Author Topic: Len Mason's "Mastiff" - chewed from the solid  (Read 21171 times)

Offline deltatango

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #105 on: August 26, 2017, 03:22:05 AM »
Progress on Mastiff has slowed down lately, winter viral infections and an unheated workshop don't go well together.

When I first re-drew Mastiff I'd decided to have the valves seating directly in the heads but after further thought I've gone back to Len Mason's original design with inserted, one piece, valve guides and seats. Doing it that way makes getting good alignment between the seats and valve stem guides much more likely. In addition the seats are then easily replaceable if the material (2011 called "machine rod" by the supplier) proves unsuitable.

The mounting holes in the cylinder blocks were reamed 8 mm so 10 mm rod was turned to a "Loctite" fit in the heads using the collet chuck:



then drilled 6.4 mm for the port then 2.9 and reamed 3.0 mm for the valve guide hole:



The seating is at 45 so the top slide was set over:



and a small boring tool ground up from a broken end-mill to machine the seating:



I had much finer control over clamping forces in the 3-jaw chuck than in ER32 collets so, after parting off the pieces were turned around and held carefully to machine the seating for the valve spring:



The products (including three of what Roger would call "test pieces") look like:



The reason for the rejections was mostly poor surface finish on the valve seatings.

I've managed to make one "test piece" for the valves leaving the top slide set up, holding the valve by the stem in a collet and taking very small cuts - pictures when I have the 8 valves finished.

DT

Offline deltatango

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #106 on: September 14, 2017, 09:15:15 AM »
The valves are made from free cutting stainless and the angle and finish on the seating surface, and the size and finish on the stems, need to be good. After turning the seats in the inserted guides I left the topslide set over and hoped that it would be possible to get a tool to reach the seats on the valves from the "inside" rather than trying to reset the topslide angle. The stems need to be 31 mm long, 3 mm diameter.  The length was set with gauge blocks and the saddle stop:



The tangential tool took 1 mm cuts to start with:



followed by a very sharp tipped tool intended for Al alloy to give a fine finish and form a radius under the head. The edge doesn't last very long but two were enough to finish all eight valves. After some fiddling with the angle of the tool holder, and holding the valve stem in an ER16 collet these tips (DCGT11T304 it says on the box) were also used to form the seating:



and this end of the valves now looked like:



With the large overhang of the work I expected to have to turn out some "spring" and this worked fine, however, the valve stems were still not quite parallel which was puzzling and a portent of a nasty discovery later. I'll try these valves when the time comes to run the engine, if they are no good then that will be the time to remake them.

A bit of good fortune allowed the valves to be reversed in the collet:



and project just far enough to turn in the groove for the cotters:



The cotters were turned and parted off and the slots cut by hand. The recess for the spring was formed using a slot drill then the collar parted off and Superglue'd to a stub so the cotter recess could be formed the same way:



With the seatings now Loctite'd into the blocks the bits could be assembled and tested for "feel" which seems OK right now:



I then moved on to making the cylinder liners and it quickly became clear that the lathe doesn't bore parallel holes. Everything came out beautifully concentric and the poor abused DCGT11T304 tips gave a very fine finish to the CI but when I measured the bore at each end of the 85 mm blank (two liners back-to-back) the chuck end was nearly 0.2 bigger, which matches the differences I found in the valve stems. A length of ground bar in the GripTru chuck showed a similar angularity and I'll now buy in a proper 4MT test bar before doing anything more drastic to the machine. It looks like the headstock may be out of line with the bed and the lathe did spend around 25 years in a Tech School so accidental abuse is quite possible.

I now have a month to relax a bit with a visit to the UK including the Forncett day out to look forward to from Sunday on.

Regards, DT

Offline Roger B

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #107 on: September 22, 2017, 06:58:26 PM »
Still following along  :ThumbsUp:  :ThumbsUp:  :wine1: I have made my valves from stainless steel screws and bolts which are already forged to something near the right shape.
Best regards

Roger

Offline deltatango

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #108 on: September 24, 2017, 09:46:06 AM »
Thanks Roger,
I've thought of using bolts as a source of materials, never thought as far as finding parts near the right size to use as forgings. Great idea!
DT

Offline deltatango

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #109 on: November 09, 2017, 03:49:41 AM »
I've now got this project back on track and the lathe adjusted to turn and bore parallel. The lathe bed was slightly twisted and must have been like that since I installed it. Tweaking the mountings and measuring with a dial gauge and 4MT test bar has brought the machine just within Schlesinger's limits for "Finish turning lathes" which are 0 to 0.02 mm per 300 mm for "work spindle parallel with bed in horizontal plane". My apologies to the lads and lasses of the Tech!

The Forncett St Mary Industrial Steam Museum is a great credit to Rowen Francis and his volunteers and very well worth a visit if you are anywhere nearby. I also got to meet some other MEM members and see their work - which set standards that I have to aim for. Thank you again Willy, Andrew, Ramon and Simon, and to Bill for the organisation.

To complete the story of the cylinder liners these started as two 80 mm lengths of continuous-cast iron which machined beautifully (cast iron is probably my favorite material to machine despite the mess). These were drilled:



then bored to lapping size:



Turned between centres on an expanding mandrel:



then separated and finish turned on the outside to a glue-in fit in the cylinder blocks and the top flange skimmed to thickness:





The 4-jaw SC chuck is a great help for minimising distortion whilst getting a firm grip on delicate parts.

At this stage I measured up and found the out-of-parallel error in the bores. I decided to clean this up with an adjustable reamer which got the bores parallel but left the finish noticeably rougher than that from the boring tool.

I made a lap as described by Len Mason (and Ramon in his wonderful MEM treatise on lapping):



and finally got the bores parallel and to what I hope is a useful finish (beyond grinding in car engine valves I haven't lapped anything before) :



The bores ended up a little over size, particularly #4, but this can be corrected for in making the pistons which are the next bits on the list.

DT

Offline Ramon

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #110 on: November 09, 2017, 01:12:15 PM »
The Forncett St Mary Industrial Steam Museum is a great credit to Rowen Francis and his volunteers and very well worth a visit if you are anywhere nearby. I also got to meet some other MEM members and see their work - which set standards that I have to aim for. Thank you again Willy, Andrew, Ramon and Simon, and to Bill for the organisation.

Glad to see you back in the workshop DT and nice to think you remember your 'Day Out' at Forncett with fond memories. I notice elsewhere the bemoaning of the loss of some exhibition facilities particularly with being able to run engines. Well Forncett always has encouraged this and hopefully will continue to do so without the restrictions that others find  - maybe it will encourage one or two new faces to join us next year and we'll look forwards to you returning at some stage David.


I made a lap as described by Len Mason (and Ramon in his wonderful MEM treatise on lapping):

Ah, that confirms it then - I thought it was Len Mason's design but was never certain. Hope it was as successful for you as they have been for me. I set out years ago to make a Mastiff, bought the castings and drawings (Reeves :-\ ?) and the book but like several other ideas it waned to the point where it was finally sold on unstarted. I think I may have said elsewhere on here before - 'Intention' and 'Reality' are quite opposing forces at times  ::)

I haven't been on here for some time so have not been privy to your thread before now. I have a copy of Masons book 'Building the Mastiff' on the shelf. Not my original but another passed on when a friend died. If you don't have a copy and would like it I'd be more than happy to send it you - just say.


Regards - Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Online b.lindsey

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #111 on: November 09, 2017, 01:52:54 PM »
Still with you DT. Nice to see and update on this build  :)

Bill

Offline deltatango

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #112 on: November 11, 2017, 12:36:05 AM »
Thanks for the offer Ramon but I already have a copy of the book. I don't know what the drawings are like in your copy but in mine they are poorly reproduced and that was one motivation for re-drawing the whole thing in Alibre. I also wanted to avoid the use of castings and use metric fasteners and dimensions where possible.

Bill - I pleased your are still following along, hope you will hang in here until I'm forced to open a YouTube account for the videos...

David

Offline Ramon

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #113 on: November 12, 2017, 11:21:07 AM »
No probs DT - it was just a thought in case you didn't have one. As I haven't followed your thread I was unaware too that you had redrawn it. I checked the book, an original hard back version, and as you say the drawings at times are indeed 'poor' at best.

Enjoy your shop Time

Regards - Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline deltatango

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #114 on: December 05, 2017, 11:21:22 AM »
The Mastiff pistons are made in two parts and then silver-soldered together. This allows you to form the gudgeon pin bosses to a shape that would be impossible if machining from the solid. The outer sleeves are turned from cast iron (my favourite material) and the chips were flying:



The sleeves have an internal step that locates the steel core:



which starts out looking like:



the groove on the narrower portion is a tell-tale that, during silver soldering, shows when the sleeve has slid down to where it should be. The larger diameter end will become the gudgeon pin bosses and first has a flat machined on each side:




so it looks like:


and the top is rounded over by hand filing:



To cut the groove across the gudgeon pin hole the core has to be aligned carefully which I did using a v-block and square:



and the whole lot secured in the machine vice:



to cut the slot:



and finally looks like:



I don't take the camera anywhere near the brazing hearth so the next pictures show the soldered assembly being trued up and brought close to size in the lathe prior to lapping and internal boring:



The outer sleeve has extra length which will end up being parted off to form two piston rings.

Time for a breather - next post I'll finish off the four pistons.

DT

Offline Roger B

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #115 on: December 05, 2017, 11:28:30 AM »
That seems quite a complicated way to make a piston. I wonder if it has any real advantages? Still following along  :ThumbsUp:  :ThumbsUp:  :wine1:
Best regards

Roger

Offline deltatango

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #116 on: December 05, 2017, 10:38:48 PM »
Hi Roger, I'm pleased to know you're still following! I agree about the pistons being complex, I'm following Len Mason's book and that is how he makes them. This is my first IC engine and I'm learning a lot, in future I should have the confidence to re-design bits that I don't like. I did think about making the pistons from solid alloy or scrounging up an old piston and having a go at casting some. After all aluminium pistons in a cast iron bore are a very well known good combination!

Any advice (or pointers to existing books/web pages) about alloys for pistons, or the tricks and traps of casting piston alloys, would be appreciated.

Regards, DT

Offline deltatango

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #117 on: December 12, 2017, 11:52:31 AM »
Silver soldering isn't a precise method so the embryo pistons were trued up in the lathe, leaving (I thought) enough over size for lapping. The lap used was to a design I found in Ramon's treatise on this forum, thanks again Ramon!:



In the book Len Mason suggests wrapping a strip of copper into a cylinder and securing with a hose clip which didn't sound too safe to use. After one piston I ran out of grinding paste and went and bought a tube of paste that claimed to break down and become finer with use, well some of the grains did, some didn't, at least in time before the piston was to size. This left the finish with visible scratches but with the finish feeling smooth. Without any more metal left to remove I have to be content with the finish as-is and hope it serves the purpose. Another lesson learned!

The outboard end of the piston skirt was left over long to provide metal for the rings and this portion was bored to size to a plug gauge:



and two rings parted off to leave the skirt at the correct length:



the ring groove turned in. In this picture you can see the silver solder in the tell-tale groove shown earlier :



Here is a little family group shot of the progress so far. The little extra "piston ring" is the burr that came off at the end of the parting cut. I wouldn't deliberately try to make a ring of cast iron 11/16th diameter and 0.008" thick but it is possible if you don't try too hard!:



The next task that really needed to come out right was to drill and ream the gudgeon pin holes. I thinned down one end of a stub of square stock to a close fit between the lugs inside the piston, set the side of this vertical with the part in the chuck and scribed the centre with a sharp lathe tool:



The same setting piece was then used to align and clamp the piston in a V-block:



and line up under the drill and reamer on the mill table:



Each piston had been number stamped early in the process:



to make sure I can tell which is which when they get mixed up together:



There's been a bit of a break in the Mastiff work to catch up getting the garden ready for summer (37C forecast for tomorrow) and to fit a DRO to the Aciera mill. Obviously the folks at Aciera in 1950(?) weren't thinking about DROs...

Regards, DT


Offline Jo

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #118 on: December 12, 2017, 12:02:34 PM »
Looking good DT  :)

I fitted DRO's to Sexy if you need any ideas for mounts.

Jo
Usus est optimum magister

Offline deltatango

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Re: Len Mason's "Mastiff" - chewed from the solid
« Reply #119 on: December 18, 2017, 10:11:46 AM »
Thanks Jo,
I'm sorry not to have asked the forum  for advice before fitting the DRO, I still haven't quite got used to having access to all that expertise! By the time I wrote the previous post I'd already finished the process:



The x-axis scale mounting looks a bit hairy but the Al bar behind it is stiff. The z scale makes it impossible to fit the z limit stops but the bar on which they run is still there and provides a bit of mechanical protection. The y and z scales are the small cross-section versions, any bigger and they wouldn't fit, particularly the y-axis which is tucked in behind the stepped pulley that drives the head. Apart from the tapped holes I didn't make any non-reversible changes to the machine, nor are any of the travels limited by the scales.

Using the DRO is just magic! The z movement always gave me problems, the other lead screws have a 1/8" pitch, z has "one turn = 78 thou" stamped on the dial! I suppose this is a nominal  2 mm but the DRO show up a repeating pitch error that was causing problems.

OK, back to Mastiff in the next post.

DT