Maudslay 1807

This page describes a project I did a few years ago. Once again it's one of Willy Schneeberger's designs. Willy calls this one Maudslay 1807, but having done some looking around on the web, I think it would be more accurate to call it a Table Engine roughly based on Maudslay. This one was written up for "Model Engineer".

The castings were supplied by Willy - don't know where he gets them made, but they certainly know how to make 'em!

I think Willy must have had some spare time because he's already done a lot of the work for me, centring up the flywheel, cleaning up the side frames and generally machining faces flat.

The castings as supplied

What we hope to end up with.

So, lets get started. First of all take some time to study the drawings so we know where we're going and how to get there.

Machining the Base

The edges of the base casting are filleted but, as you might expect, they're pretty rough, so the first job is to run around the edges with a ball nose endmill. Having measured the fillet it seems we need a 15mm tool and again as you might expect I haven't got one. Luckily my friend Noel had a 5/8" one (15.9mm), well within tolerance! (well it's not critical - just has to look right).

Milling the filleted edges

Next we need to drill and tap the M3 mounting holes

Tapping the mounting holes

This is a simple job so long as you take care to get the holes in the right places. The observant might notice that the casting is a bit shinier than in the previous photo. This is because I have already started polishing it. I'm a great believer in doing things a bit at a time: the more effort I put in now, the less I have to do when all the parts are complete and I'm dying to get the engine built up.

The Side Frames

Do you ever get days that just don't go right? Well today was one of them. I started by joining the two side frames together by turning up a bit of mild steel rod so it was a tight fit in the circular hole in the castings and squeezing them together in the vice. I had put a centre mark on the rod so I knew where the hole centre would be and I could use it as reference for both the main shaft hole and the frame lengths. So far, so good. I then held the frames in the mill vice, the outer end supported by a piece of wood. The intention was to find and drill the hole for the main shaft. It was an easy task to find the reference mark and move the table the appropriate amount for the hole to be drilled. As I came down with ( luckily a small ) centre drill, I saw it wander slightly and with a probably rude word, I pretty quickly raised the drill.

The side frames mounted in the mill vice

Why had it wandered? I soon realised that having removed the collet holder and replaced it with the jacobs chuck, I had forgotten to lock the head of the machine. As it is a round column design it was free to move. I should have known better!

After locking the head and finding the reference again, I successfully drilled the hole deliberately a little under size as the next operation would be without the vice to hold the parts in registration and with a bit of scrap round bar jammed in the newly drilled hole.

The next operation would be milling the ends to length, so the frames were clamped to the table on another piece of wood.

Milling the side frame feet

The milling operation went well, bringing first one end to size then turning the parts round and trimming the other. Then disaster struck again!

Changing over from the milling cutter to the drill chuck, then finding the position of the first hole to be drilled and all seemed well with the world. Start the drill and the chuck drops out onto the workpiece. I didn't know how fast to hit the stop button! A few more words that I can't print, then the realisation that the clout I gave the chuck wasn't clout enough! Luckily the workpiece wasn't too badly damaged - just a 'ding' on the top edge which with any luck I can hide on the inside of the job - but my pride was. I did manage to finish the drilling without any further problems so I suppose that was a positive. Some days are just bad days!

The almost finished side frames.

You can see the damage on the end of the left-hand frame. Not quite finished, still need a lot of polishing, although I have made a start.

The Table Top

The table top is a stepped rectangular casting with a hole cast through the middle. This hole has to be bored out to 28mm and its centre becomes the reference for all the other holes and the sides.

The table top mounted in the 4 jaw, ready for facing off and boring.

I had noticed that the cast hole was nearly perfectly circular, so I thought I might try centring it using my rotating centre. As the hole becomes the reference and there is plenty of metal waiting to be removed from all sides, it doesn't have to be perfectly centred. With the centre in the hole and just backed off from contact, it was easy to see which jaw needed adjustment. A couple of minutes and it seemed satisfactory, but just out of curiosity I checked it with a DTI. I was pleased to see that it was within a few hundredths of a millimetre.

I started boring and the thought occurred to me that the hole is going to be a good bit bigger than the hole in my 4 jaw chuck! I needed space behind the workpiece so I reversed all the jaws and re-mounted and re-centred. This gave me a couple of mm clearance, but I didn't think this was enough. I ended up with a bit of wood behind the workpiece. I should have thought this one out earlier!

The workpiece remounted and being bored

I completed the boring and faced off the workpiece. Then I changed to the 3 jaw and made a plug for the bored hole with a centre mark to use as a reference for drilling and sizing.

The table top with its plug, ready for milling and drilling

There was still a lot of work to be done, milling the sides and the other face and then the steps had to be cleaned up and sized.

The table top being side milled

All this took a lot longer than I had expected, but eventually I was ready to drill and tap the side frame fixing holes,the cylinder mounting holes and form a slot for the valve connecting rod. All in all, this piece has taken some 9 hours to machine.

The Cylinder

The first job is to find the centre so that the cylinder can be bored. Measuring the outer diameter I found that the casting was fairly regular, so I found the centre using dividers and pop marked it. I then mounted it in the 4 jaw and set about centring it in the lathe.

Centring the cylinder in the lathe

I used my home made wobbler to centre the cylinder and then proceeded to drill the bore progressively larger, until I could fit my boring tool into the hole. I used the boring head to finish off the bore and I was very pleased to find that the bore was very smooth.

Boring the cylinder

Milling the port face

I made a mandrel to fit the cylinder bore so that I had a reference to set it up level in the machine vice. It might also come in handy later when it comes to drilling the flange holes. Milling the port face was pretty straightforward, just get it flat and take it down to the right level.

Disaster!

I'd been having trouble with my home made DRO ( made from a kit ) for quite a while. Every now and then it would fail to display one or more axes, usually when I was in the middle of a cut! Well, the fault has got worse and it has become totally unreliable. As the milling machine dials are hopelessly inaccurate ( about 10% out ), I am temporarily without a milling machine, so no progress on the engine.

I've had a look around at DRO's and found a Chinese one which comes with 3 glass scales for a reasonable price, so I've ordered one. Watch this space!

Well the new DRO has arrived. I've checked it out and all seems to work ok. All I need to do is install it. I'll do that tomorrow, this evening I'll read the instruction book

Help! I've read the instruction book and I really am no wiser. We've all heard of Chinglish but this takes the biscuit! How about this.....

"Process the queen on entrance. Handle person press (down arrow) which number holes queen to choosing...."

"Function: The god of the earth who points out that the obvious form of number....."

AAARGH!

The new DRO installed on the mill / drill.

OK, so now the new DRO has been installed and I'm beginning to understand it ( trial and error seems to work better than the instruction book ). I can even drill holes in circles, so I set about drilling the cylinder flanges. Success! Now,back down to earth. My earlier problems of forgetting to lock the milling machine head have reminded me that I need to do something about the raising and lowering of the head. With having a round column, there is no way of maintaining registration once the head lock has been loosened. The head is free to rotate until it is locked again. Now, when you've just centre drilled your hole and want to change to a bigger drill, you need to ensure that the drill is pointing to the right place. So, let's do something about it.

Modifying the round column mill / drill

After discussing this problem with other club members, we came to the conclusion that if a round steel bar is mounted parallel to the column and fastened to a mounting plate at the bottom of the column, a bearing could be attached to the head such that it would run up and down the steel bar as the head is raised or lowered. The parts would, of course, have to be substantial as very little movement ( laterally ) can be tolerated. I decided to use a mounting plate of 20mm aluminium attached to the bottom of the column and a 20mm ground steel bar. The top bearing would be an aluminium block 80mm wide by 30mm high, protruding 50mm from the side of the head and carrying a bronze bush to run on the steel. So, rather than working on engines, I've spent the last while making the parts.

A quick draft of the top bearing and bottom plate.

The mounting plate needed a 70mm hole to accommodate the column, so I thought I would mount it on the faceplate and bore it out on the lathe. No. It was too big for the faceplate and could not have been securely mounted. After a good think I decided that I could remove the circle with a slot drill, but how to mount it? I have a 4" rotary table but it seemed far too small for the job until I realised that if I could live with 3 unused holes in the mounting plate, then I could mount it. ( Following this logic, I could have used the faceplate, but that would have given me 4 holes! ). Well, it worked. It was a bit tedious, but using a 6mm slot drill I eventually ended up with a 70mm hole. I drilled 2 bolt holes and split the block across the diameter of the hole. I then tapped the holes in the front of the plate and opened up the holes at the back. A trial fit and it seemed very snug.
As the steel bar was 20mm, it wouldn't fit into the headstock of my Myford lathe, so A friend at the club turned down and threaded the end M12. I drilled and tapped the plate to match.
The top bearing block was brought to size and shape in the milling machine and then transferred to the 4 jaw to be bored out for the bronze bush. The bush was also turned and bored on the lathe. I'm very pleased to say that the bearing fits on the steel shaft 'like a glove' with no obvious play. Just what I wanted.

The three parts finished and ready to fit. The three holes are for ventilation!

The finished job - side view.

The finished job - front view.

I'm pleased to say that the job was a success. Checking with my laser centre finder indicated that I could raise and lower the head and keep to within 0.1mm ~ about 4 thou. OK, if i'm rough with it, then I can't expect this accuracy, but with a reasonably gentle touch it is repeatable.

Maybe now I can get back to engine building. Where was I?

The Cylinder - Continued

As I mentioned earlier, I'd drilled the flanges for the cylinder head bolts but now it was time to make some real progress. I blued the port face and marked it up on the surface plate. I do this more for reassurance, so I know I'm in the right place when I use the DRO to direct the milling. The milling was fairly straightforward. I pre-drilled the ports to get rid of a lot of metal to make the milling easier. I just had to remember to go slowly as I was only using a 2mm cutter. A few passes and the jobs a good 'un! While I was at it I swapped over from the collet holder to the jacobs chuck and drilled the holes for the steamchest bolts. It was great to be able to raise the head and still maintain registration. All that's needed now is to drill the exhaust port and the steam passages.

The cylinder - almost finished.

The Steam Chest and its bits

As supplied, the steam chest casting incorporates a length of flange material so that the steam chest flange and the valve rod stuffing box flange can be made at the same time. This is a bit of a pain as the end of the flange material seems a long way out from the 4 jaw chuck. I started by drilling through the flange and into the steamchest to accommodate the valve rod. I then turned the valve rod flange and parted off. Next I brought the steam chest flange down to length and drilled it to take the valve rod flange. Now to the milling machine to bring the chest to size. No problems here, just a bit of end milling. I changed over to drill mode and drilled the holes for the mounting bolts and for the valve rod cap. I would have tapped the valve rod cap hole as well, but I didn't have the headroom to fit my tapping aid, so I transferred to the bench drill press and tapped it there.
Now back to the lathe with a bit of 6.3mm hex brass to make the valve rod cap. Drill, turn, thread and part off. Now how to hold it while I turn a half round on the other end. I made up a holder from a bit of scrap steel round bar, tapped to take to the M5 thread of the cap and proceeded to turn the other end of the cap. Now a bit of hacksaw and file to make the steam chest cover. I spotted through the steam chest and drilled the cover. I also drilled for the steam inlet.

The steam chest parts ready for a good polish.

The Top Cylinder Cover

The top cylinder cover consists of a cylinder head which incorporates a flange, mating with another flange to provide a stuffing box for the piston rod. The casting again has an extended flange so that the parts can be machined on the same centre. So, with the round end mounted in the 3 jaw chuck, drill for the piston rod, turn the piston rod flange and part off. Bring the cover flange to length and drill for the piston rod flange then mount the flange end in the 4 jaw and turn the cover and boss to the right size. Now to drill for the flange securing bolts. First of all I glued the two parts together, ensuring that the flanges were correctly aligned. I then drilled ( tapping size ) through the top flange and into the cover flange. This way I know that they will mate up - not much room for error here, the bolts are M2! I also drilled for the cylinder studs. When all was done, I applied a bit of heat and pulled the parts apart.

The cylinder cover and piston rod flange - the discolouration is due to heating and will easily remove.

The Bottom Cylinder Cover

The bottom cylinder cover consists of a block with a boss on the top and bottom, the top one fitting the cylinder and the bottom fitting the table top. It is drilled to take the cylinder studs and also for the 4 bolts holding it to the table top. The casting as supplied is just a rectangular block of bronze, so the first operation is to give it squared up flat sides - a quick job in the milling machine. Now for the proper work. Using the surface plate, I marked a centre on both sides of the casting and then gave them both a light centre pop. Next, the block is mounted in the 4 jaw and centred using a wiggler. The first boss ( doesn't matter which ) is then turned to the right diameter and depth. The block is then checked for thickness and turned over in the 4 jaw and the centring re-checked. The block can now be brought to correct thickness and the other boss turned.

Turning a boss on the block.

The block is now transferred to the milling machine and the 4 sides brought to size. Change over to drilling and the 4 mounting bolt holes drilled. Now, this is where we see that drilling them with a smaller drill paid off. It is obvious that something has gone wrong. If I open up the holes to the required size, then the drill will come out through the side of the block. Back to the drawing and the digital callipers. OK, so I've mis read the drawing and made the block 2.5mm narrower than it should be."NAUGHTY WORDS!"

Bringing the block to correct size (ha ha).

What to do? I thought about this for a while and then decided that as I'd taken off too much metal, I had to put it back. I found a few scraps of 3mm brass sheet and chopped them up to just over size. As this part of the block didn't need to take any stress, I decided that soft soldering would be adequate and I proceeded to tin the parts and then sweat them together. A bit more milling and drilling and the part was finished.

The bottom cylinder cover after repair. You can just see the extra bits stuck on the sides.

The Exhaust Flanges and Elbow

The flanges are turned from a casting supplied as part of the kit. Not difficult, but I just hate the intermittent load this puts on the lathe.

Turning the flange from the casting.

The finished flanges.

The elbow similarly is part of a purpose made casting. Willy suggests drilling the two ends of the elbow and then glueing in a rod to hold the part in the lathe while the end is turned down to fit the flange. My glue wasn't good enough!. I ended up tapping the ends and holding them with a sawn off scrap bolt.

The finished elbow.

The almost finished exhaust elbow and flanges - just needs soldering.

The Upper Side Frames

The upper side frames sit above the table and are used as guides for the crosshead. They were supplied as castings but, unusually for Willy's castings, these were unuseable due to being undersized. It turns out that Willy had let someone else source the castings and he had forgotten to allow for either shrinkage or machining. As Willy didn't have any useable spares, I re-drew the parts in a CAD package and sent them off for laser cutting. The new parts were superb and required only a little work to clean up the edges.

The upper side frames, laser cut from 3mm brass.

The Small Rod Ends

The small rod ends are used for the valve gear. There are five of them! They start life as a length of 9mm square brass rod. The first operation is to mount the rod in the 4 jaw chuck and turn the end. This is then drilled and tapped and the appropriate length parted from the rod. The next operation is to mill the square end down to size.

Milling the ends down to size.

Now for the interesting part - rounding off the end. I had to turn up a pin to fit into the centre of my rotary table and the centre of the rod end. I found a scrap of aluminium to prevent me milling the table, and another to clamp the part by its boss end. I could then round off the rod end using a small end mill.

Rounding off the rod end.

All of this had to be done five times and then the parts were finished off by filing and polishing.

The five finished rod ends.

The Valve Drive Lever

Just a simple pivoted lever which takes the drive from the eccentric and pushes the valve rod up and down. Easier said than done! This time, I'm going to show you the finished part first, so you can understand the thought process.

The finished valve drive lever.

On the face of it, it seemed easy enough. Just find a bit of brass bar, mill off half of one end and slit the other. But what about the boss on the top? I finally realised that this would have to be done by turning the boss from the side of a bar, as shown in the following picture.

Turning the boss on the side of the bar - note all the packing to keep it proud of the jaws.

After turning the boss and drilling and tapping it, the part can be transferred to the milling machine for drilling, milling and slotting.

Milling the side of the lever.

Slotting the fork.

I finally made up a filing button ( a steel disc with a pin ) to fit the end of the lever and filed around it to round off the ends of the lever.

The Other Valve Lever

This one sits at the other side of the valve drive, to balance things up. It's a fairly simple part, requiring only a bit of milling to get it to size and a few drilled holes.

The other valve lever.( needs a slit in the left end, but I'd run out of junior hacksaw blades! )

The Cranks

Yes, cranks plural, 'cos there are two of them. Made from a bit of round bar, two holes are drilled for the shaft and the connecting rod end. Then the bar is mounted in the 4 jaw and centred on the shaft hole. The boss is turned down to size and the first crank parted off. The second boss can now be turned and the second crank parted off.

Turning the boss on the crank.

I turned up a filing button and used it to mark the outline of the finished crank. I then bolted the two parts together and hacksawed and filed to get the correct profile. ( I hate that bit! ).

The finished cranks.

The Eccentric Disc and Sheave

The eccentric sheave is supplied as a casting so into the 4 jaw to clean up the sides and bring them to size. Drill and tap the holes for the bolts and valve connecting rod. Split the sheave, bring the halves to size and bore out the hole for the disc. Next mark out the end of a round bar for the shaft centre, offset in the 4 jaw and turn the boss. Transfer to a 3 jaw and turn the eccentric disc. Sorry, no pictures of the various operations as I didn't have my camera to hand, but here's a picture of the finished product.

The finished eccentric disc and sheave - still needs a lot of polishing.

Odds and Ends

Not much left to do now, in fact the only major component left is the flywheel and I'll cover that next. The last couple of sessions in the workshop have been making various bolts, shafts, spacers etc. I have also started trial assembly of the valve linkage and the steam chest and valve. As you might expect, this has required quite a lot of fitting and fiddling. At the same time, I've been doing a lot of polishing in an attempt to save a lot of work at the end of the job.

The Flywheel

The flywheel casting as supplied has already been partly machined, making it a very easy job. First, bring to correct diameter, then take half the excess width off the side. Next, bring the boss to diameter and length. Chuck the newly machined boss and finish the other side, then remove the redundant boss. All that's left is to drill and tap for a grub screw. No photo's - you really don't need them.

Where Have We Got To?

OK, so having made all these parts, do they all fit together? Time for a trial assembly ( although there are still some bits missing - I'm waiting for them to arrive from Switzerland.)

The engine so far.

Well, I'm still waiting for the ornate brass rods! Unfortunately Willy has been unwell and unable to do them, so I've made up a set from plain steel rods. I've also spent many hours relieving tight spots and generally finishing the engine. Now it runs "sweet as a nut" on just a low pressure of compressed air. When my son saw it, he called it a "steampunk pepper pot". Praise indeed!

Almost The End

So, after 3 1/2 months and 90 hours of work it is reasonably complete and I've even made a box to transport it. I will be displaying it on the City of Sunderland Model Engineering Society stand at Doncaster MEX this May.

The Final Cut ( until I get the brass bits from Willy)

Well, about 2 months later and I had the opportunity to finish the engine. Willy had supplied the ornate turned rods so I set to and stripped the engine down and rebuilt with the new parts.

The engine in its finished state - one to be proud of.)