Stuart Twin Victoria (Princess Royal) Mill Engine

[Dr_GMJNParticipant @dr_gmjn]

Ramon,

Understood, thanks. Re. using the castings, it was the pad for the oil cup that was puzzling me in terms of how to machine it into a solid aluminium cap with the machines I have, but I guess I could drill it and JB Weld a small spigot on top, then face it and drill it. Since it will be painted, nobody would know…As noted below I do have some bronze, but thanks for the kind offer.

Jason,

The CAD you posted is pretty much exactly what I want to end up with. Would the mounting holes need elongating as per the plans, presumably for fine adjustment during assembly? Small radii in the foot-upright joint might be nice too depending on washer/nut clearances.

I'd like the boss ODs to match the crank boss, which is specified at 11/16" (c. 17.46 mm). The cast crank bosses will just about clean up to that.

The materials I have that might be suitable are:

1" x 1/2" x 7.5" Aluminium (spare from the fabricated beds).

50 mm x 44 mm x 28 mm GD250 Cast Iron (spare from the valve chest covers).

1 1/4" Dia. x 50 mm LG2 Bronze (was for the pistons, but I can get some more).

I don't have the 1/2" reamer or end mill, but I do have to place an order with ARC shortly to get some new small diameter mills, so I could easily order those sizes.

Cheers.

[JasonBModerator @jasonb]

The aluminium will do us for the two halves.

At a push you could use the round bits of the castings to make the bearings but it's not nice stuff to machine so probably best to go with new. so really you want enough to be able to get two rectangles a little over 11/16 x 11/32" out of that will turn down to 11/16" dia. and about 2" long.

For the oiler boss I usually counterbore the oil hole with a plunge cut of a milling cutter then loctite in a pre threaded boss and fillet with JBW/Milliput. I've also not shown that all external corners should be rounded which I tend to do with a file as its easier that trying to mill small radii and the softer look more suits the look of a casting.

It's a bit tight around the 3BA fixings particularly if a washer is used but you could Milliput a small one if if you have the room.

Regarding 1/2" cutters, You are going to need bigger anyway, I was hoping it could be plunge cut on the mill but I think boring on the lathe will be the way to do it particularlu now the soft GM is not being used

With 11/16" dia bearings

[Ramon WilsonParticipant @ramonwilson3]

Ah! you mean like this Jason The oil cup holes on these two caps are just a push fit for the oilers but yes they are usually threaded

Another benefit of square bearing blocks is that they are easily shimmed (out of sight) to fine tune the crankshaft level (important) and, of course, they don't need extra work to prevent them rotating in the housing

When it comes to milling the feet that's where a home radiused cutter (done on an offhand grinder) gets pressed into use.

Wouldn't see that LG2 bronze as a machining problem – that would be a good choice with a turned steel shaft

but then we're all different

[Dr_GMJNParticipant @dr_gmjn]

Thanks both.

Jason – is the radius on the top of the cap done in the R/T with a small cutter, so it would have small radii where it meets the flats?

I'll see if I can get hold of some square section bronze, then I can keep the round for the pistons.

The round bosses on the lower castings are slightly too small in width to clean up to the correct size, so I can't use them anyway.

[JasonBModerator @jasonb]

Having your feet separate also makes the home made cutter a lot easier to use. Won't be so easy for Doc to do his integral feet and get into the internal corners, likewise following a curved top cap.

Doc, I drew it to match the PR drawings as you said you wanted. there are several ways to do the top and the rotary table method will leave fillets which I don't mind myself but not what's on the drawing so other methods can be used.

Quite a few beginners have been able to make them like this from my Jowett and Muncaster designs

The R/T method takes longer to setup but produces similar with the fillet

As shaping really needs to be done before the hole you have a more delicate part to hold for boring, easier in the mill as you can spread the packing easily

Ramon it was not so much the actual material I was thinking about but preparing the blocks from the chopped up castings and holding them as you said half rounds are more trouble than rectangular but as they are undersize to start with that option is out.

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason – I’m happy with the fillets so I’ll use the R/T I think. The counterbores give it some form in that area anyway, and as you say they are supposed to be cast, so a few radii aren’t an issue.

Apologies if I’ve missed something, or am being thick, but I’m still not clear on how to make them:

I understand the split bushes fine, but my initial question was really around at what point – and how – are the bushes fitted into the aluminium housings? Do you machine everything to size separately then glue in the bronze, or do you glue in the bronze first, machine the joints, then bolt together and bore…or?

Any chance you could give a basic sequence?

The other question was, is the width of the base good enough to locate on the 4-jaw, to guarantee the bored axis will be perpendicular? Do you also use parallels to the face of the chuck and the flanks of the part to ensure this is spot-on, or do you finally ream to size with them set up sitting on their feet?

 

Edited By Dr_GMJN on 15/07/2022 17:29:08

[Ramon WilsonParticipant @ramonwilson3]

I don't know what else I can say here Doc but …

Twin Victoria, Waller engine, Double Diagonal engine, McOnie Oscillating Engine, Stuart Double Ten rebuild, Throp Corliss engine – have all had bearings done as described above. They are two part, as Jason shows too, the pedestal and the bearing. Make the pedestal first then make the bearings to fit the pedestal

Use the four jaw by all means but don't be surprised if a, you distort something or b, they are not both the same. Personally I would not for the reason you state too – the front face may be in line but what about the back inside the chuck.

Just trying to guide you on a path to ensure minimum time and good success.

When I did the bearing caps for the Corliss engine I just filed them from rectangular blanks of cast iron after putting in the lower recess and drilling the holes for the bosses. The plinth that the oil box sits on was a separate insert JB Welded in. There's really no need to complicate things – as Jason alludes, it's a casting you want to represent not a precisely machined component.

Here's a different approach on the marine engine build

Rectangular slots cut in line in the bed plate

Split bearings and caps

As said previously – it's much easier to shim a square bearing into line than a round one – vertically or laterally. Though ideally this should not be a guiding principle – aiming to get it right is – just that if it does need a tweak then you have the means. Relying on movement of the pedestals will work but is not an ideal way to approach matters in my book especially if stripping down in the future.

I hope this helps – obviously having two sources of help is confusing at times but I really cant see how I can help you further on this particular aspect of the build.

Regards for now – Ramon

[JasonBModerator @jasonb]

As Ramon has failed to convert you to rectangular/square bearings I'll carry on with round ones.

I think you missed my hints that the caps cut with the edge of the cutter which leaves a large radius will bring a lot more issues to the build and that the other option is likely to be the best for you. Some fillet can still be included or added later and the counterbores are needed anyway.

Have a look through the jowitt thread and see how the cylinder was done, it's the same basic method of setting the height of the cutter to the radius of the curve and rotating the part under the cutter in a number of steps

The pedestal/cap is made separately from the bearings and they just assemble as though you bought in bearings. Glue does not get a look in, the bearing halves are soft soldered together for machining and then melted apart. we'll do it properly and pin the lower half of the bearing so it does not rotate in the housing.

The lack of a boring head really means you are going to have to bore the housing in the 4-jaw. The face of the 4-jaw is used as the ref face so parallels off that to set the part at right angles to the lathe axis. Should be able to get the two holes close enough if they are set out on the mill using the DRO rather than marking out and punching, then pick up the position with a dti.

Will sort out a sequence tomorrow

As Ramon says it's not easy to shim up a round bearing but on assembly if needed you can shim up under the foot of the low one then skim the thickness of that shim off the other one so they then are at the same height without shims that can get lost or mispositioned. I would not slot the 3BA holes at this stage, if there is a problem on assembly it can be dealt with then.

Talking of which it would be a good time to start thinking about mounting the model so you can start to "fit" the parts together and make any adjustments as you go which is far better than waiting until the end and assembling all the parts and then trying to track down where something is tight.

[Ramon WilsonParticipant @ramonwilson3]

Posted by JasonB on 15/07/2022 19:20:36:

Talking of which it would be a good time to start thinking about mounting the model so you can start to "fit" the parts together and make any adjustments as you go which is far better than waiting until the end and assembling all the parts and then trying to track down where something is tight.

Totally 100% behind this advise. Especially on a two bed engine. Build, and paint, if you can, as you go so that at each stage the engine is fitted and running as it will finish. Building it to a running fit then stripping it down for painting nearly always results in misalignment issues – slight I agree but can be troublesome

When the Waller was built I did this on a 'building plinth', a direct dimensional copy of which I created as a base and plinth for the final mounting. The engine ran lovely until after the strip down for painting and reassembly when issues arose and the most annoying knock was prevalent that took quite some time to trace and fix.

Just another comment

[Dr_GMJNParticipant @dr_gmjn]

Yes..the base. As previously mentioned, I’d really like to try a wooden parquet floor type effect. Someone gave me a load of lolly sticks, so I thought I’d trim them to short lengths, and stick them to the ply upper base in a herringbone pattern. Then use some grain filler, flat back with abrasive paper over a flat block, then varnish and flat again until I get a nice satin finish.

I can make a start, but I guess there is still a long way to go before setting up – for example the crosshead slides, linkages, crank, flywheel, eccentrics etc?

Of course any advice on finishing the base is appreciated. I was going to follow the article instructions for the basic structure.

[JasonBModerator @jasonb]

Just bear in mind scale, average parquet is about 3" wide so that is going to be less than 1/8" wide at the scale of this engine not lolly widths.

So given the recent posts about preparing stock and a sequence to make the parts I hop eyou are sitting comfortably.

Preparing stock.

After sawing up and deburring four pieces of your 1/2" bar you will be ready to go.

Start by making sure your vices fixed jaw is clocked true in X as that will be our ref face, I assume the base of the vice is parallel to the mill table.

A few sharpie marks will help to keep track of what is to come off where, I'm using an offcut and may later regret leaving that hole. I'm just going to make one but repeat each stage for the other before moving on to the next.

As the two half inch faces are parallel we can make use of them to go against the vice jaws, rest the base stock on some parallels, tighten vice and tap down then take a cut over the sawn surface to clean it up. I'm using a 10mm 2-flute cutter specific for non ferrous.

remove from vice and deburr then rotate 190 deg keeping the marked face to you and mill the opposite face to the required 0.625".

We now have the two thin edges machined and parallel so they can now be used to hold the work while the thickness is brought down to 0.375", start by taking approx 1/16" off the first face

Then after deburring replace the other way up so the remaining material can come off the second face

Go through the same process on the material for the caps then you have four pieces of the correct cross section.

Next stage is to skim a little off one end of each piece to give a square end, full height cuts about 0.25mm per pass.

Set up the vice stop and then set the part with the squared end against the stop and machine to final length, 1.75" for the lower half, 1" for the caps

Time for a refresh of the sharpie marks then I'll carry on in a second post

[JasonBModerator @jasonb]

Machining the pedestal and caps

Now that we have some easy to hold blocks of known size it will be quicker and easier to do the remaining work.

Add the vice stop and grip the base material while packed up on parallels and locate it's centre. I do this by locating opposite faces and halving the reading on the DRO, if you have an all singing one do this on the absolute.

Spot and drill sufficiently deep for the 3BA clearance holes

Remove, deburr and then rotate 180deg keeping the same face to you and spot, drill and tap 5BA (I'm using M3 for this demo)

If you have a handwheel or basic DRO then relocate the caps centre, if a better DRO move 0.375" towards the stop and switch to incremental and zero X at that position. You can then keep the stop in the same place to locate the cap while toy drill the two 5BA clearance holes and a 1.5mm oil hole right through

No pic of that

Change to a 1/4" milling cutter and zero it's height on the parallel packing, raise up 0.250 and then take full height cuts to produce the two flats that stop 0.319 from the middle so 0.444" to spindle ctr

Without altering the height come in from each side on Y0 to a spindle position of 0.375 which will gibe the "spot face" around the hole. repeat for opposite side

raise the cutter, position spindle at 0,0 and plunge down to a height of 0.350 which forms the pocket for the threaded boss.

You can then deburr all the holes and assemble with a couple of screws while holding the two parts down on a flat surface to keep then sitting true

The assembly can now be treated as one for some time. Hold with the bottom against the fixed jaw and on parallels then drill a small ctr drill hole 0.625" up and on the centre line for length.

That will do for now.

 

Edited By JasonB on 16/07/2022 14:51:57

[JasonBModerator @jasonb]

I had been considering leaving the lower half as is for boring but decided to cut the feet first. So set the assembly in the vice packed up on parallels and touch off a cutter on the joint line. It can then be lowered 0.500" and a series of full depth cuts taken to remove the required 3/8" width at which point the cutter should just we brushing the edge of the cap. Keep the packing in place so the foot does not get bent downwards should the cutter be a bit blunt.

Moving over to the lathe, fit the 4-jaw chuck and select a couple of parallels so the face of the pedestal sits just proud of the jaws. A quick tip to stop the parallels sliding out while adjusting is to clamp them either side of a jaw.. Use the tailstock ctr to lightly press the work against the parallels and just nip up the jaw screws placing a piece of packing onto the flat top of the cap so the thin material won't get distorted.

Replace the tailstock ctr with a sprung one and set the dti to read how much it moves as the chuck is rotated by hand, adjust the jaw screws to get as near as zero movement as you can.

REMOVE the parallels before drilling out the hole, I went with 6mm, 10mm and finally 12mm, don't apply excess pressure as we don't want to part to move.

The hole can then be opened up to final size by boring, as you get close to a measured size switch to a suitable piece of bar to act as a plug gauge, I used a piece of 9/16" bar. keep this handy a sit will be used later to compare the bearing diameter with when that is made.

Remove from the lathe and before doing anything else mark the two halves so you know how they go back together and heavily deburr the holes particularly if you use GTN type parting inserts as they will leave a fillet on the internal edges of the bearing so the deburring gives this fillet clearance.

[JasonBModerator @jasonb]

BEARINGS

rather than waste bronze I'll use a bit of Corian.

Start by preparing two blocks that when soldered together will be a bit larger than the required 11/16" dia and at least long enough for 2 x bearings x parting cuts and enough to grip. 3/8" x 3/4" section will be ideal

Tin and then sweat the two parts together with soft solder as described by Ramon earlier and then after cleaning off any excess flux set to run true in the 4-jaw with about 3/4" material sticking out.

Face off the end

Spot drill and then drill out to 10mm in a couple of stages for 3/4" depth. Then bore to final size, again using some of the crankshaft material to gauge the size as you get close to 7/16"

The outside can then be turned down to 11/16" dia

With a sharp parting tool start to machine the waist to just over diameter eg 0.060" infeed until you can get a calliper jaw in to measure the flange width, use the topslide to take off what is needed to bring the flange to 1/8"

Then carry on along the work until the waist is wide enough to accept the pedestal plus a little allowance for paint

The final diameter can now be turned by gradually feeding in and then traversing side to side until it measures the same as your gauge material

A final check is to fit the two together, when the screws are tightened you should just notice a slight resistance to the pedestal turning.

The bearing can now be parted off, pause th ecut part way so the corners can be deburred with a fine file before completing the cut

mark the two halves, deburr the hole each side and then gently warm to melt the two halves apart. any slight trace of solder can be removed by rubbing an abrasive laid on a flat surface.

[JasonBModerator @jasonb]

ROUNDING THE CAP

A simple way to round the cal is to make a series of cuts at angular increments and then just blend the cuts with a file.

Rest the cap on a pivot, in this case a 3mm spot drill and bring the cutting tool down onto the top. Lock Z.

Bring the vice towards you and then reposition the cap at a slight angle while still supported by the pivot. Approx 5deg will do

Feed the cap into the cutter and then back out and you will have a slightly angled cut

keep doing this until you can't cat any further without hitting the flat area where the nut sits, you will have to move the work sideways as to get the best position.

Now repeat for the other side of the arc which will give you a part like this.

A quick swipe with a file will blend the facets into a single curve

The bearing can now be assembled into the pedestal and the oil hole extended down through the bearing and right into the bottom half. A short length of brass rod is loctited into the hole in the bottom half of the pedestal so just a small amount sticks out which will act as a peg to stop the bearing rotating.

All that remains is to drill and thread a bit of 1/4" material to take the oil cups and then part off two short lengths that can be bonded into the top of the cap. Use a needle file to take off all external corners and fillet internal ones if you want but there is not much room for a 3BA nut on the foot.

here it is up against an overtall Stuart one that I had knocking about a sit did not get used from a part built engine I was given

[Ramon WilsonParticipant @ramonwilson3]

NIce work Jason and a neat result. – that's exactly how I did the Corliss caps BTW – series of fine flats before filing

Looks like you are spoilt for choice now Doc

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason for taking the time and effort to outline your process in so much detail.

I have managed to replicate the work in your first two posts – pretty much – but ran out of time this evening. No point repeating your images, but for my own record, these are they:

A few notes and queries:

I didn’t have a 10 mm cutter for the initial squaring, so used an 8mm one.

I don’t have a 1/4” cutter for the counterbores, so used 6.5mm.

I couldn’t find any reference to the height of the caps, so made them large and left them like that. They will be trimmed later anyway.

With two pre-machined sides clamped, when turning through 180 degrees keeping the faces to the front and tapping down, for facing the blocks, most of the time one of my two packing parallels underneath would be loose. If I turned through 180 degrees on a vertical axis (reversing the faces), the parallels invariably were both firm.

I am considering making brass washers to put under the cap nuts. I think the aluminium spot faces will get chewed up otherwise. Obviously standard 5BA washers won’t fit, due to the minimal clearances.

Could you show your vice stops in more detail please? My home made threaded ones aren’t great for this type of thing, but worked well enough for the lower parts. I’ve never really used this method before for multiple identical parts.

Quickly skimming through the new posts today – I guess I could use the R/T to mill the cap upper arch bit? I tried the bore/rod method for the 10V cylinder flanges, but I didn’t particularly get on with that method. Presumably I could mount the assemblies in the R/T chuck with a stub mandrel, fixed with a cap head and washer, then incrementally rotate as per the cylinder casing you linked to previously?

Cheers.

[Dr_GMJNParticipant @dr_gmjn]

BTW when sizing the bronze bearing I/D, I don’t have any pre-sized crankshaft material. I’ve got some 1/2” bar that IIRC has to be turned down to 7/16”. So presumably I can make the bearing bore nominally 7/16”, then size the shaft to be a running fit later on? The bearing bores should be identical due to boring them as one pice in the 4-jaw, before parting off, therefore the turned 7/16” crankshaft sections should also end up being identical, assuming similar fits?

Thanks.

[JasonBModerator @jasonb]

cap height is found by drawing it, this is also how the 0.319" dimension was found as it is the point where the radiused top meets the 0.250" high "flats"

Bespoke steel washers would look better than brass

My vice stop won't work on your type of vice as it clamps to the removable jaws but it's here anyway

You won't get to all the arch if doing it on a rotary table as the screws needed to hold it to something solid will get in the way. Practice makes perfect and a bit of filing won't hurt.

I've always tended to do my crankshafts quite early on as particularly with larger ones that may be one piece if you end up going a bit under size chasing a good finish then it's easy enough to bore everything else to fit – bearings, flywheel, eccentric, gears etc. For the sake of 10mins turn your 1/2" material to size now and then you can use that to gauge all the rest of the parts that fit to it.

By skimming yesterdays post you may have missed that I suggest doing the machining of each bearing separately. 1. it reduces the overhang of teh boring bar so should help maintain a tapered hole. 2. Less overhang for the parting tool work. 3 many a beginner has burst the solder joint on their first attempts at split bearings, having the work closer to the chuck will also clamp the joint together and help reduce this risk. Brilling (and reaming) bronze can make it quite hot and soften the joint.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 18/07/2022 08:09:56:

For the sake of 10mins turn your 1/2" material to size now and then you can use that to gauge all the rest of the parts that fit to it.

10 minutes for the crankshaft…interesting ha ha.

Ill continue with the bearing housings tonight. Need to get some bronze or gunmetal for the bearings though.

Thanks.

[Dr_GMJNParticipant @dr_gmjn]

Made some washers and bolted the halves together tonight:

Planned to do more, but thwarted by other mundane tasks again.

I’ve got a 6mm, 1mm corner radius cutter. At full depth, the shank would touch the edge of the cap. I was wondering if this might be a good thing as a kind of gauge to prevent cutting into the cap side – they are already right on the edge of being too small. I’d increment in until the shank just scraped the cap end?

[JasonBModerator @jasonb]

I did think of a 1R cutter but the fillet would have encroached on the 3BA washers I have so just went with a square internal corner that a fillet could be added to if desired. It's also a long stick out for a 6mm cutter to clear the cap and reach down to the foot.

Just put a sharpie mark on the side of the cap and creep up to the final cut.

EDIT Flute length is 12mm so won't do 1/2" full depth

Edited By JasonB on 19/07/2022 09:05:14

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason. I’ll add whatever fillet I can with Milliput. I can always make some non-standard washers to suit.

I’m still apprehensive about the bar in vice method for the upper cap radius. If I get the rotation angle of the clamped bit wrong, I could end up with a mess (like with the 10V cylinder).

Is the another way? BTW I quite like the look of the radiussed ones you posted previously, if that opens up other options:

I realise the bolt heads will still be an issue, but could they be removed and replaced in turn? I can’t imagine the cutting forces will be very high?

Edited By Dr_GMJN on 19/07/2022 10:27:37

[JasonBModerator @jasonb]

Posted by Dr_GMJN on 19/07/2022 10:26:10:

Is the another way? BTW I quite like the look of the radiussed ones you posted previously, if that opens up other options:

Did those on the CNC but as I said risk of distortion as you have to bore in the lathe could be an issue, it was easier to set that up in the mill to bore with clamping force not on the arch. Similar could be done with a rotary table but still the distortion to think about.

With care this method can be used, removing a screw for the last couple of cuts. cutter offset from ctr by half it's diameter

[Dr_GMJNParticipant @dr_gmjn]

So I made a bit of progress, but paused to evaluate: This is current state of play with the first one after centre drilling, mating marking and side milling:

But unfortunately I went a bit far with the side milling on one side, damaging the washer. It means the bolt head points are right on the edge of the spot face, which doesn’t look right:

Trouble is, turns out it needs to be like that in order to fit the mounting bolts (nuts):

The other side cap looks ok:

…but the mounting nut doesn’t fit:

So it needs milling back to be like the other side.

I guess I could make the cap washers even smaller, and turn the nuts down to shave the points off, but would that look right?

It’s also clear I should buy new milling cutters. Any recommendations for range of sizes? Jason, you mentioned specific ones for aluminium. What would you get? Thinking the Arc Premium range – metric. Obviously I’d also need ones suitable for ferrous materials.

Thanks.

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