Not for the weak minded.

John Deere 3hp, Episode 8: Finishing Touches

January 21st, 2009 Josh

After rewiewing my last post, I think the ball bearing idea in the breather is not a good one. The breather should have filter material so that any air sucked into the crank case goes through the filter material. The negaive pressure will help prevent oil leaks in a poorly sealed gasket, however I tried to make sure to properly seat all gaskets, so that should not be an issue. 

In this episode, I will be reviewing the carburetor rebuild and first run. 

 

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The carb on this engine is just about as simple as a carb can get. There is no throttle, only a choke plate and a needle valve. The needle valve is essentially directly exposed in the venturi of the carb, and controls the fuel flow. A check valve at the bottom of the fuel pickup tube ensures that the fuel is always in the tube up to the point where it can be sucked into the venturi on the next intake cycle. 

 

The reason for not having a throttle plate is that the speed of the engine is controled by a “hit and miss” style governer. This means that every intake cycle is “wide open” and provides maximum power. When the engine hits the governed speed, it simply holds the exhaust valve open and does not intake another cycle until the speed has dropped back down. This is extremely efficient because the carb can be tuned using the needle valve to give the ideal fuel/air ratio. 

 

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This carberuator was missing the needle valve, so a new one had to be made. It was easy to find the thread size and a bolt that fit. I cut the new bolt down and then used a belt grinder to make a “needle” point. This was not accurate enough, and I had to use a lathe to make a better point. For a handle I used a piece of sheet metal cut to match the shape of the handle on the other 1.5 HP JD that my Grandpa has. I welded that to the end of the bolt and then added a stiff spring to keep it from rotating while the engine is running.

After routing the fuel lines to the finished carb, I still had to plug the bottom of the water jacket, and then finish painting everything. (by this time I had put a preliminary coat of paint on just about every part) Once everything was in order I decided to try to run it.

 

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The first run was a shot in the dark. It was all together, and should run, but I had no easy way to test the carb or spark. So the easiest thing was just put gas in and run it! I put oil in the crank case (I had been using oil during assembly up to this point too) and a little bit of gas in the gas tank. I screwed the needle valve down and opened it 2 turns then shut the choke plate. I started cranking and after a few seconds, it actually fired. I couldn’t believe it! I tweaked the carb a little and cranked it again. After a few tries it fired up and ran for a good 20 seconds or so. I didn’t want to run it without water so I shut it off. 

When my Grandpa came back I showed him. I let it run for about 15 seconds and was about to shut it back down but he told me to keep it running and that it won’t hurt it.

 

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The next thing I knew there was a lout pop and the engine lost compression and coasted to a stop. The engine just blew the head gasket. I was actually able to stick my camera into the water hopper and look up the water passage into the head where the gasket was now protruding. This was a little upsetting because I had spent about $6 on that gasket at a mail-order supplier. Luckily my Grandpa had loads of gasket material. (…and yes that is asbestos gasket material! He has the good stuff saved up!)

After cutting out a new head gasket, I put it on using some high temp RTV instead of just a thin coat of oil. This worked great and the engine ran for hours with no gasket failure after this. I am actually greatful that my Grandpa told me to keep running the engine with no water. The head gasket blew because it wasn’t properly sealed. If I had put water in it, it would have seeped into the cylinder and I could have hydrolocked it and that would have been the end of a year of work.

Sooner or later (probably later) I will have to organize my pictures and get the videos of it running on YouTube. Until then, if you want to see a video just ask! Here is a link to the entire gallery of posted John Deere pictures from the restoration. If you want something explained that is not in my posts, just ask!

John Deere 3hp, Episode 7: Upper Assembly

January 2nd, 2009 Josh

(GASP) I’m actually going to continue this series! A whole year after the engine was completed! Crazy huh? 

Well since I’ve waited such a long time, I am going to have to resort to looking at my pictures and trying to remember what I did. Hopefully I don’t leave out too much good content!

By “Upper Assembly” I am going to refer to the parts that are left to be written about: crank case cover, head and valves, rocker arm, mag, valve rod and ignitor. This will be a loooooong post.

 

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When I removed the head, it had a fair amount of rust and sludge buildup inside the water jacket. Using a hefty piece of wire, I was able to scrape it all out and blow the dust and loose chunks out with a compressor. Other than the water jacket, the other critical part of the head is the valve seats and guides. I checked the guides for play and the valves did not wiggle enough to worry about so I started into grinding them. 

Grinding valves is easy to do on an antiqe engine- no crazy equipment or computer controled cnc machine. The only things needed are a valve grinding tool and a can of grinding compound. If you don’t have a valve grinding tool a screw driver can be used if the valve is slotted, or make your own tool that can be twisted between the palms of your hands as if you were trying to start a fire with sticks. 

IMG_0812.JPG On the right is a picture of the job half complete, on the right is the unground valve and seat, and on the left is a seat and valve after grinding. On the unground seat you can see some pitting and surface flaws that will not make for a great seal. The left side is a mostly completed valve and seat. Most, if not all, of the pits are gone, and for the few pits left there is plenty of valve seat surface around them that no compression will be lost. 

To start the process, a small amount of course grit grinding compound is applied to the landing on the valve. (For clarity, the “landing” is the area of the valve that contacts the valve seat. I’m not quite sure that is the proper term- and I’m too lazy to look it up- so you can comment freely and let me know what the proper term is.) A spring is placed over the valve stem and the valve is inserted into the guide so that the spring keeps the valve off of the seat. Using the valve grinding tool, apply light force to the top of the valve to bring it in contact with the seat while grinding. This force to use could be compared to an average-sized school textbook, 2-3 lbs at most. If using a screwdriver or manually grinding, the valve should rotate about half a turn one way, then slightly more than half a turn the other, a few times a second. The valve should turn back and forth, but rotate slowly overall so that all parts of the valve landing grind all parts of the valve seat. When properly ground it should look like this.

Click here for the valve grinding gallery.

 

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Once the valves were ground and reinstalled in the head, the head bolts and studs were cleaned up with a tap and die, and the head was torqued down on to the block. I didn’t use a torque wrench, but I probably put between 40-60 ft-lbs on them.  With the head installed, the rocker arm could be installed next- but it had to be repaired first. 

The rocker arm is a lever with a yoke on one side that attaches with a pin to the push rod, and the other side has an adjustment screw that depresses the exhaust valve. The intake valve is actuated by the vacuum created by the piston and held closed with a light weight spring. The problem with the rocker arm was that one side of the yoke was broken off and missing completely. In that picture I already ground down the broken portion in order to braze a new piece on. 

 

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I chose a piece of steel bar (no idea what alloy or composition) from my grandpa’s abundant stock piles of old random rusty pieces and cleaned it up. I ground it to be about the same profile as the lower yoke piece and drilled a hole in it. Luckily my grandpa had a second engine that I was able to measure for the proper yoke spacing, and I used a bolt and  stack of washers to hold down the new yoke end in the proper position. 

With the new piece held in place I brazed it with an oxy-acetylene torch. I checked the brazed part for fitment before finishing it with a grinder. I left enough material that I was able to grind away to leave a small boss on the top to mimic the boss on the bottom of the yoke. After finishing and painting it, it is almost indiscernible from the original. Only a trained eye could tell that it was repaired and not a completely cast piece. I don’t have a close up picture, you’ll just have to take my word for it! 

After finishing the rocker arm, I was able to install the ignitor, ignitor trip assembly, and push rod. The ignitor was luckily functioning quite well, and didn’t require disassembly or repair. I say this is lucky, because this is not a part that I would have been able to easily repair. I cleaned it in mineral spirits and painted and installed it. The ignitor is an interesting piece of equipment in that it was used to create the spark inside the head prior to the invention of spark plugs. It functions by having a set of points inside the head that are sprung closed. The ignitor trip assembly preloads a second rotating mechanism on the outside of the head, and at a timed point, releases this rotating mechanism. It snaps to rest, impacting a rod connected through the head to the points causing them to open for a split second. This is timed to coincide with the magneto’s ignition point. The magneto is a small permanent magnet generator with a hefty coil assembly. During ignition, the magneto is “generating” the maximum current through the points in the ignitor. By snapping these points open the magnetic flux in the coil collapses, causing a voltage increase within the coil. This increase is on the order of tens of thousands of volts, easily sparking across the points of the ignitor and igniting the compressed gas mixture in the head. This is a very simple design because there is only a single coil, not a primary/secondary coil as in today’s ignition systems. If you are interested in different ignition methods, I highly recommend researching antique engines. There are quite a number of ingenious designs prior to battery powered ignition systems. Most of these systems (spark plug based) are still used in small engines powering lawn mowers, weed-whackers, and other small battery-less engines. 

The magneto I left to more capable hands. I removed it in the beginning and sent it to a guy that my grandpa knows who overhauled it for $100. Well worth the money for a properly functioning mag. I installed it with the timing marks on the cam gears and it functioned beautifully. 

The final piece of the “upper assembly” is the crank case cover. There is not much to it, other than a rather intricate gasket and a breather. The breather was nothing more than the bottom half of a grease cup. My grandpa had a new grease cup top that I was able to use. I drilled holes around the side of the top without drilling into the thread. I then put brass screen on the inside to keep large particles out of the breather. I also put a large ball bearing in the bottom of the cup to act as a one-way valve. This ensures that the crank case is negatively pressurized while the engine is running. Without this valve the engine would alternate blowing and sucking outside air in through the breather. This is more effecient, however there is a large chance that dirt and debries can make it past the breather filter and into the crank case. By negatively pressurizing the crank case, oil is also less likely to seep out of any gaskets. The downside is that there is a chance that a loose piece of gasket gets sucked loose into the crank case. I’ll have to monitor it over time and see if my fears are warranted. I can easily remove the ball bearing and pack the breather with filter material. 

That’s it for this episode. Last up is the carborator rebuild and first run! Hopefully it won’t take me another year to write those!

John Deere 3hp, Episode 6: Lower assembly

January 16th, 2008 Josh

For this article, I’m going to call all the parts inside the crank case and below the “lower assembly.”

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This was an easy, but at the same time frustrating, part of the project. The frustrating part was using the wrong gasket sealer. I used some black tar-based sealer called “Form-a-gasket” that my grandpa likes to use. The problem that I had was this stuff seemed to liquefy and run right out the sides when I bolted the parts together. This wasn’t too bad since it meant that the parts had a good fit and didn’t need much of the sealant, but there were two places that kept leaking. The parts in this assembly are the main crankcase, then a gasket, then the oil pan, then another gasket, then the gas tank, then a support casting that bolts the engine to the runners. These 6 parts formed a sandwich, and the problem is that the oil pan must seal to 2 passages on the bottom of the crank case, but there is no support on the other side of the oil pan to press the metal against the gasket. So every time I bolted the whole assembly together, there was a huge leak.

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My solution was to weld 2 plates on to the bottom of the oil pan, so that the pan will resist deflection. These plates were also bowed slightly upward so that they must be compressed by the gasket and passages above. This worked, and while pressurizing the gas tank to check for leaks, there was a funny sound followed by a rush of air and the gas tank lost pressure. I thought for a few seconds that the tank gasket had failed, however, I noticed that I could feel the air rushing out next to the gas filler neck, where there was no gasket. There I found a vent hole that I had never seen before, and may have been the cause of the gas tank not holding pressure the whole time! Either way, all the gaskets held and the lower assembly was bolted to a set of wooden runners.

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The other parts of the lower assembly (shown from the bottom of the engine before putting the gas tank and runners on) are the governor and cam gear. These were installed and tested for bearing play (using the old-fashioned method of wiggling with the hand) and appeared to be in excellent condition.
Once all the parts in the lower assembly were together, the biggest hassle was cleaning the black tar form-a-gasket left on the side of the engine. It was resistant to gas, solvents, water… The only solvent I found that was effective enough to remove it was acetone, and even that took liberal amounts. Once the lower assembly was complete, the piston and rod were installed and the parts for the governor and cam were installed in the box on the side of the crank case.
The only thing left is the upper assembly and final detail!

John Deere 3hp, Episode 5: Epic Welding

December 5th, 2007 Josh

As I got to the point where I decided to start reassembling the engine, I discovered the worst broken part of the entire build. The left side flywheel was bent and 3 of the spokes were cracked all the way through.

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This repair took about 6 months to complete, and involved about 9 different attempts to weld the spokes back together. The reason it took so long is simply the time involved in welding the cast iron. The best way to weld cast iron is to heat the piece to within a few hundred degrees of the melting point of the braze, then braze the piece with any method that is most comfortable (Stick, MIG, torch), then put the piece back in the heat and slowly cool it back down. Unfortunately, I had no way to do that with the size of the flywheels. So I had to resort to the slow method: quick weld, followed by lots of peening, and waiting for the piece to cool back down to touchable temperature. This process took about 3-4 separate visits to the shop (at 1-2 visits/week) for just one complete weld on the 3 spokes. The process also proved very touchy. Letting the piece get too hot, welding too cold, not peening enough, or getting too much flux inclusion can all lead to a crack in the finished product.

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After about 6 months of attempting to weld the spokes, I successfully welded 2 of them, and then finally the last one. I used bondo-glass to fill in the aesthetic details. I used a rotary file to contour the bondo’d areas and cut or sanded the flat areas. The holes had to be drilled out as well, and for that job I started with a small hand drill for the first pilot holes, then moved up to a 1/2″ chuck drill, but the chuck wouldn’t keep a good grip on the bit, so I had to break out Thor.

IMG_p980.JPGThor is a beast of a 1/2″ drill, it has an on/off trigger, full cast aluminum case, handle, and trigger. This drill is made by a company called Industrial Pneumatics Inc, is about 60+ years old and is the toughest drill I have ever used. It powered through the tough welding that intruded into the holes without breaking a sweat.

After the holes were drilled out I put a few coats of paint on and it was finished. It’s pretty amazing how long it took to do, but how short it took to write about. Check out galleries one, two, and three for all the flywheel repair pictures.

John Deere 3hp, Episode 4: Broken parts

October 8th, 2007 Josh

During disassembly, there were several parts that were broken because of poor handling on my part. Several more parts were already broken, and several parts missing completely. Except for the Flywheel, which I will elaborate on further in another article, the most disturbing part was the cam shaft. After several weeks of soaking, it still seemed hard fast.

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So I put a little leverage on it, and of course it snapped right off. I dropped the nut with the broken end of the shaft into a small can with blaster and left it for several weeks.

One night after an unusually depressing day, I felt like taking some frustration out by freeing that nut. This was probably not a very good idea since I had the notion to get it free no matter what it took. I pulled it out of the blaster, put it in the vise, and pulled out the torch to prepare to use heat to get it free. Before I fired up the torch I thought I would try to get it out as it stood, so I stuck the easy-out into the hole (nicely provided already for the governor actuator shaft) And put a nice 12″ adjustable wrench on it. It started to turn with almost no effort! BUT it was turning the wrong way! If I had studied this just a little bit closer, I could have noticed that it was a left hand thread, not a right hand thread, and prevented the next bit of headaches.

So after freeing the nut from the shaft, the next task was to get the shaft put back together. My grandpa suggested using silver solder, so that was what I tried.

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The first attempt to solder this together seemed like a good idea, but failed terribly. We cut a ring of silver solder sheet the same size as the shaft and put a long bolt through the center of the long end of the shaft, slipped the solder ring over the bolt then put the broken end of the shaft over that- sort of like a sandwich. A spring was used to apply pressure to the broken end as the solder melted. I used the torch to heat the whole assembly to the melting point of the silver solder, but after the solder melted and I removed the heat, the broken piece just fell right off again. Somehow my grandpa was able to repair it the next day while I was at work. I believe that he heated the pieces first separately, applied solder to them (tinning them) then put them together with heat. It worked beautifully. After cleaning the threads, it is as good as new.