Another Radial - this time 18 Cylinders
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Your control panel is very cool. I never knew miniaturized instruments like this even existed. Just curious from your trials & tribulations, what industry or hobby pursuit do they serve? ie. gutted from another application or kind of ground level developed with modern electronics?
Peter,
I assume the tach was an actual cockpit instrument from a plane. There was only one being offered for sale by the seller, but I seem to remember he was offering some other aircraft gauges as well. The 6 volt panel meter, on the other hand, was being offered by its seller in quantites up to ten pieces. These may have been manufacturer's surplus from some piece of cheap equipment - maybe a battery charger. The tach was well made, but the 6 volt meter was very cheaply made. In fact, the clear front cover was secured to the main body of the movement with a piece of tape. One of the reasons I machined such an elaborate pocket for it in the rear of the panel was to provide an alternate way of holding it together. - Terry
I assume the tach was an actual cockpit instrument from a plane. There was only one being offered for sale by the seller, but I seem to remember he was offering some other aircraft gauges as well. The 6 volt panel meter, on the other hand, was being offered by its seller in quantites up to ten pieces. These may have been manufacturer's surplus from some piece of cheap equipment - maybe a battery charger. The tach was well made, but the 6 volt meter was very cheaply made. In fact, the clear front cover was secured to the main body of the movement with a piece of tape. One of the reasons I machined such an elaborate pocket for it in the rear of the panel was to provide an alternate way of holding it together. - Terry
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Ah, sorry I misunderstood. I thought you meant miniaturized units, maybe like what car guys are adapting for trendy functionality or whatever. Classic instrumentation seems to be all the rage, even wristwatches.
http://www.egauges.com/Gauges-Senders-and-Accessories-s/13.htm
I made a functional rectangular oil tank for my H-9, but I was never satisfied with its 'blocky' appearance. For this engine, I decided on a more conventional looking cylindrical tank. My initial plan was to construct it entirely from aluminum and thread/Loctite the various pieces together, but I changed to brass at the last minute after finding a short length of 2-1/2" brass tube among my scrap.
I squared up the ends of the tube and then turned a pair of brass end caps for it. A shoulder was turned on each end cap with a .002" interference fit to the main tube so they could pressed/Loctited into the ends into the main tube.
A common way of mounting a cylindrical tank to a flat surface is with metal bands, but for a different appearance I decided to solder a pair of mounting feet to the rear of the tank. These feet will serve as brackets to secure the tank to the engine firewall. In order to limit heat-induced distortion of the thin wall tube created by the high heat of silver-soldering, a pair of stainless end caps were temporarily pressed into both ends of the tube. I didn't use my finished end caps for this since I needed center holes for a puller to remove them after soldering. The mounting feet were also bolted to a temporary steel plate to maintain the whole assembly in alignment during soldering.
Midway through the bracket soldering I had second thoughts about using silver solder instead of soft solder. I was surprised at the difficulty I had in getting sufficient heat to all the mass involved in the joints, and I eventually had to switch from the map gas torch I started with to a small acetylene rosebud. I used thin solder ribbon between the brackets and tank in order to keep the solder lines neat, and this made it difficult to tell when the joint had been sufficiently heated. It seems that every solder job I attempt comes with a new learning experience.
Two threaded bungs were turned and attached to the outer perimeter of the main tube with high temperature soft solder. One was soldered to the top of the tank for a filler cap, and the other to the bottom of the tank for a drain plug. The filler cap was drilled with a .070" diameter hole since the oil tank also acts as an oil separator in the crankcase ventilation system, and the filler cap is the ventilator. The whole assembly was dipped in a pickling bath of 10% sulphuric acid for about 10 minutes to remove the flux residue before neutralizing the assembly in a baking soda solution.
The end caps were drilled and tapped for an oil control valve on the output side of the tank as well as a sight gauge and flare fitting for the engine oil return line on the tank's input side. Drilling these relatively large NPT holes in the thick brass end caps proved to be the biggest challenge of the tank's construction. The finish-machined circular pieces were difficult to hold down on the drill press table; and when the material grabbed the drill as it exited the backside, a twisting torque was generated that overcame my best attempts at keeping the caps clamped down. I finally had to limit the topside drilling depth until the tip of the drill barely pierced the backside, and then I used a manual tapered reamer to finish the hole from the rear.
The sight gauge was simply constructed from an 1/8" brass street elbow, a short length of acrylic tubing, and an 1/8" brass pipe cap. I used Goop plumbing adhesive to seal the tube to both the elbow and end cap. The adhesive and the acrylic are compatible with engine oil, but I'm pretty sure they would not be suitable for use with fuel.
It's no secret that oil flow to these dry sump radials needs to be carefully controlled. A drip feeder, similar to those used on medical IV lines is almost a requirement on the output of the oil tank. I began by looking through my collection of brass fittings, and without a plan I started modifying them and turning the additional parts I needed to create an oil control valve. I don't like working this way as it's not satisfying and seldom turns out well, but I just couldn't get myself moving in the direction to create a proper design. It might have been the holidays, but when I looked through my notes on my H-9 build, I remembered I had likely done the same thing since I hadn't made a single drawing related to the oil control on that engine. Maybe I just don't like thinking about oil control valves. I had incorporated a cool looking sight window into the H-9 drip feeder, but when using transparent oil lines it adds little value in exchange for a lot of complication. So, I left it out of this feeder. I filled the tank with oil and allowed it to sit for a few days to check for leaks.
Unfortunately, the lathe work on the tank also uncovered the depressing fact that my earlier replacement of the spindle control relays on the Mach breakout board hadn't solved my intermittent spindle problem after all. Since I can't easily monitor signals on the breakout board because of its convoluted packaging, I'm going to take out some time to create a bus monitor for insertion in the DB-9 cable between the spindle motor and the Mach interface to see what signals may be getting lost when the spindle fails to start up.
The last component required for the firewall is the throttle control. But, I think it would be wise to first create the firewall and start laying out the components I've already made before starting this last one. - Terry
I squared up the ends of the tube and then turned a pair of brass end caps for it. A shoulder was turned on each end cap with a .002" interference fit to the main tube so they could pressed/Loctited into the ends into the main tube.
A common way of mounting a cylindrical tank to a flat surface is with metal bands, but for a different appearance I decided to solder a pair of mounting feet to the rear of the tank. These feet will serve as brackets to secure the tank to the engine firewall. In order to limit heat-induced distortion of the thin wall tube created by the high heat of silver-soldering, a pair of stainless end caps were temporarily pressed into both ends of the tube. I didn't use my finished end caps for this since I needed center holes for a puller to remove them after soldering. The mounting feet were also bolted to a temporary steel plate to maintain the whole assembly in alignment during soldering.
Midway through the bracket soldering I had second thoughts about using silver solder instead of soft solder. I was surprised at the difficulty I had in getting sufficient heat to all the mass involved in the joints, and I eventually had to switch from the map gas torch I started with to a small acetylene rosebud. I used thin solder ribbon between the brackets and tank in order to keep the solder lines neat, and this made it difficult to tell when the joint had been sufficiently heated. It seems that every solder job I attempt comes with a new learning experience.
Two threaded bungs were turned and attached to the outer perimeter of the main tube with high temperature soft solder. One was soldered to the top of the tank for a filler cap, and the other to the bottom of the tank for a drain plug. The filler cap was drilled with a .070" diameter hole since the oil tank also acts as an oil separator in the crankcase ventilation system, and the filler cap is the ventilator. The whole assembly was dipped in a pickling bath of 10% sulphuric acid for about 10 minutes to remove the flux residue before neutralizing the assembly in a baking soda solution.
The end caps were drilled and tapped for an oil control valve on the output side of the tank as well as a sight gauge and flare fitting for the engine oil return line on the tank's input side. Drilling these relatively large NPT holes in the thick brass end caps proved to be the biggest challenge of the tank's construction. The finish-machined circular pieces were difficult to hold down on the drill press table; and when the material grabbed the drill as it exited the backside, a twisting torque was generated that overcame my best attempts at keeping the caps clamped down. I finally had to limit the topside drilling depth until the tip of the drill barely pierced the backside, and then I used a manual tapered reamer to finish the hole from the rear.
The sight gauge was simply constructed from an 1/8" brass street elbow, a short length of acrylic tubing, and an 1/8" brass pipe cap. I used Goop plumbing adhesive to seal the tube to both the elbow and end cap. The adhesive and the acrylic are compatible with engine oil, but I'm pretty sure they would not be suitable for use with fuel.
It's no secret that oil flow to these dry sump radials needs to be carefully controlled. A drip feeder, similar to those used on medical IV lines is almost a requirement on the output of the oil tank. I began by looking through my collection of brass fittings, and without a plan I started modifying them and turning the additional parts I needed to create an oil control valve. I don't like working this way as it's not satisfying and seldom turns out well, but I just couldn't get myself moving in the direction to create a proper design. It might have been the holidays, but when I looked through my notes on my H-9 build, I remembered I had likely done the same thing since I hadn't made a single drawing related to the oil control on that engine. Maybe I just don't like thinking about oil control valves. I had incorporated a cool looking sight window into the H-9 drip feeder, but when using transparent oil lines it adds little value in exchange for a lot of complication. So, I left it out of this feeder. I filled the tank with oil and allowed it to sit for a few days to check for leaks.
Unfortunately, the lathe work on the tank also uncovered the depressing fact that my earlier replacement of the spindle control relays on the Mach breakout board hadn't solved my intermittent spindle problem after all. Since I can't easily monitor signals on the breakout board because of its convoluted packaging, I'm going to take out some time to create a bus monitor for insertion in the DB-9 cable between the spindle motor and the Mach interface to see what signals may be getting lost when the spindle fails to start up.
The last component required for the firewall is the throttle control. But, I think it would be wise to first create the firewall and start laying out the components I've already made before starting this last one. - Terry
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Another simply beautiful and instructive piece of on-the-fly engineering.
Thanks for posting the entire process so we can all be inspired.
Sorry about your controller problem. I know you'll get it solved.
--ShopShoe
Thanks for posting the entire process so we can all be inspired.
Sorry about your controller problem. I know you'll get it solved.
--ShopShoe
Never considered using the lathe chuck to hold parts in the band saw. Great posts! Thank you for taking the time to make them.
I took some time off from my radial engine project to build a breakout box for monitoring the control signals in the DB-9 cable between the spindle motor and the Mach breakout board in my CNC lathe. Since my spindle start-up problem is intermittent and recently infrequent, I thought it best to build something robust enough to be left in place indefinitely. My biggest concern with adding something like this is dealing with potential grounding issues. The motor controller circuit 'ground' is at a different potential than the grounds of either the breakout board or my computer's parallel port. A failure inside this new box that mixes these returns could create some spectacular and expensive damage. Another ground related issue is electrical noise. I spent a lot of time carefully routing and shielding the numerous cables in my shop to get my mill and lathe to run error-free from a single computer with much longer than recommended USB and DB-25 control cables all within a pretty nasty electrical noise environment. At that time, when I had access to the proper test equipment, I discovered the spindle VFD noise was one of the culprits affecting the reliability of my set-up. So, it's possible my break-out box could introduce a new problem with similar symptoms to the one I'm trying to solve. In addition, since the lathe work on this engine is pretty much completed, it could take a while to realize any change I may have made to the noise environment or to capture the spindle acting up.
But, getting back to my radial build, progress has slipped a bit due to holiday stuff. I started a SolidWorks layout of the engine's firewall since I already had or could easily complete models for the various components that will be mounted on it. With CAD I'm able to shuffle virtual blocks around for a workable layout before cutting or drilling any holes in some expensive pieces of metal.
My highest priority for the layout is the placement of the ignition modules. They need to be located so their susceptible trigger cables are routed directly to their distributors and away from the high voltage tower wiring. The tach needs to be located close to the particular ignition module that will drive it since the driving signal is also low-level and noise susceptible.
A second priority involves the height of the oil tank. The tank's drip feed outlet wants to be at or about the same level as the engine's oil input tube for best operation. The tank's return fitting, on the other hand, must be higher than the engine's oil return line.
Due to its design, the placement of the components in the recirculating fuel system is less critical. The only requirement is that the fuel tank must be below the carb bowl in order for the gravity return line to work as needed.
Almost immediately, though, I realized I should have been working on the layout simultaneously with the design of its components. Although I had designed each of them with a minimum volume for a reasonable degree of maintainability, it quickly became apparent that I should have been more concerned with packaging envelopes and less concerned with packaging volumes. For example, my arbitrarily selected locations for the oil tank drain plug and the fuel tank inlet/outlet tubes significantly affected my choices for placement of the electrical components that don't like getting wet. As a result, because issues like this weren't were considered early enough, I had to settle for a larger firewall than I really wanted with excessive space between its components.
In order to reduce the width of the firewall size somewhat I ended up designing a new fuel tube assembly for the fuel tank. The issue was not only an interference problem with the electrical control panel but also my initial selection of the fuel tank return tube diameter. With the small volume carb bowl I'm using, it's important that the return line be as free-flowing as possible in order for the stand pipe return inside the bowl to regulate the fuel level over a reasonably wide range of fuel pump pressures. I used a 3/16" (o.d.) return line in my H-9, but I had reduced it to 1/8" in the T-18 tank for compatibility with a nice looking anodized cap that came with the polyethylene tank that I purchased. When I tested the operation of the fuel loop mocked up with the firewall's trial placement of the fuel components, I found the back pressure in the 1/8" return tube was too high. The fuel pump voltage, even with a .022" restrictor in the high pressure side had to be carefully adjusted to prevent pressurizing the bowl and squirting fuel out its vent. The solution was to increase the return tube to 3/16", but the minimum 90 degree bend radius for this diameter tube exiting the fuel tank created placement issues with the control panel. So, I made a new fuel tank tube inlet with machined 90 degree exits. The six tubes making up the new assembly were soft soldered into a brass cap using high temperature solder for the inner three, and low temperature solder for the outer three. The long internal tube with the bend is the tank's air vent while the tube with the flexible 'clunk' is the fuel pickup. The large diameter tube is, of course, the new return. The cap is sealed to the tank by a sandwiched rubber stopper drawn up between the cap and a metal backing disk using a long SHCS.
Eventually, after arriving at a compromise placement that was more functional than esthetic, I was able to finalize the dimensions of the two large aluminum plates that will make up the engine's display/running platform. My scrap pile had final approval over the design with the bottom plate ending up 1/2" thick. Both plates turned out to be larger than the working envelope of my mill, and so a lot of time was spent re-indexing both workpieces so I could machine the features I wanted. I was careful to not waste any of the 1/2" plate material by recycling the drops from the machined baseplate contour into support brackets for the firewall.
With the engine weighing over 40 pounds, I'm estimating a total assembly weight at around 65 pounds. Therefore, in addition to making it a robust platform, I also added a provision for carrying it without damaging months of work.
I assembled the basic platform which pretty much locked in my current component placement before the throttle and advance linkages were designed. Now that I have a concrete platform to work with, I'll next focus on them. Hopefully I haven't painted myself into some corner, and I can have some fun with their design even though my CAD tool doesn't handle rod ends. - Terry
But, getting back to my radial build, progress has slipped a bit due to holiday stuff. I started a SolidWorks layout of the engine's firewall since I already had or could easily complete models for the various components that will be mounted on it. With CAD I'm able to shuffle virtual blocks around for a workable layout before cutting or drilling any holes in some expensive pieces of metal.
My highest priority for the layout is the placement of the ignition modules. They need to be located so their susceptible trigger cables are routed directly to their distributors and away from the high voltage tower wiring. The tach needs to be located close to the particular ignition module that will drive it since the driving signal is also low-level and noise susceptible.
A second priority involves the height of the oil tank. The tank's drip feed outlet wants to be at or about the same level as the engine's oil input tube for best operation. The tank's return fitting, on the other hand, must be higher than the engine's oil return line.
Due to its design, the placement of the components in the recirculating fuel system is less critical. The only requirement is that the fuel tank must be below the carb bowl in order for the gravity return line to work as needed.
Almost immediately, though, I realized I should have been working on the layout simultaneously with the design of its components. Although I had designed each of them with a minimum volume for a reasonable degree of maintainability, it quickly became apparent that I should have been more concerned with packaging envelopes and less concerned with packaging volumes. For example, my arbitrarily selected locations for the oil tank drain plug and the fuel tank inlet/outlet tubes significantly affected my choices for placement of the electrical components that don't like getting wet. As a result, because issues like this weren't were considered early enough, I had to settle for a larger firewall than I really wanted with excessive space between its components.
In order to reduce the width of the firewall size somewhat I ended up designing a new fuel tube assembly for the fuel tank. The issue was not only an interference problem with the electrical control panel but also my initial selection of the fuel tank return tube diameter. With the small volume carb bowl I'm using, it's important that the return line be as free-flowing as possible in order for the stand pipe return inside the bowl to regulate the fuel level over a reasonably wide range of fuel pump pressures. I used a 3/16" (o.d.) return line in my H-9, but I had reduced it to 1/8" in the T-18 tank for compatibility with a nice looking anodized cap that came with the polyethylene tank that I purchased. When I tested the operation of the fuel loop mocked up with the firewall's trial placement of the fuel components, I found the back pressure in the 1/8" return tube was too high. The fuel pump voltage, even with a .022" restrictor in the high pressure side had to be carefully adjusted to prevent pressurizing the bowl and squirting fuel out its vent. The solution was to increase the return tube to 3/16", but the minimum 90 degree bend radius for this diameter tube exiting the fuel tank created placement issues with the control panel. So, I made a new fuel tank tube inlet with machined 90 degree exits. The six tubes making up the new assembly were soft soldered into a brass cap using high temperature solder for the inner three, and low temperature solder for the outer three. The long internal tube with the bend is the tank's air vent while the tube with the flexible 'clunk' is the fuel pickup. The large diameter tube is, of course, the new return. The cap is sealed to the tank by a sandwiched rubber stopper drawn up between the cap and a metal backing disk using a long SHCS.
Eventually, after arriving at a compromise placement that was more functional than esthetic, I was able to finalize the dimensions of the two large aluminum plates that will make up the engine's display/running platform. My scrap pile had final approval over the design with the bottom plate ending up 1/2" thick. Both plates turned out to be larger than the working envelope of my mill, and so a lot of time was spent re-indexing both workpieces so I could machine the features I wanted. I was careful to not waste any of the 1/2" plate material by recycling the drops from the machined baseplate contour into support brackets for the firewall.
With the engine weighing over 40 pounds, I'm estimating a total assembly weight at around 65 pounds. Therefore, in addition to making it a robust platform, I also added a provision for carrying it without damaging months of work.
I assembled the basic platform which pretty much locked in my current component placement before the throttle and advance linkages were designed. Now that I have a concrete platform to work with, I'll next focus on them. Hopefully I haven't painted myself into some corner, and I can have some fun with their design even though my CAD tool doesn't handle rod ends. - Terry
I wasn't yet ready to transfer the heavy engine from its assembly stand to the running/display stand, and so I made a simple wood bracket for the display stand on which to temporarily mount the carb assembly. This bracket positions the carb assembly in the same position where it will sit when the engine is finally installed, and it will allow me to pre-test the operation of the finished carb linkage without having to deal with the engine.
At least one rod-end will be required in the final carb linkage since the plane of rotation of the throttle arm in many RC carbs changes as the throttle is rotated. My CAD tool doesn't handle rod ends, and so I played around with approximate virtual linkages that operate in a single plane.
My original plan included a throttle control that fits in the space available under the oil tank on the rear of the firewall and connects to the carb through complicated vertical and horizontal linkages connected with bell-cranks. The complexity got the best of me, though, and so I settled for a single linkage running straight between the throttle control and carb. It isn't at all what I originally had in mind, but it's functional and reliable.
The base for the throttle control was milled from a block of Delrin, and the control lever was machined from aluminum plate stock. The lever's rotational resistance is adjusted by pinching it within the slotted Delrin base with a captured locknut on its shaft. Simple spherical rod ends purchased from a local hobby store were threaded onto each end of a brass rod to create an adjustable length link capable of handling the carb's non-planar throttle arm. Since I had to cut an opening through the firewall for the linkage, I made it wide enough to handle two other carbs I happen to have on hand just in case my Perry carb, which is Plan A, doesn't work out.
I also machined a pair of brass feed-thrus for routing the fuel loop through the firewall. The return feed-thru has an i.d. of .150" while the one between the pump and the carb contains a .025" diameter restrictor to reduce the flow rate to the tiny fuel bowl. While working on the fuel loop routing I realized I had mixed up the positions of the inlet and outlet tubes on my custom fuel tank cap. Rather than make a new one I added a flexible extension to the return tube inside the tank and secured it to the tank's vent tube so it stands high inside the tank. This may or may not help reduce the back pressure in the return line seen by the stand pipe, but it was easy to do.
I also filed-to-fit a pita bracket to support a tank filler valve that needed be shoe-horned into a crowded area on the firewall. The filler valve is hobby shop RC component.
My final Ebay pig-in-the-poke purchase for this engine arrived just in time to claim a place on the firewall. It's a tiny elapsed time meter that I figured had been lost in the holiday mail. It's capable of running off any dc source between 4.5 and 35 volts, and so I plan to power it with the switched fuel pump voltage in order to keep track of the engine's runtime. It's not resettable, but it will record up to 10,000 hours, and so I probably won't have to worry about rollover.
I've put a few hours on my lathe since I added the the spindle monitor, but I haven't yet seen the spindle act up again. There's an outside chance the problem could be related to the Mach software. After thinking about it for a while, I'm pretty sure that every time I saw the intermittent spindle starting problem it was during the same Mach session where I had previously run the spindle in reverse. If I can accumulate a dozen more running hours with no problems, I'll try adding in some reverse spindle cycles. - Terry
At least one rod-end will be required in the final carb linkage since the plane of rotation of the throttle arm in many RC carbs changes as the throttle is rotated. My CAD tool doesn't handle rod ends, and so I played around with approximate virtual linkages that operate in a single plane.
My original plan included a throttle control that fits in the space available under the oil tank on the rear of the firewall and connects to the carb through complicated vertical and horizontal linkages connected with bell-cranks. The complexity got the best of me, though, and so I settled for a single linkage running straight between the throttle control and carb. It isn't at all what I originally had in mind, but it's functional and reliable.
The base for the throttle control was milled from a block of Delrin, and the control lever was machined from aluminum plate stock. The lever's rotational resistance is adjusted by pinching it within the slotted Delrin base with a captured locknut on its shaft. Simple spherical rod ends purchased from a local hobby store were threaded onto each end of a brass rod to create an adjustable length link capable of handling the carb's non-planar throttle arm. Since I had to cut an opening through the firewall for the linkage, I made it wide enough to handle two other carbs I happen to have on hand just in case my Perry carb, which is Plan A, doesn't work out.
I also machined a pair of brass feed-thrus for routing the fuel loop through the firewall. The return feed-thru has an i.d. of .150" while the one between the pump and the carb contains a .025" diameter restrictor to reduce the flow rate to the tiny fuel bowl. While working on the fuel loop routing I realized I had mixed up the positions of the inlet and outlet tubes on my custom fuel tank cap. Rather than make a new one I added a flexible extension to the return tube inside the tank and secured it to the tank's vent tube so it stands high inside the tank. This may or may not help reduce the back pressure in the return line seen by the stand pipe, but it was easy to do.
I also filed-to-fit a pita bracket to support a tank filler valve that needed be shoe-horned into a crowded area on the firewall. The filler valve is hobby shop RC component.
My final Ebay pig-in-the-poke purchase for this engine arrived just in time to claim a place on the firewall. It's a tiny elapsed time meter that I figured had been lost in the holiday mail. It's capable of running off any dc source between 4.5 and 35 volts, and so I plan to power it with the switched fuel pump voltage in order to keep track of the engine's runtime. It's not resettable, but it will record up to 10,000 hours, and so I probably won't have to worry about rollover.
I've put a few hours on my lathe since I added the the spindle monitor, but I haven't yet seen the spindle act up again. There's an outside chance the problem could be related to the Mach software. After thinking about it for a while, I'm pretty sure that every time I saw the intermittent spindle starting problem it was during the same Mach session where I had previously run the spindle in reverse. If I can accumulate a dozen more running hours with no problems, I'll try adding in some reverse spindle cycles. - Terry
I machined a tiny enclosure for the elapsed time meter and then wired it to connect to the wiring harness through the same blade terminals I've been using on the other firewall components. I also finalized the placement of the ignition modules and machined the firewall plate to clear the low and high voltage towers protruding from their rears. After temporarily bolting all the finished components onto the plate, I sketched out a wiring harness so I can locate and drill holes for the harness cable clamps.
A few weeks ago when I cut the handhold into the top of the firewall, I made a mistake in the CAM program that was intended to round over the edge of the opening. I inadvertently specified the depth of the finishing operation in the quarter inch thick plate to be 2.0 inches instead of 0.2 inch while my 1/4" diameter finishing tool was only 1-1/2 inches long. Oblivious to what I had done, I started up the machine, watched it run for a few minutes, and then left the shop to rake up leaves in our front yard. When I returned, the operation had completed, but the shop was filled with an odor of burned metal. What I saw were the results of my first really serious CNC crash. Fortunately, I had a two inch thick sacrificial plate under the workpiece that saved my table; but after burying and eventually snapping off the carbide cutter, the mill also tried to bury the tool holder into the workpiece. The friction created between the end of the tool holder and the aluminum workpiece literally melted a ring of metal around the inner perimeter of my intended handhold.
After checking out the mill and finding, thankfully, there was no serious damage, I changed the design of the handhold in an attempt to salvage my workpiece. I increased the size of the opening and created a two level fillet around its inner periphery to save as much undamaged metal as possible. The new stepped contour around the opening turned out to be pretty dumb looking, and so I tried to give it some purpose by turning it into a builder's plaque. Without knowing anything about how it had evolved, my wife remarked that she liked it, and so I decided to keep it.
A problem with the new design, though, was that the material around the opening had been thinned so much that the handhold was very uncomfortable. And, combined with the larger opening, the plate might have been weakened too much to carry the weight it needs to support.
To make matters worse, I damaged my hands several years ago using a poorly designed staple gun while building my shop, and now I have a condition known as 'trigger finger.' With a narrow line of pressure across the right area on some of my fingers, they will lock tightly closed and must be painfully pried open. My new handhold was now the perfect tool to demonstrate this. So, in a continuing effort to save my nearly finished firewall, I machined an additional part that bolts onto the front of the plate and increases the thickness of the handhold around its opening. I contoured it for a comfortable grip, and now I can lift it without grossing out my wife when I pry my fingers open.
In addition to wiring up the firewall, the final task before trying to start the engine is to fabricate a manual spark advance control. I left room for it on the firewall between the ignition modules. Since my H-9 only marginally benefitted from timing control during running, this functionality is really just a 'nice to have'. It should be an interesting little project since, in this engine, both distributors need to be simultaneously rotated in opposite directions by the same amount in order to advance the timing. Even though I won't be spending much time in the shop during the holidays while the kids and grandkids are visiting, I'll likely be thinking about its design. - Terry
A few weeks ago when I cut the handhold into the top of the firewall, I made a mistake in the CAM program that was intended to round over the edge of the opening. I inadvertently specified the depth of the finishing operation in the quarter inch thick plate to be 2.0 inches instead of 0.2 inch while my 1/4" diameter finishing tool was only 1-1/2 inches long. Oblivious to what I had done, I started up the machine, watched it run for a few minutes, and then left the shop to rake up leaves in our front yard. When I returned, the operation had completed, but the shop was filled with an odor of burned metal. What I saw were the results of my first really serious CNC crash. Fortunately, I had a two inch thick sacrificial plate under the workpiece that saved my table; but after burying and eventually snapping off the carbide cutter, the mill also tried to bury the tool holder into the workpiece. The friction created between the end of the tool holder and the aluminum workpiece literally melted a ring of metal around the inner perimeter of my intended handhold.
After checking out the mill and finding, thankfully, there was no serious damage, I changed the design of the handhold in an attempt to salvage my workpiece. I increased the size of the opening and created a two level fillet around its inner periphery to save as much undamaged metal as possible. The new stepped contour around the opening turned out to be pretty dumb looking, and so I tried to give it some purpose by turning it into a builder's plaque. Without knowing anything about how it had evolved, my wife remarked that she liked it, and so I decided to keep it.
A problem with the new design, though, was that the material around the opening had been thinned so much that the handhold was very uncomfortable. And, combined with the larger opening, the plate might have been weakened too much to carry the weight it needs to support.
To make matters worse, I damaged my hands several years ago using a poorly designed staple gun while building my shop, and now I have a condition known as 'trigger finger.' With a narrow line of pressure across the right area on some of my fingers, they will lock tightly closed and must be painfully pried open. My new handhold was now the perfect tool to demonstrate this. So, in a continuing effort to save my nearly finished firewall, I machined an additional part that bolts onto the front of the plate and increases the thickness of the handhold around its opening. I contoured it for a comfortable grip, and now I can lift it without grossing out my wife when I pry my fingers open.
In addition to wiring up the firewall, the final task before trying to start the engine is to fabricate a manual spark advance control. I left room for it on the firewall between the ignition modules. Since my H-9 only marginally benefitted from timing control during running, this functionality is really just a 'nice to have'. It should be an interesting little project since, in this engine, both distributors need to be simultaneously rotated in opposite directions by the same amount in order to advance the timing. Even though I won't be spending much time in the shop during the holidays while the kids and grandkids are visiting, I'll likely be thinking about its design. - Terry
Ah that pesky little decimal point of destruction. 
Nice save though, the extra piece on the front looks intentional and functional.
Thanks again for all the extra work of sharing this with the rest of us. Very , very nice.
Scott
Nice save though, the extra piece on the front looks intentional and functional.
Thanks again for all the extra work of sharing this with the rest of us. Very , very nice.
Scott
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CAM error? Been there, done that, broke the bit, de-trammed the head. Good recovery there.
camm-1
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Teŕry I read all your posts and also your 9 cyl build and love it.
Thanks for so much good info and pleasure to see your amazing craftmanship.
I have start building the 9 cyl and is finished with the crancase exept the tapping.
Now I am working on the cylinders and just have a simple question. The threads are says 1.24 42 or something and I have tested out the dimensions for threading 1.5 mm pitch.
Is that to big ? I think that a bit bigger than that inch thread that Im not used to.
Cheers
Ove
Thanks for so much good info and pleasure to see your amazing craftmanship.
I have start building the 9 cyl and is finished with the crancase exept the tapping.
Now I am working on the cylinders and just have a simple question. The threads are says 1.24 42 or something and I have tested out the dimensions for threading 1.5 mm pitch.
Is that to big ? I think that a bit bigger than that inch thread that Im not used to.
Cheers
Ove
Ove,
My H-9 planset calls out 1.25-24 for the cylinder threads which, as far as I can tell, is a non-standard thread even in the U.S. I used this spec for my threads and made a matching set of thread gauges using my own major and minor diameters before starting on the cylinders.
The 24 threads per inch is equivalent to a pitch of .0417" or, in your case, 1.058 mm. So if you use a 1 mm pitch so you can cut the threads on your metric lathe, you should be OK. You'll just need to come up with your own major and minor diameters while you're making your thread gauges. - Terry
Ove,
If you stick with the stock dimensions for the cylinder and take into account all the subltle details such as thread relief, etc., you will have just over 3 engaged threads if you use 1.5 mm pitch, and you will have 5 engaged threads if you use 1 mm pitch. The decision is yours, but if it were me I would use 1mm. If I remember correctly, I torqued my heads onto the cylinder at 35-40 ft-lbs; and that seems like a lot to ask of 3 threads in the aluminum heads.
You're getting ready to put hundreds of hours into the machining of those cylinders, and you may not want to base an important foundation decision on just several minutes of already invested time. - Terry
After a much too-short holiday I slowly migrated back into the shop. In addition to helping clear away some of the brain cobwebs it also became a sanctuary from the dreary wet and cold weather that's settled into central Texas. My older son who visited during Christmas was looking forward to seeing the new radial run, but at the time I was still 2-3 weeks away from the finish line. Anyway, it's been my experience that starting up a new engine for the very first time in front with an uninitiated audience can be a frustrating experience.
While helping my grandsons with their new quad-copters I realized I had set up the throttle on my engine backwards, and so I made a few minor changes to correct it. It now works opposite to the one on my H-9, and so I will also correct that one the next time it comes down from it's shelf.
After finishing the sketch for the firewall wiring harness I removed all its components (again) and then drilled and tapped the mounting holes for the harness cable clamps. I then turned my attention to what should be the last component of this build - the manual spark advance control.
After some investigation I realized the two distributors have significantly different resistances to rotation in the crankcase, and they are dominated by differences in the flexibilities of the bundled wires going to their caps. This means that each distributor will need its own separate link back to the control lever instead instead of the 2-into-1 bell-crank that I had been considering. The distributors rotate in opposite directions in different planes, and the linkage attachment points on the perimeters of their housings can move with three degrees of freedom. All this means that spherical rod ends will be required. Unlike with my throttle linkage I was not able to come up with a useable single plane approximation within SolidWorks to work around its lack of rod end support. Therefore I gave up using a CAD simulation and actually constructed a pair of distributor facsimiles in wood which I glued into position atop the distributor support I created to develop the throttle linkage. This hands-on simulator allowed me to better visualize the linkage requirements and to test the design as it progressed.
I eventually decided on a control lever similar to the one I made for the throttle. The link rods intersect the firewall in the middle of the oil tank, and the lever allowed me to move the actual control point above the tank and away from the filler cap.
The completed linkage appears to work well, and it feels very smooth while controlling the wood models. The lever base has two adjustable stops that limit the range of the control to between 0 and 30 degrees BTDC.
What remains now is to wire up the firewall, retest the fuel loop, and then transfer the engine from the assembly stand to its final position on the running stand behind the firewall. - Terry
While helping my grandsons with their new quad-copters I realized I had set up the throttle on my engine backwards, and so I made a few minor changes to correct it. It now works opposite to the one on my H-9, and so I will also correct that one the next time it comes down from it's shelf.
After finishing the sketch for the firewall wiring harness I removed all its components (again) and then drilled and tapped the mounting holes for the harness cable clamps. I then turned my attention to what should be the last component of this build - the manual spark advance control.
After some investigation I realized the two distributors have significantly different resistances to rotation in the crankcase, and they are dominated by differences in the flexibilities of the bundled wires going to their caps. This means that each distributor will need its own separate link back to the control lever instead instead of the 2-into-1 bell-crank that I had been considering. The distributors rotate in opposite directions in different planes, and the linkage attachment points on the perimeters of their housings can move with three degrees of freedom. All this means that spherical rod ends will be required. Unlike with my throttle linkage I was not able to come up with a useable single plane approximation within SolidWorks to work around its lack of rod end support. Therefore I gave up using a CAD simulation and actually constructed a pair of distributor facsimiles in wood which I glued into position atop the distributor support I created to develop the throttle linkage. This hands-on simulator allowed me to better visualize the linkage requirements and to test the design as it progressed.
I eventually decided on a control lever similar to the one I made for the throttle. The link rods intersect the firewall in the middle of the oil tank, and the lever allowed me to move the actual control point above the tank and away from the filler cap.
The completed linkage appears to work well, and it feels very smooth while controlling the wood models. The lever base has two adjustable stops that limit the range of the control to between 0 and 30 degrees BTDC.
What remains now is to wire up the firewall, retest the fuel loop, and then transfer the engine from the assembly stand to its final position on the running stand behind the firewall. - Terry
