. Have a few thoughts so will see what looks the best. 

For the most part I used the Roundhouse Cylinders, expansion link and eccentric but made the rest of the rods as they are much smaller. Its built on my 18" wheels with a metal bushing for dual gauge should I want and also all new frames as its about 7" long. The boiler will be a huge 2.125" OD but 4" long

Fun part is building with real rivets.

A video of the chassis here 





Slight progress, added the deck plate. Designed the boiler and started to make the necessary parts. Bees at a standstill since Thursday as Ive been getting the house in order for Christmas. 



Some boiler progress today with my torch regulator here from warranty replacement. Its alot of boiler for only 4inch length. Internal throttle and dry pipe. One last bush to add them make some plugs and pressure test. 



Pressure tested to 120 and retested with the glass installed to 40 to check for leaks. Need to replace the rod in the glass with SS but all I had was tool steel in 1/16" or brass. Need to design and make a burner now.


Spent part of the last day of 2016 doing the boiler mounts and boiler wrapper. Put a front smokebox ring to support the front of the wrapper and also mount the front plate. Cut out the front plate and finished off the door and latch. Its all non operational as the burner can be lit underneath or from the stack. Also removes with 2 screws. 



Light progress today. Made the gas valve and lubricator. Need to design the burner and make that next. Then I can plumb and mount the gas valve. Gas tank will mount between the frames and be hidden. The gas valve is based on my fine spindles and is a really scale stand. 



Burner sorted. Its a shorter version of the RH drilled. Mike McCormack has been making them like this for a few years for Accucraft replacememts and are very good output. Very happy how this one came out except fpr that 3rd hole is off center. Hah


For right now I am focusing on getting a few things done. Plus a short list of customer work. After that I may make a small batch of valves. Its not terrible to make but I'd guess it was almost 1-2hrs sketching, planning and cutting.


Got the gas tank fabricated, laid out and built. Had to drill all the clearance and mounting holes on the floor. All drilled and just about fit and needed minor filing. Very happy with the concealed look. Tomorrow need to make the jet holder. Then I can get the last pipe plumbed and mount the burner.




Sept 2018!


Been 2 years since I worked on this. scratchbuilt 2.75T Decauville built by Couliet. Today I finished the smokebox door by adding the hinges and tackled the hardest part yet, the stack. 4-5 hours of lathework. Due to the length I had 1" stubs on each end to use the collet to hold both sides to work from. Of course the taper being 2.6" long I had to do it in 2 steps as I have about 2.25" of travel on the compound. The base is a Trackside detals and will be silversoldered on. To mount its a tight fit into the hole and will make a collar with a setscrew. Id is .350" at the base and tapered to .700" at the top but no pipe obstruction as the exhaust pipes are cut just below the base.. I can still bore the base to about just under .400 after its soldered together but worried about the setscrew tension and stack strength then as the wall would be about .040

I have been running the loco for 2 years and have been very happy with it.


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## Kovacjr (Jan 2, 2008)

Photo set 2


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## Kovacjr (Jan 2, 2008)

Photo set 3


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## Kovacjr (Jan 2, 2008)

Made my plans and layout for the side tanks. For the rivets I emboss with the NWSL dies. No4 are what I used here. I have 1/8" angle that will be the upper framing around the tank tops. Bending the sides were done on a wood former and bent around. Took 3 annealings. The tank front section will bolt to the front panel and the rear will be soldered to the cab sections and will bolt to the deck. Hopefully.


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## Tom Bowdler (Jan 3, 2008)

Nice!


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## Kovacjr (Jan 2, 2008)

Put a few hours Thursday afternoon making a few more parts and soldering up the one side tank for my 2.75t Decauville in 7/8ths scale. Other isnt far behind.


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## seadawg (Jan 2, 2008)

Kovacjr said:


> Photo set 3


 Love that stack. Is the inside tapered as well?


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## Kovacjr (Jan 2, 2008)

Dave, Why yes it is. Was easy to tapercut it at the same time as the outside. Though the inside itsn't as nice as a cut as Id like. It was singing away while machining as I left the inside for last so I got real nice finish on the outside.


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## du-bousquetaire (Feb 14, 2011)

Hi Jason those Couillet 040s are really my favourite Décauville, it really looks great, they are like a boy's dream come true, almost toy size.
Great photos of your build. and a very nice job of it.
Best Simon from France


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## Kovacjr (Jan 2, 2008)

Completed the hardest part yet the domes. Well so I thought. Much easier then I expected but the hard part yet to come. The steamdome has a throttle cover in front of it. A squared cover. Need to figure the best way for it. Steam dome top is a 2 part so I can do all the safety detail on it.

Ive also cut and rolled the roof. Plan for it to be a lift off with 4 locating pins in the corners.


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## se38005 (Oct 18, 2010)

That is a cute little engine, thank you for sharing.


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## Kovacjr (Jan 2, 2008)

Had another little fiddley part. The forward section of the steamdome. Its actually a throttle cover, I machined up a block and flycut both the saddle profile and the dome profile to mate up. I had to file some of the front flair of the domebase to mate up but then I JB Welded the 2 parts together. 24hr version. I also drilled 2 holes on each side to allow the JB Weld to bite in. Scuffed the area too with a 80 grit wheel on the dremel. Need to make the steam pipes now and drill and attach them to the dome. Sander lines are also next as is the cosmetic safety valve and spring housing. Amazing the little part took a few hours of machining. Ended up radiusing with a 1/16" radius endmill I have. Thought it would be more uniform

Time for a little sanding and cleanup after the JB is fully cured.


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## bille1906 (May 2, 2009)

Jay
Looks awesome. Glad the throttle box worked out.
Just one question
How is the sight glass sealed in the tubes?


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## Kovacjr (Jan 2, 2008)

Thanks. I always wanted to make end sealing glasses. Problem was the glass has to be perfect square ends. I sanded them then torched to seal. There is a Oring inside and the threaded rod is the tension. 0-80 nuts and washers. It was more of a fun project. Its such a cleaner look.


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## bille1906 (May 2, 2009)

Got it
Cool idea
Thanks


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