Author Topic: Another Halo (Read 55205 times)

kvom · « **Reply #100 on:** December 09, 2009, 09:04:03 PM »

That's a good suggestion, Chuck. I'll try that next shop session.

After dinner, I did a test on the one "good" head, as I described above. The seal is not perfect, as there's a very slight leak on both balls. When I activate the plungers, there is a very good air flow, so I think this one might work. I decided to reassemble the engine with just this head, add the pushrods, and see if I can get it to run on one cylinder. In a moment of absentmindedness, I dropped the brass couplers into the cam housing without inserting the balls first.

Then it was a royal PITA to get them out, a process which resulted in one of them flying off the workbench and into oblivion. So unless it shows itself there's at least one part to remake. Guess the lesson is don't work in the shop at the end of the day when you're a bit tired.

cedge · « **Reply #101 on:** December 09, 2009, 11:34:28 PM »

Kirk
Tapping a valve ball into its seat is a common practice in hydraulics. One sharp strike will usually deform the edge of the seat to fit the ball, giving a nice full contact fit and seal. I've fixed many an old valve that way rather than charging a customer for a whole new valve.

Steve

ariz · « **Reply #102 on:** December 10, 2009, 04:38:57 PM »

kvom you're really near the end of this complex build
concentrate yourself, don't work whem tired

and solve the last problems
we want see this beautiful engine running, and surely it'll run

kvom · « **Reply #103 on:** December 10, 2009, 06:47:54 PM »

Thanks to a suggestion to seat the balls in the valve bores (from Cedge and Chuck Foster, thanks guys

) by tapping them in with a drift and a hammer, I think I can get the valves to work. I did the first 4 before it was time for dinner and a rest. The seating isn't absolutely perfect in all of them, but hopefully good enough.

I did find a few things for other builders to watch out for. First, the hole for the inlet barb isn't completely over the inlet valve bore, and the threaded portion of the barb is thicker than the valve cover. So when I tightened the barb I got leaks between the cover and the head. So when seating the balls I also gave the inside surfaces a rub with 360 sandpaper and Scotchbrite.

I was also finding a fair amount of small swarf, including some round "wires" that seem to result from the drilling/reaming process. I made sure to pick these out with tweezers and also to blow air through all the passages. I think the wires are burrs created when drilling/reaming the holes for the plungers. I drilled these holes first and the valve bores last, but perhaps the order should be reversed.

kvom · « **Reply #104 on:** December 12, 2009, 08:51:03 PM »

There are two sizes of balls used. The 3/16" for the valves, and 1/8" balls for the rod lifters. These small balls ride on the cam surfaces; the rod plungers sit on top of these; the pushrods connect the plungers to the rocker arms.

Rather than any assembly drawings, Liney provides a set of transparent sheets with various assemblies drawn to scale. By putting these on top of each other you get an idea of how the parts interact.

Today I spent a couple of hours in the shop. The first order of business was to make a new "flywheel", as the one I made from the end of an axle shaft was too hard to tap for a set screw. I made the one in the photo from a scrap piece of hex 12L14 steel. I drilled the cross hole 1/8", then counterbored with a #7 drill and tapped for the 1/4-20 screw. There are 3 #4 lead shot between the engine shaft and the set screw.

After finishing seating the valves in the last head, I worked a bit on the pushrods. These are simply 1.4" lengths of 1/16" drill rod. I cut them a bit long with a wire cutter, then filed both ends flat and to length. However, my first fitting showed them to be a bit short. So now it seems that either I need to have longer rods, or else the valve plungers need to extend higher from the heads. The latter means that the springs may need to be longer.

From the plans, the cams have a radius difference of only .05" between the open and closed valve positions. This means that the plungers will only move .05" to open the valves. Somy next shop session goal will be to determine where then plungers need to be in the closed position, and adjust to suit.

kvom · « **Reply #105 on:** December 14, 2009, 02:16:55 PM »

Did a couple of small tasks on the engine:

First I remade the crank pin a bit longer so that I could tighten the screw without binding the piston rods. There is really no reason that it can't be longer than the plan's dimension.

I "discovered" that I had failed to machine the pocket in the head that I was test fitting the pushrods on. That meant that the rocker and its arms were .05" too high. Hopefully the next time I put it together things will fit better.

As far as I can tell, I have everything set to try a test run the next time I get into the shop.

kvom · « **Reply #106 on:** December 17, 2009, 04:15:22 PM »

I did the recommended tuning and adjustments as recommended by Liney for the first cylinder, and after some fiddling got a runner. Here's the evidence:

http://www.youtube.com/watch?v=IvhgMdTBUYM

To get enough flywheel weight I clamped my tapping station chuck onto the shaft. On the video, I started it at 40 PSI and gradually reduced the pressure to 20 PSI at which point it stops. With more cylinders and some run-in I expect it will run at a fairly low pressure. For other builders I will reiterate the setup process and some issues I encountered.

My first "concern" was realizing that the pushrod holes in the cam housing are not centered on the cylinder. It seems that my setup on the rotab was a bit off. While the drawings from Liney show the pushrod for the inlet valve connected to the rear hole, I decided to reverse this to make the rods more upright. Since the cams are symmetric, this isn't a problem as long as all cylinders are set the same.

The first adjustment is to set the crank pin/conrods relative to the cams. This is the sole timing adjustment and is needed only for the first cylinder. I slightly loosened the screw that holds the crank to the shaft and then turned the shaft until I felt the inlet cam contact the ball bearing that pushes the inlet rod. Holding the shaft steady, I pushed on the crankpin so that the piston was at TDC (i.e., you want the inlet valve to start to open at TDC). Now it's time to tighten the crank to the shaft; however, the conrod blocks access to the screw head, so I needed to slowly rotate the shaft and crankpin together until I could get to the screw with a small screwdriver. It's for this reason that you need some friction with the screw initially: loose enough to be able to adjust the crank pin but tight enough so that the pin turns with the shaft. Note that I set it up so that the engine turns CCW as seen from the front; to reverse this direction turn the crank pin 180 degrees relative to the cam.

Next, the travel of the rocker arms needs to be adjusted. Connect air at low pressure and turn the shaft until the inlet valve is open. Then adjust the outlet rocker via the SHCS until air is coming out of the exhaust. Next back it off until no air is exhausting. The exhaust pushrod length is now set. Now you can lock the adjustment screw with a 2-56 jam nut. The small issue I had with this is that the screws supplied may not be long enough to protrude out the top of the rocker. For this reason, I plan to use longer screws on the other cylinders and cut off any excess once the jam nuts are in place. A 3/16" nut driver is an excellent tool for tightening these small nuts.

The same procedure is followed for the other pushrod. Turn the crank so that the exhaust is open and adjust the inlet pushrod until air enters the inlet valve; then back off and lock the jam nut.

Bernd · « **Reply #107 on:** December 17, 2009, 04:18:29 PM »

ALL RIGHT Kirk.

Lookin' good.

Bernd

NickG · « **Reply #108 on:** December 19, 2009, 09:36:04 AM »

Wow Kirk, looking very good. How far away are you from a run with all cylinders? It sounds fantastic even with just one!

Nick

kvom · « **Reply #109 on:** December 19, 2009, 01:13:09 PM »

My first 5-cylinder trial was not a success.

First I had to remake the skewed rocker arm, and the blank I had left over from the first batch was too thin. So I spent probably an hour making one from a bit of 1/4" thick aluminum. Note to self: finally buy a set of thin parallels.

Once assembled, the last head seemed pretty leaky on the output valve, but I decided to hook it up anyway. Applied air up to 60 PSI without a runner. Then I noticed that the crank had become loosened from the shaft so that it wasn't turning. By then it was to late to pursue a readjustment.

With all cylinders attached, there is a fair amount of force needed to turn the shaft by hand.

kvom · « **Reply #110 on:** December 30, 2009, 02:12:11 PM »

I decided to make the hose barbs myself using some .25" brass round. Nothing too complicated other than some tedious tool changes on the lathe. Outer barb diameter is 3/16", with the inner diameter 1/8" and the air passage 1/16". I then drilled the mounting holes in the manifold cover, reamed oversize, and fixed the barbs with red loctite. The inlet barb I just cut from a store-bought connector and loctited to the body of the manifold.

With the loctite cured overnight, I assembled to the mount and crankcase.

Then it was time to connect some platic tubing.

I gave the moving parts a dose of oil and hooked up the air. Unfortunately things went less well from there. It turns out that the inside seal between the manifold cover and body isn't airtight, and all the air is exiting there rather than going to the cylinders. So my plan is to make a gasket from oiled kraft paper, as shown on a recent thread.

As I was disassembling the manifold from the engine, I noticed that it wasn't screwed tight. So now it seems that the mounting screws are several threads too long, meaning that the cover was not cinched down tightly to the body. Rather than cut the screws down, I'm still going to make the gasket first.

While everything was assembled, I did a few minutes run-in with the electric drill, and the mechanism doses seem to be turning with less force. I may attach it to the mill spindle and let it turn at low speed for a longer period while the gasket making gets underway.

kvom · « **Reply #111 on:** December 30, 2009, 05:00:31 PM »

We have a runner.

That is all.

Film at 11 (or when my daughter tells me where she hid the camera)

kvom · « **Reply #112 on:** December 30, 2009, 08:50:21 PM »

After the early afternoon trial, I made a paper gasket and oiled it to try to seal the manifold. I still needed to shorten the screws to get everything tight. I also hooked the shaft to the mill and ran it for about 30 minutes at ~300 rpm. At the end, the mechanism was slightly less tight.

I then needed to readjust the timing. The connection of the crank to the shaft is by a single flat-head screw. If the engine is turned the wrong way, the screw will loosen and the crank will not be turning. So it is important that the engine only turn clockwise as viewed from the front.

I also adjusted the timing so that the piston is slightly past TDC when the inlet valve opens.

Once all this was done I reattached the air and started to turn the engine by hand via the attached chuck. I started to feel a bit of a kick, and then it sprang to life. The manifold is still leaky, but not as badly as before so that the cylinders are getting air. I imagine that with a better sealed air supply it should run at lower supply pressure.

Powder Keg · « **Reply #113 on:** December 30, 2009, 09:49:19 PM »

Those sound awesome!!! Great job!!!

sbwhart · « **Reply #114 on:** December 31, 2009, 03:59:16 AM »

Well done great Job

enjoyed the build

Stew

Darren · « **Reply #115 on:** December 31, 2009, 08:41:10 AM »

Simply brilliant

Bernd · « **Reply #116 on:** December 31, 2009, 12:21:53 PM »

Finally a runner all right Kirk.

You deserve a few of these

I'm sure once it's run for a while the engine will take less pressure.

Bernd

NickG · « **Reply #117 on:** December 31, 2009, 12:28:07 PM »

Nice 1 kirk, a brilliant project and brilliant result! you must be chuffed.

Nick

kvom · « **Reply #118 on:** January 01, 2010, 05:58:17 PM »

I spent the afternoon rethinking and then remaking the manifold. Here's the result:

The body, made of 12L14 steel is actually two pieces. The first piece I turned as a disk 2.000" in diameter, .5" thick, and bored out to 1.250". I then used a grooving/cutoff tool to turn a groove into the outside .25" wide and .35" deep to provide the air channel. The second piece I turned 2.25" in diameter and bored .199. I then pressed piece one into the bore of piece two. Then it was off to the rotab to drill the mounting holes and holes for the air barbs.

I mounted it to the engine, and while it's not 100% airtight at the pressed seam, it's a lot better then before.

Unfortunately, the engine then decided not to cooperate by running at any pressure. Seems the crank screw had loosened up again. Arghh!

So next shop session I'll adjust the timing again and tighten the screw. I also want to check all the valve again as I didn't seem to feel proper airflow from every exhaust port.

kvom · « **Reply #119 on:** January 02, 2010, 04:10:43 PM »

I spent a while in the shop this afternoon getting a start on the base.

One lesson learned was that when cutting a deep slot with a small endmill, clearing the swarf as it cuts is a good idea. Cost me a 3/16" carbide endmill to learn this.

Bernd · « **Reply #120 on:** January 02, 2010, 06:02:53 PM »

Kirk,

That engines starting to look real good. A bit of polish after you get it all straightened out and you got a winner.

Bernd

Powder Keg · « **Reply #121 on:** January 08, 2010, 09:43:01 PM »

How's your engine coming? I sure like the way it sounds.

kvom · « **Reply #122 on:** January 09, 2010, 08:50:21 AM »

I did get it "finished", although in the first test run the crank pin came loose. I was running it in the wriong direction. Since it needs partial disassembly to be put back together and retuned to turn in the correct direction, I decided to do the bling polishing while it's apart.

Learning polishing now, with the beam engine as my first target.

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Author Topic: Another Halo (Read 55205 times)