30cc Inline Twin 4-stroke Engine based on Westbury's Wallaby

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Eccentric

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I have been developing the capability to cut the gears for the Wallaby. I will be using the tools and techniques I picked up from Chris over at ClickSpring. If you are not familiar with his work, look him up on YouTube, he is very talented and makes beautiful videos. I will not repeat his instructions here as I could not do them justice. To make a gear you need to be able to cut the spaces between the teeth with a properly shaped cutter, and to make the cutter you need special lathe cutters, mandrels, cutter blanks, and sharpening tools. This is where I started. Below is a picture of the print for one of the spur gears and an aluminum test gear, the final spur gears will be made of brass and the pinions of steel.
1631390122816.png



This is the print for one of the two pinions
1631390140352.png



Sheet two has the information necessary to create the cutter to cut the space between the gear teeth.
1631390165940.png



Below I am practicing making gear tooth cutter blanks from 01 tool steel.
1631390186260.png





Below is the beginnings of one of the button cutters that will cut the profile into the gear tooth cutter. these are precision diameter made from 01 tool steel and hardened. In the back ground is a tool that allows the proper relief angle to be cut into the button cutters and is also used to precicley sharpen them.
1631390204199.png



As seen below two of these button cutters are mounted in a holder and cut the proper profile into the cutter on the lathe.
1631390218525.png


Then the mill is used to create the face of the cutter.
1631390240323.png



Below is the gear tooth cutter ready for heat treatment.

1631390254168.png








This is a rotary table that I picked up from Amazon and uses the same chucks as my lathe. I use some Arduino code and a PC to advance the gear blank the correct amount so the mill can cut each tooth space.
1631390267400.png



I cut the gear blank to diameter on the lathe, then move the entire chuck and work piece to the rotary table on the mill. then I cut each leaf (the space between the gear teeth).
1631390290280.png



Finally I move the chuck back to the lathe and perform the other operations to finish off the gear.
 

Richard Hed

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I have been developing the capability to cut the gears for the Wallaby. I will be using the tools and techniques I picked up from Chris over at ClickSpring. If you are not familiar with his work, look him up on YouTube, he is very talented and makes beautiful videos. I will not repeat his instructions here as I could not do them justice. To make a gear you need to be able to cut the spaces between the teeth with a properly shaped cutter, and to make the cutter you need special lathe cutters, mandrels, cutter blanks, and sharpening tools. This is where I started. Below is a picture of the print for one of the spur gears and an aluminum test gear, the final spur gears will be made of brass and the pinions of steel.
View attachment 129021


This is the print for one of the two pinions
View attachment 129022


Sheet two has the information necessary to create the cutter to cut the space between the gear teeth.
View attachment 129023


Below I am practicing making gear tooth cutter blanks from 01 tool steel.
View attachment 129024




Below is the beginnings of one of the button cutters that will cut the profile into the gear tooth cutter. these are precision diameter made from 01 tool steel and hardened. In the back ground is a tool that allows the proper relief angle to be cut into the button cutters and is also used to precicley sharpen them.
View attachment 129025


As seen below two of these button cutters are mounted in a holder and cut the proper profile into the cutter on the lathe.
View attachment 129026

Then the mill is used to create the face of the cutter.
View attachment 129027


Below is the gear tooth cutter ready for heat treatment.

View attachment 129028







This is a rotary table that I picked up from Amazon and uses the same chucks as my lathe. I use some Arduino code and a PC to advance the gear blank the correct amount so the mill can cut each tooth space.
View attachment 129029


I cut the gear blank to diameter on the lathe, then move the entire chuck and work piece to the rotary table on the mill. then I cut each leaf (the space between the gear teeth).
View attachment 129030


Finally I move the chuck back to the lathe and perform the other operations to finish off the gear.
This should work for steel as well as alu, right?
 

petertha

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Thanks for showing these details!

Post 61 shows the Cad diagram of the gear & then on separate sheet looks like you are developing the resultant button diameter & spacing. Did you import the gear solid model from a vendor website or develop it yourself? Just wondering because there was a good YouTube video showing gear tooth generation for Solidworks (which looks like you are using?) entirely using equation driven dimensions for the tooth profile. I don't have it handy but could locate it. But taking it to the next step for cutting tool buttons is very crafty. I was told to be wary of manufacturer downloads because they can vary in their details depending on the source. Some are quite accurate with important details like relief & fillets etc. Others are just meant for spotting into assemblies with no real intent to make the gear itself.

Can you show some more details of the fixture that cuts the relief angle? How did you determine how much to off center the cutter? Then you mentioned re-sharpening - how is this accomplished
 

Eccentric

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Steamchick - thanks for the kind words. I don't think there is anything I am doing here that is not standard machining practice and well within your abilities.

Richard, you are correct, this will work for steel. My two pinions will be made from steel and the two spur gear will be made from brass. I am working in aluminum now to refine my technique. But the smaller gears (pinions) will be cold rolled mild steel, then I will case harden them with the case hardening compound available from Brownell's. It is difficult cutting steel gears so as not to harm the cutter, it is very important to keep the chips cleared and to progress slowly, both the cutting speed and the spindle speed. I will make several passes to cut each leaf. Brass is different, one pass works well.

Peter - you are correct, I used the built-in SolidWorks gear tool to create the drawing, BUT I am NOT using this profile to make my cutters. Involute gears have a complex tooth shape that can be closely approximated with a constant radius arc. I am using Chris' spreadsheet (Clock Making and Home Machining) to calculate the dimensions shown on the second sheet of my gear drawing. The button cutters are turned on the lathe from 01 tool steel as shown in my last post, and bonded into a block of steel as shown in the following fotos. The button cutters are mounted with a 15 degree relief angle, and they themselves are cut at 15 degrees.

The following picture shows the formed cutter fit into the forming tool.
1631482371167.png





Here is a closeup of the cutter tool for the gear cutter, you can see the 15 degree relief marked in red.
1631482387771.png



Below is the mandrel used to cut the gear cutter. the gear cutter is mounted off center in order to create the 15 degree relief angle when actually cutting the gear. The pin holds the cutter in the proper position as the cutter profile is turned on the lathe, then the cutter is rotated to the next position and the lathe operation is repeated. This mandrel is also used in the mill to cut the notches which reveal the cutter faces.
1631482411987.png



Below is the setup for sharpening the gear cutter. It presents the face of the cutter perfectly to the grinding stone. This same set up is used to sharpen the button cutters. I have highlighted in red the holes that the button cutters are mounted in while they are sharpened.
1631482433163.png



You asked the question: How did you determine how much to off center the cutter? Below is a drawing of the gear cutter blank, I have circled in red the desired 15 degree relief angle that is presented to the gear as it is cut. Then I have also circled in red a small point that represents the rotational axis the cutter blank needs to be turned on in the lathe to create this relief angle.
1631482452824.png



Below is a test fit of the practice aluminum gears on the engine. How do you like my precision carbide 1/4" gear shafts? The top right gear is connected to the cam shaft and the bottom gear drives the oil pump.
1631482515387.png



Below is a mega close up of the two small gears meshed. The leaf cut depth is .07" for scale.

1631482563128.png
 

Richard Hed

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Steamchick - thanks for the kind words. I don't think there is anything I am doing here that is not standard machining practice and well within your abilities.

Richard, you are correct, this will work for steel. My two pinions will be made from steel and the two spur gear will be made from brass. I am working in aluminum now to refine my technique. But the smaller gears (pinions) will be cold rolled mild steel, then I will case harden them with the case hardening compound available from Brownell's. It is difficult cutting steel gears so as not to harm the cutter, it is very important to keep the chips cleared and to progress slowly, both the cutting speed and the spindle speed. I will make several passes to cut each leaf. Brass is different, one pass works well.

Peter - you are correct, I used the built-in SolidWorks gear tool to create the drawing, BUT I am NOT using this profile to make my cutters. Involute gears have a complex tooth shape that can be closely approximated with a constant radius arc. I am using Chris' spreadsheet (Clock Making and Home Machining) to calculate the dimensions shown on the second sheet of my gear drawing. The button cutters are turned on the lathe from 01 tool steel as shown in my last post, and bonded into a block of steel as shown in the following fotos. The button cutters are mounted with a 15 degree relief angle, and they themselves are cut at 15 degrees.

The following picture shows the formed cutter fit into the forming tool.
View attachment 129076




Here is a closeup of the cutter tool for the gear cutter, you can see the 15 degree relief marked in red.
View attachment 129077


Below is the mandrel used to cut the gear cutter. the gear cutter is mounted off center in order to create the 15 degree relief angle when actually cutting the gear. The pin holds the cutter in the proper position as the cutter profile is turned on the lathe, then the cutter is rotated to the next position and the lathe operation is repeated. This mandrel is also used in the mill to cut the notches which reveal the cutter faces.
View attachment 129078


Below is the setup for sharpening the gear cutter. It presents the face of the cutter perfectly to the grinding stone. This same set up is used to sharpen the button cutters. I have highlighted in red the holes that the button cutters are mounted in while they are sharpened.
View attachment 129079


You asked the question: How did you determine how much to off center the cutter? Below is a drawing of the gear cutter blank, I have circled in red the desired 15 degree relief angle that is presented to the gear as it is cut. Then I have also circled in red a small point that represents the rotational axis the cutter blank needs to be turned on in the lathe to create this relief angle.
View attachment 129080


Below is a test fit of the practice aluminum gears on the engine. How do you like my precision carbide 1/4" gear shafts? The top right gear is connected to the cam shaft and the bottom gear drives the oil pump.
View attachment 129081


Below is a mega close up of the two small gears meshed. The leaf cut depth is .07" for scale.

View attachment 129082
It seems to that your clearance of 15deg on the cutter is not necessary. Would 6 or 7 work just as well? If it would, as you sharpen it it would not be used up as quickly. Maybe this is moot as how often will it be used? Not likely every day, probably not more than once or twice in a year.
 

xpylonracer

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With aluminium the cutting forces are not as great as when cutting gear steel so I wonder if the stepper will have sufficient torque at standstill to prevent the workpiece moving away from the cutter, recently there was an article on the Emco F1 cnc mill iO group detailing the addition of a brake to prevent movement should the need arise.
 

Eccentric

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Hi,

The torque of the stepper in the rotary table is reasonably secure, but I can grab the chuck and rotate it using both hands using some effort. I do not think what you describe will be an issue though (but we will see, I'll let you know). To turn the chuck when the stepper is energized and holding position I need to apply a fair amount of radial force to the chuck. However, when cutting the leaf (the space between gear teeth) the forces are not radial to the chuck, that is they do not try to turn the chuck. The cutter is attempting to push the work piece into the chuck (an axial force vector) and at the same time pushing the work piece away from the cutter (a longitudinal force vector). Because of the force pushing away from the cutter, using a tail stock is a good idea.

You have made a good observation, there is quite a bit of vibration cutting steel due to the nature of the interrupted cut, and the chuck cannot move even slightly or the shape of the gear teeth will be compromised. A solid chuck brake would address this. I am hoping my small gears do not give me this problem, but we will see.
 

Eccentric

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Now that I have made my gear cutters and a set of practice gears in aluminum it is time to make the real deal. I have two brass gears to make and two steel; I'll start with the brass. I have to say that I love working in brass, it machines so nice.
1632510479794.png

I mount a mandrel in the four jaw chuck, I like using a centering four jaw for cutting gears as they are a little more rigid. I face the mandrel end and cut a few grooves for the super glue to flow into.



1632510503446.png

I then super glue the gear blank to the mandrel. I use a rag so I don't drip super glue on the ways. The tail post is used to press the work piece onto the mandrel. You can see I have punched a center point and scribed the rough gear blank outline. I have found that the thin super glue works better for me than the thick glue shown in the picture.


1632510519187.png

This particular brass gear will drive the oil pump and is mounted on a 1/4" shaft, so the first operation is to face the brass, drill and ream to .251". I then follow up with a #20 drill into the aluminum and tap for a 10-32 screw. This provides extra holding power to the mandrel while turning down the outside diameter and cutting the gear leafs.


1632510535141.png

I use a stepper driven 4th axis on the mill table to cut the gear. It uses the same chucks as my lathe so I transfer the entire chuck and am able to maintain concentricity. It is very important to precisely establish the correct Z position for the mill spindle, it needs to align with the gear blank center or the teeth will be misshapen. If you look at the bottom of the gear you can see some scratches in the dykem. I get the cutter as close to center as I can, then I scribe a line on the blank with the cutter. the gear is then turned 180 degrees in the 4th axis and the cutter Z position is compared with the scribed mark on the opposite side. If it is off a little, the cutter Z position is moved to split the difference and the test is repeated. I have had very good results with this centering method.

Brass cuts so nicely that I cut the leaf full depth at one go, I run the spindle at about 2000 RPM and use the X table power feed to make the cut. I find that if I cut both directions, I end up with a better finish on the gear tooth. I use the sound of the cut and the size of the swarf to set my cut speed.

1632510567031.png

I then transfer the chuck back to the lathe to finish the machining.


1632510582709.png

My first attempt at making a steel gear was a fail, the cutter wore out before I made it half way around the gear. In hindsight I was being too aggressive in my cuts and I was running the spindle too fast. I may have gone to the other extreme, I successfully used a spindle speed of 500 RPM and I removed .007" of material in a pass. My cutter cut two pinions of 20 teeth each with no noticeable wear. I also constantly bathed the cut with oil. You can see my cardboard splash guard in the right side of the above photo. Another change I made was the tempering I put on the cutter. The first cutter I made, the one that wore out, after heat treating the 01 tool steel cutter I tempered it to a pretty dark straw color, almost into the blues. This trades off some hardness for less brittleness. Since the first cutter did not fracture, but wore down, I tempered the second cutter a light straw. This can be seen in these photos.

An aside: I was wondering what the difference is between a "pinion" and a "gear". A pinion and gear mesh, the pinion is smaller, is the driver and the gear is driven. I also have a secondary "pinion" between the crankshaft pinion and the camshaft gear that is really an "idler". A spur gear is a straight cut gear like mine, these are the simplest kind. A bull gear is the larger of two meshed spur gears, ... I digress.

The procedure I used to cut the steel pinions differed from the way I manufactured the brass gears.

First I made the steel gear blank turned to proper diameter, all machining on both sides completed, the center hole drilled and reamed; basically complete except the teeth. Then I mounted an oversized steel rod in the lathe chuck to form the mandrel. I turned an area smaller than the internal leaf diameter so the cutter would not cut the mandrel, then I turned a spigot on the end matching the diameter of the pinion blank center hole and not quite as long as the width of the pinion. Finally I faced and spot drilled the end of the mandrel to interface with a dead center.


I then super glued the pinion blank to this mandrel and moved it over to the 4th axis on the mill. If you look at the above picture you can see I am using a dead center in the tail stock that has been relieved on one side to clear the cutter. This provides a ridgid setup.


1632510849275.png

The total depth of cut for the leaf was .070", for each I made multiple passes of .007" depth increments until I hit .063" then moved on to the next leaf, when all leafs were cut to this depth I locked the mill Y axis at .070" and made another complete turn of the pinion cutting each leaf to this final depth.



1632510880228.png

The above picture shows the cutter after cutting my two pinions and it can be seen that there is no noticeable wear. I consider this a win. :)



I used excel to create the GCode for the 4th axis. I know how many steps it takes to turn the spindle 360 degrees so I simply divided this by the number of teeth on the gear. this is an example:

G1 F500 <-------- this sets the feed rate, or in my case how fast the spindle moves from tooth to tooth.

M18 S5000 <----------- this sets the stepper motor timeout, if it is too short the motor will

de-energize before the cut is done and you will lose your place.

G92 X0 <----------- this command sets the current position to zero on the axis

G1 X0.00 <--- this tests to see if we are really at zero

G1 X-5.93 <--- then each of the following commands move to the next tooth position

G1 X-11.85

G1 X-17.78

G1 X-23.70

G1 X-29.63

G1 X-35.55



I copy and paste one line at a time to my motor controller when the time comes to move to the next cut position on the gear. I am doing this on a laptop with a usb cable to my motor controller.

In my next post I will show the gears mounted on the engine.
 

awake

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My first attempt at making a steel gear was a fail, the cutter wore out before I made it half way around the gear. In hindsight I was being too aggressive in my cuts and I was running the spindle too fast. I may have gone to the other extreme, I successfully used a spindle speed of 500 RPM and I removed .007" of material in a pass. My cutter cut two pinions of 20 teeth each with no noticeable wear. I also constantly bathed the cut with oil. You can see my cardboard splash guard in the right side of the above photo. Another change I made was the tempering I put on the cutter. The first cutter I made, the one that wore out, after heat treating the 01 tool steel cutter I tempered it to a pretty dark straw color, almost into the blues. This trades off some hardness for less brittleness. Since the first cutter did not fracture, but wore down, I tempered the second cutter a light straw. This can be seen in these photos.
Eccentric, I am surprised by the speed you are running the cutter. The rule of thumb that I have always used is 500 RPM for a 1/2" diameter HSS cutter cutting mild steel. If if I understood correctly from an earlier post above, your gear cutter is actually 1.125" in diameter, which calls for a little less than half that RPM. Using a high-carbon cutter such as you have made, I'd want to drop it down even slower.

But since you report that you are getting good cuts at 500 RPM with no discernible wear, either you made one heck of a cutter, or the liberal use of cutting oil is keeping things cool, or the rule of thumb I learned is malarkey - or maybe all three! In any case, well done on making the gears.
 

Eccentric

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Andy,

Thanks for the input, I did not calculate the best spindle speed as I should. I have seen calculators, but never used one. I think I got lucky with the high spindle speed as I used a small depth of cut and a slow feed rate. The steel swarf came off as tiny bits of glitter in the dripping oil.

When the spindle speed is running slower I have a hard time hand feeding the work piece into the cutter slow, a little bit of a jerkiness will present too big of a cut and the cutter makes a twack sound. The power feed will run this slow, but it kind of drives me crazy because at the really slow feed rates it takes what seems like a long time to take up the backlash when starting the cut. I know, I know, I need to be more patient, right?
 

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You probably got away with it because of the low radial engagement of the cutter, basically each tooth only cuts for a fraction of a revolution then has the rest of its time to cool down (by conducting heat into the body of the tool) before re-entering the cut. If you tried the same speed with a carbon steel tool in a turning operation it would probably burn up in no time.

My general rule of thumb is that carbon steel cutters need to run about 1/2 the rpm of HSS. Have even machined 4140 HT with carbon steel in this way, but it took forever and needed a lot of water based coolant to keep the temperature down.
 

L98fiero

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You probably got away with it because of the low radial engagement of the cutter, basically each tooth only cuts for a fraction of a revolution then has the rest of its time to cool down (by conducting heat into the body of the tool) before re-entering the cut. If you tried the same speed with a carbon steel tool in a turning operation it would probably burn up in no time.

My general rule of thumb is that carbon steel cutters need to run about 1/2 the rpm of HSS. Have even machined 4140 HT with carbon steel in this way, but it took forever and needed a lot of water based coolant to keep the temperature down.
Carbon steel cutters should generally be run about 18-20 surface feet per minute. As for which 'carbon steel' to use, A2 is slightly better than O1 but not much, it's used more industrially because it's an air hardening steel and doesn't require oil quenching/tempering and that makes the heat treating process quicker and cheaper. Here is a chart from the book 'Heat Treatment, Selection and Application of Tool Steels' by William E. Bryson, it's a good general tool steel selector.
AIM chart.jpg
 

Nerd1000

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Carbon steel cutters should generally be run about 18-20 surface feet per minute. As for which 'carbon steel' to use, A2 is slightly better than O1 but not much, it's used more industrially because it's an air hardening steel and doesn't require oil quenching/tempering and that makes the heat treating process quicker and cheaper. Here is a chart from the book 'Heat Treatment, Selection and Application of Tool Steels' by William E. Bryson, it's a good general tool steel selector.View attachment 129420
Hmm so that would be more like 1/4 the speed of HSS. Perhaps I got away with 1/2 due to only taking light cuts and keeping it flooded. Or maybe the tool was actually some kind of strange HSS that spark tests like high carbon steel, I got it in the toolbox with my lathe so I'm not entirely sure what it is. Concluded that it was carbon steel when I sharpened it and the sparks were yellow white feathery sparkles rather than orange lines like you get from HSS.
 
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Eccentric

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In My Humble Pinion
1632843534207.png


While I am in the mode of making gears, I thought I would make the last two, the oil pump pinions. They are .375" in diameter, 32 DP, 20 degree pressure angle, and have 10 teeth. I am going to make them in brass so I figured I could get away with a single flute fly cutter to cut the gear leafs. I am making the cutter from 01 tool steel on the CNC router. I use a gear profile spreadsheet I have for the cutter design, then capture the cutter in SolidWorks with an 8 degree clearance angle. To cut this clearance angle I clamp the 01 tool steel blank at an 8 degree angle as seen in a few photos below. So I take a section of the cutter in the following CAD model to present this tilted cutter blank to the mill.
1632843553525.png


Above is how the cutter will sit in the vise and how it will be cut. The blue area is the remaining part to be used, the rest of the model is trimmed away. This CAD model is then transferred to Fusion360 to generate the tool paths

1632843571275.png


I am using a two flute 3/32" flat end mill because I have an internal radius of less than.125", otherwise I would have used my go to 1/4" end mill. I am making lots of tiny little cuts. Above is a simulation of the tool paths.
1632843592077.png


Above is the completed cut in the CNC router vise. I have used a second scrap cutter blank to even out the vise clamping force. You can see that it is clamped at the 8 degree angle.
1632843617866.png



This is the standard heat treating kit with the MAP gas torch, boric acid to eliminate scale and quenching oil. The tin can is used to hold boiling water to remove the boric acid after heat treat. I warm the cutter tip and roll it around in the boric acid which adheres and melts. Then I bring the cutter tip to a bright red hot and plunge in the quench oil.



After removing the melted boric acid by rinsing in boiling water, I temper the cutter by heating it with the torch on low. I aim the heat at the middle of the cutter and watch the color change propagate out toward the tip, when I see the light straw color I am aiming for, I again plunge it into the quenching oil. Finally I sharpen it on the Arkansas stone.

1632843657029.png

Above is the mandrel used to hold the cutter.

1632843679683.png

I prep the pinion blank by bringing the OD to size, drill and ream the 1/8" hole down the middle. Then I transfer the blank and chuck to the 4th axis on the mill.

1632843719716.png

I set my gear cutting rig up with a tail post, but the pinion is so small the cutter hits the dead center in the tail post, even though it was relieved. Cutting the pinion hanging into space like above causes the blank to vibrate and there are slight machining artifacts on the teeth. since this is not a set of power train gears, these should have no effect on the function of the oil pump.

1632843743149.png

Once the teeth are cut, it is back to the lathe to part them off and finish the ends.


1632843763971.png


Done with gears, whew.
 

Basil

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Thanks, nice work. I have not made gears yet! 👍
 

Eccentric

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This is the current state of my design for the Wallaby:
1633045189872.png


I need to complete the work on the front of the engine including the Oil Pump housing, ignition triggering system and the distributor. The oil pump housing needs its intake and output on the same side, so I need to work on that. I think the timing sleeve with a magnet for the ignition trigger is straight forward, but I need to design the little housing for the hall effect sensor. The distributor for the two cylinders will be driven from the end of the camshaft.

But I am going to direct my attention to the design and fabrication of the camshaft next. I have deviated from Westbury's design by using ball bearings at each end of the camshaft. I will be using 1018 cold rolled steel and case harden the cam lobes. This is the current state of the camshaft design:
1633045248488.png

I know this is not dimensioned using proper GD&T standards, but when I am machining I like LOTS of dimensions.

Below are the lobe designs using numbers gleaned from Westbury's construction article: Cylinder 2's lobes are 180 degree mirror images of cylinder 1's. The nose radii are reference dimensions, to specify them would over constrain the design as all curves are tangent and sufficient to describe the cam profiles.
1633045294978.png


My machining approach is to use the lathe to turn all features with the exception of the cam lobes themselves. I am going to then use a 4th axis on the mill to machine these. This will be the adventure. I am going to machine some aluminum test articles first.

One thing about model engines (and full size engines as well) I dont' quite understand is the need to be able to adjust cam timing. The timing of the valves with repect to the crankshaft are rigidly defined by an engine design, so why do I need to adjust the cam position on the cam timing gear? Is it because of variation in manufacture of the timing gear train? Am I just adjusting out slop or inaccuracies in the manufacture of the associated components?
 

Basil

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👍When receiving a performance cam they come with a degree sheet showing open and closing events and duration usually at 0.050” lift . Degreeing a camshaft with a degree wheel on the crankshaft and dial indicator on the lifter just makes sure the setup checks out as designed. Adjustment brings everything in line if not correct.
When dynamometer testing it is sometimes advantageous to advance or retard a cam to improve low end torque or to improve top end power.
Valve lash to some degree can also help with getting the desired opening and closing events and adjusting such things as overlap.
 
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Eccentric

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Camshaft Continued

The majority of the last week has been spent working on tool paths for the Camshaft Lobes. This is my first exposure to using a 4th Axis on the CNC Router. Below is my first attempt cutting an exhaust cam lobe on a piece of test aluminum rod. I used a ball end mill for the entire operation.

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Operation in process

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Operation complete. I was quite pleased with the surface finish and the dimensional accuracy.

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I continued to experiment with various tool path options ending up using a 1/4" flat end mill for the roughing and then a final pass with a 1/4" ball end mill. I offset the tool .3" to the side so I used the edge of the cutter, not the center. I worked initially in aluminum, then a final test with steel.

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The camshaft print.

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First I rough machined the camshaft focusing on the cam lobe blanks. These are 5/8" in diameter and 5/16" wide. I went back and forth on how much lathe work I wanted to do before milling the cam lobes. I finally decided to minimize the amount of lathe machining before moving to the CNC router to minimize lost work in case of a failure there.

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Instead of creating a tool path for the entire camshaft, I created two tool paths for the intake lobe and two tool paths for the exhaust lobe (roughing and finishing). This required four set up changes as I would re-zero the CNC router and rotate the camshaft to the proper orientation for each cam lobe before starting the machining on each. To insure I didn't skip a step or mess one up, I created a checklist for the machining of the cam lobes.

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Here three of the four cam lobes have been machined from a 1018 cold rolled steel rod on the CNC router.

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Back to the lathe to complete the machining. Above I have completed both bearing surfaces, you can see a bearing test fit next to the live center in the tail stock. And started working on the taper that will secure the cam timing gear.

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Once I finished the machining and cut off the cam I found that the camshaft was too tight between the bearing holders and the taper need some more material removed to properly mesh the cam timing gear with the idler timing gear. I had to figure out how to chuck up the camshaft again to do this work. Gotta love collets.


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Camshaft Installed in the Engine. The outside lobes are exhaust and the two center lobes are intake. You can see the timing of the lobes.

I still have a little bit of clean up on the camshaft, then I need to case harden the cam lobes. I sure hope this does not ruin it.
 

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