Construction of 'Red Fred' (RM55) Railmotor

by Peter Nixon

This article is based on a series of Railfan.net forum postings during 2010 by the author, plus additional material from him.
The content is used with permission.

Hi all, I'm Pete, a newbie to the hobby from Australia. I marvel at the building and running skills of the live steam hobby, but with no metalworking skills necessary for a steamer I decided to build a railcar. I laugh now when I look back to knowing nothing and getting nowhere, and asking for help or advice. Maybe it'll give some encouragement to those who have the desire but no skill, because I'm real happy with the outcome.

I decided to build a Queensland Railways (QR) railmotor named 'Red Fred', or officially as RM55. These railmotors were custom built in Qld to keep unprofitable rural lines running in far away towns. 'Red Fred' was built from a second hand AEC truck chassis (the same chassis as the London buses with the ouside spiral staircase). The original 'Red Fred' is now in the Rosewood museum, who kindly allowed me to take many pictures and measurements.

The original 1930 AEC bus chassis railmotor, kinda reminds of the US Galloping Goose as it did a very similar job on lightly laid narrow gauge tramways (shortlines)

. . . and the 7¼" gauge 2in/ft scale model end product

Click here for a video of a similar railcar in outback rural Queensland.

This was the atmosphere I wanted to recreate, and it wasn't going to happen with electric drive, or Briggs and Stratton and hydro drive, so it had to have a low revving petrol engine and manual gearbox.

A neighbour bought his kids a Chinese Honda clone quad bike like this one at the right, for Christmas, but he didn't tie it down properly for the trip home . . . and well it got all re-arranged . . . however the motor still worked fine, so I had my engine (110 cc) with 3 speed clutchless manual, and as a bonus it had electric start!

This is it fitted to the framework of the car. Perfect fit after a few passes with the angle grinder and still leaves a bit of daylight at window level.

 

The body.
All good builders usually start with the wheels and work up. But my build experience came from 0n30 sized critters, so I built the body first, and then worked out how to drive it later! To quote the [late Australian racing car driver] Peter Brock "Bite off more than you can chew, then chew like crazy".

Some line drawings at build scale, were made, and as I planned to sit over the (single) drive axle to increase adhesion, the frame was welded together using 12mm square bar for the verticals (easy to bend, hard to blow holes in), and 12mm square tube for the horizontals (easier to rivet or screw to). The roof had 2 angle iron spreaders to hold the plywood seat area, with a gap behind for a small roof mounted fuel tank. A loop at the front would support the roof overhang.

The body framework

As you can see, the frame got changed from time to time, and there's probably a few of the original bits still there. Part of the plan was to make the rig light enough to be transported in my Subaru station wagon, so the bodywork was cut from 0.8mm aluminium. The edge laps were bent by clamping with a block on one side and the shed door frame on the other, the roll was guestimated against the carport support poles, and the windows cut with a jigsaw with fine blade.

When it came time to fix the sides, I used construction adhesive and countersunk pop rivets at the corners.

The body framework in the car

I still had the plywood floor at this stage, it was scrapped later as I had cut so many holes in it that there was nothing left. It still has no floor. The roof front was a stack of ply pieces. The "grain" in the ply makes it easy to check the contours, and to compare corner shapes.

One of the 'workers' taking a break during construction and checking out the roof contour

It's amazing how many new ideas you can come up with when you don't have other people's ideas to cloud your perception.

I'll come back to the bodywork later. Meanwhile there was the problem of the cutout in the floor and the fact that motorcycle engines generally hang from above. I tried two chassis rails of 50mm angle, but it left the motor way too high. What it needed was a box with a coathanger-like strap over the top. I decided to take a bit of liberty with the dimensions of the fuel tank and battery box of the prototype, and had some 100 x 100 square tube. With the angle grinder I gouged out the side of the tube until it fitted flush with the crankcase, then repeated for the other side. Some 6mm plate across the rear and a strap across the front and I had my box. The angle iron chassis could then attach front and rear, and when this photo was taken, the swing arm is on, and the full length side steps give a bit more bracing.

Chassis part built with swing arm in place

Here's the same view but with the motor installed.

Chassis with motor and swing arm in place

The hanger for the motor top mount is the lengthways bar. I used this also as the electrical centre so its a bit crowded. I chose the swing arm option as it meant the chain drive was very simple and gave lots of travel without tension change. The swing holds two housings for self aligning ball bearings, and the crossways bar holds the coil springs for the rear suspension. The side steps have grown a bit and now have timber treads, which were more foot friendly, while providing some resistance to rollover if derailed.

Disc brake to the axle

Here's the rear swing arm, looking from the rear. Tubes for pivot bolt, and spring pads with wiping pads at rear. In the photo I am in the process of mounting the quad's disc brake.

And finally the "road kill" view. Looks a bit tidier here, and there's a pretty good airflow aroung the motor, but I decided not to refit the floor. A coat of black satin makes it all disappear into the shadows. The brake disc is an old alloy pulley turned down, with an offcut of 5mm plate bolted to it. Works a treat.

Under side view of the 'works'

Just one photo to keep you going

photo legend

I will describe the rear truck axle setup.

The real one

The model one

Fred kept it's original truck axle and brake drums (external contracting) and used a 36" cast rail wheel. This design was not used on any other rail equipment so as a distinguishing feature, I had to attempt to copy it.

Since this is the only known Fred in 2" scale, it was a waste of time looking for one ready made. So on to the woodlathe with a piece of 30mm MDF (ex kitchen benchtop, sink cutoutout ) and carve away with a photo propped up behind and some guide dimensions. Basically I made a disc wheel, but I changed the offset slightly, partly because of overscale width and partly to give a flat back for cheaper casting.

Then I marked out the holes as a circle, and bored them with an adjustable auger. A bastard round file made the holes pear shaped, then I marked the six ribs. A large handsaw had a suitable kerf width so slowly the ribs were cut, right down to the inner disc depth. 3mm ply strips were glued into the grooves, and when dry were sanded down (the strips had a slight taper, or draft as I had read up on casting requirements) Then the wheel went back on the lathe to smooth the tread again. This photo shows the master glued to backboard. The white filler was added by the foundry.

Pattern for the wheels

Every foundry told me to 'go away', but finally one accepted, but only if they used investment type plaster moulds. I nodded and tried to look intelligent and left it with them. Five months and $200 later I had my two castings, in SG no less, and they had ground the skin off for me.

By now I was an old hand on the Myford (I had turned the front wheels as my first ever lathe exercise), I looked though the collection of bits that came with the (deceased estate) lathe, and found a faceplate and some dogs. A bit of argy bargy as the wheel fouled the bed, but eventually it moved. Set on the slowest speed, and with a brand new carbide tip, I gingerley started a cut. As I had underestimated the shinkage, there was not a lot of meat to remove, and with my lack of machining knowledge I just cut until it looked right. The tread profile is AALS but with a 10 degree taper on the back of the flange as I percieved that the long fixed wheelbase might cause riding up. Working on the inner radius in this photo.

Working on tyre terad and inner radius

The back took a bit of work, and those six holes caused the lathe to complain loudly. Now I know the speed should have been way faster.

Next came the problem of keying to the axle. A search through some forums and Youtube and a plan was hatched. 3/16th key steel seemed about right and a spare lathe toolpoint was sharpened to angled flat 3/16th wide. Lots of hand filing first, then lock the chuck and push the tool (it now had a name . . . broach) with the carriage screw. Repeat a few hundred times.

Broaching the rear wheel keyway

Then put the axle in the chuck and repeat. The axle was mild steel so less filing and more broaching.

Wheel with keyway broached

You might have noticed that the hub was not cast with the wheel. I turned a shouldered "washer" to look like the hub, then used it, with a countersunk allen screw, to secure the wheel to the axle. When I fitted the sprocket and brake disc, I simply drilled a vee into the axle and used a grub screw (and a bunch of loctite.)

And here's the finished article.

All the Red railmototors had the same front end, a really short archbar setup with springs that dont look like they'd hold up a shopping trolley. Check out the Commisioner's car (Gov't archive photo)

The Commissioner's Car

Fred must have been the luxury model as it had mudguards over the wheels. All had the cow (or kangaroo) catcher bars on the front, and mudguard mounts on the rear, which reduced twisting articulation to near zero.

Prototype Red Fred

Like the galloping goose, all of the "works" are visible, so it was a case of "how near the prototype can I make it look"?

The bodywork begins to take shape

I have very few photos of bogie manufacture, but an article in Australian Model Engineering about passenger cars, mentioned using box section to hold axles, so I found some bearings at 32mm outside, 17mm inside and 12mm wide. As a bonus they had an outside circlip on one end.

34mm i.d. square tube could be opened slightly with a crowbar to give 32 wide by 36 high, which would compensate for the twisting. The article also mentioned that uneven bearing wear didn't happen, even with heavy passengers, but to make sure I put two bearings back to back (I did say I could have made it simpler).

My welding experience at this time was still measured in days, so the 12 x 3 flat iron side frames suffered badly from heat stress and distortion (not to mention "bird's poop" welds). I got round this by making the axle tubes, and the larger (40mm) bolster tubes, continuous and this kept the shape better. The current bogie is No. 6, the other five went in the bin.

In the photo the bolster tube has been cut but the axle tubes are still full width. Notice that the bolster inner is also the same tube as the axles. No springs are yet fitted, but the pivot is. Brownie points if you recognise the Toyota Hilux engine mount as a pivot. Just enough movement, self centring, and a ride thats as smooth as . . . a Toyota engine.

The wheels were my very first mechanical object made in large scale. I tried to get some experienced model engineers to help but they all refused (I could find lots of helpers now, but then I was just considered a nuisance, it's a hard hobby to get into if you are not a kid). I then tried to get a local engineering works to make them, but they wanted $400 for materials and CAD program.

I came to the conclusion that it was do-it-yourself or give up. Ebay produced a Myford lathe for $1500, and a steel merchant found me some 100mm 4140 bar. I cut the first blank with a hacksaw, Then I bought a $300 bandsaw (worth every cent!).

The wheels, then slowly emerged, about one every two days, the first one had cost $2000, but next ones were free. They have a 17mm inner, the same as the bearing, and a hub nut and washer. My machining wasn't up to press-fit standard, I just wrenched them up tight and used 601 loctite.

The wheels with double bearings and inner circlip (and a very untidy bench!)

And here's the part finished truck.

Finished truck

All this beefed up suspension was because I, who scale at about 14tons, was going to sit on the roof. So in order to get springs strong enough, I had to first find out how much weight the front carried. After much head scatching I finally worked out that if I placed bathroom scales under the wheels, sat in the appropriate place and held a camera out, I could get an accurate answer.

Weighing the front end

You might also notice the axle washer. I forgot to allow for the radius in the bearing, and that was the quick fix. It's still there, of course.

As for mentoring, its sadly lacking possibly because the "strike" rate of keeping the interest, is low. I now have a mentor. Robert is a third of my age but has been a godsend with his knowledge. He has little money and no access to machines, so its worked well for both of us. I gave him a 7-1/4 Tich chassis that came with the lathe. He lent me movies and magazines and drawings, and printed some operating instructions for my steamer. Without his help I would still be floundering.

Rob putting the first fire in a restoration project

Back to the wheels. The trailer was noted as PL (passenger luggage) and also had archbars, but with leaf springs. It looked a bit spindly for a load that could be three adults, so a different approach was called for.

Archbar bogie on trailer car prototype

With the footboard frame on, there wasn't much turning space so an inside framed bogie seemed right. I liked the self aligning bearings so set them on the inside of the 60"x"6 stretchers. Now we were cooking. Self aligners lock up once fitted, so I made some 10"thou shim washers between the halves and that gave it a little give, enough for articulation. This is what I came up with.

I'd seen a design for 2-stage springs (didn't want derails when no load on) so made two towers from 25mm box, with strong short spring, inside which was a slightly longer weak spring. By chance one was left handed, the other right, so they don't bind on each other. A coach bolt was inserted from the top (dome end up) and with a dab of grease, makes a nicely progressive support. The centre pivot is a tee bar that engages in two tubes, one each side, which are welded to the stretcher. All held in by the bearings.

Trailing car bogies nearly finished

All that remains is to hang them in and make a thin arch frame for appearance only. The wheels, by the way, were machined from flame cut plate. I'd finally learned how to get the cheapest good result.

Here they are ready to install (minus the trim frame)

Bodywork.

The body well underway

As I mentioned earlier, the frame was 12mm square tube, and 12mm solid bar. Bar being easier to weld, tube works better for fixings. Its a bit hard to find a good photo of the sheeting, but basically it is 1mm aluminium (tough enough to resist the odd foot contact) sheet. I got the merchant to bend a 10mm edge on 4 sides, and when I made the frame I left it 5mm short, so that there was room for a lap with pop rivets, on each corner. The rivets were countersunk, but not installed until the construction adhesive (no nails) had set, to prevent "bagging" where the rivets pulled in. Car bog filler covered the divits.

This was much stronger than I expected, and would recommend it ahead of timber sides, specially where there is a "tumble home curve" (not sure what you folks call that it wasnt in the critter-speak spell check). The windows were marked out and the frame made 10mm larger, so that I could glue in U channel for the windows.The photo sort of shows the window tracks, and while were there, the painting method. The computer fan sits behind the battery and in front of the cylinder head and comes on automatically in neutral gear.

Outside trim included waist mould (10 x 3) gutter mould (10mm Dee), and window surrounds (8 x 3) all in aluminium. All glued with no-nails and rivetted at the ends. Big trick with aluminium is to use etch primer and DON'T rub it down before the colour coat.

More body details

The body a bit further avanced

The bonnet took a bit of work. Three rolled corners and a taper were more than I could draw, so I just winged it . . . several times but eventually it worked. A section was cut out and a small kitchen vent panel glued in, near perfect match! The grille surround came from some thin box section, cut lengthways to an L section, then snipped to go round the corners, and finally soldered to a frame of brass section. The grille bars came from irrigation pipe pegs (though fence wire could also work) and care was taken to leave out one bar, like the original. The radiator then sits on a piece of 25mm angle, which also holds the bull-bar, and sneakily hides the hinges. The whole bonnet assembly hinges forward to access the battery, and secures with the crank handle.

Roof is ply, up to 60mm thick, overlaid with automotive vinyl roof fabric. The seat was robbed from my ride-on mower, and is very comfortable. The roof is strong enough without the seat though. The trailer roof has 3mm foam padding under the vinyl. I've discovered that thick padding is a waste of time if you have decent suspension.

The windows are 3mm acrylic and are fixed open for maximum airflow, and while the trailer windows were made to operate, they are now screwed shut. They do have the "don't bang you head circles" stuck on the inside, like the real one, cut from vinyl sheet, along with the lettering, by a local signwriter.

Doors are marked by scored lines which have had a marker pen run over them, so far it hasn't worn off. Door handles are short lengths of welding rod soldered to a washer, then glued on (easy to replace if damaged) and the grab handles came from the U.S. Headlight is a headband reading light and the parklights are dash warning lights with the red lens taken out and substituted with a disc of tupperware (don't ask!)

A challenge from a "rivet counter" colleague meant some head scratching, but finally the front windows DO work, hinged at the sides, and louvred in the middle.

The final flurry.

Interior

Spurred on by making working windows, it just didn't seem right not to have passengers, so some seats and things appeared. Seats are pine skirting board with black vinyl cloth glued on. The rollover seats (strange for a vehicle that rarely went backwards) were jigsawed from MDF and dont swing. and the walls are more MDF. And the passengers? How about George Bush and Barbie , courtesy of my granddaughter. There's even doll's house ceiling lights (near perfect match) for those long, dark night runs.

Controls. Originally I was real smart and made a gear lever diguised as the top step. It looked great, but was impossible to find with clumsy feet, so the gear lever appeared about the same time as the fireside tools went missing. Dashboard has an ignition key switch for safety, a couple of switches for fan override and lights, warning lights for nuetral and reverse gears (strangely the gearbox has switches for all gears) and a button for the horn, which is an oogah type, just because . . .

While the building was happening, I used half the quad's handlebars as a temporary measure. It's still there because it works real well. One day I'll work out something that looks more appropriate.

There is a hole in the right side box that lines up with the oil level window, and the filler can be accessed through one of the windows. Gets some strange looks pointing an oilcan in the window. Lastly, the family station wagon died, so I made a trailer which goes behind the work car when the boss isn't looking. One day I'll make a cover for it.

Loaded, ready to go for a run at last!

I hope you found some useful ideas, its certainly been a learning curve for me!

 

 

 

This article is based on a series of Railfan.net forum postings during 2010 by the author plus additional material from him.
The content is used with permission.

Another article on Red Fred also appeared in Australian Model Engineering magazine, Nov-Dec 2010, Issue No. 153, pp 11-14.

Bearings supplied by Miniature Bearings Australia