82004

[JeffP]

Markits do some turned ones.

[doilum]

Thanks. I have tried making some, but my reject rate is 90 percent!

[doilum]

Birthday came and went, so I now have a set of wheels, pick ups and brake shoes. Time to start the frames. These are quite thin, probably scale thickness, and easily cut from the etch with an exacto#2 pressing into the grain of a softwood offcut. The axle holes required only a single wipe round with a file for a perfect bearing fit. Top marks so far.

Next step is to mark out the position of the plunger pickups. Getting these central onthe back of he rim is essential for good running. A simple matter of putting a wheel on a axle with bearing and pushing though the frame. A nogging of 3x2 with a hole drilled through makes a good support. I scribe round the outside of the wheel with the exacto and once done, pencil in the nner edge of the metal tyre. Having decided the best position, the spot is marked using a gravity rivet tool and then piloted with a 1mm drill. The resulting hole can be checked by gently scratching the back of the wheel with the drill. It must be a good day to model. Spot on first time.

Once all three are done, clamp the frames together and transfer the pilot holes through.

All that remains is to open out the pilots with a drill that leaves the final hole ever so slightly tight. This can be opened up one stroke at a time with a file for a perfect non interference fit. Essential for the Slaters unit to work.

[pwr]

Birthday came and went, so I now have a set of wheels, pick ups and brake shoes. Time to start the frames. These are quite thin, probably scale thickness, and easily cut from the etch with an exacto#2 pressing into the grain of a softwood offcut. The axle holes required only a single wipe round with a file for a perfect bearing fit. Top marks so far.

Next step is to mark out the position of the plunger pickups. Getting these central onthe back of he rim is essential for good running. A simple matter of putting a wheel on a axle with bearing and pushing though the frame. A nogging of 3x2 with a hole drilled through makes a good support. I scribe round the outside of the wheel with the exacto and once done, pencil in the nner edge of the metal tyre. Having decided the best position, the spot is marked using a gravity rivet tool and then piloted with a 1mm drill. The resulting hole can be checked by gently scratching the back of the wheel with the drill. It must be a good day to model. Spot on first time.

Once all three are done, clamp the frames together and transfer the pilot holes through.

All that remains is to open out the pilots with a drill that leaves the final hole ever so slightly tight. This can be opened up one stroke at a time with a file for a perfect non interference fit. Essential for the Slaters unit to work.

 

 

I always find I need to cut the springs in half or they make the chassis too stiff. How do you approach this?

 

Paul R

[doilum]

To be honest, I use them as supplied. The ten hunslets all run 40:1 gears and bar one, have decent motors. I also try to find the lightest multistrand wire and ensure the unit is freemoving before and after installation.

[doilum]

Having read Jims carefully engineered solution to the variable frame stretchers, I took another path. I started with the main cross your heart item and once folded up compared it to all my other locos. Then decided it was wider than all of them and opted to file it down to 25mm to match the Premier component spacers I had just bought. I also made up additional spacers to match.

The spacers were soldered to one side only and then assembled with the screw in spacers using the holes drilled for the plunger pickups. Front and rear wheels and axles were added and the whole assembly tested on pate glass and flat track. Perfect first time. Four wheels dead level and square. Now solder the other side, recheck, and remove the screw spacers. Still perfect. How long will my luck last?

[doilum]

The answer is not long. Time to try the frames into the superstructure. I seem to have found a new challenge, so I will share before resorting to a new disc in the dremel and some "slight adjustment" to the frames. The superstrucure is flat, straight and square. The frames are a less than perfect fit. At the front. At the rear. The rear wheels foul the cab floor and front. Ever so slightly.

Is this the result of frames designed to fit the 4mt tender loco?

It shouldn't take much to sort but opinions welcome before I commit butchery.

[doilum]

Another happy hour.

Before butchery, I decided to add the frame mounting points. I had already put a stretcher with a captive nut into the superstructure under the smoke box saddle. By pure serendipity it aligns with the solid screw in spacer that I had temporarily located twixt the holes between the cylinder mounting slots. A rear mounting point was added and when tightened up everything looks a lot straighter with frame and superstructure touching in most of the right places.

If I were to build another, I might follow the instruction sequence and build the frames first and fold the front footplate to fit.

The loco still sits dead level on four wheels. The rear wheels just scrape on the cab floor. Not sure if the frames are locating half a mm too far back or if a little surgery to the cab floor is needed.

My.new concern is that the whole loco appears to be sat a little high. It measures 25 mm from railtop to centre line of buffer.

The drawing in the RTCS book shows this as 3'5 and half''. This would scale at 24 mm. Not much.but looks wrong.any thoughts??

Another happy hour.

Before butchery, I decided to add the frame mounting points. I had already put a stretcher with a captive nut into the superstructure under the smoke box saddle. By pure serendipity it aligns with the solid screw in spacer that I had temporarily located twixt the holes between the cylinder mounting slots. A rear mounting point was added and when tightened up everything looks a lot straighter with frame and superstructure touching in most of the right places.

If I were to build another, I might follow the instruction sequence and build the frames first and fold the front footplate to fit.

The loco still sits dead level on four wheels. The rear wheels just scrape on the cab floor. Not sure if the frames are locating half a mm too far back or if a little surgery to the cab floor is needed.

My.new concern is that the whole loco appears to be sat a little high. It measures 25 mm from railtop to centre line of buffer.

The drawing in the RTCS book shows this as 3'5 and half''. This would scale at 24 mm. Not much.but looks wrong.any thoughts??

[doilum]

Back to the chassis. Today had a trial fit of coupling rods using the Slater 12ba crank pins. I will swap these later for 10ba once I get round to tapping the bushes. For those new to this, the received wisdom is to treat the chassis as a pair of four coupled locos and ensure that the front and rear sets work perfectly before trying them together.

Only a small amount of fettling needed to get them rotating sweetly and the full 6 coupled chassis gliding down the test track.

Dont forget to keep checking the crankpin nuts before they try to escape. I did have one minor disaster when the end of one coupling rod broke off whilst opening up the hole anda repair effected from nickel silver scrap.

[doilum]

Now back to the cylinders. I had prefabricated these off the job and with a bit of slot widening they will sit at a correct height and angle.

I tacked a set of pre fettled slidebars to the hanger casting. This seems too wide. Before rushing into more butchery, I had a good look at my inspirational picture of 82047. The hangers are curved at the top and sit everso slightly outside the line of the tank valance. On close inspection, so do the cylinders. The superstructure is 60mm wide, so to stay proportional, the cylinders need to have an outside width of 62mm or about 8'10''.

As previously mentioned, the Scorpio kit includes the narrow cylinder profiles from the kits earlier incarnation. This has allowed me to cut and widen the part to 62mm o/d.

Suddenly the casting provided lines up. I am now temted to scratch build a pair of alternative cylinders and see where we go from there.

[doilum]

Sometimes you must follow the wrong road to the end to discover where you made a wrong turn. Once my alternative cylinders were added together with the slidebars,it was obviously far too wide. Taking the original Scorpio cylinders and trying them under the superstructure I found them perfect.THE SCORPIO CYLINDERS ARE CORRECT.

Lightbulb moment! It must be the hangers. I went back to Jim's Acorn build and read it carefully. We are not using the same hanger casting. Mine were either intended for a crab or frames with 22mm spacers.

Time to start again.

[doilum]

Start again.

Write down on paper all of the critical design criteria.

* Cylinder block must be square in every plane.

* Cylinder block must be inclined so that the piston rods are in line with the center  of the middle axle.

* Slide bars must be square and at 90 degrees to the cylinder end castings.

* Hanger brackets should be at 90 degrees to the slidebars.

* Slidebars must remain parallel to the frames at all  points.

 

It is now time for all serious model engineers to look away as I execute the "Margate solution". 

Having disassembled the slide bars and hangers, I cut a length of 3mm square tube to solder between the hanger castings. This ensures they will have exactly the same spacing as the correct Scorpio cylinders and will remain perfectly in line with each other. This will also allow me to lift a completed set of motion in and out of the frames. On this prototype the bodge is invisible once the loco is on the track. 

Attention now returned to the cylinders. Lacking Jim's engineering skill, I settled for a couple of pencils to find the correct inclination. A new spacer plate was cut and soldered between the frames so that the cylinders would always return to the correct location. Likewise another spacer was cut and soldered between the cylinders to ensure that they always remain square and locate perfectly equidistant in the frames.

I had got the slidebar/ cylinder end casting just about right first time so these were retained and added to the new hanger assembly. This took a full 3 hour session as each step was double checked with set squares and calipers. It is of course critical that the length of the slidebars from casting to hanger is identical on both sides.

The completed slidebar assembly could now be tack soldered to the cylinder block and trial fitted in the frames. Happy with the result take some photos and quit.

Pictures to follow from the tablet.

[doilum]

As promised, the pictures

[JeffP]

Loving the Margate solution to engineering.

[doilum]

Not sure why these didnt load

[doilum]

All the 3MT builds seem to have gone quiet. I am awaiting parts to convert crank pins to 10ba, so have spent an hour or so each day addressing the issue of brake shoes. The ones provided are white metal with little clearance to the rims. I have never been happy with metal brake shoes and had already stocked up on Slaters plastic shoes. The metal hangers were Monday's work, yesterday I fitted shoes to the hangers and today soldered in the support wires. These went as far back in the oversized holes as possible in order to clear the rims.

The wheels are the ones specified in the instructions, and came from Slaters with a 3MT label, but look ever so slightly large especially when compared to photos. I hope it is an optical illusion, but as shown earlier, the loco seems to ride about a millimetre high. We shall see.

[doilum]

Next installment from the tablet of trouble.

Whilst I await a 1.2mm drill to tap the crankpin bushes 10ba,I returned to the valve gear itself. Being currently without an RSU, I have been rediscovering that of laminating using a small 60W iron. Various linkages went together well, the problems started when I tried to assemble the pre assembled valve stem, combination lever and radius bar into the casting that tries to pass for the valve stem guide. This nasty little lump has already claimed two drills, blood and has been repositioned three times.

Time for some tips.

Previously soldered castings can be removed with a piercing saw, carefully cutting through the soldered joint and snapping off cold. This minimizes collateral damage. Old solder can be removed with the dremel.

The valve guide should not be attached to the cylinders until all its associated parts are ready and working.

Google walschearts valve gear and draw your own fully labelled diagram. Very few kits even refer to the components by their correct name.

[84B Oxley]

If you are using Slater's bushes then they should tap 10 BA without any opening out.

Jeff

[doilum]

The photos show the lack of alignment. This only became apparent when trying to introduce the valve stem and radius bar.

The valve stem was far too tight in its guide. Careful use of the dremel opened the guide until it was "waffer" thin. More careful filing almost removed the rivet head on the joint with the combination lever. This did not solve the hole in the casting. Tight and off centre, the thought of redrilling it triggered all my alarm bells. At best it would destroy another drill, or explode and scatter itself around the room. At worst, I could spend the rest of the day in A&E having it extracted from my face.

Drastic action needed. First, find a way of securing the patient to the bench. A short length of scrap rail and a pair of crocodile clips did the job. Now for some open heart surgery. I had found some brass tube that was an easy fit on the valve guide and cut a deep channel in the top of the casting to put the tube into the correct place.

The tube was soldered with normal high melt solder so that it wouldn't move when I close up the wound with low melt solder. The tube was left long to help with alignment and secure the work in the vice.

Now, with all the linkages in place, the valve guide casting could be replaced correctly.

Tomorrow I will tackle the other side.

[JeffP]

Not being funny, but I wish you had a better camera. I find this thread very interesting, but the photos are often impossible to understand.

 

Are you taking them with a tablet? Phone?

 

Might be better to be further out and crop them?

[doilum]

This tablet is particularly poor. Previous one was quite good. Need to sort out which daughter last had the good camera last. Sadly, I lost interest in photography when it went digital. Need to learn some new skills.

[doilum]

If you are using Slater's bushes then they should tap 10 BA without any opening out.

Jeff

thanks for that tip. Will give it a try.

[doilum]

Can confirm the tapping of slaters crankpins. For those new to this, I chose to mount the tap in the vice and grip the bush in a pinvice. The trick is to gently rotate clockwise until you feel it biting and then back off. This 2 twist forward and one twist back is repeated a couple of times. Then unwind completely and clean the swarf from the tap. Now replace the bush and repeat until you break through. A drop of light oil or washing up liquid helps. Once done check your work by carefully threading onto a 10ba bolt, or to be engineering pedantic, screw.

[JeffP]

This tablet is particularly poor. Previous one was quite good. Need to sort out which daughter last had the good camera last. Sadly, I lost interest in photography when it went digital. Need to learn some new skills.

Sent you a PM.

[doilum]

Sent you a PM.

PM? Personal Message?

Pardon my technical ignorance, but how do I access?