Ullypug's tales from the tinking table

Having done the conversion to Create Coombe Martin from a Wilton (from the original notes by JDS) I have some further notes to add. This is because CM failed with a worn out chassis very quickly and another conversion "Ottery St Mary" by JDS also started to have some problems.

These notes apart from the first should help overcome these problems.

 

When glueing the front bogie try and add some liquid lead into the void. It really helps with the trackholding.

Right now the problems we found.

Look out for those Gibson Wheels!!! They have been in production for many years but no one has noticed that the crankpin throw is 4,5mm instead of 4,00mm! This wasn't identified when the manual sheet was created. The slidebars are just long enough to cope with the extra travel but piston rod barely enters the cylinder. We have added some additional glands of brass tube to ensure reliable movement.

We have also found that my conversion (Combe Martin) suffered exceptional wear on the driving wheel bearings. We have not looked at the original coversion (Wilton) yet to see if the same has happened there. It sounds happy (no knocking sound). We also found that wear had occured on the bearings of another similar Hornby Conversion "Ottery St Mary".

Out thoughts are that this wear could have one or more contributing factors.

These may be;

1. The bearings are quite a way inboard, even for OO. (I have lost the note I had as to what was measured 12mm is in my head but could you measure and confirm?) But the widening of the wheel base may have just pushed the axial loading of the bearing too much especially if the coupling rods are tight or not quartered correctly. (It was an early build for me and I think that I might have done one or both of these errors.)

2. The bearings (when the models were stripped for investigation) were found to be able to rotate in their bearing holders. A simple fix is to glue them into position. This worked on "Ottery St Mary" but "Coombe Martin" was too far gone and required major surgery.

3. Lubrication. Make sure the bearings are lubricated with a light oil. I definetly didn't use a light enough lubricant. I now use Singer oil. Tip, if you can't get through a hyperdermic needle then it is too thick.

 

The front end improves greatly with the addition of drain cock pipes and filling in the space behind the bogie wheels.

Further fixes on Coombe Martin that I must do are.

Add proper coal to the tender

Add a canvas sheet between the cab and tender.

Add crew.

Hi Andrew,

 

Have you seen this ? http://www.clag.org.uk/Hornby-wc-conversion1.html

 

Good luck with the project,

 

Geoff

Thanks for the comments folks.

Brightspark - I've got a selection of Albert Goodall parts, hopefully there are some drain cocks in there. If not, I'll have to make some.

Geoff - I'd forgotten about the CLAG site. Very useful thanks.

Looking good Andrew. You might possibly want to try using plastic spacers for the loco rather than brass as they don't conduct electricity quite so readily as the former does! It's purely from the pickup interface side of things of course....

 

They happen to be cheaper and a lot easier to modify if you make them that little bit too long once everything has been nipped up together.

 

Good luck!

Tim

How will you do the brake gear on this?

 

if you do need and are able to wait a month or so i should have a etch done for the brake gear and pull rods, part of the improvements and additions to the Albert Goodall range.

Drain cocks by RT look good. I did mine with Copper wire.

The one thing that I picked up from the Clag site was that it stated that the piston rods were almost fouling with the front of the piston block. We found that the piston was more likely to fall out the back! I wonder if there differences between batches of chassis. I think when Doug (JDS) did Ottery St Mary he had to cut away the rear pony truck as the whole thing was solid.

 

RT, The EM sheet suggests cutting the Hornby brake gear in half down the center line and fixing it with a screw and washer was our solution. An etch would be more elegant.

 

Andrew, are you going to shorten the drawbar as well? It is worth it.

 

Andy

How will you do the brake gear on this? if you do need and are able to wait a month or so i should have a etch done for the brake gear and pull rods, part of the improvements and additions to the Albert Goodall range.

Sounds good to me!

Andrew, are you going to shorten the drawbar as well? It is worth it. Andy

I'm planning to. Did you make a new one or move the tender pin back? Both look 'doable'

to add to this, with all mine, i never reused the original drawbars but made my own using a split pin with a cut down smiths spring behind it on the loco and a pivoted hook on the tender which means these are at the correct height plus your not straining the pony truck with the locos load.

 

By doing this it means you lose the tender pick us but ive never had a problem personally.

I followed the EMGS sheet exactly as is. So the replacement drawbar was made as in Para 4.1 and Fig 4.1. For those that do not have access to the EMGS manual (it is worth joing the EMGS for this alone even if you model in P4 or OO) the drawbar is made from 0.020" brass* with centres at 15.5mm. Then used the original Hornby wipers, fixed with araldite to maintain the tender pick up.

It has been suggested that the pin could be moved but this may compromise stength and reliability.

 

 

*With hindsight we would now specify HH Brass.