The following narrative has been describes the construction of the 1.22.5 mallet loco "Doris Ellen" using the running gear from two Bachmann "Anniversary" locos

The conversion is one of my latest project. I hope the following article will be of some use to any one who decides upon a similar venture. The use of Laser cutting for the chassis frames and coupling rods is a new departure and thanks go to Bob Jones for taming his monster industrial machine.

The engine is named for my Late mother.

Rod Hayward 2005

Here are the Two Sam's Club Annie's chassis ready for the chop. After moving the cylinders back and spending some time just staring at it one thing strikes me straight away. The wheelbase on the Annie block looks too long to me. If you take a look at the Sumpter jobs the drivers almost touch.

I think I'm going to have to move the axles closer together. I reckon if I do this and shorten the coupling rods this will obviate the need to make new con rods and associated linkages. 

Here is a comparison, the smaller rod set is 3/4 " shorter and with two blocks that's an inch and a half of the length of the boiler, so less overhanging.It also means that the blind driver will now always be over the railhead on 8 ft curves.
That means that I can have the front two drivers compensated and that in turn means the middle drivers will be working for a living. I hate the center drivers flapping around in the breeze.  
 
Here's a pic of the rods with the inset showing how the rods were cut and pinned. I used cyano with brass pins that I tapped with a small hammer after fitting, to swell them in the holes a bit.
That ZAMAC is ghastly stuff to work with. Pins up your files etc.
 
Here's a simple jig I knocked up to ensure they all ended up the same length. Its just a couple of bits of brass tube tapped into a bit of wood, with styrene guides. It does n't have to be complicated
I am really pleased with this, I wish I thought of this when I did the USA tank. Bringing the wheels closer together not only improves the appearance it means that 4 sets of con-rods etc don't have to be chopped about.
It also means that it does n't end up with a long a spindly con rod. Oh and by the way, you can see the reverser gear is set differently now :)

Last picture gives an indication as to how much shorter this chassis is now. I think you could easily do this for a mogul, prairie, or even stick another driver on the back for a 2-8-0 if you mucked about with the firebox ?
Mucking about comparing the old concept (was it really 2 years ago? )with the stock Annie chassis with the latest version. The new blocks have been overlaid on the lower picture. I prefer the short smokebox and parallel boiler also.

It does manage to keep the boiler relatively short if I omit a rear truck. Have nt decided on that yet.
Most every one I have seen has them, but it does mean that the body would be longer, something I am trying to avoid.
Here is an underside view of the rear motor block. It shows the new sub chassis mated with the original chassis. The rear of the sub chassis has a slot in it so that it can be adjusted to ensure no rod binding before fixing.
You can also see here how the flanged drivers have been machined to match the blind driver size. The front two axles sit on the compensation beams and because of the reduced wheelbase they will go around an 8 ft Dia curve without dropping inside.
I have now got access to a laser cutter on an ad hoc basis. After spending all that time on the chassis mods, it's tough, but I'm going to junk them. There's nothing wrong with them, but 2 pairs of laser cut, 2mm thick stainless steel chassis halves have got to be the business. Here's a Cad pic I've done of the front and rear frames. The rear set has the motor reversed in the frame, that's why that wee hole for the pin is in a different place. That way it's out of the way of the spot where the pivot is going to be sited.
Ignore the circles, there are just there to check the screw holes aren't covered by the wheels. (The circles represent the flanges btw, not the treads.) 
Dressed off and lapped the new rods. The rest of the Annie valve gear remains unchanged.
 Here is a pic of the front frame set, the rear is identical, with the exception of the front extensions over the leading pony truck.
 These are cut from 2 mm stainless and are as rigid as you can expect. The slots accommodate the Annie bearings, which with the exception of the rear fixed motor shaft will sit on the torsion bar as before. 
First up the experiment to make ladder sides in 1mm stainless came up trumps, don't be put off by the rubbish pikky, they are spot on.

The two holes at either end are for when the they are bent at right angles so as to bolt to the tender.
I thought I would take advantage of my pal's help by using the time saved to do something else while I am waiting. So this is how the tender got built before the loco. Here is the mallet tender, it's an old Connie one that's been lowered and about 12mm cut out of the center from front to back. The usual bits of waste pipe, mains wire and the first use of my laser cut ladders. You have to laugh, all that scrap stuff thrown together, topped off with a precision bit of stainless steel.

Some more tender shots.

 
I thought I'd finish off the new rear driving axles, so here's a few pics on something I discovered. Firstly I faced off the crank pins cut from the center axle. Inspection reveals that some one drilled these with a Back and Decker whilst holding the wheel in their feet ?
Which results in this when you screw it on to a 3mm set screw inserted from the back of the wheel.
 So it ended up back here. I don't have a 4 jaw chuck so I leave the screws long and stick them in the chuck and then cut them off after. I Had to do all 4
First up the assembled front and rear chassis, some of the screws are temporary and will be replaced.
The overall size with tender

Some more shots of the general arrangement.
Finally put the cylinders together. The next two pics show the relationship between the Low Pressure (Front) and the smaller High Pressure set(rear). It looks like there is a marked outward slant, there is a slight outward bias so the valve gear does n't foul, but its nothing like it appears in the photo. It's just a distortion of perspective.
The pics are n't up to usual standard, but it's got a lot colder since I took the previous shots and I am not going outside and freezing my arse off, not even for you lot :) Fitted the cylinders. You can see in these shots that the outward slant is not a severe as suggested above.
Dec1-05 Here are some shots of the the latest version of the frames I received recently, thanks again Bob. If you look closely you can also see the Annie pilot truck chassis, which has been incorporated into the pilot truck
Dec12-05 Here is a drawing of the next phase of the project. The pivots mounts are going to be 2 mm stainless again and the swash plates are shown below. The rear end is going to be pivoted also to cut down on overhang. The loco is not completely accurate, but near enough to look right.

Dec 27-05 I have now installed the pivot mounts. They are made from 2mm laser cut stainless bolted to styrene cross members. They have a channel underneath to accommodate the motor and gear box. Now they are in place the business of determining the placements of the pivots and the boiler assembly can be started. The cylinder block supports and cross members have also been added, these are made of laminated styrene also.

In front of the cylinder block mounting is the pilot truck and pilot deck cross member. You can just make out the spring and guide assembly here that keeps the truck in check. Also noteworthy is the addition of two stainless steel flanges to the once blind center drivers. As yet the reverser gear is not fixed or the cylinder brackets completed.

Here is a shot of the two units sitting on 8ft diameter curves. Strictly speaking as both units are pivoted it's not really a true Mallet, a Meyer would be a better description. Looks as if it may just fly with all the wheels flanged. Clearly visible are the two pivot bearing assemblies.

Placing the boiler mock-up on the assembly reveals that the overhang is not to ridiculous. I am convinced it would have looked daft if I had fixed the back end. Now the chassis is nearing completion the next challenge will be the construction of the pivot assemblies and the associated piping that feeds the steam to the cylinders and takes the exhaust to the stack.

Here is a side on shot of the loco, again sitting on the 8ft diameter curve. Some more work has been done on the boiler, cab and fittings. The bulk of the fittings is coming from the two Sam's club Annies that were broken up, although the cab is from an earlier Annie "wood burner". The brake tanks are 3/4" waste pipe sections.
This is a view taken a little higher up an and shows the position of the whistle and safety valve housing, sand dome, steam dome, bell and stack. The sand for the front chassis would be kept in the box on the pilot deck, forward of the smoke box door. Damn, forgot to place the generator
The last shot shows the position of the front sand box and the headlight, which will eventually be supported by a bracket. Now the pilot deck has been covered it gives an better indication of the amount of boiler overhang, and as suggested above, looks like its a flyer. Next update will be after the priming, which is n't far off.
Almost time to prime the boiler assemblies, so the smoke box wrappers needed to be finished off. As with the tender and other areas of detail I prefer to use the "cladding" method, with a little variation, I use two layers. The first part is the familiar punching of the rivet detail from a piece of 20 thou styrene sheet, the templates I drew are shown here. There nothing really hi-tech about this procedure
Care when marking out is essential. Bare in mind this is the front of the loco and it's going to catch the eye, any irregularities are going to be very noticeable here. Here is a picture of the toolkit. A good steel rule, compasses, paper templates and the riveting tool. This is a piece of brass rod that has a steel point on the end with a drop hammer made from a piece of lead wrapped around a slider. The higher you raise it, the bigger the rivet, and its consistent.
The picture here shows the tool placed in a small nick that has been pierced in the template by a compass point. Since the eye will most notice any rivet deviating from a line, rather than a rivet being slightly closer that it's neighbour I work looking down the "long" side of the template, with the line going away from me. The templates are held to the styrene with tape. Make sure you have plenty of light on the job.
The same procedure was performed for the smokebox front. The templates were produced together so that the rivets on the wrappers matched up. Again its really noticeable at the sharp end if they get out of sync as they go around the smokebox. The green arrow was to remind be to place the "best end" to the front. You can see that the rivets follow the edge of the tube nicely. This is where the two layer method comes in I mentioned.
Since the styrene wont stick very well to PVC tube with the usual styrene welds my preferred choice is to use the thinnest Cyano I can get my hands on. Since getting a six by two inch wrapper positioned accurately with an instant glue is very difficult I cheat, I use two. The first 20 thou wrapper is stuck to the PVC tube, this has no detail and is just wrapped around and trimmed off, this allows a little licence. The next wrapper to go on is the rivet detail and now I have a piece of styrene to stick it to I have time to manipulate it as I apply the usual poly weld stuff.

The end of the smoke box was faced off in a lathe, so I know it to be true. The boiled is placed down on a piece of glass and rotated as the wrapper is carefully applied. It seems very long-winded but the net result is worth it and it produces consistent results.

Oh I almost forgot, I also made a new cab front. The doors are from a Connie. Just whack out one of the planks and they fit like a charm. Very Colorado I thought

Made up some high pressure steam pipes from odds and ends. The bend into the smokebox is a plastic drawer handle cut in two. The pipe body is 7/16" styrene with a piece of window blind rod in the middle which was heated to provide the bend. The joins are 1/2" styrene and the lagging is string (tightly) wrapped around the 7/16th pipe.

Now you might think that string is an odd choice, but it really looks the part. Lagging is usually pretty soft and shows all the vagaries of scorching and filth. The trick is to soak the string with cyano after fixing it, this turns it rock hard, but maintains the textured apperance. Add a few weathering powders to suit and voila, there ya go. Here they are in place

The latest so far

Here is a view of the motor blocks. You can see the 5 mm pins that plug into body which allows both blocks to pivot. The reverser gear has been added and the first run should not now be far off. In reality the rear block would not have the reverser hanging down in the firebox area. The motion assemblies would be shorter and further foward, but i'm buggerd if I'm going to cut that lot about, so the demon compromise wins this time. You can also see where I have added

the pilot deck, headlight, sand box and footboard. Next up will be to finish off the wiring of the chassis and paint the wheel rims. This has been very tedious and getting back to detailing the body will be nice. Not long to go now...
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