Maxitrak Dixie 0-4-0St overhaul.

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Tony Bird

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Hi,

Dixie 2014 Major Overhaul.

Dixie is a commercial 5” gauge 0-4-0ST narrow gauge model steam locomotive made by a company known as Maxitrak. It is a reasonably close-to scale model of a small contactors locomotive that was made by Kerr Stuart and known as its Wren class. Like its full size prototype Dixie is a very simple locomotive, the steam is not super-heated the boiler having an external steam pipe, it has a cross head and a hand pump but no injector to supply water to the boiler. There is a simple mechanical lubricator to supply oil to the cylinders; the valve gear is Hackworth using slide valves. There is no suspension the driving axle being solid in the frames, the leading axle can pivot giving what is known in the smaller gauges as a three point suspension. Having a solid driving axle means that the valve events won’t alter because the axle has moved a problem with the Hackworth system, on full size locomotives it was usually arranged that the driving axle had little movement. Like its larger brother Dixie has a minimum of controls, regulator, blower valve, by-pass valve, reversing lever, whistle and a brake. The locomotives name might have come about because there is a preserved Kerr Stuart Wren class locomotive named Pixie.

Dixie was bought a little over four years ago and was purchased because for its size it is comparatively light. I have two other 5” gauge tank engines which my father and I built many years ago fitted with the usual steel frames and brass tanks, Dixie has aluminium frames, buffer beams and saddle which are cast in one piece. The saddle tank and coal bunkers are also of aluminium which along with its minimal cab saves a lot of weight; this does of course reduce its tractive effort but Dixie is a lot easier to move around. It is only required to pull a couple of adults or an adult and two children and Dixie manages these light loads very well. When driving the lack of sprung suspension is not noticeable.

Dixie is 30 years old being made in 1984, it was I think a part machined kit as the important parts are well made and parts like the brake gear less so. As has been mentioned it was bought four years ago having previously spent about 10 years uncovered in a damp wooden shed, despite having some surface rust it was in fair condition. At some time the locomotive had met with an accident that removed part of the front buffer beam, Dixie was taken apart and cleaned up its general moving parts having been worked on were in reasonably good condition the only real problem being its boiler. When the boiler was tested a couple of the stays in the firebox were found to be leaking; this might have been caused by some water which was still in the boiler freezing in cold winters. No longer having access to suitable welding torches the boiler was sent to Maxitrak for repair and testing which they did and charged only a modest amount.

Like most full size and model 0-4-0’s Dixie has a lot of overhang at the footplate and tends to be tail heavy. I have had this problem before where there is a lot more weight on one axle than the other which reduces the locomotives adhesion. So as the front buffer beam was broken a steel buffer beam with a set of heavy dumb buffers was fitted which made the locomotive better balanced. These were the only initial alterations done to the locomotive before it was run; subsequently automatic drain cocks have been fitted. There is a thread in the forum that describes the making and fitting of them.

In this thread I hope to describe the fitting of ‘0’ rings to the pistons and other small jobs before the start of this year’s running season.

The prototype.



Dixie as bought.




First run in over 10 years.



Usual load.



Before starting overhaul today.



Regards Tony.
 

Tony Bird

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Hi,

Yesterday having watched the Irish beat the Welsh at rugby I started to take Dixie apart.

1. The buffer beam was removed and will need painting as the holes for the automatic drain cocks were drilled after its last paint job.



2. One of the cylinder covers was removed to check that the 1.1/4" '0' ring would fit otherwise it would either be soft graphite packing or make piston rings. Luckily it fitted.



3. The union on the lubricator pipe is leaking which won't stop when the nut is tightened.


Though the main job is to make and fit new pistons with '0' ring seals I prefer to do jobs as they come up so.

4. A new lubricator pipe was made and fitted to the lubricator.




5. The screws that held the buffer beam to the chassis were shortened and blued and the buffer beam given a coat of paint.



A long way yet to go.

Regards Tony.
 

Tony Bird

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Hi,

Yesterday started with Dixie more or less in one piece.

1. The smoke box door is a push fit into the extended part of the boiler which makes up the smoke box.



2. The cab and bunkers come away in one piece.



3. One piece cast aluminium saddle tank containing hand pump.



4. Boiler with lagging? between boiler and saddle tank.



5. Underside of chassis showing the one piece aluminium casting used and the plumber block bearings for the axles, the front axle is mounted on a plate that can pivot



6. Top view of chassis.



There are a few bits and pieces to do to the parts taken off before removing the cylinders from the chassis.

Regards Tony.
 

Tony Bird

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Hi,

Did a little more work on Dixie today.

1. To remove the boiler from the chassis the extension tube on the blow down valve needs to be removed. The original copper tube was difficult to unscrew so a brass one with a hexagonal end was made and fitted. Note the boiler stamping 70 9.10.84. Cheddar Models boiler No.70 tested 9th. November 1984.



The cross-head water feed pump was cleaned and a new '0' ring fitted on its ram no photograph.

2. Dixie's front axle rocks as it suspension. But it rocked rather a long way, it didn't effect the running of the model but it was a little disconcerting if you pushed on the front buffer bead and it went down about an inch! So washers were fitted that restricted the movement to about a 1/4", this shouldn't effect Dixie running on rough track. I hope! The diameter of the washers can always be made smaller so increasing the rocking moment.



3. The front axle fitted back on the chassis.




Regards Tony.
 

Herbiev

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Tony. Should that read " tested 9th October 1984" ?
 

Tony Bird

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Hi Herbie,

Should that read " tested 9th October 1984" ?

Didn't November come early in 1984? Its the only excuse I can think of other than the obvious.

Regards Tony.
 

Tony Bird

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Hi,

The cylinders on Dixie are of a somewhat unusual construction instead of the cylinder steam and exhaust ports being in the cylinder casting they are in the bottom of the steam chest and line up with slots cast in the cylinders. When the steam chest and cylinder are bolted together they sandwich the steam and exhaust pipes between them. The sealing is done using Loctite which is smeared on the mating faces and around the steam and exhaust pipes before bolting the steam chest to the cylinder. In practice both cylinders have to be done at the same time and it isn’t easy, first the cylinders were bolted to the chassis with the common steam and exhaust pipes loose between the frames. The Loctite was applied to the top face of both the cylinders and around the steam and exhaust pipes, the steam chests were then bolted down. When I originally took the cylinders off it was found that both the steam and exhaust pipes were loose in the cylinders so I made some clamps that held them so they couldn’t move. I used this system when I first overhauled Dixie 4 years ago, it works. However when the pistons needed new packing the cylinders had to remain on the chassis because I didn’t want to break the seals by removing them, so it took a lot longer than it should to do the job. This assembly system I assume speeds up manufacture, which might be OK on a model stationary steam engine which is rarely used but on model steam locomotive that might travel many miles during a year so needing regular maintenance it is a bit of a pain.

Last year it was thought there might be a blow on one or other of the cylinders and there was a reduction in power, this was put down to the soft packing needing replacement or a failure of the seal between the steam and exhaust slots in the cylinder. Materials had been bought for the next time the pistons need some work new ones could be made using ‘0’ rings as seals. To make new pistons the cylinders would have to be removed so the seal between the cylinders and steam chest could also be addressed.

So yesterday the first of the cylinders was removed from the chassis.

1. Clamps to keep the steam and exhaust pipes from moving.



2. Steam chest cover removed. Note steam passageway in steam chest wall.



3. Steam chest removed from cylinder. Note remains of Loctite. couldn't tell if there was a leak between steam and exhaust slots.



4. Decided to solder steam chest and cylinder together using 'Comsol' a high temperature soft solder which melts at 296-320C.



5. Cylinder soldered and threads in the steam and exhaust holes.



6. The slots and steam passageways don't line up well so I will try and get a milling cutter in to improve things.



7. While the cylinder cooled about 45 minutes a start was made on the piston. Decided to use the original pistons as there was room to fit the '0' rings on them. It should work. Starting slots with parting tool.



8. Slots opened to size by hand turning which I find a lot quicker than using a fixed tool. The slot is opened until the '0' ring will fall out. The depth when the inside of an inverted '0' ring is level with the piston.



9. Piston finished.



Regards Tony.
 

Heffalump

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I know I'm quite new, but I've not heard of anyone turning metal with a hand tool, how interesting. Could you post a picture of the tools you use?
 

Tony Bird

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Hi,


I know I'm quite new, but I've not heard of anyone turning metal with a hand tool, how interesting. Could you post a picture of the tools you use?

I will take and post some photographs of hand turning the piston of the second cylinder.


This might me of interest. Polly Engineering in the UK list 3 types of '0' rings the type plumbers use which is OK for hot and cold water. Silicon which will stand oil and steam temperatures that models use. The third Viton which will stand even higher temperatures. I usually use Silicon as Viton has nasty side effects if it burns, the ones fitted to Dixie are Viton as they were out of stock of the Silicon and I wanted to get on with the job. I had meant to mention the '0' ring should be capable of just rotating in its slot if it is fitted correctly.

1. Set up for milling the steam and exhaust slots in the cylinder. I don't have a machine vice that was deep enough to hold the cylinder so used a 4-jaw chuck mounted on a rotary table. This made the job a little high so much so that the bulb had to be taken out of the light above the mill. Also being of a sensible height (short) I needed steps (only the first rung) to see what the milling cutter was up to.



2. Milling cutter used for the larger exhaust slot.



3. Slots milled.



4. To remove any residue of the Bakers Fluid (flux) that was used with the Comsol the cylinder was boiled in washing soda. Bring to the boiler and simmer for ten minutes or until the gunmetal turns a gold colour and serve with........ This is best done when the domestic authorities are away, the pan is a dedicated workshop equipment and not used for soup!



5. The cylinder was lapped.



6. Lapped cylinder.



7. Packing the valve rod with graphite yarn.



Regards Tony.
 

Tony Bird

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Hi,

I have started a thread on hand turning in the 'Tips' section.

Today's efforts.

1. The first engine is back together.



2. The chassis looks a little sad.



3. The ports line up better on this engine.



4. I think it was this engine that was leaking to exhaust looking at the ports.



5. The steam has marked the gunmetal and the part between the ports is the same colour.



The '0' rings have been fitted to the piston of the second engine and the steam chest has been soldered to the cylinders.

Regards Tony.
 

Tony Bird

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Hi,

Well this is the end of the thread unless other work is decided on while completing the assembly. In theory all the machining is done, the valve gear needs to be set up, then hopefully its just put all the parts back on the chassis. The model clubs first running day is on March the 1st. so if the weather has improved by then Dixie will get a run after the annual check of her pressure gauge and safety valve.

Today the following was done.

1. The unions and their nuts were finished and the cylinders joined together.



2. The PTFE tape seals used about 2 foot (600mm) of tape which was twisted then halved and put around the pipe to be sealed, the tape was wound around the pipe until it was used up and the nut tightened on the union.




3. The cylinders back on the chassis, permanently, I hope!



4. Dixie back horizontal again.




Regards Tony.
 

Tony Bird

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Hi,

Just an up date. The valve gear has been set up, the oil and water pumps fitted along with the rod to operate the exhaust valve. The steam chests are sealed, so the chassis is more or less complete.

1. Setting Hackworth valve gear is relatively easy. With the reversing lever in mid gear and the piston at bottom or top dead centre the expansion link should be at right angles to the connecting rod. This is achieved by moving the reversing stand back and fore then locking in place. This done the valves are adjusted so that the ports open similar amounts.



2. Completed chassis.



3. Chassis running on air.



4. VIDEO running on air.



Given that the engines will be little tight and running on 20 psi I am reasonably happy with the results.

Regards Tony.
 

Tony Bird

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Hi,

Decided to have a go at lagging Dixie's boiler which had no form of insulation except for some cork between the saddle tank and the boiler which I think was for fit rather than anything else. The lagging cannot be very thick as it has to go under the saddle tank and there is not much clearance behind there reversing pedestal either.

1. The materials, next day delivery from Blackgates! 12"x24" 26g brass sheet, 4 'Kaowool' 2mm tiles and 6' of 1/4" boiler banding.



2. Tool used to cut the brass sheet


3. Brass sheet cut.



4. Using a step drill to cut clearance holes for the boiler bushes.



5. Kaowool held to boiler with masking tape.



6. A test fitting of the brass sheet using cable ties.



7. Brass sheet painted and boiler bands made and fitted.



8. As Dixie looked at end of play today.



Next is to figure out how to lag the fire box. Then is just a matter of a final check of the valve settings and put all the pipe work back on.

Regards Tony.
 

Tony Bird

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Hi,

It took a lot longer than I thought it would to lag the fire box. To use up the brass sheet that was bought it was necessary to solder extension pieces to the fire box wrapper. Forming the ogee shape to the sides of the wrapper were a pain! The front of the fire box wrapper is held by the last boiler band and the bottom of the wrapper has an angle formed on it which the boiler clamps hold but getting the reverse curve right took forever. I had hoped to finish the job today but there is still some pipe work to fit and checks to be made maybe tomorrow.

1. Fire box wrapper showing extension pieces.



2. Fire box wrapper painted and fitted



3. As far as the assembly got today.




Regards Tony.
 

Tony Bird

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Hi,

I'm a little surprised that no one has commented that on the video posted the locomotive is in reverse yet the wheels are going forward!

VIEO




Regards Tony.
 

Tony Bird

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Hi,

Dixie is all back together run on air and now ready for a steam test.

1.



2. I didn't get very far tweaking the valve gear because who ever altered the direction of travel of the reversing lever had to elongate the reverser pedestal holes because the original reach rod was too long. Getting the reversing lever in the correct place so that when in neutral at TDC the expansion link was at right angles to the connecting rod was very difficult if not impossible. Having done quite a lot of work on Dixie I wanted to improve the valve events so did a bit of surgery on the pedestal securing holes. As it was.



3. Slotted.



4. Filled ready for brazing.



5. Fitted and the original reach rod bent to length.



6. Check on expansion link setting.



7. New straight reach rod fitted.



8. New Reach rod finished, painted and fitted.



9. Last job was to fit a union on the blower pipe where it went into the smoke box as it was a major job to remove it as designed. As it was.



10. The union fitted.



With luck within the next week or so Dixie will be removed from the shed for a steam test. It needs either our son or members of the CMES to visit to help lift and transport her.

Regards Tony
 

Tony Bird

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Hi,

The following might be of interest if you haven't seen a model coal fired steam engine fired up. We had to go away yesterday so didn't get to take Dixie to the CMES play day. So today as Old South Wales basked in sun shine the usual wet sort I decided to give Dixie a static steam run after her major overhaul.

1. On blocks and on a stand ready to go. Boiler and saddle tank filed with water, oil in the lubricator and the motion oiled around. Handle fitted on hand pump a battery fan fitted in chimney to create a draft and except for the weather everything perfect?



2. With layer of charcoal which had been soaked in paraffin in the fire box it is lit with a further piece of paraffin impregmented charcoal and the fan switched on.



3. After a few minutes and the charcoal well alit coal is added.



4. The coal has started to burn.



5. First leak on a union from the crosshead pump into the boiler it wouldn't stop after tightening the nut might need a new nipple.



6. Half a glass and up to pressure 90psi.



7. Safety valve check.



8. With the blower full on he pressure went up to 95psi where it stayed on closing the blower safety valve closed at 85psi. Which is thankfully is within the boiler regulation limits



9. Running showing a leak on one of the front cylinder covers, also one of the drain cocks hadn't closed.



10. The video.



11. After about a twenty minute run the fire was dropped.



12. Dixie blowing down and saddle tank draining.



13. Cleaning the flues. When running with no load there doesn't get much ash in the smoke box.



14. Back in its transport container.




15. Along with her brakes Dixie is held in the container via her front coupling.



Well a couple of things to sort out, all leaks. I was glad to find that the new pipe work hadn't leaked and Dixie running well with no sign of a blow and a good exhaust beat. Well its fix the problems, another static steam test and all things being equal the CMES for a run.

Regards Tony.
 

Tony Bird

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Hi,

My last post left Dixie in her transport container in the garden where she stayed for the next six days before some friends carried her back into the workshop. I had managed to slip a disc, not as one would expect lifting Dixie, but putting a camera memory card into the hard drive of our computer! That was 10 painful days ago, thankfully pain killers and anti inflammatory pills have got it under control and I'm allowed limited access to the workshop.

1. Dixie out in the wet.



2. The leaking cylinder cover was fixed after making and fitting a new gasket. I think the drain cock that wouldn't seal is OK there was some muck in it. The union leaking was caused by a cracked nipple which has been replaced.



3. Dixie has a very small capacity saddle tank so it is easy to run out of water and as the cab had been taken off it was decided to drill and tap the tank for a water gauge.



4. The tank plugged until a water gauge can be made.



Next a water gauge to make.

Regards Tony.
 

Tony Bird

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Hi,

Some notes on making a water gauge. The water gauge made for Dixie’s water tank only needs to be of the simple type as it doesn’t have to stand any great pressure and is not likely to suffer from any mineral deposits. As the tank already has a drain valve it doesn’t need one and should either of its fittings become blocked they can be cleared from inside the water tank which saves the fitting access screws. When making small water gauges it is advisable to fit the largest possible glass that looks OK doing so makes them more accurate and responsive. The water gauge on Dixie’s boiler is 5mm OD so this is the size chosen for the water tank. When deciding on the design of the water gauge fittings the minimum size of any water/air/steam passageways through the fitting should be the same as the ID of the glass tube. The design of Dixie’s water gauge fitted to the tank is based on the water gauge used on the boiler.

The components of the fitting part of the gauge glass are: two similar main bodies, two supports which will be soldered to the main body, two gland nuts, one access bolt for the top fitting and two ‘0’ rings for seals.
The materials used 3/8” (9.5mm) hexagonal brass rod for the fittings body and gauge glass nuts and some 3/8” (9.5mm) square for the top nut. The top and bottom main parts of the fitting are the same size the difference being that the top one is drilled through and threaded to allow the glass tube to be inserted. First a 5.5mm hole is drilled transversely nearly all the way through the hexagonal rod. The hexagonal rod is set up in the lathe and a 5.5mm hole is drilled until it breaks through into the transverse, this hole was then threaded ¼”x 40. The hexagonal brass rod was then turned to 9mm diameter and parted off. The work piece was then returned to the chuck the blank end facing out; a 5.1mm hole (clearance for the 5mm glass tube) was drilled until it broke through into the transverse hole. The outside of the work piece was turned down to take a 9/32” thread. The bottom fitting is simpler and doesn’t have the internal thread in it but the 5.1mm hole for the glass tube doesn’t break into the transverse hole, it stops 1mm short and a 3.5 mm drill is used to break through so forming a shoulder that the glass tube can rest on.

The nuts are straight forward being drilled for a 9/32” thread followed by a 5.1mm hole for the glass tube before parting off.

The main body supports are also straight forward. The hexagonal rod is left hexagonal drilled 3.5mm for the water/air/steam passageway; one end is turned and threaded ¼”x 32. The work piece was parted off and its other end shouldered to fit into the main body. The main body and its support were hard soldered together.

The last component to be made was the access bolt that allows the glass tube to be fitted. Dixie’s gauge glass on its boiler had a square top which was replicated using 3/8” square brass rod. The rod was turned to 9mm OD and shouldered to take a ¼”x 40 thread. The squared part of the rod was held in a machine vice on the milling machine and the square top milled, back in the lathe the bolt was parted off. So finishing the making of the water gauge.

The water gauge fitting were sealed to the water tank using Loctite nut lock and lined up using a 5.1mm drill.

1. Hexagonal brass rod cross drilled.



2. Parting off top fitting body.



3. Checking gauge glass fit.



4. Parting off gland nut.



5. Checking gland nut fit.



6. Body support.



7. Body and its support hard soldered.



8. Turning top bolt.



9. Milling square on top bolt.



10. Parting off top bolt.



11. Test fit.



Awaiting longer gauge glass from Blackgates which was ordered yesterday.

Regards Tony.
 

Tony Bird

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Hi,

The gauge glass has arrived and has been fitted and tested no excuses for an empty tank now.

Regards Tony.

152 Dixie water gauge finished LR.JPG


153 Dixie water gauge finished LR.JPG
 
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