Model Engine Maker

Engines => From Plans => Topic started by: kvom on April 29, 2015, 06:18:59 PM

Title: Roy Ozouf's Coventry
Post by: kvom on April 29, 2015, 06:18:59 PM
I saw this engine running at NAMES, and was able to locate the source for plans.  It's a booklet that's sold on EBay titled "Three Elegant Oscillators", published by Cammelback Press.

Here's a video of it running:

zHMdw0xglFI
The name Coventry relates to an Englishman, Don Coventry, who found a similar engine in a surplus store and published a picture in Model Engineer.  It's unusual for having the pivot at the bottom of the cylinder rather than at the center, as is the case with the McOnie.

Since NAMES, I received the booklet with the plans and have been modeling it in Solidworks for the past few weeks.  The parts are all numbered neatly and total 66 unique ones.  Obviously a few need multiples.  I found only one minor issue with the drawings, which are all in imperial dimensions.  The flywheel is 5.25" in diameter, to give an idea of its size.  The following are renderings which show how the engine is built:

I ordered a flywheel casting from Martin's Models, and the rest will be built from bar stock once time allows.

Title: Re: Roy Ozouf's Coventry
Post by: sshire on April 30, 2015, 11:45:05 AM
OK. You're definitely ahead of me.  :ROFL:
I've been looking at the plans on and off and they are nicely done.
It will be next in line after the PMR horse vertical. I'm still kicking around the idea of modeling the frame, 3D printing it twice  and having Cattail do a set of castings.
Title: Re: Roy Ozouf's Coventry
Post by: jeff l on April 30, 2015, 01:54:50 PM
I think that this engine was featured in MODELTECH  many years ago , Roy included his method on machining the frames from solid stock using a fixture plate on a rotary table .Jeff
Title: Re: Roy Ozouf's Coventry
Post by: tvoght on April 30, 2015, 02:10:55 PM
I received the book yesterday. It appears the book is a reprint of the Modeltech article Jeff mentioned (and two others). It's a nice set of plans. The engine was high on my list, but while waiting for the book, a couple more engines have creeped onto the drawing board. Now the list is being reshuffled -again-. Sigh.

--Tim
Title: Re: Roy Ozouf's Coventry
Post by: kvom on April 30, 2015, 02:23:21 PM
Since several have received the book, I'll mention the problem I found with the plans.

On the valve block, the exhaust channel passes too close to the bottom steam port.  Easiest solution is to make that port less wide and the exhaust port wider.

Solidworks says frame volume is 78.17 cubic centimeters.  STL loaded to Shapeways says 78.28.
Title: Re: Roy Ozouf's Coventry
Post by: Jasonb on May 01, 2015, 08:05:17 AM
I'll be following this one along but wondered if as both of you are going for "mass" production of the frames either by CNC or casting that you may want to consider this :LittleDevil:

(http://www.floridaame.org/Shows/Gears%202007/images/DSCF0188.jpg)

(http://m7.i.pbase.com/g5/42/428142/2/67723327.UKroESfo.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: kvom on May 01, 2015, 01:00:46 PM
Very cool.  Thanks for posting, Jason.

I am going to CNC the frames, but it's unlikely I'll do more than 2 of them.  :ShakeHead:
Title: Re: Roy Ozouf's Coventry
Post by: sshire on May 01, 2015, 05:36:18 PM
That's great. Thanks, Jason.
It's not the frames. It's making 3X the number of parts.  :ROFL:
Title: Re: Roy Ozouf's Coventry
Post by: Jasonb on May 01, 2015, 07:54:25 PM
Well you should get them right by the third time of trying :mischief:
Title: Re: Roy Ozouf's Coventry
Post by: kvom on May 08, 2015, 04:42:37 PM
Some thinking about the valving led to the following reasoning:

1)  The pivot rod and crank are positioned vertically relative to each other, so that at TDC and BDC the cylinder will also be vertical.

2) The link needs to be 180 degrees out of phase so that when the piston is at the top the valve is at the bottom.  Therefore the eccentric needs to be placed on the crank with its throw opposite to the crank throw.

Then to verify the valve motion I drew up the attached in Draftsight using the eccentric throw of .109 and the two lever arm lengths of 1/2 and 11/16.  This shows that the valve will move .15" from its center position.  The length of the valve is .55, so that when it move .15" the edge of the valve exactly exposes the steam port.  QED.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on May 08, 2015, 04:49:55 PM
And thinking about that triple cylinder version, it looks as if each cylinder must exhaust directly, with the pivot rod having only the air supply passage.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on May 18, 2015, 09:25:30 PM
I received the flywheel from Martin today.  Looks really nice.  Must leave it alone until the other engine parts are completed.  In any case I have a setup on the mill that I can't tear down yet.
Title: Re: Roy Ozouf's Coventry
Post by: sshire on May 18, 2015, 10:45:43 PM
Big thumbs-up for Gary Martin's flywheels. They're cast very well and machine beautifully.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on October 22, 2016, 12:05:57 AM
Only 17 months since my last post, during which time Stan has already built his.  After a couple of months of doing nothing in the shop, I decided to actually make a start.  My first parts are the two crank shaft spacers and the crankshaft side shafts.  My veterans copy of Solidworks expired, and until I get the 2017 version I can't generate any DXFs from the model.  So mostly I'll be doing manual lathe parts for a while.

A friend of mine is building a large CNC plasma table, and as an experiment I'm going to cut the frames using it.  Supposedly it's accurate to a couple of thou, and the software takes into account the width of the kerf.  I'll probably draw it with 15 thou roughing clearance and finish machine on my mill. 
Title: Re: Roy Ozouf's Coventry
Post by: philjoe5 on October 22, 2016, 04:11:44 AM
Thanks for this link:

http://www.ebay.com/itm/Build-Roy-Ozoufs-classic-THREE-ELEGANT-OSCILLATORS-model-steam-or-air-engines-/6011011919

I will be following this build.    Definitely an engine on the bucket list.

Cheers,
Phil
Title: Re: Roy Ozouf's Coventry
Post by: kvom on October 24, 2016, 10:32:56 PM
After a few days work, something more to show.

I bought the flywheel casting a year ago, so decided to work on it.  The rim as cast was quite round, so I was able to chuck it using my large 3-jaw with the reversed jaws, and get it to run pretty true.  Then faced the hub and drilled and reamed the center .501".  I was also able to face the rim being careful to avoid the protruding chuck jaws.  With some 1/2" drill rod loctited, I could then turn the rim.  Took .100" off; nominal size to start was 5.25" diameter.

(http://www.pbase.com/kvom/image/164364903/large.jpg)

Most of today was spent on the pivot shaft.  This is where the cylinder rocks back and forth via the main bearings and through which the air is supplied and exhausted.  I took a lot of care with this part to try to insure everything is parallel.  Material was a 12" piece of 13/16" diameter 4140 stressproof steel rod.  First chucked in the 6-jaw to face, drill and tap one end, and then turned that end down to .626" diameter.  Then sawed off a bit more than needed and faced the sawed end and center drilled it.  Now with the other end in the collet chuck I could turn the entire length to .751", one thou over the target diameter.  This shaft mounts to a pivot block, and I want to avoid any leaks between it and the air supply holes, so a good tight (non-press) fit is my goal.  I own a .75" reamer and will wait to see if I need to shave it after the block is made.  At this point I have this:

(http://www.pbase.com/kvom/image/164364896/large.jpg)

Now I could use the collet chuck on the main shaft.  I faced the unfinished end to length, drilled and tapped it, and turned it down to .626" as well.

Next I needed to drill a 1/8" hole crosswise through the center.  This hole is used to locate its position in the block.  In addition, I needed to drill and tap two 2-56 holes the secure the shaft to the block with screws.  Here's the setup for this:

(http://www.pbase.com/kvom/image/164364898/large.jpg)

Finally, I need two holes at a 45 degree angle to the others and which connect with the air passages in the bore.  A spindex would have made this pretty easy, but lacking that I set the angle on the surface plate:

(http://www.pbase.com/kvom/image/164364900/large.jpg)

And moved the V-block to the mill for drilling:

(http://www.pbase.com/kvom/image/164364899/large.jpg)

Done!

(http://www.pbase.com/kvom/image/164364901/large.jpg)

And for completeness, here's the parts from this weekend:

(http://www.pbase.com/kvom/image/164364904/large.jpg)

Title: Re: Roy Ozouf's Coventry
Post by: philjoe5 on October 25, 2016, 02:01:03 AM
Good progress kvom, and I like the workaround for not having a spindex.

Cheers,
Phil
Title: Re: Roy Ozouf's Coventry
Post by: kvom on October 25, 2016, 10:40:50 PM
Today was cylinder day.  It's 2" diameter, and I had a choice of 4 materials on hand in order of increasing cost:  steel, cast iron, brass, and bronze.  Tried turning some 2" HRS and the finish was awful, so went with grey CI.  My stock piece was 2.5", do needed to turn a section down:

(http://www.pbase.com/kvom/image/164380941/large.jpg)

After reversing the piece and facing to length, I step drilled the bore using S&D drills to 15/16, then bored to a target of 1".  Overshot so ended up 1.007", but measurement shows the same on both ends.  So hopefully no taper.

(http://www.pbase.com/kvom/image/164380942/large.jpg)

Next on the mill for a preliminary slot to provide a datum for aligning the holes in each end.

(http://www.pbase.com/kvom/image/164380943/large.jpg)

With a parallel in the slot and against the face of the vise, I found the center of the bore in order to drill the air passages.  I also spot drilled the cover mounting screws but didn't drill/tap them.  Plans call for 4-40 screws of which I have none, but I had lots of 5-40s.  I'll wait until I make the covers to see if 5-50 will work just as well.

(http://www.pbase.com/kvom/image/164380944/large.jpg)

Next I needed to finish milling the slots for the port block, so needed to set the initial slot parallel again.

(http://www.pbase.com/kvom/image/164380948/large.jpg)

Cylinder finished except for threaded holes for covers and threaded holes to secure the port block.

(http://www.pbase.com/kvom/image/164380950/large.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: kvom on October 27, 2016, 12:50:23 AM
Shorter shop session today, but I managed to get the piston and its rod made today.  Piston started as 1.5" bronze rod.  I cut off a piece, faced both sides to 1/2" long, and drilled/reamed to .254".  After threading one end of the rod 10-32, I pressed the other end of the 1/4" drill rod into the piston.  This took a fair amount of effort using my bench vise as the press.  I doubt it will come loose.

Then with the rod mounted in the lathe's collet chuck, I turned the piston diameter down to a close fit with the cylinder.  The fit seems excellent throughout the length of the cylinder with no light showing around it.  Seems to confirm lack of taper in the bore.

(http://www.pbase.com/kvom/image/164385603/large.jpg)

Ouzof shows a groove in the center of the piston.  He used a pin to secure it to the rod, but I'm not sure if it's needed to reduce friction as well.  It will be easy to add if needed.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on October 27, 2016, 10:06:25 PM
Finished the crosshead that I made a start on yesterday.  It was from a bronze cutoff from a prior project, so I won't post the steps I went through to carve it out.  Some 1" round as a start would have been more straightforward.

Here's the finished (except for an oil cup TBD) piece attached to the piston rod and crank pin.

(http://www.pbase.com/kvom/image/164390113/large.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: kvom on October 28, 2016, 08:46:15 PM
Today's project is the top cylinder cover and its gland.  First, cut off some 2" brass rod, chuck it, and turn a 3/4"x1/2" spigot:

(http://www.pbase.com/kvom/image/164394758/large.jpg)

Reverse, face to length, and cut a tight fitting spigot to match the cylinder bore.

(http://www.pbase.com/kvom/image/164394759/large.jpg)

Over to the mill to drill the clearance holes for the mounting screws.

(http://www.pbase.com/kvom/image/164394760/large.jpg)

Mount the cover to the cylinder, chuck on the lathe, and drill-ream the center .251".

(http://www.pbase.com/kvom/image/164394761/large.jpg)

Test that there's no binding between the cover, piston, and piston rod.  Happy dance follows.

(http://www.pbase.com/kvom/image/164394762/large.jpg)

Use a 7/16" endmill to form pocket for the gland

(http://www.pbase.com/kvom/image/164394763/large.jpg)

After turning the gland to a good sliding fit to the cover pocket, use the mill to drill clearance holes for 2-56 mounting screws.

(http://www.pbase.com/kvom/image/164394764/large.jpg)

Drill and tap matching holes on the cover.

(http://www.pbase.com/kvom/image/164394765/large.jpg)

There are still a couple of operations to do on the cover and gland, but I need some short 2-56 screws to continue.

(http://)

Title: Re: Roy Ozouf's Coventry
Post by: philjoe5 on October 28, 2016, 09:10:38 PM
Looking good kvom; life is good when it all fits together :ThumbsUp:

Cheers,
Phil
Title: Re: Roy Ozouf's Coventry
Post by: kvom on October 30, 2016, 01:45:20 AM
Today's target is the bottom cylinder cover and the pivot block.  Chuck a piece of 2" round brass and turn a 1" spigot that's a close fit to the cylinder bore.

(http://www.pbase.com/kvom/image/164401361/large.jpg)

Over to the mill to drill all the necessary holes.

(http://www.pbase.com/kvom/image/164401363/large.jpg)

Back to the lathe to face and adjust length.  I left it a little thick for wiggle room on next ops.

(http://www.pbase.com/kvom/image/164401362/large.jpg)

For the pivot block I failed to take many pics, but the initial job was to cut off a piece of 1.75" square brass bar, square it, and drill many holes.  The .75" through hole for the pivot shaft was not going to be a success using drills, so I spiral milled it on the CNC mill.  My first pass resulted in a hole that could have been a press fit.  I tried opening it up with successive passes adding .001" to the diameter, but that just resulted in rubbing instead of cutting.  Finally put the shaft back on the mill and shaved a few thou.  Result is a sliding fit, but not as close as I'd hoped.

(http://www.pbase.com/kvom/image/164401365/large.jpg)

Finally to drill the air passages, the block is set at a 45 degree angle, and the X-axis is centered on the pivot shaft.  Then the passages are drilled after the hole is started with an endmill.

(http://www.pbase.com/kvom/image/164401366/large.jpg)

Test to see that all the holes in 4 pieces line up and another happy dance.

(http://www.pbase.com/kvom/image/164401367/large.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: kvom on October 30, 2016, 08:24:57 PM
I made a start today on the port block, which mates to the slot in the cylinder.  This  needs to be a tight fit to the slot to prevent air leaks.  I started with a 1" cutoff of some 1.875" hexagonal brass bar that I faced on both sides on the lathe.  Then on the CNC mill machined the outer profile.  The cylinder slot is dimensioned 1.25" wide, and a 1-1/4 parallel fits it with a loose sliding fit, so likely several thou wider.  Therefore I set a .005" roughing clearance on the profile and used a new HSS .375" endmill.

(http://www.pbase.com/kvom/image/164408314/large.jpg)

After moving to the manual mill and machining off the bottom, I measured the width of the block as 1.257".  It would not enter the slot, so followed a series of applications of 200 grit paper on the surface plate until the block started to want to wedge into the slot.  Then some final fitting using 600 grit until I have a tight sliding fit.

(http://www.pbase.com/kvom/image/164408315/large.jpg)

The block is still too thick.  I am going to diverge from the plans and sandwich a some .125" ground plate between this block and the steam chest.   By doing so I avoid needing to machine 3/32" port openings through thick material, and the ground plate will provide a good surface for the slide valve.  The total of the two needs to equal the plan dimension of 7/16" thick, so the block will have a finished thickness of 5/16".

Next shop session will involve drilling the air passages and mounting holes in the block.
 
Title: Re: Roy Ozouf's Coventry
Post by: Tennessee Whiskey on October 30, 2016, 10:25:44 PM
I've been quietly following along with interest.  I am waiting for the next step.  I think I know where you're headed,  but,  not sure.  Surface finishes look great BTW.

Cletus
Title: Re: Roy Ozouf's Coventry
Post by: kvom on October 31, 2016, 07:29:21 PM
Lots of holes needed in the port block.

First, the two holes that connect the end of the piston to the steam ports.  Ouzof drew them such that the bottom of the hole is tangent to the bottom of the slot, but as made there is approximately 30 thou above the slot.  In any case I don't want the drill to break through the bottom so it's drilled 1/8" above.  Then I faced the bottom unless the holes looked aligned with the cylinder.

(http://www.pbase.com/kvom/image/164418950/large.jpg)

Then the two holes are drilled from the top to meet these passages.  There are the only two holes that are not through the block.  The holes for the air supply and exhaust are also drilled.

(http://www.pbase.com/kvom/image/164418951/large.jpg)

Next, reverse the block and mill passages to connect the supply and exhaust holes in the cylinder.  1/8" wide and 1/16" deep.

(http://www.pbase.com/kvom/image/164418952/large.jpg)

Spot and drill 10 mounting holes through the block.  I'm not crazy about how Ouzof dimensions from the edges while I'm referencing the center point.

(http://www.pbase.com/kvom/image/164418953/large.jpg)

Face mill to reduce thickness to 5/16".

(http://www.pbase.com/kvom/image/164418954/large.jpg)

Tap 4 holes 2-56 and countersink 4 others.

(http://www.pbase.com/kvom/image/164418955/large.jpg)

Finished!

(http://www.pbase.com/kvom/image/164418956/large.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 05, 2016, 09:14:07 PM
Todays' effort is the "link".  It slides up and down on two guide bars attached to the right frame, and is driven by the eccentric.

Squared some brass bar ~ 2.5x1x.6", and then machined this shelf 5/8" above the bottom and 1/4" in/

(http://www.pbase.com/kvom/image/164469666/large.jpg)

Then drilled and reamed the holes for the slide bars (3/32").

(http://www.pbase.com/kvom/image/164469667/large.jpg)

Some more shaping on the manual mill.

(http://www.pbase.com/kvom/image/164469668/large.jpg)

Now ready for final profiling on the CNC mill.

(http://www.pbase.com/kvom/image/164469669/large.jpg)

Per the plans, the guide bars would pass through separate pieces soldered to the link.  This method avoids the soldering, and ensures that the holes for the bars are parallel.

In operation, a small die block in the slot provides motion to the valve linkage.
Title: Re: Roy Ozouf's Coventry
Post by: sshire on November 06, 2016, 02:03:21 PM
Kirk
Nice way to make the block. Without a CNC mill, I had to do mine the old-fashioned way. I drilled the two guide rod holes after soldering the blocks to the oval piece so that they'd be parallel. Seemed to work with no binding.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 07, 2016, 10:08:03 PM
Today's bit was the two "cheeks" for the crankshaft.  Having squared two bits of 1.5x.5" HRS, I used the CNC mill to produce this:

(http://www.pbase.com/kvom/image/164484050/large.jpg)

The holes were spiral milled with a 1/4" 2-flute endmill, and then reamed.  Then I used the same outer profile to mill a matching pocket in some soft jaws.  After a bit of hacksaw work to remove most of the sides, I could hold the parts in the vise jaws in order to reduce the thickness.

(http://www.pbase.com/kvom/image/164484051/large.jpg)

After some deburring, a test fit with the rest of the crankshaft pieces.

(http://www.pbase.com/kvom/image/164484052/large.jpg)

Then noticed I'd mis-remembered the plans, so the cheeks are currently 7/16 thick instead of 5/16.  I'll correct that next time.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 10, 2016, 07:54:23 PM
I loctited the cheeks to the separator, so they're ready to be pinned.  I still need to mill a key slot in one of the shafts and then make a gib key to fit the shaft and the flywheel.

I had intended to work on the eccentric strap today, but with only a little time in the shop elected to work on the valve.  I discovered that while the 3-48 die I'd just bought is 13/16 diameter, I don't have a die holder that size.  So threading the valve rod will have to wait too.  The valve itself was milled from a larger bronze cutoff from another project, and the majority ended up as chips.  Once down to a correct size oblong, I milled the bottom pocket using a 1/8" endmill.  Then for the cross slots, I used this setup.

(http://www.pbase.com/kvom/image/164504206/large.jpg)

Finished:

(http://www.pbase.com/kvom/image/164504207/large.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: Admiral_dk on November 10, 2016, 09:25:04 PM
Looking good Kirk - still following along  :popcorn:
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 15, 2016, 02:48:05 AM
Working on the eccentric strap the last two days.  The first step is CNC profiling the two halves in some 3/8" thick CRS.  The material is about 2.5" square, and the slots are milled with a 1/4" endmill.

(http://www.pbase.com/kvom/image/164529711/large.jpg)

Next, following a technique shown by Terry Mayhugh on HMEM, I filled the slots with epoxy, in this case Darvon 5 from Lowes.

(http://www.pbase.com/kvom/image/164529712/large.jpg)

After a 24 hour wait for the epoxy to cure, I reversed the work and milled off the bottom material on the Bridgeport.  Then in theory an hours in a 250F over should have caused the epoxy top release completely.  Didn't happen and it was a bit of a struggle to free the pieces;  I believe I used a bit too much.  But then it was on to drilling and tapping the holes for joining the halves.  While this job was done 'OK', the holes were still a little off resulting in a slight mismatch which will have to be milled away to make the strap flat on both sides.

(http://www.pbase.com/kvom/image/164529713/large.jpg)

I also left the center hole a bit smaller than the plans, so that it can be milled to target size with both halves connected.  This will be done next time out.

And for a bit of last minute chagrin, behold this part sculpted from a length of 1.5" hex brass bar (meaning a 90% swarf penalty):

(http://www.pbase.com/kvom/image/164529714/large.jpg)

Rather than two pieces soldered together, I decided to make it a one piece project.  Unfortunately when time came for the photo I discovered I'd made it a mirror image of the correct part.  Less than two hours invested in that one, and the redo should go faster.
Title: Re: Roy Ozouf's Coventry
Post by: philjoe5 on November 15, 2016, 02:58:05 PM
Kirk,
Still following your adventures.   :popcorn:

Never heard the expression "90% swarf penalty" but will use it.  I often go the route of cutting over soldering myself.

Cheers,
Phil
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 15, 2016, 09:08:59 PM
A shop day of eccentricity.  First task was to enlarge the bore of the strap to nominal 15/16", which I did with the CNC mill using a 1/4" endmill.

(http://www.pbase.com/kvom/image/164532991/large.jpg)

Then on to the eccentric itself.  My first try was done without doing the eccentric hole first, and I found myself without a good way to hold the piece at the end.  So for try #2 I turned a length of 1.5" bronze rod down to 1.4", parted it off, and used the CNC mill to bore the 5/8" hole.

(http://www.pbase.com/kvom/image/164532992/large.jpg)

I also scribed a line from the center of the piece to aid locating the grub screw and also for helping with eventual timing.  Then back to the lathe to turn the groove to match the strap.

(http://www.pbase.com/kvom/image/164532993/large.jpg)

The collar on which the eccentric mounts was a few thou to large, and needed to be pared down to fit.

(http://www.pbase.com/kvom/image/164532994/large.jpg)

Title: Re: Roy Ozouf's Coventry
Post by: Dave Otto on November 15, 2016, 11:59:18 PM
Hey Kirk
Nice work on the eccentric assembly!


Dave
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 16, 2016, 10:36:50 PM
Thanks for looking in guys.

Two sessions today for some reason.  Must be something in the air.  Morning goal was to thread the valve rod, but for that I needed a die holder for the 13/16 die.  Starting with a piece of 1-1/8" steel rod, I did the following ops on the lathe:

(http://www.pbase.com/kvom/image/164537446/large.jpg)

(http://www.pbase.com/kvom/image/164537447/large.jpg)

(http://www.pbase.com/kvom/image/164537448/large.jpg)

After drilling and tapping two 5-40 retaining screw holes, I was ready to go.  Here's the setup:

(http://www.pbase.com/kvom/image/164537449/large.jpg)

Finger pressure on the screw head was enough to turn the die, but for a larger thread the holder likely needs something better.

(http://www.pbase.com/kvom/image/164537450/large.jpg)

With the valve rod threaded, I needed the valve nut.  Parted off a bit of 1/2" square brass bar, drilled and tapped the hole, machined to size, and fettled a bit to fit the valve.

(http://www.pbase.com/kvom/image/164537452/large.jpg)

Time for lunch.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 16, 2016, 10:46:00 PM
I received two pieces of nice 8x8x1/2" pieces of 6061 from an eBay vendor to be used to make the frames.  I decided to start on these this afternoon.  Too large for the 6" vise's normal jaws, so I mounted the 12" aluminum soft jaws and milled two new ledges to serve as parallels.  By keeping the tool at a constant Z they are perforce level.

(http://www.pbase.com/kvom/image/164537453/large.jpg)

Took a scan across the surface, and the face is flat to within .0025".

(http://www.pbase.com/kvom/image/164537454/large.jpg)

Results of the first ops.  The 4 3/16" holes will serve as registers when boring the pivot and crankshaft bearing holes.  The center  of the round hole is the machining origin for  milling the back side.

(http://www.pbase.com/kvom/image/164537455/large.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: Tennessee Whiskey on November 16, 2016, 10:47:13 PM
Looking great.  What was for lunch? 

Cletus
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 16, 2016, 11:44:09 PM
Mixed Salad. 
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 20, 2016, 03:13:56 AM
Continuing with the frames, Each was turned over, pocketed, and had the profile cut out leaving 4 tabs to keep them attached to the main matrix.

(http://www.pbase.com/kvom/image/164546388/large.jpg)

Then the tabs were cut through with a handheld hacksaw blade and the tabs carefully machined away manually.

(http://www.pbase.com/kvom/image/164546389/large.jpg)

With the two frames aligned using the pins through two of the separator holes and screws through the other two, the pockets for the pivot shaft bearings were cut.

(http://www.pbase.com/kvom/image/164546390/large.jpg)

The two bearing blanks were turned on the lathe to a close sliding fit and loctited to the frames.

(http://www.pbase.com/kvom/image/164546391/large.jpg)

Next the holes for securing the crankshaft bearing cap were drilled and tapped.  I used 5-40 rather than the 4-40 specified by Ouzof.

(http://www.pbase.com/kvom/image/164546392/large.jpg)

For the mounting holes in the feet, I was not sure what size screws will be used, so I just spot drilled them.  These can be drilled from the bottom like this, but counterboring on the top would need as very long end mill.

(http://www.pbase.com/kvom/image/164546393/large.jpg)

(http://)
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 20, 2016, 03:20:21 AM
To bore the holes through the pivot shaft bearing, I plan to use my face plate which I acquired a year ago at Cabin Fever and haven't as yet used.  As seen here, the frames will easily clear the lathe's ways.  I center drilled one bearing on the CNC mill, and am using the live center to hold the two joined frames in the center of the plate.
(http://www.pbase.com/kvom/image/164553655/large.jpg)

I don't have any square nuts needed to fix the frames, and that will be the next project.  Ouzof used a counterweight on his, but given the weight of the faceplate vs. the frames, I suspect that turning like this won't shake the lathe.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 21, 2016, 12:49:50 AM
Made 4 square nuts this morning threaded 3/8-16.  I didn't have any really convenient scrap, so spent way more time than I expected machining down some 1x1.5 to .7" square.  In any case, I was able to mount the joined frames on the faceplate and drill 1/2" starter hole.  No shaking of the lathe at 600 rpm.

(http://www.pbase.com/kvom/image/164559842/large.jpg)

Then some careful boring out to 5/8" using the pivot shaft to test for fit.

(http://www.pbase.com/kvom/image/164559843/large.jpg)

(http://www.pbase.com/kvom/image/164559844/large.jpg)

Title: Re: Roy Ozouf's Coventry
Post by: sshire on November 21, 2016, 05:03:37 PM
My God! You're on a roll. Completed by Cabin Fever?

No 13/16 die holder? No problem. 13/16 5C collet.
Title: Re: Roy Ozouf's Coventry
Post by: Dave Otto on November 21, 2016, 05:54:14 PM
Looking good Kirk!


Dave
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 21, 2016, 07:49:04 PM
My goal is to have it assembled by CF at least.  Whether it will run is another issue.  Today's goal (after lunch) is to machine the bearing caps and crankshaft bearings.  With both pivot shaft and crankshaft in place, I can figure out the correct length for the frame separators.  I tried making some temporary ones, and it was very easy to bind the pivot shaft if they are too short or the screws too tight.

The 5C collet plan would have saved me that work.  Hold the die in the lathe chuck and the drill in the tailstock.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 22, 2016, 03:22:55 AM
Today I cut out two pieces of aluminum from one of the remainders from making a frame, machined them down to the overall size of the bearing caps.  Then I drilled clearance holes for 5-40 mounting screws and counter-bored them.  This allowed mounting to the tops of the frames.

I discovered that the sides of the caps didn't like up sufficiently well to the frame.  I would have done better to make the caps first and spot the holes onto the top of the frame.  That said, by enlarging the clearance holes I could get the caps pretty close.  However, the bearings themselves have flanges that will impinge on both, so I decided to take off a bit on once side to leave the frames proud of the caps.

That done, back to the CNC mill to machine the pocket for the bearings;  both frames together to ensure alignment.

(http://www.pbase.com/kvom/image/164567972/large.jpg)

Afterwards I marked the frames and caps with some punch marks to ensure that they go back together the same way.

Next tasks will be turning the bearings, and then profiling the caps.

The pictures in Ouzof's booklet show oil cups for these bearings, but the drawings don't show a provision for this.  Best guess is a small hole through each bearing that is lined up to match the oil cup and passage in the cap.  The cap clamps down on the bearing to prevent it rotating.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 22, 2016, 10:53:28 PM
Today's shop progress:

1) Made the upper bearings from bronze round, but didn't take any pics.

2) Machined a 3/32 square keyway in one of the crankshaft arms

3) Glued up the crankshaft arms to the cheeks using loctite

4) Test assembly to the frames of the crankshaft, bearings, and flywheel.

(http://www.pbase.com/kvom/image/164570887/large.jpg)

I also finished the cam link by removing the material between the guides.  I realized the the guides need to go into the channels created in the frame.

(http://www.pbase.com/kvom/image/164570886/large.jpg)

Almost ready to assemble the cylinder to the pivot shaft and crankshaft to verify the major motion.   :)
Title: Re: Roy Ozouf's Coventry
Post by: crueby on November 23, 2016, 02:21:45 AM
Looking great! That is going to be a really pretty model.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 25, 2016, 12:43:23 AM
The smaller the parts get, the harder it is for me to figure out how to make them.  These little brackets are a prime example.  To get the 4 needed I started about 9.  Basically I CNC machined the profiles on the end of .5" brass round held in a vertical 5C collet.  Then parted off with some extra on the lathe, and finally trimmed to final thickness on the Bridgeport.

(http://www.pbase.com/kvom/image/164580391/large.jpg)

My sense is that these need to be fairly precise with the holes properly centered. The means I came up with is to hold them in the small vise, using a surface plate to ensure that they're mounted squarely.

(http://www.pbase.com/kvom/image/164580392/large.jpg)

Then I placed the machinists vise in the Bridgeport vise using a stop for repeatability.  I'd initially zeroed the DRO to the corner of the small vise's fixed jaw.  In this way I could find the proper location of the holes (#43 drill).

(http://www.pbase.com/kvom/image/164580393/large.jpg)

A similar reorieintation enabled the second set of holes.

(http://www.pbase.com/kvom/image/164580394/large.jpg)

I then made the guide bars as 1.5" of 3/32 drill rod tapped 2-56 in each end.  A sample assembly:

(http://www.pbase.com/kvom/image/164580395/large.jpg)

The brackets need to screw into the inside of the right hand frame and allow the link to slide freely up and down on the bars.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 26, 2016, 12:08:39 AM
To mount the sliding link one first drills and taps two 2-56 holes in the inside of the right hand frame.  Then the link, it's guide bars, and the four brackets can be attached by screwing the two upper brackets to these holes.  The frame holes for the lower bracket can then be spotted from their brackets once  it's verified that the link can slide smoothly.  These lower holes will wait for another day.

Next I wanted to verify that the tail of the eccentric strap could connect to the upper hole in the sliding link.  I then noticed that I failed to machine the slot in the strap, so that was the next order of business.  With everything back in place, it looks as if everything lines up.  This means that I can loctite the spacer on which the eccentric rides to the crankshaft, as it doesn't need trimming to align the eccentric strap to the link.

(http://www.pbase.com/kvom/image/164584503/large.jpg)

At this point the only parts needed to be finished are the small "fiddly bits" that transfer the vertical motion of the slide to the motion of the valve.  I do need to finish up some drilling and tapping for the cylinder assembly before I can attach it to the crankshaft by means of the piston rod.  But the end is in sight.

One fiddly bit I made a start on is the gland for the steam chest.  Here it is as macined onto the end of some .5" brass round.

(http://www.pbase.com/kvom/image/164584504/large.jpg)

Next time out I want to fit it to the steam chest spigot before parting it off.

Today I ordered some 2-56 hex screws, nuts, and washers from Godshall;  these will be used to replace the temporary socket head screws currently in place.

Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 27, 2016, 01:26:03 AM
Today's adventure was sandwiched around the GA-GA Tech football game.  The pre-game activity started with finishing the valve gland and fitting it to the steam chest.

(http://www.pbase.com/kvom/image/164590869/large.jpg)

Then in order to assemble the 4 layers above the cylinder to the steam chest cover, it's necessary to drill and tap 6 2-56 holes in the cylinder cutout.  Following Ouzof's advice these were spotted from the port block.  Did the first hole, screwed the port block to the cylinder using this hole, then spotted the rest.

(http://www.pbase.com/kvom/image/164590870/large.jpg)

I prefer to tap these small holes by hand on the tapping stand as it's easy to feel the tap pressure and the bottom.  The port block is attached to the cylinder using 4 of the 6 holes.

(http://www.pbase.com/kvom/image/164590871/large.jpg)

Post game was mostly about shortening screws.  Two of the these secure the steam chest to the cylinder through the port block.  Then the steam chest cover's twelve screws secure to the port block with 4 screws and to the steam chest itself with the other 8.  I will wait for my order from Godshall before doing any more screw sizing of 2-56s.

I was then ready to assemble the cylinder to the pivot block and pivot shaft, insert the piston and assemble the crosshead to the crankshaft to see how things line up.  Poser shot:

(http://www.pbase.com/kvom/image/164590872/large.jpg)

The piston slides pretty easily when the crankshaft turns, but bottoms out on the cover, where I have yet to machine off the extra large spigot I left earlier.  I also haven't finished drilling and reaming the top cover and its gland.  This will be done in the next shop session using the cylinder as the fixture.

A little over a month since the first parts produced, so I'm definitely moving faster on this one than is my habit.  I think my month's layoff in October plus wanting to finish it for Cabin Fever has something to do with it.





Title: Re: Roy Ozouf's Coventry
Post by: Dave Otto on November 27, 2016, 02:30:30 AM
Nice progress Kirk!

Dave
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 28, 2016, 12:51:07 AM
Thanks for looking in Dave.

I had only a couple of shop hours today but managed to get the top cylinder cover and gland drilled and reamed.  With them on the cylinder the piston moves up and down very smoothly, so everything seems well centered on the bore.  I discovered I should have drilled the holes for the glands at 45 degrees to the plane of motion, but I don't believe that will cause any problems as the crosshead won't hit the gland screws.

I may have an issue with adjusting the piston travel.  When the piston rod is at BDC it still is barely touching the bottom cover spigot.  I can't adjust this with the crosshead currently as it's screwed all the way down.  At TDC I have about 1/4" of space between the top of the piston and the top of the cylinder.  Not sure what the optimal spacing should be.  Clearly I can face off a bit from the cylinder bottom, but to reduce the top clearance I'll need to add a couple of threads to the piston rod.

(http://www.pbase.com/kvom/image/164596205/large.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: crueby on November 28, 2016, 01:08:41 AM
That is looking wonderful!

Since the cylinder rocks during the stroke, how does the steam get in? Does it come through the bottom pivot rod? Or does it use a flexible hose?
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 28, 2016, 01:38:47 AM
Chris,  the air and steam enter though the left side of the pivot shaft to passages in the pivot block and then through the lower cover.  The exhaust exits via a similar set of passages to the right side.

For testing I'll just use tubing with a press-on adapter, but eventually there should be a globe valve on the side, and the supply pipe will need to be a slide fit with packing to the pivot shaft.

I did some calculation knowing that the length of the swept volume is 2*crank throw + piston length.  Subtract from the length of the cylinder divided by 2 gives the design space at the ends of the stroke, in this case 1/8".  Since my space at the top is > 1/8", either the piston is too short (pretty sure that's not the case) or the cylinder is too high.

The height of the piston can be affected if either the pivot block or the bottom cover are too thick, so that will be checked next time.  I'm pretty sure the pivot block can use a trim anyway.

Given how short a distance the valve moves, I suspect that it's sensitive to the sum of all the movements in the "fiddly bits" that connect the eccentric to the valve rod.  I know Stan had some issues with timing adjustments.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 29, 2016, 12:01:12 AM
After disassembly and measurements, I determined that the cause of my piston travel issue was the piston rod.  I didn't thread the crosshead end far enough so that the crosshead was 1/8" or so too high.  The simplest fix was just to reduce the unthreaded portion with a grooving tool to less than the minor diameter.

In most of my prior builds the plans called for extra threads and a jam nut to adjust the piston travel.  However here the crosshead descends right to the gland.  In fact, I may need to relieve the gland a bit if the packing causes some contact.

Aside from that, today's shop time accomplished the following.

- Marked, drilled, and tapped the bottom mounting holes for the guide bars on the right hand frame.  The link slides pretty smoothly with the bars screwed down on both ends, so I'm quite happy with that delicate job done.

- Made the rocker shaft in two parts, loctited together.  Pics next time

- Ditto on the die block

- Did the drawing and CAM for making the valve rod end, which should be the first task tomorrow.
Title: Re: Roy Ozouf's Coventry
Post by: sshire on November 29, 2016, 02:37:05 PM
It is a fiddly engine. So many different movements it seemed to be a constant "adjust this, which changed something else. Fix that, which changed some other movement." Eventually it all comes together.
Once I had it running, I made the mistake of taking it apart for paint and polish. Reassembly required the Repeat-the- "adjust this" step.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 29, 2016, 06:22:33 PM
Stan,  I remember that at NAMES it wasn't running.  Good to hear that you've gotten it running since then.  Don't bring it to CF, or at least keep it far away from mine.  I will name it "Lady Godiva's Ugly Sister".  I doubt I'll paint it.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 30, 2016, 12:23:36 AM
Took me all day to make the valve rod end because of various idiocies in setups.  My plan was to cut the profile in some round stock and then turn the collet block sideways to cut the slot with a 5/64 endmill.  Third time was a success although the slot came out slightly off center, which I suppose had something to do with the work sticking out so far.  I doubt it will cause any problems since the position of the rocker arm, that fits into the slot) is adjustable.

(http://www.pbase.com/kvom/image/164607937/large.jpg)

Here's the 3 fiddly bits I've worked on the past 2 days:

(http://www.pbase.com/kvom/image/164607938/large.jpg)

That leaves only the remake of the rocker bracket and the the rocker arm to complete of all the valve motion pieces.  I'm waiting for my order of Crystalbond to show up to make finishing the arm easier, but I can cut the profile in advance.  I also need to start on the frame spreaders plus a means to attach an air supply to the pivot shaft before a test can be contemplated.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on November 30, 2016, 11:33:13 PM
Today was remake the rocker bracket day.  If you remember I made it in mirror image previously, so I modified the CAD file and basically followed the same process.  The main difference was clearing the material around the profile, where I tried out a new trochoidal pocket machine operation now available in CamBam.  Here's the pocket:

(http://www.pbase.com/kvom/image/164612312/large.jpg)

Using this operation, the tool is at full depth and uses a series of arc moves to remove material.  My stepover was .025 using a .25" endmill, so 10% radial engagement, 11 IPS feed rate.

The finished part:

(http://www.pbase.com/kvom/image/164612313/large.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 02, 2016, 02:26:01 AM
First job of the day was to start on the rocker.  Drill/ream the 1/8 mounting hole and profile on CNC mill from 1/8" ground sheet material, then move to the manual mill to drill and tap the grub screw.

(http://www.pbase.com/kvom/image/164617258/large.jpg)

I still have to come up with workholding to take the .02" off each side in order to fit the valve rod end.  The assembled fiddly bits of the valve motion are shown interconnected here:

(http://www.pbase.com/kvom/image/164617259/large.jpg)

Next job was to mount the rocker bracket to the top cylinder cover.  For this a 1/16" slot was milled for a tight fit.  The bracket is secured by a 2-56 screw countersunk underneath the cover.

(http://www.pbase.com/kvom/image/164617260/large.jpg)

Note that the gland is now secured with 4 screws and the small washers, and there's no more interference with the crosshead at BDC.

Finally did a first fitup of most of the components.

(http://www.pbase.com/kvom/image/164617261/large.jpg)

Things are quite close together, and without the eccentric and rocker attached  it's hard to see where there may be interference.  One problem that catches the eye with close inspection is that the rocker bracket arm is slightly out of parallel with the top of the cover.  That will need to be corrected before anything else.

The rest of the afternoon I spent shortening screws, mostly for the steam chest cover.
Title: Re: Roy Ozouf's Coventry
Post by: 10KPete on December 02, 2016, 12:35:04 AM
I really like the look of that engine. Excellent work!

 :popcorn:

Pete
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 02, 2016, 04:04:16 AM
That's why I wanted to build one.  Saw it running 2 years back at NAMES.

I think it's particularly well suited for CNC for a fairly fast build as there are relatively few parts.  The parts list shows 71 different items of which 21 consist of screws, nuts, washers, or pins needing no machining.   The remaining 50 are mostly single one-offs.

Other than flywheel, frame material, and some screws, I had all the materials on hand.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 03, 2016, 12:04:19 AM
With the eccentric attached to the sliding link the motion is much different.  I have one place with a tiny rub between the rocker shaft and the screw head on the link, but a little filing can clearance that.  I made an effort to square the bottom of the rocker bracket and the tube, but the tube still is at a slight angle to the top cover.

First task today was to make an air supply attachment.  I found a 3/8-24 grade 8 bolt at the hardware store;  drilled though with a C drill and tapped 1/16-27 NPT into the head.  Screwed into the inlet side of the pivot shaft.  When I attached air supply the good news is that I can feel air coming out the exhaust.  But manually moved the valve rod had no impact on moving the piston rod.

Next I made some temporary frame spreaders from 10-32 threaded rod.  The idea is to be able to adjust the separation to avoid any binding, and then measure to get price lengths on the eventual spreaders.  With these in place I let the lathe turn the crankshaft for about 20 minutes total at 150 RPM.  Loosened it up somewhat but there's still too much friction.

(http://www.pbase.com/kvom/image/164622627/large.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 05, 2016, 12:41:49 AM
The rocker needs to be "thinned" down to fit into the slot in the valve rod end.  My plan to machining this was based on getting some Crystal Bond adhesive, as introduced some time back by Stan Shire.  This adhesive melts at 175F, and also releases when heated with almost no residue.  So I used it to glue the rocker onto a round disk, with a 5-40 screw to center it.  Then the DRO on the lathe guides the cutting, which I tool with several .005" DOC passes.

(http://www.pbase.com/kvom/image/164635030/large.jpg)

The other side was done the same way with piece of .020" shim stock underneath.

Afterwards, it took a bit of filing to make the valve rod end fit, as the rounded ends of the slot were keeping the rocker from entering.  Eventually I ended up with a fit.

(http://www.pbase.com/kvom/image/164635029/large.jpg)

A test fit to the rocker bracket was very tight, needing to relieve the bracket on the side with the rocker.  Installing all piece of the valve train is a nifty puzzle.

Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 06, 2016, 10:27:31 PM
I had to skim off 20 thou from the side of the rocker racket in order to get the rocker and valve rod end to line up, but I now have all the pieces installed so that the valve now moved when I rotate the crank.  That means that I can actually try to time it.   8)  I removed the steam chest cover to observe the valve motion, and it's not far off being centered.  However, I have slack between the eccentric strap and the sliding link that I want to reduce first.  I've been using a 5-40 screw instead of the bolt Ouzof specifies.

With air applied to the input I got good flow into the steam chest, so those tight 1/8" passages don't clog it up as much as I'd feared.

Off to make the bolt mentioned above, plus a gib key to fasten the flywheel.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 07, 2016, 08:27:17 PM
After making the gib key for the flywheel and replacing the screw for the link, I did an initial timing, buttoned it up, and prayed for karma when applying air.  No luck there, and a fair bit of leaky hissing.  I'll start  by installing some packing for the rods before making any gaskets.
Title: Re: Roy Ozouf's Coventry
Post by: crueby on December 07, 2016, 09:50:15 PM
Yup - the usual last minute filing, fussing, fettling, fusing, flattening, and general farting around to get the engine parts all seated just right!
Title: Re: Roy Ozouf's Coventry
Post by: Tennessee Whiskey on December 07, 2016, 10:13:14 PM
Don't forget the cussing and a big plate of Chinese food,  may not help,  but,  it darn sure won't hurt  :lolb:

Cletus
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 07, 2016, 11:54:04 PM
Thumbs up on the Chinese food.   :ThumbsUp:

I stripped it all down and have ordered a sheet of PTFE to make gaskets.  At least there is almost no leakage if any between the pivot shaft and pivot block, so I just need three round gaskets for the cylinder covers and three square ones for the steam chest.  I doubt a flat gasket can seal the port block to the cylinder so some sort of silicone may be needed there.
Title: Re: Roy Ozouf's Coventry
Post by: Tennessee Whiskey on December 08, 2016, 12:50:17 AM
Try the duck sauce first  :lolb: :lolb:.  Build looking great BTW.

CLETUS

Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 08, 2016, 10:26:53 PM
I decided against PTFE gaskets for now since they would add height to the cylinder assembly and potentially screw up other things.  I found a potential liquid gasket:

https://www.permatex.com/products/gasketing/gasket-sealants/permatex-aviation-form-a-gasket-no-3-sealant-liquid/

That seems should go a long way to sealing the air leaks.  I made a test piece with two machined aluminum surfaces, and leakage was minimal.  So I'm using it for the moment.  It's easy to clean off with alcohol, so if it doesn't work well I can regroup.
Title: Re: Roy Ozouf's Coventry
Post by: Tennessee Whiskey on December 08, 2016, 10:54:18 PM
Great stuff.  Back in the day it was a very heavy shellac base,  don't know about now.  Their Copper spray is good also.

Cletus
Title: Re: Roy Ozouf's Coventry
Post by: 10KPete on December 08, 2016, 11:23:14 PM
That Permatex Aviation was specifically designed for sealing aircraft engines without gaskets. I've been using it for 60 years and can't live with out it!!

Pete
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 13, 2016, 04:23:44 PM
After liberal application of the Permatex fluid the leakage is more less.  I also used some PTFE tape to make stuffing for the glands.

I adjusted the valve rod to give approximately (i.e., eyeball precision) even valve travel and the eccentric, but no joy on operation.  A closer examination of the valve showed that when exactly centered over the port openings both ports were cracked open.  In reviewing the plans, the outer edges of the ports are 17/32" apart.  The length of the valve is supposed to be .550".  In reviewing the solidworks model I see that I drew the valve as .500" square, but I can't find any evidence I used the model when making the valve. 

In any case a remake is in order, and as soon as I disassemble the steam chest enough to remove the valve I'll know where the error lies.   :disappointed:

-edit-

Yep, made the valve .5" square.  This afternoon's job is now set.   :-[
Title: Re: Roy Ozouf's Coventry
Post by: Admiral_dk on December 13, 2016, 07:35:16 PM
Well the most important thing is that you have discovered the reason why + we can't be talking about much in wasted material either  ;)

Will be looking forward to a nice video of it running as it should  :popcorn:
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 13, 2016, 08:21:22 PM
CNC carving valve from some .780" round bronze bar.

(http://www.pbase.com/kvom/image/164680257/large.jpg)

Test fit with the valve nut:

(http://www.pbase.com/kvom/image/164680258/large.jpg)

Bottom cavity after trimming to thickness on the manual mill:

(http://www.pbase.com/kvom/image/164680259/large.jpg)

Then the magic happens.

jmcFkxD5KiI
This was running on 50+ pounds of air with leaks, and it hesitates at TDC, so the timing is still off.
Title: Re: Roy Ozouf's Coventry
Post by: 10KPete on December 13, 2016, 08:26:51 PM
Well, it runs! Still stiff and a big leak somewhere but it runs!! :whoohoo: :cartwheel:

Congratulations!!

Pete
Title: Re: Roy Ozouf's Coventry
Post by: vcutajar on December 13, 2016, 09:46:34 PM
Congratulations.  In my book that's a runner.  Now the fine tuning begins.

Vince
Title: Re: Roy Ozouf's Coventry
Post by: Tennessee Whiskey on December 14, 2016, 01:19:58 AM
Well, it runs! Still stiff and a big leak somewhere but it runs!! :whoohoo: :cartwheel:

Congratulations!!

Pete
Hell Pete,  that sounds like me.  Great job Kirk.  You'll get it loosened up.

Cletus
Title: Re: Roy Ozouf's Coventry
Post by: 10KPete on December 13, 2016, 11:24:47 PM
Well, it runs! Still stiff and a big leak somewhere but it runs!! :whoohoo: :cartwheel:

Congratulations!!

Pete
Hell Pete,  that sounds like me.  Great job Kirk.  You'll get it loosened up.

Cletus

 :lolb: :lolb:

Pete
Title: Re: Roy Ozouf's Coventry
Post by: Dave Otto on December 14, 2016, 12:01:37 AM
Congrats on a runner Kirk!


Dave
Title: Re: Roy Ozouf's Coventry
Post by: crueby on December 14, 2016, 12:14:10 AM
That is a very mesmerizing motion - love it!
Title: Re: Roy Ozouf's Coventry
Post by: b.lindsey on December 14, 2016, 03:51:44 AM
Fantastic Kirk...just down to some fine tuning now. Love it!!!

Bill
Title: Re: Roy Ozouf's Coventry
Post by: sshire on December 14, 2016, 03:27:17 PM
Excellent!
I loosened mine up by running it on the lathe for about 20 minutes. I did find that setting the timing was much easier with an acrylic steam chest cover. It was to be temporary and then the brass cover would replace it. However, seeing yet another moving part was too interesting so the clear cover remains in place.
Title: Re: Roy Ozouf's Coventry
Post by: fumopuc on December 14, 2016, 09:38:37 PM
Hi Kirk, congratulations, a nice runner.
Title: Re: Roy Ozouf's Coventry
Post by: Kim on December 15, 2016, 03:43:42 AM
Congratulations on a beautiful runner!  I love all that moving stuff!   :)
Kim
Title: Re: Roy Ozouf's Coventry
Post by: Flyboy Jim on December 15, 2016, 03:47:37 PM
I'm with others............I love the motion. Nice work.

Jim
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 16, 2016, 09:33:10 PM
Went to refine the timing and discovered that there was slack in the valve linkage.  I took the engine apart to discover that the hole in the eccentric strap used for connecting the sliding link had wallowed out into an oval shape.  This essentially meant that there was lost motion in both directions of the eccentric.

Since I had made the eccentric to fit the strap, I thought it worthwhile to try to save the strap itself rather than remake another.  What I came up is to cut off the arm of the strap, drill and tap a hole in the head, and mount a new arm. 

The cross section of the arm is 1/4" square.  Having only a 1/2" square collet and some matching steel bar, I elected to start with these planning to mill the arm to final dimension.  Here's the intermediate steps, using 8-32 threads:

(http://www.pbase.com/kvom/image/164701893/large.jpg)

Screwed together with red thread locker:

(http://www.pbase.com/kvom/image/164701894/large.jpg)

Once the thread locker cures a bit I'll start machining it down to size.
Title: Re: Roy Ozouf's Coventry
Post by: philjoe5 on December 16, 2016, 10:26:02 PM
Good runner and nice to watch.  Congratulations :ThumbsUp:

Cheers,
Phil
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 18, 2016, 12:33:08 AM
After a reassembly with the repaired eccentric strap I had to spend more time and frustration attempting to time it.  Taking a cue from Stan, I made a temporary acrylic steam chest cover (this one really is temporary since I didn't take any care with the overall size.  After more fiddling I got it to run at about 60 RPM (opposite direction this time) but at 80 PSI and leaking air heavily. 

As seen through the "window" the valve looks pretty good, so perhaps I need to try another gasketing material.  I ordered some Loctite 518 and will give that a try when it arrives.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 18, 2016, 01:42:03 AM
After some musings on the valve linkage, I think I have a handle on the proper way to approach timing it.  My thoughts are as follows.

1) The position of the sliding link is solely dependent on the orientation of the eccentric.

2) The cylinder is vertical at TDC and BDC.  That means that if the throw of the eccentric is orthogonal to the crank then the sliding link will be at the same height at both TDC and BDC meaning that the valve will also be at the same position regardless of anything else, and the engine clearly cannot run in that case.  That means in turn that the eccentric throw must be somewhat aligned with the crank.  So the starting point is to align the throw with the crank, with the orientation depending on which direction you want the engine to run.  My early mistakes were to try to adjust the other motions with the eccentric in a randomly installed orientation.

3) Next one can adjust the rocker on its shaft so that it at a minimum doesn't hit the cylinder cover on the downstroke and the setscrew doesn't hit the gland.

4) Now adjust the valve rod in its nut so that the valve has a symmetric range of motion.  To do this I remove the steam chest in order to be able to turn the head of the valve rod.  Then slip the rod end over the rocker and lower the check using its two mounting screws as guides.  Until the eccentric is in final position this is hard to do get exact by eyeball, and later adjustment might be needed.  Since the thread on the valve rod is 3-48, a half turn moves the valve about .01".

5) Now with the crank at TDC adjust the eccentric so that the top edge of the valve is near to opening the top port.  Doing so should slightly reduce the total valve travel so that the same occurs with the bottom edge and port at BDC.  An adjustment of the valve rod might be needed here.  The vertical length of the valve looks critical here as I discovered earlier.

I'll verify whether my theoretical musing match reality in the coming days.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 18, 2016, 08:47:42 PM
Tried the above recipe with mixed success.  I needed a two stage process.  After getting the eccentric  fairly close the range of motion needed to be adjusted once again with the valve rod, and then  fine adjustment of the eccentric.  I also learned that the eccentric adjustment needed to be done with the engine vertical since there remains some slack in the valve linkage at TDC and gravity sucks.

I know we like steam engine models that run at slow RPMs, so here's a really slow one:

XMRqFUIV8ak
Unfortunately that's at 60 psi air pressure.   ::)
Title: Re: Roy Ozouf's Coventry
Post by: Kim on December 18, 2016, 07:13:17 PM
Very nice! And that certainly is really slow!  :popcorn:
Kim
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 19, 2016, 11:23:03 PM
As an experiment, I replaced the 1/8" air supply tube with a 1/4" tube.  The increased volume of air meant that the engine can run as low as 25 psi even with its current leakage.  That's encouraging.   :)
Title: Re: Roy Ozouf's Coventry
Post by: MJM460 on December 20, 2016, 03:06:33 AM

Hi kvom,

A great thread and a beautiful engine.  Beautifully made.
I am sorry that you you are having such a learning exercise in getting it going, but learning from successes is often limited.  I hope you do not mind if I stick my neck out and offer some suggestions.  I hope it will be helpful, and at worst, we will both learn something if some of our more experienced colleagues are kind enough to step in and correct me.

First, you are correct in noting that with the valve dead centre and the cylinders at top or bottom dead centre, the engine will not run.  That is why a double acting single cylinder engine is not self starting at all positions, but the dead spot is less than a single acting single cylinder engine.  It is the correct position to start your timing.  When the engine is running, the flywheel will take it past this point, and as soon as one inlet port starts to open, another power stroke begins.  Let's assume the design and manufacture of the other side of the valve is correct as we can't see it to check.

Second, very few valve linkages give a truly symmetrical valve motion.  Even the crank and conrod do not give a truly sinusoid all motion.  The main thing is that the valve fully uncovers the steam port, it does not matter if it opens further than this.

The simplest valve exactly spans the outside edges of the steam ports so that starting from piston top dead centre, and the valve mid stroke, any rotation in the right direction starts the power stroke.  You have to work against the steam pressure to rotate it the other way, so the engine will tell you which way it wants to run. 

More advanced design has the valve a little wider than this.  That provides lap and lead which we can discuss later.  Once you know which way it wants to spin, you can rotate the eccentric a little to the point of opening in that direction if you want to.

So first piston top or bottom dead centre, eccentric 90 degrees ahead of the crank in the direction you want to run, adjust the valve position to equally cover both ports, and then adjust the other points of your linkage so it does not interfere anywhere through the complete revolution.

With air pressure and a little spin to start it should run. 

So the next point is to follow through on the valve fit and also fix that leakage.

The valve needs to be a nice free sliding fit on the nut, no slack in the valve rod direction and no friction, like a Stirling engine piston!  However it must have a little slack perpendicular to the valve face so the air or steam pressure can move the valve against the port face well enough to seal.  I assume it goes without saying that the valve face and port face must be flat enough to seal when in contact.  Other tight spots will wear in, or you will help them along with some mechanical procedure, but if the valve nut is tight, the valve will not seal against the port face.  This is one place where a little slack never stopped an engine from running.

You did not mention where the leakage is occurring, or did I miss it, but you did mention gaskets.  So I assume not valve blow by, but a leaky joint.  Liquid gaskets are really good when you are on your final assembly, but tend to be difficult if you still have a few strip downs for final tuning.  I use brown paper gaskets, preferably not a highly glazed type, but one that will absorb a bit of oil.  Smear both sides of the gasket with light oil, and assemble tightening bolts evenly.

I am sure that you know most of this stuff, but I hope that I might just have mentioned something critical that you have overlooked.

MJM
Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 20, 2016, 04:39:58 AM
That's a very good summary.  I have build a number of slide valve engines where the valve rod is attached to the eccentric is a fairly rigid manner so that there's no appreciable slack.  The problem with this one is that there are 7 separate parts from the eccentric to valve inclusive, meaning any fitment errors can add up more than we like.

In this engine the valve is 1/32" wider than the ports, so there is that much potential lead.

For the steam chest I introduced an additional part:  a  valve plate made from ground steel sheet primarily to assure a good sliding surface for the valve.  So the chest is a 4 layer sandwich meaning 4 surface mates subject to leaking.  It's all held together with 2-56 screws, so I can't really clamp down too hard.  I can feel air escaping to one side of the chest, and when I press the layers together manually the leak lessens.  Next session I want to take the chest apart, clean the parts, and examine the fits more closely.

Title: Re: Roy Ozouf's Coventry
Post by: kvom on December 20, 2016, 11:06:12 PM
Disassembled and removed all the gasket material by soaking in acetone.  I'll try the loctite gaskets next;  it should arrive in the mail tomorrow or Thursday.
Title: Re: Roy Ozouf's Coventry
Post by: kvom on January 22, 2017, 04:41:47 PM
A few posts were possibly lost in this thread, but I did take the engine to Cabin Fever, where it ran slowly at times on the 40 psi air provided at the display table.  It needed its own spigot on the air pipe as running other engines on the same manifold reduced the available flow too much.

Got it home and disassembled the lot, cleaned the port block and cylinder of old sealant, and came up with a new plan.  I went back to the Permatex aircraft gasket sealant, but figured I needed to press the port block into the cylinder rather than slide it in in order to keep from scraping the sealant off the mating surfaces.  So my technique was as follows.

First, apply to the bottom of the port block fairly thinly, and wipe away any sealant in the supply and exhaust channels.  Leave exposed to air for several minutes as recommended by Permatex.  Next, insert 6 screws into the tapped holes in the cylinder to keep sealant out of the holes.  Here I brushed on a thicker layer than on the port block.  After letting it sit for several minutes, I removed the screws and used a paper towel to soak up any sealant around the holes.  Next I inserted 6 long screws though the pot block and used them to screw into the cylinder.  These screws would then guide the port block as it was pressed into the cylinder.  I did the press using the vise and a piece of 1" brass rod against the port block.  Finally wiped away any sealant that squeezed out.  I removed the 6 long screws and replaced them with the 4 short screws per plan. however I'm pretty sure that they're unnecessary given the tight fit of the block.

After several hours of curing, I screwed the steam chest cover onto the port block attached the air to the pivot shaft; I was happy to not feel any leaks around either the port block or the cylinder covers.  After removing the steam check cover I applied air to the steam port openings in the port block and saw that the piston moved in both directions, confirming that the sealant did not cause any blockage.

After reassembling it was the moment of truth.  Engine started running immediately at 20 PSI, and continued to do so at 10.  In this video it's running at 10, and then I increase it to 20.

DhFdTjbsr9Q
Title: Re: Roy Ozouf's Coventry
Post by: vcutajar on January 22, 2017, 04:52:49 PM
Nice one KVOM.

Vince
Title: Re: Roy Ozouf's Coventry
Post by: sshire on January 22, 2017, 05:05:49 PM
Oooooh! I have the aircraft sealant but was waiting for your results.
I'm on it.
Thanks
Title: Re: Roy Ozouf's Coventry
Post by: b.lindsey on January 22, 2017, 06:16:06 PM
From 60 psi down to 10 psi...obviously the fine tuning was a great success. And the smoothness of seeing it run proves it!!  Well done and a lovely model  :ThumbsUp:

Bill
Title: Re: Roy Ozouf's Coventry
Post by: kvom on February 20, 2017, 11:25:51 PM
I finally got the mini-CNC lathe working "reasonably", so it was time to make the decorative turning on the frame spreaders.

Here's the setup:

(http://www.pbase.com/kvom/image/165002661/large.jpg)

The screw on the chuck end was necessary to allow enough room for the tool.  Finish is not great and there was chatter on this one.  Played around with feeds, and the last one came out the best.  Some work with emery paper and scotchbrite made them look a bit better.

I am not that happy with the inserts on the Shars turning tools.  Finish in brass is just OK, and it terrible on aluminum.  I ground a HSS bit to try on AL, and that worked much better.  Still I prefer inserts, so will likely try the Arthur Ward HSS inserts.

Installed on the engine:

(http://www.pbase.com/kvom/image/165002663/large.jpg)
Title: Re: Roy Ozouf's Coventry
Post by: gary.a.ayres on March 14, 2019, 09:38:33 PM
Very interesting build log and a beautiful, well-made engine.

Way beyond my skill level but I can appreciate anyway...
Title: Re: Roy Ozouf's Coventry
Post by: Johnmcc69 on March 15, 2019, 12:16:51 AM
Nice work Kvom!
 I like the design of the "stays" at the top of the supports, I saw George B. Use the same technique & will copy it on one of the next designs I have in the works.

 Some really nice work you've done,

 John