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6" Mc Laren road Loco build by Andy Smith

Mclaren Build Diary Part 2

Mr Smithy has been a busy chap!

 

 

 

 

 

 

 

 

 

 

 

Progress or what!


- Progress Update 25/08/2008 -

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 front irons with stays on the engine

You will have already seen the pictures of the assembled engine that Colin has posted in part 2 and my son and I had a busy day doing the assembly and fitting everything together. All my pre-work / checking made the process go fairly seamlessly. It was a great feeling to see her all in one lump and it is certainly a squeeze to fit in the garage now!

Picture of board fitting

The infamous connecting rods were next on the list and I just have the little end bearings and adjusters to go and they are done! The straps were flame cuts and after a lot of machining they have come out really well but I did ignore the drawings and followed information once again very kindly supplied by Richard Morris. The straps have the correct profile and slotted sections as well as a straight backed bearing pocket which was actually much easier to machine than the curved one shown on the drawings. The oilers were lost wax castings supplied by Double B and just required some careful machining and polishing all over.

Picture of assembled big end

The main rods were CNC machined and have come out really well and I have decided to fit correct pattern adjustable little end bushes as the engine is big enough to warrant this. The drawing shows just plain non adjustable bushes but this is not correct so armed with Colin’s adjustable bearing drawing and some photos from Richard these will be underway in the workshop tonight!

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!

 

 


- Progress Update 02/07/2009 -

Apologies for the lack of updates recently, the time just seems to slip away. Colin and I visited the MRSVS rally at Tewksbury at the weekend and were asked by numerous people ”What has happened to the updates?” So ROBERT this update is just for you!

Colin and I have both been busy working on our houses fitting new kitchens, bathrooms and numerous other stuff so have been somewhat distracted from the workshop and we are both struggling to pick up the pace again with the projects but I am slowly getting back into gear and trying to get all those little jobs finished off before stripping for painting.

As stated in previous updates we now have the paint and I decided that sign writing the canopy side boards was beyond me but I wanted to do all the prep and top coats so that Adam Meredith could work his magic on the boards. I gave the wording a lot of thought and finally decided to copy “Boadicea” but with a bit of a twist. After discussing with Adam we went for gold leaf and to say I am pleased with the finished result is an understatement as Adam has done a superb job.

Picture collecting the side boards.

I debated whether to fit the boards on for a look but eventually my enthusiasm overcame me and we fitted them to see what she looked like, it is amazing just how much the look changed with a little bit of paint!

Picture with side boards on

Close up of the sign writing

I am now working on a 40 odd item to do list and working from the front back but have in the meantime have finished the ashpan. This required a bit of research to get right as the drawings don’t reflect the prototype in this area but I am very pleased with the finished result. I have also cut in the “keyhole” slots for the drain cock operating rods and made the operating rods as well.

Picture of the finished ashpan

Back to front end again and I have been working on the front springing making the knuckle that the spring leafs are located in as well as the mounting brackets and links etc. - Note: GM cylinder under B&D, Colin!

More to come!

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Call back later to see how Andy's Mac is progressing!

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