Ford 300 Inline Six
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The helical drive gear in the center of the full-size camshaft was most likely machined using a specialized hob. George came up with a clever solution for the model that requires only a lathe and mill. The camshaft was divided into two halves with machined end tenons fitted together inside the gear. The Loctited assembly was then cured in a simple v-groove fixture.
The tenons were tackled first. I started with two lengths of 5/16" drill rod cut longer than needed for the assembled camshaft so the extra stock could be used for a second chance at a good fit. I got lucky on my first attempt which wound up with a snug fit that rolled flat over a surface plate. Since the tenons were also used to reference the starting orientations for the lobe machining operations, Loctiting was left until the very end.
The intake and exhaust lobe profiles are identical, and so 4-axis g-code was compiled for a single lobe and run twelve times in as many setups. Minimum workpiece stick-out required a new setup for each lobe operation. A brass end-cap temporarily fit to the end tenon and center-drilled for the mill's tailstock stabilized the workpiece for the longer stick-outs. A 10-32 cup set screw tightened against the tenon's flat surface (through a protective pad) held the cap in place so its milled flat top surface could be used to indicate the starting angle for each lobe.
I usually find camshafts confusing parts to machine. This one required working from its center toward its two ends which meant, for machining purposes, the lobes on the two halves rotate in opposite directions. In addition, my CAD, CAM, and controller software all indicate 4th axis rotation angles in different ways. My particular mill's 4th axis also happens to be wired in reverse - something I should have corrected long ago instead of adding G51 A-1 to my coding.
The mental gymnastics got the best of me, and so my heavily rehearsed machining steps eventually included color-coded workpieces and worksheets. In order to reduce the chances of setup errors, the lobe boundaries were 'scratched' into the workpiece ahead of time on a lathe and picked up on the mill with a spindle microscope. (Of course, the 'scratches' really had two 'sides' which were reversed under the microscope.)
The g-code included pair of roughing operations spaced 180 degrees apart that prepared the lobe for its finishing step - a continuous 4-axis rotary operation. Each lobe required about 5 minutes of setup time and some 15 minutes of machining using a conventional 1/8" cylindrical end mill. Tiny step-overs minimized the ridges left by the end mill's relieved cutting edges. The residual machining marks were easily 'shoe-shined' away with 800 grit paper. For cosmetic purposes, the material between lobe pairs was then carefully removed from both camshaft halves using a thin parting tool.
In the original drawing, the 60 tooth timing gear is attached with a pair of set screws. I added a flange to the front end of the camshaft to which the gear will attach with four SHCS's. Machined slots in the gear will allow the camshaft to be timed to the crankshaft before the screws are tightened. The flange was a separately machined part that was Loctited to the camshaft. - Terry
The tenons were tackled first. I started with two lengths of 5/16" drill rod cut longer than needed for the assembled camshaft so the extra stock could be used for a second chance at a good fit. I got lucky on my first attempt which wound up with a snug fit that rolled flat over a surface plate. Since the tenons were also used to reference the starting orientations for the lobe machining operations, Loctiting was left until the very end.
The intake and exhaust lobe profiles are identical, and so 4-axis g-code was compiled for a single lobe and run twelve times in as many setups. Minimum workpiece stick-out required a new setup for each lobe operation. A brass end-cap temporarily fit to the end tenon and center-drilled for the mill's tailstock stabilized the workpiece for the longer stick-outs. A 10-32 cup set screw tightened against the tenon's flat surface (through a protective pad) held the cap in place so its milled flat top surface could be used to indicate the starting angle for each lobe.
I usually find camshafts confusing parts to machine. This one required working from its center toward its two ends which meant, for machining purposes, the lobes on the two halves rotate in opposite directions. In addition, my CAD, CAM, and controller software all indicate 4th axis rotation angles in different ways. My particular mill's 4th axis also happens to be wired in reverse - something I should have corrected long ago instead of adding G51 A-1 to my coding.
The mental gymnastics got the best of me, and so my heavily rehearsed machining steps eventually included color-coded workpieces and worksheets. In order to reduce the chances of setup errors, the lobe boundaries were 'scratched' into the workpiece ahead of time on a lathe and picked up on the mill with a spindle microscope. (Of course, the 'scratches' really had two 'sides' which were reversed under the microscope.)
The g-code included pair of roughing operations spaced 180 degrees apart that prepared the lobe for its finishing step - a continuous 4-axis rotary operation. Each lobe required about 5 minutes of setup time and some 15 minutes of machining using a conventional 1/8" cylindrical end mill. Tiny step-overs minimized the ridges left by the end mill's relieved cutting edges. The residual machining marks were easily 'shoe-shined' away with 800 grit paper. For cosmetic purposes, the material between lobe pairs was then carefully removed from both camshaft halves using a thin parting tool.
In the original drawing, the 60 tooth timing gear is attached with a pair of set screws. I added a flange to the front end of the camshaft to which the gear will attach with four SHCS's. Machined slots in the gear will allow the camshaft to be timed to the crankshaft before the screws are tightened. The flange was a separately machined part that was Loctited to the camshaft. - Terry
Are those tenons semi-circular so that when they're in the right place they'll create a small cylinder with the gear bored to that diameter?
They appear to be that way. I guess the alternative would be flats with matching slots machined in the gear.
They appear to be that way. I guess the alternative would be flats with matching slots machined in the gear.
You're correct. When fitted together they completely fill the bore through the gear. I could see it also as a way to construct a built-up crankshaft. - Terry
Terry, what sort of bearing does the camshaft ride on? Is it just steel (camshaft) on aluminum (case), or is there something else in there? (bronze insert??)
By the way - marvelous work, as always!!!
By the way - marvelous work, as always!!!
No bearings. Just polished drill rod turning in reamed 7075 block. Being open to the crankcase it should get plenty of oil due to windage. - Terry
I have seen many designs that run steel in aluminum with lubrication, so thought that might be what you were doing. Again, marvelous work!!
Wow. Just plain Wow! I read your posts, admire your photos, and keep hearing in the back of my head the haunting refrain from Wayne's World - "We're not worthy!" You play at an entirely different level and I'm very grateful to you for sharing all your knowledge.
With the massive rotary still set up on the mill, it was a good time to machine the timing gears. These 48 DP gears were machined from 1144 and are very similar to those made for the Offy. I may have gone overboard with the timing gear's cosmetics, but I didn't want just another plain disk. The spacing between the block's already machined crank and camshaft bores was laid out for a pair of error-free gears, and so great care and a 4-jaw chuck were used in their machining. After finishing the timing gear, its machining was checked by measuring its pitch diameter spacing with a known good (spare) 60 tooth Offy gear.
Although the bronze main bearings haven't yet been machined, the crank was temporarily installed in its two outer ballbearings. The 30 tooth crankshaft gear meshed smoothly with the 60 tooth timing gear inside the block with no tight spots and just a touch of backlash. The crank gear was then broached for a 1/16" key to match the slot machined much earlier on the front of the crankshaft.
I modified the design of the carrier for the front oil seal to include a mounting flange for the crankshaft pulley. This carrier, machined from 12L14, was keyed to the crankshaft and spins inside an o-ring fitted in the neck of the timing cover.
The crankshaft pulley was machined from 12L14 and attached to the flange with four SHCS's. Its runout was minimized by a snug fit between its bore and the crankshaft. The pulley was marked with a tiny divot adjacent to the crankshaft key so it can be mounted to the crankshaft with a consistent orientation. Later, once the engine is timed, the pulley's outer rim will be scribed with the number one cylinder's TDC. The pointer added to the timing cover will be used to set and indicate ignition timing.
A hex bolt screwed into the nose of the crankshaft completed the crankshaft assembly. A center boss on the rear of its washer bottoms on the nose of the crankshaft and the washer limits the forward travel of the crankshaft components. The backside of the washer was counterbored for clearance around the heads of the pulley's mounting bolts. The pulley, washer, and hex bolt were bead blasted and cold blued.
The drag on the crankshaft created by the seal will hide any tight spots during the fitting of the main bearings, and so the o-ring will be removed during that step. The final machining operation on the timing cover was a shallow bore for a pressed-in bronze button to limit the forward travel of the camshaft. A .010" Teflon timing cover gasket completed the internals associated with the crankshaft's front end. - Terry
Although the bronze main bearings haven't yet been machined, the crank was temporarily installed in its two outer ballbearings. The 30 tooth crankshaft gear meshed smoothly with the 60 tooth timing gear inside the block with no tight spots and just a touch of backlash. The crank gear was then broached for a 1/16" key to match the slot machined much earlier on the front of the crankshaft.
I modified the design of the carrier for the front oil seal to include a mounting flange for the crankshaft pulley. This carrier, machined from 12L14, was keyed to the crankshaft and spins inside an o-ring fitted in the neck of the timing cover.
The crankshaft pulley was machined from 12L14 and attached to the flange with four SHCS's. Its runout was minimized by a snug fit between its bore and the crankshaft. The pulley was marked with a tiny divot adjacent to the crankshaft key so it can be mounted to the crankshaft with a consistent orientation. Later, once the engine is timed, the pulley's outer rim will be scribed with the number one cylinder's TDC. The pointer added to the timing cover will be used to set and indicate ignition timing.
A hex bolt screwed into the nose of the crankshaft completed the crankshaft assembly. A center boss on the rear of its washer bottoms on the nose of the crankshaft and the washer limits the forward travel of the crankshaft components. The backside of the washer was counterbored for clearance around the heads of the pulley's mounting bolts. The pulley, washer, and hex bolt were bead blasted and cold blued.
The drag on the crankshaft created by the seal will hide any tight spots during the fitting of the main bearings, and so the o-ring will be removed during that step. The final machining operation on the timing cover was a shallow bore for a pressed-in bronze button to limit the forward travel of the camshaft. A .010" Teflon timing cover gasket completed the internals associated with the crankshaft's front end. - Terry
Phenomenal, absolutely beautiful Terry. I especially like the way your camshaft gear came out; the way the lightning holes blend so well into the gear ring and the center spigot is wonderful.
The water pump is another one of the model's very realistic parts. As a Solidworks rendering it could easily be mistaken for the real thing. It wasn't until I was well into its machining that I was struck by just how tiny it actually is.
I didn't want to muck with the pump's design, but earlier changes made to the block to accommodate crankshaft and timing gear modifications required an increase in the length of the pump's body and impeller. I also adjusted its filleting to limit the diameter of the smallest finishing cutter to 1/8".
Construction began on a one inch length of 2" diameter aluminum starting workpiece. After truing it, pockets for a pair of ball bearings and an o-ring seal were machined through what would eventually become the front of the pump. The workpiece was then flipped around in a set-true chuck where the rear was bored for an inlet plenum behind the impeller. A mounting boss was also added to locate the pump to the block.
The workpiece was then moved to the mill where the pump's four mounting holes were drilled and temporarily tapped. All features reachable through the rear face of the workpiece could then be machined. A fixture plate attached to the rear face of the workpiece allowed the remainder of the pump to be machined through its front face. The fixture'd pump was then repositioned so the coolant passage through the pump's angled neck could be drilled. A final operation reamed out the tapped holes for clearances around the pump's 1-72 mounting screws.
Some already on-hand 3/16" i.d. ball bearings established the diameter of the impeller shaft. After pressing on a bronze disk and truing it to the shaft, the impeller's seven blades were machined using a 1/16" end mill.
An included diagram shows the pump's exploded assembly which includes a silicone greased o-ring seal and a pair of ball bearings with their associated spacers. A mounting flange for the drive pulley is secured to the shaft with a grub screw which holds the assembly together. A flat was machined on the shaft for the grub screw.
An aluminum drive pulley and Teflon gasket will complete the pump assembly. The pump will be painted to match the block after the coolant outlet is machined. The pulleys will be be air-brushed flat black Gun Kote. - Terry
I didn't want to muck with the pump's design, but earlier changes made to the block to accommodate crankshaft and timing gear modifications required an increase in the length of the pump's body and impeller. I also adjusted its filleting to limit the diameter of the smallest finishing cutter to 1/8".
Construction began on a one inch length of 2" diameter aluminum starting workpiece. After truing it, pockets for a pair of ball bearings and an o-ring seal were machined through what would eventually become the front of the pump. The workpiece was then flipped around in a set-true chuck where the rear was bored for an inlet plenum behind the impeller. A mounting boss was also added to locate the pump to the block.
The workpiece was then moved to the mill where the pump's four mounting holes were drilled and temporarily tapped. All features reachable through the rear face of the workpiece could then be machined. A fixture plate attached to the rear face of the workpiece allowed the remainder of the pump to be machined through its front face. The fixture'd pump was then repositioned so the coolant passage through the pump's angled neck could be drilled. A final operation reamed out the tapped holes for clearances around the pump's 1-72 mounting screws.
Some already on-hand 3/16" i.d. ball bearings established the diameter of the impeller shaft. After pressing on a bronze disk and truing it to the shaft, the impeller's seven blades were machined using a 1/16" end mill.
An included diagram shows the pump's exploded assembly which includes a silicone greased o-ring seal and a pair of ball bearings with their associated spacers. A mounting flange for the drive pulley is secured to the shaft with a grub screw which holds the assembly together. A flat was machined on the shaft for the grub screw.
An aluminum drive pulley and Teflon gasket will complete the pump assembly. The pump will be painted to match the block after the coolant outlet is machined. The pulleys will be be air-brushed flat black Gun Kote. - Terry
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How tiny is it? I was trying to extrapolate from those fillets around the base being 1/8" diameter and it seems to be coming up to 3/4" tall. Maybe 1" tall.
I took this photo but forgot to include it.
Beautiful work! But the problems of scale make me wonder how successful it will be at moving adequate coolant in reality? I'm sure you'll have used very fine clearances between the rotor and housing.. How much clearance is there?
K2
K2
Always inspiring and intimidating. Thank you for your posts.
Where do you get the 2" match sticks?
Where do you get the 2" match sticks?
Fantastic build thread.
I will have to go back and read it from the beginning.
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I will have to go back and read it from the beginning.
.
This particular 'pump' is really a circulator. Although coolant enters the block from the radiator through the pump, gravity has more effect on the flow than the pump. The pump's impeller sticks inside the block and really just helps to circulate the coolant between the block and the outlet located in the head. I agree that the coolant system systems don't scale very well. Thermo-siphoning is probably a major component of the coolant system in these models. To answer the question you didn't mean to ask, the impeller rides against the face of the locating boss on the rear of the pump with essentially zero clearance. It will be lubricated by the coolant and so I wouldn't expect any wear. - Terry
Congratulation Terry!
This is really wonderful work.
Did you machine the Camshaft using CNC or did you machine it manually?
Thanks,
Edi
This is really wonderful work.
Did you machine the Camshaft using CNC or did you machine it manually?
Thanks,
Edi
Thanks Terry. I asked because a friend at my Club has a 3 cylinder side-valve engine that runs for 5 - 10 mins on petrol, and while his water pump is about the same size as yours, his "scale-looking" cooling system cannot cope with any longer, idling, without boiling! It needs a radiator bigger than the engine, and "larger than scale" water pipes. He uses 2mm bras tube. The pump does work well, his runs at above engine speed, belt driven. I think about 3/8" dia rotor. But his is made from non-metal (clear window one side), and is stand-alone, unlike your conventional packaging. I'll try and find a picture....
K2
K2
It was done with CNC, one lobe at a time, with each lobe positioned for minimum stick-out before starting (12 setups). - Terry
