Muncaster Joy Valve Steam Engine 1/2 scale

[raveney]

I find that it is helpful to review the photos posted and self critique the work. Modern cellphones take such high resolution images that details not apparent at first are noticed.

A good and bad example are this engine's fasteners. The out of scale acorn nuts looked cartoonish in the previous post. Decided to slog out some scale hex nuts and studs to keep the tedium at the end of the project more manageable.
I used a chart I found online, and trusted the tooling and work stops set on the lathe to make the chamfer and thicknesses the same. It appears in the close up that it worked well, and I feel the model looks much better.

 

[raveney]

The connecting rods seemed reasonable to be next to make. They are unusual in the big end similar to the crossheads. Mr. Muncaster favored rectangular bearings and wedges. Original plan states that they are to be forged, but I lack any blacksmithing facilities so chose to carve out of 1" 1215 round bar.


KVOM had used a neat setup that allowed 3 faces of CNC access to machine these that I copied to manually make these parts. Using ER32 square collet blocks also allowed me to elevate one end and make the taper. At first I only registered the collets with two angle plates and two clamps, but found the vibration loosened these up so added c-clamps and additional t-bolts and studs where arrows indicate.


This all took the better part of a day, so I adapted the process to include reducing the material using the lathe reasoning that I can take a depth of cut of 0.025 each pass effectively doubling the material reduction. This pleased the shop boss greatly, and we moved on to the rotary table for the cosmetic features. I made up two additional centering pins for my RT collection (thanks again Peter) This saved a bunch of time as the scale of these rods required a 1/8" endmill which are too short to catch both sides of the yoke eyes in one sweep. The fishtail features on the big ends were also cut on the table by just clamping alongside a parallel.

 

[raveney]

The big end of these rods uses a through bolt and a small block I called a keeper that needs to be removable, but a tight fit. I made them out of the same 1215 round bar stock by slitting them and side milling to a close fit, and thru drilling while still attached to the parent material. Another idea I picked up from CNC folks on this forum.


Then the part was broached and the bearing blocks soldered together and sized. I made little wedges similar to the plan, but made an error on which side of the split line that I milled them. See the image where I drilled and tapped the #4-40 adjustment screw.

I almost drilled and reamed the crank hole through the wedge. I reversed the bearing and drilled another #4-40 tapped hole. The meatier side of the bearing needs to be towards the keeper end. I am using set screws and positioned these bearing wedge/adjustment holes underneath the rods in the assembly. The "extra" tapped hole was dilled down into the brass bearing to help capture it in place.

Then the bearings were sized side to side to each crank web, by clamping them in a small machinist clamp and filing and sanding for a loose (.003ish) fit. Oiled everything and it spins over nicely, happily huffing and puffing out the cylinder passages at the end of each stroke.

 

[peterl95124]

nice looking hex nuts !
for making my rods I didn't want to create so much swarf
so silver-brazed them up from smaller bar stock

 

[raveney]

Thank you Peter,
Appreciate the likes from KVOM, Richard and Stan

I kept thinking about brazing these parts also, but was committed once I started one of them. I think I will give brazing a go on the valve links as they appear to be about 75% waste also. Curious if you folded the yoke or machined it from rectangular stock after it was brazed?

 

[peterl95124]

R,
I brazed slabs onto the sides of the end of the rod to make it thick enough,
that left a slot that was square at the bottom which I rounded with a mill,
the thick piece at the crankshaft end is more or less butt brazed but I did mill
a shallow slot in the end that the long bar fits in to keep everything from going
wonky during brazing.

here's an obsessive-compulsive way to get perfectly symmetrical rods, put them
side by side and slide drill rods in the ends to hold them together, now when you
file the top and bottom this helps keep the file level, then switch one of them over,
now you are getting the tops and bottoms to be symmetrical, also keep switching
which one is on your right and which one is on your left as you file them to avoid
any unconscious left-right affect of your filing pressure to affect the rods, alternate
switching this way with flipping one of them over. if you are as OCD as I am you
should be pleased with the results.

-P.

 

[raveney]

Hello again,

Thank you Peter. I believe anyone in this hobby has some compulsive behaviors. I recall knocking a shelf down accidentally that held 4 drill indexes and reamers. I tried to just turn off the lights and go inside, but I couldn't. Sat there on the floor and mic'd each of the small bits to put them back where they belonged. Unbelievable, but I did feel better after that was done.

Work continued on the lower linkages, and tidying up the visible tool marks on the connecting rods and crankshaft. The lowest linkages were cut out of a scrap of 1/4 hot rolled steel on the rotary table because I saw others do it this way. I sacrificed $30 worth of inexpensive carbide end mills due to the backlash in my rotary table before disassembling it and cleaning the sliding surfaces. I have good luck with these Speed Tiger endmills in non ferrous materials but they seem to snap at the collet in steel. I finished up the job with a necked down HSS endmill (3/8 shank x 1/8 cutter).

Assembled onto the connecting rod and had a very small interference with the aft oil well. I had held these back about 0.060" from the corner of the base casting and this had caused an issue with the forward edge of the crosshead also.

I thought it best to build out the steam chest before fabricating the other linkage. The steam chest is a casting, but I can only cast aluminum and brass so I chose to make it out of a scrap of hot rolled steel 1" x 3". Face milled square and to size first. A fair bit of material needs to be removed inside the chest so I did the "maths" and punched 20 holes and removed the center mass. I have rushed this part before, and encroached into the finished edges resulting in oversized parts. Happier with the results this time using some simple algebra.

The cavity is a little deeper than a standard depth of cut on a 1/4 endmill so I patiently nibbled away at it on both ends until I got called away for chores.

 

[raveney]

Continuation of steam chest.
Used degree block and set part in vice, swept indicator across front to back to ensure parallel because I only have one set of degree blocks. Its typically off a lot and it was. "Tappy-tap-tap and Bobs your uncle" as some people say . Milled out the internal cavity.


Then I counterbored and made bosses to emulate a cast part. They are a snug fit and held in place with a small dab of JB welder. I considered brazing them, but didn't want to warp the part.
Then I squared up and fly cut another rusty piece of 1/4 hot rolled steel and made a cover plate. I had watched another builder, Simon, on MEM using a radius end mill and purchased one to use here. The benefit is one can make recessed areas with a single bit rather than plunging a standard end mill and then resetting and radiusing the edges with a ball end mill. Brilliant! This is a Kodiak solid carbide 1/4 bit with 0.045 corners. $25 on Amazon.

https://www.amazon.com/dp/B007BTRIM6?psc=1&ref=ppx_yo2ov_dt_b_product_details
To complete this part there are some features at each end. First drill, tap, counterbore for valve spindle glands...
Then reverse and drill and tap for valve spindle guides. I opted to use hex type screw in ones rather than flanged and studs. I did make a flanged connection for the steam inlet pipe here.
Next up for production will be the valve plate and brass/bronze spindle parts....

 

[raveney]

Valve plate material that I had planned on using was a scrap of 304 SS 0.120" plate left over from a heat treat oven build. Not a good choice because of work hardening. Snapped a brand new 3/8 x 1/8 endmill and left a jagged mess on the slots that were cut before it snapped. That got thrown in the trash bin, and a ground piece of 1/8 cold rolled steel was ordered. Every other piece of steel plate I had was corroded, and I needed a thin, flat surface.

The tiny (3" x 6") piece cost $24 so as a precaution, I spot drilled and drilled undersized holes for the eventually milled 1/8 slots

That worked out much better, so I made up 6-32 studs and 1/4 hex nuts the rest of the morning.

I also started on some of the fussy little brass and bronze steam chest accessories such as valve spindle glands, steam inlet flange and valve spindle guides.
This was only challenging because I picked some crescent shaped bronze scraps out of the "too cheap to throw away drawer" and crafted some clever ways of holding them while getting the shape I needed. Started by center punching and drilling the follower part on the lathe, and then secured on the rotary table and milled with a brand new sharp cutter.

 

[Richard Hed]

Valve plate material that I had planned on using was a scrap of 304 SS 0.120" plate left over from a heat treat oven build. Not a good choice because of work hardening. Snapped a brand new 3/8 x 1/8 endmill and left a jagged mess on the slots that were cut before it snapped. That got thrown in the trash bin, and a ground piece of 1/8 cold rolled steel was ordered. Every other piece of steel plate I had was corroded, and I needed a thin, flat surface.
View attachment 143844
The tiny (3" x 6") piece cost $24 so as a precaution, I spot drilled and drilled undersized holes for the eventually milled 1/8 slots
View attachment 143848
That worked out much better, so I made up 6-32 studs and 1/4 hex nuts the rest of the morning.View attachment 143843
View attachment 143847
I also started on some of the fussy little brass and bronze steam chest accessories such as valve spindle glands, steam inlet flange and valve spindle guides.
This was only challenging because I picked some crescent shaped bronze scraps out of the "too cheap to throw away drawer" and crafted some clever ways of holding them while getting the shape I needed. Started by center punching and drilling the follower part on the lathe, and then secured on the rotary table and milled with a brand new sharp cutter.
View attachment 143845View attachment 143846

That is totally beautiful. How can I get one?

 

[raveney]

Thank you for the compliments,

The valve spindle guides didn't go so well. They roughed out okay in a single setup, being drilled and reamed then threaded and undercut.

It was the radius feature that went sideways. I watched someone on video use a rounding over endmill as a cutter in the lathe, and attempted to monkey see, monkey do. I knew bronze was super grabby, and was taking very small cuts until....it grabbed and bent the part and rotated the cutter.

I can see why it didn't work with my tool holders. The tightening screws come in tangentially, and there was no flat, and HSS is super hard etc...Not sure why it worked for others?

I saved the part by carefully whacking it and indicating it true again. Then resorted to file and radius template. Onto the hex collet block and cut the hex features.

They screw into the steam chest on the front tapped holes shown in post #49

 

[kvom]

If the piece was completely into the collet the "belt" would help resist bending.

 

[Zeb]

I can see why it didn't work with my tool holders. The tightening screws come in tangentially, and there was no flat, and HSS is super hard etc...Not sure why it worked for others?

Really nice work on the engine. My attempts using a radius cutter have ended similarly. I think some of it has to do with the lack of rake clearance angle coupled with the large surface area of the cutting profile. The part might rub under the cutter edge and start bouncing.

Something I haven't thought about, is that it is cutting at different feet per second depending on what part of the cutter is contacting. They're usually on a mill hitting a part like a flycutter instead.

Anyways, nice on the save.

 

[raveney]

If the piece was completely into the collet the "belt" would help resist bending.

Good eye KVOM, I hadn't noticed that the piece was pulled out from the collet also. Maybe it wasn't gripping tightly on the threads and that's why it grabbed and spun. I remember tapping the flanged part against the collet so it would resist bending.
thank you

 

[raveney]

Really nice work on the engine. My attempts using a radius cutter have ended similarly. I think some of it has to do with the lack of rake clearance angle coupled with the large surface area of the cutting profile. The part might rub under the cutter edge and start bouncing.

Something I haven't thought about, is that it is cutting at different feet per second depending on what part of the cutter is contacting. They're usually on a mill hitting a part like a flycutter instead.

Anyways, nice on the save.

Thank you sir Camelot,

That sounds right to me. I have had the same effect when using a radius tool making parts like the wheels on a tubing bender. No chatter if I used a smaller radius and worked side to side cutting a small amount on tangent. Once the full radius "bites" it goes badly as the FPS increases exponentially

Have to accept the limitations of my small equipment and take small bites

 

[Richard Hed]

Thank you for the compliments,

The valve spindle guides didn't go so well. They roughed out okay in a single setup, being drilled and reamed then threaded and undercut.
View attachment 143854
It was the radius feature that went sideways. I watched someone on video use a rounding over endmill as a cutter in the lathe, and attempted to monkey see, monkey do. I knew bronze was super grabby, and was taking very small cuts until....it grabbed and bent the part and rotated the cutter.
View attachment 143852
I can see why it didn't work with my tool holders. The tightening screws come in tangentially, and there was no flat, and HSS is super hard etc...Not sure why it worked for others?
View attachment 143855View attachment 143853
I saved the part by carefully whacking it and indicating it true again. Then resorted to file and radius template. Onto the hex collet block and cut the hex features.
View attachment 143856
They screw into the steam chest on the front tapped holes shown in post #49

I would say your order of operation was incorrect. I would have cut that diameter with the round end first, and rounded it, then cut the rest and thread it. NAH, that's wrong, I would probably do what ou did but I WOULD have chucked it up in the larger radius for sure.

 

[raveney]

Made the slide valve, valve spindle and some oil cups with covers. Used a shop built ball turner rather then the radius tool for the brass balls that go onto the mains covers.

I had some 5/32 303 SS and fabricated the eyes for the valve spindles by brazing. First attempt was using a 6-32 thread, but then realized that the minor diameter ran into the 0.125 spindle ends. 8-32 thread onto a 0.156 diameter threaded nicely and there is no concern about shearing on this part.

I have calculated 1.007 valve length and 0.519 recess on the valve at 0.6 scale of the original. This is mainly driven by my valve plate dimensions where I used 0.125 for the steam admission slots and 0.27 for the exhaust slot. So 0.250" lead and lap. Cross checked this against Simon Fraser's animation and we are fairly close in our guestimation of the ellipse.

I had to solder the bronze valve base to the upper bronze castle parts because of stock that I had. I like the castle style valve for ease of fabrication and I can make adjustments by just rotating the valve spindle. No fiddling with tiny wrenches inside the steam chest and loosening and tightening all those 6-32 hex nuts!

The oiling cups looked like they might splash all over the place, so I made tiny covers that thread in (6-32 thread) Got lucky on the snug fit of both rectangular covers on the mains. So far they seem to stay in place. Even a broken clock is right twice a day.

 

[Richard Hed]

Made the slide valve, valve spindle and some oil cups with covers. Used a shop built ball turner rather then the radius tool for the brass balls that go onto the mains covers.

I had some 5/32 303 SS and fabricated the eyes for the valve spindles by brazing. First attempt was using a 6-32 thread, but then realized that the minor diameter ran into the 0.125 spindle ends. 8-32 thread onto a 0.156 diameter threaded nicely and there is no concern about shearing on this part.

I have calculated 1.007 valve length and 0.519 recess on the valve at 0.6 scale of the original. This is mainly driven by my valve plate dimensions where I used 0.125 for the steam admission slots and 0.27 for the exhaust slot. So 0.250" lead and lap. Cross checked this against Simon Fraser's animation and we are fairly close in our guestimation of the ellipse.

I had to solder the bronze valve base to the upper bronze castle parts because of stock that I had. I like the castle style valve for ease of fabrication and I can make adjustments by just rotating the valve spindle. No fiddling with tiny wrenches inside the steam chest and loosening and tightening all those 6-32 hex nuts!

The oiling cups looked like they might splash all over the place, so I made tiny covers that thread in (6-32 thread) Got lucky on the snug fit of both rectangular covers on the mains. So far they seem to stay in place. Even a broken clock is right twice a day.View attachment 143891View attachment 143892View attachment 143893View attachment 143894View attachment 143895View attachment 143896View attachment 143897

Would you be so kind as to take at least one photo with yer hand in it? That way I can tell how big this nice engine is. Kan hardly wait to see it running.

 

[raveney]

Would you be so kind as to take at least one photo with yer hand in it?

I could have used an extra hand taking the measurements needed to estimate the radius of the trunnion shaft guides. I inserted an 1/8 drill bit in the steam passage and measured across two transfer punch rods and averaged the distances to come up with 4.050 radius

The order of operations seemed important for these pieces so I drilled all the holes after squaring up the rough parts. Then removed the bulk of the center material and slotted the keys for the bronze guides with a keyway cutter.


I then attempted to silver solder it all up using Mapp gas and fire bricks. No joy there as the solder would not flow at all. I could only seem to get one side red hot at a time. This is why I didn't silver solder the cylinders. Too much material for my setup. Mapp gas works fine for thin sheet metal and small rounds, and soft solder.
Other people may have success using oxy/acetylene, but I don't want that equipment in my garage. Too many stories about fires and explosions to risk it with my daughter living in the upstairs bonus room above the garage.

Try again tomorrow using TIG welder.

 

[peterl95124]

what type of flux are you using for the silver-brazing ?
I always use the white stuff for silver
(the black is for hotter brass-brazing, not necessary and you can't see through it which is important)
and how clean were the surfaces before you started (they should be bright and shiny
from abrasive cloth and elbow grease).

the places flux is will stay nice and clean and shiny through the entire process, I usually coat the entire
piece in flux to reduce how much blackened metal I have to clean up afterwards.

apply lots of flux, start heating, the flux first boils then melts then turns transparent,
use a steel rod (not the silver-solder) to move the flux back up where it needs to be while
gravity tries to foil your efforts. some people say apply the silver when the flux goes liquid,
but IMHO that's way too soon, the metal has to turn red first, then apply the silver. and if
the solder balls up and doesn't wet the metal use your steel rod to scratch the metal and it
will wet and the solder will flow, but more typically it is because you put the silver in there
before the metal was red hot.

the advantage of silver-braze over TIG is that the silver will flow into the joint all the way to the
other side, whereas you probably can't get that much penetration with TIG, and with these parts
its obvious you can't get your torch all the way around both sides of the joint !

yes, you can only heat one joint at a time even with MAPP, but that should not be a problem,
once one joint is done it won't take near as much time to get the next one to temp as its
part way there already.

finally, after it cools down, just about any acid works to remove the now hard and glassy flux,
even vinegar, I put the part in a pot, cover it with vinegar, put a lid on it, and bring it to a boil
on the stove, then after it cools down (or sooner if you're impatient) the part will be free of
flux, and if you leave it in there long enough it will also be free of black oxide where there wasn't flux.

HTH.