[Richard Johnson]

QUOTE (pedromorgan @ 15 Jun 2008, 15:36) <{POST_SNAPBACK}>I ordered a GT3 at ailsbury and it arrived a couple of days ago. experience has told mee that you really need to grab curiosities like this when they come around or you may never see them again. i love the unusual prototypes.

The castings are generally pretty good. there are a few bubbles along the bottom of the chassis valance. the cab and tender are both very nice. the only real weak spot is the intake grill. i dont think i can live with the supplied one and i'm going to have to etch a replacement.

It needs a hornby class 5 chassis but i may go for a comet instead.

I'm really not very good at getting loco chassis to work smoothly but i have been looking at the jig from hobby hollidays. it looks like a really nice piece of kit and would certainatly help me to get evrything square.
http://www.hobbyholidays.co.uk/masterchassis.htm

Peter

***Peter, I think you undersell yourself - you are excellent with an Iron and have all the other tools you need to make a square chassis - its just technique you need to add.

* Read Iain Rices book on loco construction for "can do" inspiration.
* Get a square of clear glass to build the chassis on.
* get a couple of say 200~250mm lengths of 1/8" silver steel rod (the same stuff loco axles are made from)
* place the glass on one of those gridded green hobby mats.

* Carefully ream axle bearing holes only enough for a smooth sliding fit of the bearings.
* Mount the bearings in the chassis sides before you assemble the chassis.
* Use the silver steel rods through the bearing holes and make sure that when the chassis sides are parallel with one axis of the grid, the silver steel rods are parallel with the other grid axis.

Thats really all U need to keep it square - the glass for vertical squareness and relativity of the two sides and the frames and silver steel rods vs the grid of the modelling mat for geometrical alignment.

The jig you are looking at is certainly an impressive bit of kit but its my experience that such things are "crutches for the skill challenged" and not the answer to "walking properly".

I've seen more than enough of your work to know you could do it well without the prosthetic help!

As the Nike adverts said "Just do it"

Richard

 

[Richard Johnson]

QUOTE (pedromorgan @ 16 Jun 2008, 13:46) <{POST_SNAPBACK}>I know what you mean richard. but how come i always make such a complete pigs ear of it??!!

i have 2 loco's that i am very proud of that are basicaly finished except that one wobbles like its doing the time warp after 6 pints and the other where no matter how hard i try i just cant get the 6 wheels running freely with the con rods on.

My first steam loco kit was a garrett (stupid i know!!) which actually runs ok. except that it grinds to a halt with more than about 4 wagons on the back!!

Next came lion.
I thought i had improved and i wanted to have a go at outside frames! (big mistake!) the trouble was that with outside frames you looke the inbuilt quatering that you get with romford wheels. maybe a quatering jig would sort it out. but having come down from a garrett, failure to get 4 wheels turing freely was a real downer!

And finally came the W1. i was thrilled with the way the body went together. i realise its not quite square but neither are the castings. and its good enough for mee. but the chassis was a complete nightmare. i tried about 20 times to get the 6 wheels running freely. my motor and gearbox runs nicely but as soon as i put the conrods on the whole thing suddenly aquires 20 units of alcohol!

I have a turbomotive chassis waiting for me. but i dont really want to touch it untill i can get the W1 working properly.
Peter

***

I think I know you well enough to say with the best of intent "because you gave up on them", not because they couldn't be tweaked into life

However its not easy to fix many issues without a bit of awareness about what is causing them and I suspect that most of the problems are due to kit part error and not in any way "peter" created - so be confident!!! I've built two of the locos in your pictures + the turbomotive and in all cases, I threw away much of the chassis and associated parts as they were manifestly rubbish!

The thing that ALL of your problem loco's have in common is that

(1) the chassis were machined or cast not etched

Or

If etched, they were created when artwork for etching was all hand drawn and then scaled with a camera - and when thats done only a master of art/photography & etching ever gets the mfg process perfect.

The common problem was that not only did the art contain lots of slight errors, sometimes the bearing spacing for the left chassis half was slightly less accurately positioned than the right chassis... and to compound this, the connecting rods also often had slight errors for their relative hole positions... so without very careful tweaking to to get these critical things right they never run well.

The way to check this and get it right is to first check that things are reasonably OK with a good quality micrometer etc then build the chassis using the method I described.

Then.

Have a set of jigs for the connecting rods. these can be sliver steel axles turned down to a long slightly tapered pin at each end (which matches say a romford/Markits crank pin in diameter at the halfway point).

Put these through the axle bearings. Both sides connecting rods should slip on nice and smoothly if the axle holes and the connecting rod holes are actually in the right position. recheck by then placing left rod on right side to make sure both sides are the same.

If not you will see the errors.

Make sure all 6 wheels sit properly on the glass sheet.

Once wheels can all turn freely and the connecting rods all fit smoothly, if you've used Markits wheels then the square ended axles will guarantee perfect quartering and the chassis will run smoothly.

to test this now put the crankpins in the wheels and put the wheels and axles onto the chassis. Slip the connecting rods on the crankpins and hold them there temporarily with a wee bit of insulation tube stripped from some wire.

If there are any tight points then enlarge the offending hole left & right a wee bit but NOT up and down (make it a flat oval not a larger hole)

To fix your current loco's. Most of your current prroblems aren't you - they are the crappy chassis, parts, wheels and motors supplied with those ancient kits.

For bad wheels (old K's kits in particular). Chuck the driving wheels out and use Markits wheels and axles.
For all old kits - chuck the gearboxes and get some new ones from Hi-Level Kits - they are sublimely smooth.
For the Garratt and anything with an old motor - the K's motors are especially rubbish - replace with Mashima - preferably one each end on the Garratt.
For possibly wonky connecting rods. Get a couple of sets of Gibson "universal connecting rods" - these are in several parts and can be made up in different lengths. build them up with precise spacing on a jig made from crankpins set into an alloy or wood block.

For the turbomotive - Just dump the K's chassis and get a princess chassis kit from Comet. Turbomotive = Princess to all intents and purposes.

Richard

PS: Re the LNER Hush Hush... If you don't mind the positive suggestion.... get rid of all the whitemetal boiler bands totally and replace with scotch tape bands (the cloudy looking sellotape stuff - put a strip on glass and cut the bands with a new scalpel blade). They really do stick fine and definately won't lift after painting is done.

Those ugly whitemetal bands are twenty times overscale....same applies to much cast on whitemetal detail and definately all whitemetal boiler bands really - garratt included.

Also... If the kit "as bought" wants you to use a screw each end to fix it modify it so that the chassis is captive under a lip or similar one end with only one screw the other - If you do as they say & use a screw each end, its very easy to slightly twist the chassis and running always goes wonky when that happens