I don’t know where the time
has gone over the last couple of months and summer (if you can call
it that) is nearly over. We have only managed to take the Wallis
out once to Woodcote so far this year but that was a conscious decision
on my part as I wanted to spend more time on the engine build. A
chance meeting at Woodcote was to lead to a small diversion from
the plan although the 48 job to do list is now down to under 20.
I met Richard Poole who owns a very nice Allchin at Woodcote and
he runs Goodman’s Steel Services in Reading and was able to
provide the ¾ X ¾ square section needed for the canopy
irons. When Colin built his canopy for “Hogwart” we
had two sets of angle rollings done so the temptation to build the
canopy was too great to resist!
A canopy will make or break the looks
of any engine if you get it wrong so after much discussion with
fellow 6” Mac builder Bill Kiddell who was next to us at
Woodcote we came up with a plan. With any model there are some
compromises to make in terms of how practical it will be to drive
with a canopy on versus the look and I decided I was prepared
to sacrifice a little practicality to get the look right. From
my own research the bottom edge of the canopy side boards just
kisses the top edge of the flywheel on “Boadicea”
and Gigantic” and it needs to accommodate a scale 6 foot
driver with Bill being a tall chap (6’6”) he reported
that he only has a couple of inches headroom when standing on
“Boadicea’s” footplate so a temporary rig was
set up and it worked out perfectly that when the bottom edge kissed
the top of the flywheel we had 3’6” to the centre
on the canopy giving a scale 7 foot. Armed with this and some
sketches of an original set of canopy irons from my friend Mark
Money in Tasmania we were able to work out a set of drawings to
work from. The main section is turned to round leaving square
section just at the top and on the section that bolts to the horn
plates so it was quite exciting trying to turn this down over
a long length but we got there and the results are pleasing along
with all the stays and cross members.
Picture of canopy irons
I decided I wanted to follow full
size practice and build all the timber section of the canopy from
Ash, no problem with the local timber merchants able to plane up
the relevant section for side rails but where to get scale T&G
in ash? I checked around and whilst small boards are available they
are not in ash and have no tongue & groove and I don’t
want a “saggy” canopy. A little digging around on the
net found a company down in Somerset who would make up cutters and
produce miniature T&G in ash at a very reasonable cost. I collected
this last week and am now in the process of fitting the boards but
more to come on that for the next update.
Picture of pair of finished rods
- Progress Update 12/11/2008 -
Apologies for the lack of updates
recently, the time just seems to slip away. The little ends are
now finished and fully adjustable so before they could be fitted
I needed to make the pistons. The pistons are made from large aluminium
billets and a simple turning job but careful consideration needs
to be given to differential expansion as the engine would run on
air but seize solid under steam. After consultation with the “Machinery
Handbook” I calculated 0.020” and 0.012” clearance
on LP and HP bores respectively and this checked out with Colin’s
experience on his engine, I guess we will find out if that was correct
on the first steaming! I am fitting “Clupet” piston
rings so all the grooves are in ready with the recommended clearances
and these will be fitted once the cylinder goes back on permanently.
Picture of finished little ends
I have been putting off fixing the
cylinder in position but was running out of excuses so decided to
bite the bullet! With the pistons and connecting rods fitted everything
turned over sweetly but the cylinder needed to be slid down the
barrel to get the correct clearances (allowing for boiler expansion)
at either end of the stroke and also to ensure its sits squarely
on the boiler. I spent several hours checking and double checking
before taking the plunge and drilling the first mounting hole into
the boiler. It is only possible to drill the four corner holes with
the cylinder block on so after the first one was in and a stud fitted
it was time to check everything was still in position and that nothing
had moved. All was well so the remaining three studs were drilled
and fitted so the cylinder is now fixed.
Picture of assembled motion
With the cylinder block
now positioned it allowed many other jobs to be completed such as
motion covers, exhaust pipe, blower, regulator rod etc but the biggest
challenge still lay ahead (although I did not know it at the time).
The next job was to fit the motion bracket and valve gear, not a
big deal as everything was made and just required fitting! One of
the eccentric rods requires a set in it as per full size so this
was checked and the ends heated and bent and everything lined up
beautifully until I positioned the motion bracket when I suddenly
became very evident that something was very wrong! It was not a
complete surprise to find the valve gear would not fit as Colin
ran into the same issue but I still had a couple of sleepless nights
figuring out how to resolve it and in the end took a day off work
and dealt with it!
I wanted to avoid the obvious choices or removing
some material from the front of the eccentric straps or shortening
the rods as that would impact the valve gear geometry so after double
checking all the dimensions and a chat with Colin we concluded that
the valve timing not being set was a key factor. I decided the only
option was to push the motion bracket a little further forward and
increase the clearance by machining a small amount from the valve
spindle guides. This is less than ideal but a workable solution
and I now have full rotation without anything colliding, I only
wish I had followed Colin’s original advice of making the
connecting rods ½” longer…………..!
Picture of engine outside with cylinder bolted on
There are numerous small jobs to do
but the largest remaining are the two gear cases. These were drawn
up and modified using Colin’s ACAD files and I have had them
laser cut / bent so I will be getting these done over the next couple
of months as my real focus is now to get her running on air. My
original to do list is now down to six or seven items so my year
end target of running on air is really in sight. I have even ordered
the paint as well now……………………..
Picture of gear case laser cuts
The last few weeks have seen visits
of fellow Mclaren builders both past and present who all gleefully
sat on the engine and seemed to enjoy the experience based on the
“big grins” Bill Kiddell who is building two and who
was responsible for the patterns is pictured first and my “Mentor
Mr Dix” is seen carrying out a quality inspection!
Picture of Bill Kiddell
Mr Dix carrying out quality inspection!
Next update should see the rods turning!
- Progress Update 18/01/2009 -
Andy has run the Mc Laren on Compressed
air, I will leave the details for Andy to describe in his next update.
Here is a link to the Video that David from Scene Scenes and Traction
Talk. Take a look. A big thank you for helping me to load the images
with the U-Tube frame. Thanks!
