The

"McVickerish" Engine

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18 April 2010:

Not much done in the last few days.  I've had to do some other stuff but now I got a little done.

Some of the drilling and tapping is done on the "Hold Together 'Til It Gets Welded" bolts.  These are 1/4-20 and only serve to hold everything stable 'til the electrical glue has done it's stuff.

 

The whole works won't get welded at the same time.  I'll bolt the assembly together enough so I can line bore the mains.  I only have to take off a few thousandths to make the bearing O.D.'s a slip fit.

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19 April 2010:

Today, some of the welding got done.

Parts bolted together and aligned prior to welding.

The clearance holes were drilled to 9/32" to give clearance for the 1/4" bolts so the parts could be aligned before tightening the bolts.  The cylinder mount will not be welded at this time, until the whole assembly is bolted to the bed plate.

After welding.

After doing my usual serviceable but not beautiful welding job, the frame was allowed to cool off before boring for the mains.

Align boring the mains.

The framework for the main bearings was clamped into the mill and align bored for a press fit of the bearings.

Ready for the next operation.

The cylinder mounting header was also bored for a clearance fit of the cylinder and the two brackets were prepared for drilling and tapping.

Cylinder headers.

The crankshaft end cylinder header was also bored, sized for a light press fit to the cylinder liner  stock.  The cylinder liner will be cut to length and the header pressed so 1/2" of the cylinder liner sticks out.  This will make the end of the liner flush with the crankshaft side of the cylinder mounting header when it's bolted up.

 

I have the engine drawn with a water  jacket made of 4-1/2" schedule 40 pipe.  What is seen in the photo is a piece of left-over 4" pipe that is just long enough to work.  If I decide to use it, I will need to turn the O.D. of the headers to fit the 4" pipe.  It hasn't been decided yet whether to go ahead and get the 4-1/2" pipe and proceed as originally designed.

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21 April 2010:

Worked on the engine frame today and am about finished with it.

Bolted together, aligned and ready for welding.

After grinding the scale off of the base plate and doing some final filing and hammering, the frame is ready for welding.

Another ugly but serviceable welding job.

Here it is welded and ready for the next stage, which will be making the cylinder and piston.  At that point, I can assemble the crankshaft.  It's going to be a bit of a squeeze to set the crankshaft without the mains then work the rod (with piston hung) onto the crankpin.  The main bearings can then be seated in the frame.

Mounted on the re-used Homebrew Hvid skid.

I am re-using the skid I used for the Homebrew Hvid after cleaning all of the clag off of it.  I do think there's nothing dirtier than Hvid slop!

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22 April 2010:

Since I'm cheap (didn't want to spend over 60 bucks for the jacket tubing), I made do with something I had in the pile.

  

The piece of pipe for the jacket and the headers.                                 Banging on the jacket.                 

I had a piece of 4" pipe left over from the Homebrew Hvid.  I needed a piece of 4-1/2" thin wall pipe but, since I could only buy a five foot length to get the six inches I needed, I made do with the 4" pipe.

 

As you can see, first, I  chucked-up the pipe and squared the ends.  Then, I went out in the driveway and made lots of sparks with my new chop saw, slitting it lengthwise.  I dug out a piece of thick wall square tubing and firmly tightened it in the vise and, after slipping the pipe onto the piece of tubing, I beat the heck out of it as shown.  With some patience, I got the pipe expanded so it now has a 5" O.D.  What I'll do later is to weld in a piece to cover the gap.

 

The piece that covers the gap will end-up at the bottom of the jacket and will make a nice flat surface for the ports to the exhaust valve actuating cylinder and the water inlet to be located.

The cylinder liner with the head header in place.

While I had the headers in the lathe cleaning up the O.D.'s, I bored the head-end header out for a press fit with the liner.  I also turned a chamfer on both headers where the jacket will be welded.

 

Then, I cut-off the cylinder liner from the stock and turned the ends true.  I also turned a step that is 1/2" deep and 1/2" long in the head end of the cylinder.  Onto this step, I pressed the head-end header.  It will be welded, the weld being on the inside of the jacket.

 

The header at the other end of the cylinder will be pressed on after the jacket is fabricated and set into place.  The jacket will be welded to the headers then the cylinder will be welded to the rear header.  This weld will be located on the outside (toward the crankshaft).  I have provided a chamfer to weld in so it can be cleaned up for piloting in the frame.  

 

The cylinder will be chucked-up and the head-end header will be faced.  The cylinder will be flipped around and the rear weld will be turned clean.

 

At that point, the holes for cylinder mounting and the head studs will be drilled and tapped.

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23 April 2010:

Some smoke, banging and chip making occured today.

 

Head-end header welded to liner.                                 Jacket with filler piece in place.          

The head-end header was hammered into place (the danged press still isn't here) and welded.  This ugly weld will be hidden inside the jacket.  The filler piece was fitted to the expanded jacket and prepared for welding.

      

Liner, headers and jacket in rough position.

Then, after the jacket filler was welded into place, the head-end header, the crankshaft-end header and the jacket were set in place and hammered into alignment.

 

Cylinder assembly in lathe being turned true.                    Working on the outside of the jacket.        

After welding the whole works together the cylinder unit was chucked in the lathe for turning.  The plug in the crankshaft-end of the cylinder was turned to a light press fit in the bore with a center drilled in it for the live center.  This arrangement kept the assembly stable enough to allow turning with only a minimum of tool chatter.     

The semi-finished cylinder assembly.

By the time I finished slicking up the cylinder assembly, I think I lightened it by at least a quarter.  A side effect of the slicking is that the ugly welds disappeared.

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24 April 2010:

Worked some more on the jug today.

 

Transfer punch made from old drill bit.                                       Using the transfer punch.         

The mounting holes in the jug were located by using a home-made transfer punch.  An old drill bit was chucked up in the lathe and a point was turned on it.  

 

Then, the mounting surface of the cylinder was coated with layout dye.  The cylinder was set into the frame, lined up and rotated so the flat portion of the jacket was at the exact bottom.  The jug was then clamped into place.  The punch was pushed into the holes in the engine frame and lightly tapped to make a mark in the dye.  The jug was removed and the marks were center punched for drilling.

Starting the tap in the rear of the jug.

A while back, I figured that a drill press was a fine way to start taps in big pieces (too big for the tapper).  Chuck the tap in the drill press and, while holding the workpiece steady, run the tap a couple or three turns in.   Then, after all the holes are started, they can be finished by hand and the threads will be square to the surface.

Locating the stud holes in the head end of the header.

Sometimes, you can cheat a bit.  Instead of clamping the jug into the mill and stepping-off the stud holes, I simply used my handy-dandy CAD program to print a 1:1 drawing of the head surface.  Then, after carefully scribing lines horizontal and vertical on the jug, exactly 90 degrees rotated from each other and exactly centered, the trimmed printout is laid on the head surface and the holes are center punched.  Drilling and tapping completes this step.

 

Jug with studs test fitted to engine frame.

Next, I will make the piston.  The piston will be hung on the rod and the assembly hung on the crankshaft and the jug mounted with Dykem in the bore.  Then, I will rotate the crank until the piston is at the bottom of the stroke and mark the location in the cylinder at the top of the piston for the valve actuating port.  I'll then turn the crankshaft until the piston is at the top of the stroke and mark the location in the cylinder of the valve closing port cylinder at the bottom of the piston skirt.  That method will eliminate any slight errors from tolerance build-up.  

 

My guess is that, at the present state of completion, the total tolerance buildup will be less that 1/32".

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27 April 2010:

After a brief haitus, I got the cylinder honed and the piston made.

Boring out the center of the piston.

The piston blank was cut out of the stock then faced and a center was put in the head end.  After reversing the piston, the back end was faced to bring the length to size then it was bored out to remove a lot of metal and make room for the connecting rod.

 

Machining the piston.

The piston was then put in the mill and the wrist pin hole was bored.  Then, it was put back in the lathe and the O.D. was turned to give a 0.010" clearance in the bore.

Turning the ring grooves.

The rings will be 1/8" wide so I ground a grooving tool that is about 0.120 wide.  This allows me some latitude in machining the groove width I want.  I've allowed about 0.002" side clearance for the rings.

Piston, hung on the rod.

My press is -supposed- to be here this week.  I tried driving the wrist pin into the piston and almost got it all the way but the hammer and punch could only get it to about 1/4" of where it should be.

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28 April 2010:

While waiting for the press and the broach set to get here, I stepped a bit ahead.  The crankshaft got cut to length and the keyway milled.

Crankshaft with keyway cut and gib key in place.

Then, it was on to the head.  First, a chunk was cut off of the length of malleable iron I got to make the spark ignition head for the Homebrew Hvid.

   

                             Blank for head.                                             Machining the combustion chamber.

First, I centered the blank in the four jaw chuck and faced one end.  After facing, I drilled a 3/4: hole to the approximate depth of the combustion chamber and followed-up with the boring bar.  This process made the usual cast iron mess of the shop.  You can see the chips a-flyin' in the right-hand photo above.

 

When the combustion chamber was to finished diameter and depth, the head was taken out of the 4-jaw chuck.  The 4-jaw chuck was removed and the 3-jaw chuck substituted.  The inside jaws were put on the chuck and the head was chucked inside the combustion chamber.  The top of the head was faced to finished thickness, then the O.D. of the head was turned, making another large bunch of chips and dust.

 

After that, the head was removed from the lathe and mounted in the mill vise and the flat for the intake or mixer mounting was flycut.  The intake port was drilled and bored to size and depth.

 

Then, the head was rotated and a spacer was used to make it lay square in the vise.  At this point, I decided to deviate a little from the original drawing.  Since I planned to use a piece of 1/2" iron pipe for the exhaust stub, I dropped the idea of using a match plate with the stub welded in and simply made a smaller flat on that side of the head, bored it to 3/4" and tapped it 1/2" NPT.  The thread fit isn't optimum but a perfect seal isn't really needed.

The head as of this afternoon.

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29 April 2010:

I worked on valves, valve guides and the head today.

The valves I chose to use.

The exhaust valve I selected is one I had in a box of small engine junk.  I didn't have a 1" diameter valve to use for the intake so I found what looks like a replacement exhaust valve for a F-M ZC engine.  I haven't got the foggiest idea where I got it but it's gonna be used.

   

     Turning the O.D.                                  Turning the face.                         Cutting down the head.

The Fairbanks-Morse valve was chucked in the lathe and the top surface of the head was faced flat.  Then the O.D. of the valve head was turned to 1.000".  After setting the compound to 45 degrees, the seating face was formed.  Using the center that was already in the valve head, and  after setting the compound back square, the thickness of the head was reduced.

Turning the stem.

Taking light cuts at high speed using a new point on the carbide bit, the diameter of the stem was reduced to 0.247" to fit in the guide that will be reamed to 0.250".   A notch was turned in the intake valve stem and a "C" washer made to act as a keeper.  The other part of the keeper was made to be a slip fit on the valve stem and the keeper.

Both valves ready for lapping.

   

    Milling the ports.                            Boring the intake port.                        Cutting the valve seats.

The head was set in the mill vise and the valve ports were machined.  First, the center of the head was found and the valve positions were drilled to 1/4".  The 1/4" drill was followed by a 0.375" bit, then by a 1/2" end mill.  The valve guide bores were then finished.  

 

Following the 1/2" milling cutter, a 3/4" end mill was plunged down to the surface where the valve guides come through the head.  At this time, the exhaust port was done.

 

The intake port was done the same way with the 3/4" end mill, followed boring to open the port to 0.850".

 

The boring cutter was removed from the boring head and a modified drill bit was substituted.  The bit had one cutting edge ground to 45 degrees and was used with the boring head to cut the seats for the valves.

 

The head was taken out of the vise and clamped to the bed of the mill with the combustion chamber facing down.  The spark plug hole (10mm) was drilled then this drill was followed by a 3/4" end mill down to 0.300" from the combustion chamber.  Then, the boring head was used to bring this diameter up to 0.850" so a deep well socket could be used to install the plug.  The 10mm spark plug tap was fitted into a collet and the mill was used to hand tap for the spark plug.

 

A couple of pieces were cut from a hunk of really dinged-up brass bar stock gotten from the scrap yard and the valve guides were made from them.

 

I've still got to shorten the valve springs and lap the valves to the seats.  Remaining on the head are the four 1/2" stud holes, the mounting bolts for the mixer and whatever I figure out to mount the exhaust rocker arm.

The almost finished head.

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30 April 2010:

A whole day worth of work and nothing much to show.  It took a couple of hours of fiddling to get the valves seated to suit me, then there were the head bolt holes to do.  By the time I got the head gasket done and the works (so far) bolted up, it was quittin' time.

The McVickerish engine so far.

I still have to drill and tap the mixer bolt holes and figure out the rocker arm placement to be done with the head end of the engine.

 

Then, there's the mixer to do and the valve actuation cylinder.  I've been told that my press and broach set are on the road but, I'll believe that one when I see the truck pull up.

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1 May 2010:

I took the better part of the day and made a mixer for the engine.  This, I did without a drawing.  For a hit and miss engine, the mixer is super simple.

Semi-finished mixer.

The body of the mixer is made from a scrapped fuel block for The Homebrew Hvid.  When I was making it, I broke off a small bit deep inside the body of the block and, after spending an inordinate amount of time trying to get the bit out, I binned it.  The broken drill bit was in the cylindrical part of the block and I simply cut that part off and trashed it.  The mixer is shown looking into the inlet.  The intake port in the head is 7/8" so I bored the head end of the mixer to that diameter but drilled the air inlet only to 1/2" so some vacuum would be developed.  I can always bore it out more if it seems to be a bit too "choked".  The little groove at the bottom of the inlet is what's left of one of the holes in the original Hvid fuel block.

 

The brass part of the mixer is a piece of my scrapyard brass rod.  The jet end is drilled with a #65 drill.  This can be increased if necessary.  The needle valve is a 10-32 machine screw that I turned the threads off at the end and made a point for fuel adjustment.  

 

The fitting below the mixer is a 1/8" pipe to 1/8" tubing connector that I modified to also serve as the check valve.   I drilled out the inside of the threaded end of the connector to 0.125" and dropped an 0.118" bearing ball into the bore.  Then I made a plug of another scrap of brass, drilled it with an 0.075" bit and turned it to a press fit in the bore, leaving some vertical space for the ball to move.  Before tapping the plug into the bore, I took the edge of a file and made a slot across the inside end so the ball wouldn't be sucked up against it and seal when drawing fuel.

 

Tomorrow, I'll lay out the holes for the mixer and get it mounted on the head.

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2 May 2010:

Another day of not a lot of noticeable progress.  

Mixer mounted on head.

Due to ongoing computer maintenance (Trying unsuccessfully to get the THIRD replacement new hard drive to work!), I got little done except to drill and tap the head for the mixer and make a knob for the mixture needle.

 

Once the broach and press come in, I can get a bottleneck of work done and resume progress.

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5 May 2010:

Fiddly bits again.

   

Making the ignition sensor mount.

I'm going to use a Hall-Effect transistor sensor for the ignition.  The time of spark will be sensed by mounting a small magnet on the flywheel and the transistor on the movable bracket above.  Moving the bracket will change the timing.  I've arranged it so I can move the spark equally on either side of TDC.  This is because I believe the engine will run equally well in either direction and it will be nice to demonstrate this "feature" of the McVicker design.

 

Speed can easily be controlled (hit and miss) by using the rev-limiter feature of the ignition module I designed a few years ago.   The rev-limiter senses engine speed by timing the pulses coming from the Hall-Effect transistor and turning off the ignition if they are too close together.  Speed can be changed by simply turning a potentiometer.  No old-fashioned, finicky and troublesome governor required!  Science is always working for you at Hoyt-Clagwell & Company!

 

The broach set came-in yesterday.  I wasn't satisfied with the bushing in the set that was to be for doing the keyway in my flywheel because it's not long enough to support the broach all the way through the hub. 

Gib key, broach and tapered broach bushing.

 What I did was to make another bushing that was both long enough and had a taper of 0.013" per inch for my gib key.  The 0.013" per inch is the figure I got by measuring the gib key I've got for the engine.

 

Now, I'm waiting for the truck to arrive with the press so I can broach the keyway, finish pressing the wrist pin into the piston and re-fit the rod bearing.

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6 May 2010:

Good news and bad news today.  I got the press yesterday, put it together this morning and pressed the wrist pin into the piston.  So far, so good except that it took almost 4,000 lbs to get the pin all the way into the piston.  The good news is that I don't think the pin's gonna wander.  Bad news is that, when I tried to fit the piston into the cylinder, it was tight in the skirt area.  I came to find out that pressing the pin in had squashed the piston, making it oval by about 0.010", so it was binding in the cylinder.

 

I fixed it by putting the piston in my press and squashing it back.  The piston's now only about 0.001" out of round and fits fine, so I can say that, since the skirt's bigger perpendicular to the wrist pin, I've got a cam grind on the piston.

 

Then, it was on to installing the crankshaft and hanging the rod.  Without a lot of fiddling with my old CAD system, it would have been hard to figure out if the rod could be hung with the crankshaft fully in position so I slipped the mains on the shaft and cocked the whole works to get the rod hung.  Then, I pressed the mains into position with "C" clamps.  After getting it fitted together, I found that I do, in fact, have room to un-hang the piston from the rod with the crank in position.

Crank with rod hung.

Next, I broached the keyway into the flywheel.  This was another good news, bad news situation.  Using my tapered bushing, I successfully shoved the broach through the first two times but, on the third shove, the broach broke!  I'm not sure if it was a defective broach or I did something wrong.  Anyway, I finished shoving the rest of the broach through and then filed off the burrs in the keyway where the broach broke.

Dang!  And it was a nice new broach.

I slipped the flywheel onto the crankshaft and did a trial fit of the gib key.  It fits so well, I won't have to trim on it at all.

 

After mounting the flywheel and assembling the cylinder to the frame, I found that the piston ended-up 0.050" proud at the top of the stroke.  This was due to having to face both ends of the cylinder.  I should have compensated for this.  The compensation came today in the form of a 0.050" aluminum shim ring placed between the engine frame and the cylinder.

Engine, so far.

If you look closely, you will see where I marked off the position of the timing transistor mount on the face of the flywheel at TDC.  When the wheel's off next time, I'll use a flat ended mill to make a depression in the flywheel for epoxying a rare-earth magnet that will trigger ignition as it passes. 

 

Next, I'll measure the piston positions for the valve actuation ports.  Then, I'll remove the  cylinder, drill and tap the water inlets and outlets and the oiler in the water jacket.  Next will be laying out the valve actuation ports and making the lines that go from the ports in the cylinder, through the water jacket and to the valve actuation block.

 

The lines that communicate between the cylinder ports and the valve actuation block are to be made of thick walled 1/8" steel pipe.  The I.D. of the pipe is right at 0.200" and that will be the port diameters.  I'll tap drill drill partway into the cylinder and tap it for 1/8" NPT at both ports.  The water jacket will be drilled for a close fit to the O.D. of the pipe.  Then, after threading the pipe, I'll check the thread fit then clean everything, butter JB Weld on the threads of the pipe and tighten the heck out of it.

 

The pipe will be cut off with a hacksaw then, using the flycutter in the mill, will be milled flush with the flat on the bottom of the water jacket.  I will drill and tap four 1/4-28 bolt holes in the flat on the jacket for mounting the valve actuation block.  A gasket between the flat and the valve block should seal both water seepage around the O.D. of the 1/8" pipe and seal the pressure going through the pipes.  Since I'll necessarily have to drill the mounting bolt holes through the water jacket, I'll have to use silicone to seal the bolt threads.

 

I haven't completely worked out the valve actuation block yet but do know what the approximate piston diameter should be and will have to come up with a check valve. 

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8 May 2010:

Today was spent catching up on the CAD.  I have the valve actuation worked out as well as layouts for the rocker arm and the rocker stand.

Valve actuation mechanism (Piston midstroke).

My drawing converter leaves a little to be desired in the sharpness department but, because it was free, I can't complain.

 

The valve actuation mechanism is below the cylinder.  There are two ports into the cylinder.  The one to the left is uncovered by the head of the piston when it is at the bottom of the stroke (start of exhaust).  This forces overpressure down the tube, past the check valve and, since the piston skirt is covering the port to the right, the pressure moves the small piston which actuates the exhaust valve.  The check valve retains the pressure until the piston again covers the port.

 

At the top of the stroke (end of exhaust) the piston skirt uncovers the port on the right and releases the pressure in the small cylinder.  The exhaust valve spring forces the little piston back to the right.  To seal the little piston, I'm using a rubber "O" ring.  You will note a small hole drilled into the bottom of the small cylinder.  This #60AWG (0.040") hole is located so the small piston uncovers it when it bottoms out.  This little port is only open for the very short time it takes the piston to move back to the right a little and allows any accumulation of oil or other crud to be expelled (says here in the fine print).

 

Now, the test of my take on the McVicker design will come when I see just how well the exhaust valve operates.  Since I've taken my best guess at critical dimensions, I may be in for some tweaking.

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9 May 2010:

It doesn't look like much, but it took the better part of the day to get the valve ports in and ready for the valve actuator block as well as the water inlet and outlet and the oiler.

   

Cleaning up the flat.                             Preparing port tubes.                          Trimming port tubes.

After clamping the cylinder to the mill table and getting it square, the flat surface was cleaned up.  Then the water inlet and the two ports were carefully stepped off.  The water inlet was a simple 1/4NPT thread.  

 

The ports are a bit more complicated.  First, a #7 drill was used to drill both the jacket and the liner.  Afterwards, a 1/8NPT tap drill was drilled through the jacket and down part way into the cylinder liner.  This made a step from the 1/8NPT to the #7 hole.  A reamer was used to enlarge the hole in the water jacket just enough for clearance for the pipes.  That's why you can see some threads in the holes in the center photo above.

 

The liner was tapped for the pipe thread.  Since the tap bottomed-out before the thread was finished, I took an old tap and ground off some of the end so it would enlarge the thread before bottoming out.  A die was run over one end of the 1/8" pipe just enough to get about five turns before it was really tight.  Before screwing in the pipes, the threads in both the pipe and the liner were washed out with lacquer thinner.  Loktite was used to make sure the threads were sealed and that the pipes wouldn't work out.

 

The pipes were cut off then milled flush with the surface of the flat.

 

This part of the job was finished by drilling and tapping the four 1/4-28 mounting bolt holes for the valve actuator.

The finished bottom of the cylinder.

    Bottom of stroke.                                   Top of stroke.                          Cylinder with oiler base.

I will now take a short vacation from the project so I can catch up on some chores.

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14 May 2010:

Back to work.  Today, I got the little check valve and nut for the valve actuation cylinder done.

 

Check valve and nut.

I made the nut a little taller than the drawing so there would be some more room for the 8-32 screw.  I can always go back and remove the 0.100" extra on the nut end if I need to.

 

Milled to size valve actuator block.

Tomorrow, barring Murphy's Law, the valve actuator block should get done.

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15 May 2010:

The valve actuator is done and on the engine.

Valve actuator assembly (upside down).

As you can see, the check valve nut had to be modified due to interference with two of the 1/4-28 mounting bolts.  The piston is made of brass with an "O" ring for sealing.  When I put the valve actuator block together, I decided to make a 1/32" thick rubber "gasket" (not shown, doesn't seal anything) that goes between the piston cover and the valve actuator block.  The "gasket" has a 1/2" center hole that lines up with the 3/8" pushrod hole in the piston.  The rubber "gasket" will act as a bumper for the piston in case it has a tendency to hammer the outer end of the cylinder.

Engine with everything but the rocker and pushrod.

After mounting the valve actuator block on the cylinder, I put the rings (gapped earlier) on the piston and slipped the cylinder over the piston and bolted it to the frame.  The head was then bolted up and torqued.

 

I gave the engine a spin and found that the valves weren't quite seating properly so off came the head and about an hour of lapping the valves.  Now, it will bounce on compression.

 

Depending on what comes up tomorrow, I may make the rocker arm and stand.  THe rocker stand will mount to the head using the two lower studs.  Since I cut the studs short before I decided to mount the rocker tower that way, I'll have to replace the two lower studs with a couple of the new ones.  

 

After that, all I've got to make is the pushrod and do the ignition trigger magnet and transistor.  At that point, it should be ready to try.

 

Since I haven't made a video of the Homebrew Hvid/Gas conversion engine, I may do that then set the camera up in the shop and roll tape the first time I try to start the engine.  Having decided to do that, the engine will NOT start on the first attempt.

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17 May 2010:

The rocker arm got done today.

Rocker arm and shaft.

When I was picking through the metal bin looking for raw material for the rocker arm, I decided to modify the drawing.  I enlarged the bearing mount to 1 inch so I could use a bronze bushing I had.  The bearing mount was turned to 0.750" for 0.250" of it's length so it could be pressed into the rocker itself, which is 0.250" hot rolled steel.

 

I also simplified the valve end of the rocker arm to just a shape on that end of the rocker instead of the circular pad on the drawing.  The rocker shaft is a piece of 1/2" bar stock that I will press into the rocker arm tower.

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18 May 2010:

Another "good news/bad news" day.

 

Valve mechanism in place.

The good news is that I've got the rocker and pushrod finished and time to test the valve actuation by introducing air into the spark plug hole.  At the bottom of the stroke, the exhaust valve should open.  If I have the piston just past TDC, applying air should make it motor.

 

The bad news is that it didn't and I've figured out why.  I didn't figure on the amount of force  required to overcome the force of air pressure on the head of the valve.  After again studying the McVicker patent, I see how he did it.  His rocker arm has a ratio of approximately 1.7:1 or 1 unit from the pivot of the rocker to the valve and 1.7 units from the pivot to the pushrod.  My rocker arm is 1:1 so it cannot make enough force to crack the valve.

 

To fix this, I've got to see just how much I can lengthen the pushrod end of the pushrod and how much I can enlarge the valve actuator piston.  After all's said and done, I should be able to get away with about 1/2" of extension on the rocker.  This probably won't be enough but I'll test it before reboring the valve actuation cylinder and making a new piston.

 

Who'da thunk it!

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Continued in Page Three

Oh, yes - I AM having  fun!

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