ModelWorks Pride of Penrhyn Overtype Steam Lorry

Steering Upgrade

Selfmade parts used to upgrade POP Steering (not a Modelworks Kit!)
 

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9 January 2006: Over a period I time I have ruggedised  my  POP and addressed most of the design's week points.   However on the last two outings the steering rack has come lose from the chassis.

The chassis rail is made from rectangular section tube and the steering rack secured by two M5 bolt tapped into the outer section.  As this is relatively thin there is a limit to how much torque can be applied to the bolts without stripping the threads.  The simplest solution would probably be to drill right through the chassis add use longer bolts.

I have reservations with this approach, have had previous trouble and a dislike of the non prototypical appearance of a worm acting on a gear.  The original had no chance and a drastic solution followed.

Inspired by what I had seen researching the Foden I set about producing a design for the POP.  The basic idea was the actuate the steering by means of a block that is moved up and down by means of a lead screw.  The block runs in a covered channel which takes the side loads and stops it turning.  Motion is transmitted  by means of a link and crank.  One of the challenges was to get high enough gearing so that lock to lock was not an excessive number of turns.  This I achieved by using the coarsest screw thread available to me and selection of the crank geometry.  

Most of the parts were made on my milling machine, in particular the main casing which was hewn from 1" square bar.  I adopted a stout fixing arrangement to the chassis rail as can be seen in the photo right. 

This picture shows the operation of the replacement steering mechanism

The new steering fitted to the POP prior to painting

When I receive Foden Kit 8 it will be interesting to compare the two versions.
 

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