Its all overwhelming amazing!! Look forward to see it run. Is the fuel gauge operational and if so how in the world??
Ford 300 Inline Six
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Don't know yet for sure but probably 2-3 average runs. - Terry
That's actually not a fuel gauge, but a screwdriver adjustable potentiometer that controls the speed of the fuel pump and therefore flow in the recirculating fuel loop. It's there to tame the flow rate of the pump which will help control the turbulence in the fuel bowl. - Terry
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For a radiator, I decided to reuse the strategy I came up with for the Offy's coolant system. My argument was that I felt the volume taken up by the fins in the core of a scaled radiator might be put to better use holding additional coolant. These fins can take up as much as two thirds of the core volume of a model engine radiator.
The real effectiveness of the fins in a full-size automotive radiator core relies upon a layer of turbulent air around them created by a healthy flow through them. Although an electric fan can force the needed air through a model radiator, the typical crank driven fan is pretty much ineffective. What's more, the thermal conductivity of the brass typically used in model radiator construction for its solder-ability is surprisingly poor compared with aluminum.
An all aluminum finless radiator seemed to work well with the Offy, and so I decided to build something similar for the Ford. I also wanted to keep its size in line with the engine's scale.
The first step was to decide upon a set of dimensions. I started with a total radiator volume of ten times the engine's coolant capacity which was measured earlier to be 30 cc. After playing with the dimensions, I settled upon a 4" x 4.5" x 1" core plus upper and lower tanks. These dimensions actually weren't too far away from those of a scaled heavy duty truck radiator.
Upper and lower tanks were machined from 6061, and the inlet and outlet locations were selected for convenient hookups to the engine. The core was also machined from aluminum. Its interior was hogged out by chain drilling through both ends of the workpiece before being finished with an end mill. The front and back surfaces were grooved for a core 'look'. The three components were bead blasted and thoroughly cleaned for painting after assembly.
JB Weld was used to bond the tanks to the core. After mixing, it was thinned with 20% acetone to improve its flowability. It was injected into a trough surrounding the core inside each tank using a syringe. The final gravity-flowed adhesive resembled the solder fillets in a full size radiator. After a 24 hour cure, the radiator was baked for a few hours at 250F to finish outgassing the epoxy. I've learned from experience that this pre bake-out step helps prevents bubbling under the Gun Kote during its oven cure. The radiator was finished in satin black. An o-ring'd cap, inlet/outlet ports and clamps, and mounting brackets should wrap up the coolant system. - Terry
The real effectiveness of the fins in a full-size automotive radiator core relies upon a layer of turbulent air around them created by a healthy flow through them. Although an electric fan can force the needed air through a model radiator, the typical crank driven fan is pretty much ineffective. What's more, the thermal conductivity of the brass typically used in model radiator construction for its solder-ability is surprisingly poor compared with aluminum.
An all aluminum finless radiator seemed to work well with the Offy, and so I decided to build something similar for the Ford. I also wanted to keep its size in line with the engine's scale.
The first step was to decide upon a set of dimensions. I started with a total radiator volume of ten times the engine's coolant capacity which was measured earlier to be 30 cc. After playing with the dimensions, I settled upon a 4" x 4.5" x 1" core plus upper and lower tanks. These dimensions actually weren't too far away from those of a scaled heavy duty truck radiator.
Upper and lower tanks were machined from 6061, and the inlet and outlet locations were selected for convenient hookups to the engine. The core was also machined from aluminum. Its interior was hogged out by chain drilling through both ends of the workpiece before being finished with an end mill. The front and back surfaces were grooved for a core 'look'. The three components were bead blasted and thoroughly cleaned for painting after assembly.
JB Weld was used to bond the tanks to the core. After mixing, it was thinned with 20% acetone to improve its flowability. It was injected into a trough surrounding the core inside each tank using a syringe. The final gravity-flowed adhesive resembled the solder fillets in a full size radiator. After a 24 hour cure, the radiator was baked for a few hours at 250F to finish outgassing the epoxy. I've learned from experience that this pre bake-out step helps prevents bubbling under the Gun Kote during its oven cure. The radiator was finished in satin black. An o-ring'd cap, inlet/outlet ports and clamps, and mounting brackets should wrap up the coolant system. - Terry
Naturally, I had to have a think about this.
In any heat exchanger, the material used for the wall makes very little difference to the overal thermal resistance. With any reasonably conductive metal the temperature drop across the wall pales into insignificance when compared with the fluid boundary layers. This will be especially true when relying on natural convection over the outer surface.
While it looks radiatorish, I think you are saying that this thing is more of a heat sink? The volumetric specfic heats of aluminium alloy and brass are about 2400 and 3200 kJ/K.m^3 repectively, so if you made to the same design out of brass, the case would have a 1/3 greater heat capacity. However, as there is less volume of metal than water, and the water has a volumetric specific heat around 4000 kJ/K.m^3, the overal difference would probably be less than 10%.
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Terry:
I was only joking about the "BIG TANKS" back in post #342. Your 300cc radiator capacity, if we "scaled" it up to full size, would come in at 37+ liters. Whether it'll keep your 300 cool or not, you've definitely exceeded the 9.2L factory cooling system capacity. If you call it a radiator or a heat-sink is just semantics, but it LOOKS very radiator-ish.
Don
I was only joking about the "BIG TANKS" back in post #342. Your 300cc radiator capacity, if we "scaled" it up to full size, would come in at 37+ liters. Whether it'll keep your 300 cool or not, you've definitely exceeded the 9.2L factory cooling system capacity. If you call it a radiator or a heat-sink is just semantics, but it LOOKS very radiator-ish.
Don
It looks excellent! I think you are probably right with your calcs/estimates of model radiators and fans... A friend made his own design of 3 cylinder petrol engine (maybe 5cc total?) and it idles nicely around 1200rpm. at shows.... But then overheats after 10 mins or so of running. His "radiator/heat sink" is 4 x 3/8" square aluminium blocks with big holes through, top and bottom brass tanks (glued on I think?) with fins machined into the square blocks. All put together make a nice radiator, with coolant driven by a water pump of the engine. Sorry I don't have a picture. The maker reckoned he needed to make it 3 times bigger.... => 4in long x 2 in high!
K2
K2
The hardware needed to mount and connect the radiator to the engine was completed next. Threaded inlet and outlet hose barbs were turned from 303 stainless and Loctite'd into the tanks. Aluminum-to-stainless bonds are challenging for Locite, and so the parts were pre-coated with the manufacturer's recommended primer to help kick off the bonding process.
A threaded radiator cap was also machined from 303 and then polished. An o-ring inside a machined groove in the filler neck seals the cap to the radiator.
The mounting bracket made to secure the radiator to the display stand may be a little over the top, but I wanted something other than a pair of boring L-brackets. It was machined from aluminum and Gun Kote'd gray to match the riser block under the engine.
For hose clamps, I had three shop-made clamps left over from my Offy build:
270 Offy (post 447).
I really needed four, but there wasn't enough space around the engine's water pump inlet for one anyway. The tiny spring clamps you can find in huge assortments on Amazon are designed for silicone tubing and won't seal the stiffer Tygon tubing that I'm using.
One of the photos shows a tool I made to twist a loop of copper wire around the water pump's inlet. My shade tree clamp isn't pretty but it's functional and well hidden under the alternator. The right angle bends in the both upper and lower hoses are tight, and metal springs were used inside them to prevent collapse.
I dread the first-time filling of a new engine's coolant system. Potential leak sources inside these little engines can be many, and internal leaks can be difficult to locate and a real pain to fix. Hopefully, my earlier liner-to-block leak repair is permanent, but I decided to add an additional preventative step.
Several years ago, I ran into porosity problems with the thin-wall head castings on my Merlin, and I investigated a number of coolant sealers to avoid an engine teardown. Regardless of a dozen manufacturers' guarantees, I found only one that I trusted for use inside a model engine. This was an OEM product developed decades ago by General Motors to solve porosity leaks in their early production aluminum heads. A couple of these tablets were dropped into the radiators of every new aluminum-headed GM production engine for many years. It's an organic material made up of ground walnut shells and ginger root whose fibers tend to migrate into and seal pinhole leaks. The same product was recommended for use at every coolant change for these cars.
My testing involved experimenting with various size holes in paper cups, and after gaining confidence with the GM product I added a bit to the Merlin's coolant system. Both pinholes were plugged within minutes during the next run with no apparent side effects and no further issues since. My small engine dose was a piece about the size of a small pea broken off a tablet and crushed into dust with my fingers. The material imparts a slight brownish tinge to glycol coolant, and under a magnifying glass its tiny fibers can be seen in suspension throughout the coolant. There's no 'goop' to clog the cooling passages in a model engine nor its water pump. It's intended for tiny pinholes and is not a radiator repair product.
I used this sealer as a preventative measure in my Offy because I was concerned about the lack of head gasket 'meat' around the coolant transfer passages. After filling the Ford with coolant and monitoring its level in the transparent upper hose for a few days to ensure no leaks, I added the sealer for peace of mind.
I was pleasantly surprised to see coolant moving through the upper hose into the radiator when the crankshaft was spun with an electric drill. It's been my experience that cranking speeds aren't high enough to move coolant through a model engine with a centrifugal. - Terry
A threaded radiator cap was also machined from 303 and then polished. An o-ring inside a machined groove in the filler neck seals the cap to the radiator.
The mounting bracket made to secure the radiator to the display stand may be a little over the top, but I wanted something other than a pair of boring L-brackets. It was machined from aluminum and Gun Kote'd gray to match the riser block under the engine.
For hose clamps, I had three shop-made clamps left over from my Offy build:
270 Offy (post 447).
I really needed four, but there wasn't enough space around the engine's water pump inlet for one anyway. The tiny spring clamps you can find in huge assortments on Amazon are designed for silicone tubing and won't seal the stiffer Tygon tubing that I'm using.
One of the photos shows a tool I made to twist a loop of copper wire around the water pump's inlet. My shade tree clamp isn't pretty but it's functional and well hidden under the alternator. The right angle bends in the both upper and lower hoses are tight, and metal springs were used inside them to prevent collapse.
I dread the first-time filling of a new engine's coolant system. Potential leak sources inside these little engines can be many, and internal leaks can be difficult to locate and a real pain to fix. Hopefully, my earlier liner-to-block leak repair is permanent, but I decided to add an additional preventative step.
Several years ago, I ran into porosity problems with the thin-wall head castings on my Merlin, and I investigated a number of coolant sealers to avoid an engine teardown. Regardless of a dozen manufacturers' guarantees, I found only one that I trusted for use inside a model engine. This was an OEM product developed decades ago by General Motors to solve porosity leaks in their early production aluminum heads. A couple of these tablets were dropped into the radiators of every new aluminum-headed GM production engine for many years. It's an organic material made up of ground walnut shells and ginger root whose fibers tend to migrate into and seal pinhole leaks. The same product was recommended for use at every coolant change for these cars.
My testing involved experimenting with various size holes in paper cups, and after gaining confidence with the GM product I added a bit to the Merlin's coolant system. Both pinholes were plugged within minutes during the next run with no apparent side effects and no further issues since. My small engine dose was a piece about the size of a small pea broken off a tablet and crushed into dust with my fingers. The material imparts a slight brownish tinge to glycol coolant, and under a magnifying glass its tiny fibers can be seen in suspension throughout the coolant. There's no 'goop' to clog the cooling passages in a model engine nor its water pump. It's intended for tiny pinholes and is not a radiator repair product.
I used this sealer as a preventative measure in my Offy because I was concerned about the lack of head gasket 'meat' around the coolant transfer passages. After filling the Ford with coolant and monitoring its level in the transparent upper hose for a few days to ensure no leaks, I added the sealer for peace of mind.
I was pleasantly surprised to see coolant moving through the upper hose into the radiator when the crankshaft was spun with an electric drill. It's been my experience that cranking speeds aren't high enough to move coolant through a model engine with a centrifugal. - Terry
Looking Fabulous, really coming along Terry. The "Ford" radiator mount is a nice touch. Interesting story about GM's use of the Cooling System Seal Tabs in early aluminum headed engines. I just went and boungt a life time supply (one package) on Amazon for $4.02.
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Very nice work Terry.
Re the wire clamp, where I thought you were going was a miniature wire hose clamp gizmo (below infomercial is typical). I found an Ebay source of small diameter flexible SS wire that comes in 0.2, 0.4, 0.6, 0.8m dia. The 0.8mm I tested have is a bit too fat & stiff to mimic the loops & tie backs but hoping one of the thinner flavors will work when it arrives.
My other option is to cut the extended ears off automotive style wire clamps so they don't look so ungainly. A bit more fiddly to install that way but the wire has the right sealing tension on my silicone tubing.
Re the wire clamp, where I thought you were going was a miniature wire hose clamp gizmo (below infomercial is typical). I found an Ebay source of small diameter flexible SS wire that comes in 0.2, 0.4, 0.6, 0.8m dia. The 0.8mm I tested have is a bit too fat & stiff to mimic the loops & tie backs but hoping one of the thinner flavors will work when it arrives.
My other option is to cut the extended ears off automotive style wire clamps so they don't look so ungainly. A bit more fiddly to install that way but the wire has the right sealing tension on my silicone tubing.
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Peter,
Thanks for the info. I was familiar with the clamp 'gizmo' but even a miniaturized shop-made version of it wouldn't have fit in the space I had to work with around my water pump inlet. It does make a professional looking clamp though. The spring clamps in the photo you provided are the ones I mentioned that I've had trouble sealing my clear Tygon tubing. They do work great on soft silicone, though. -Terry
Well done Terry! - It looks so good, I bet Henry F. would be proud to display it!
I am sure you'll be running soon and we can see the video.
K2
I am sure you'll be running soon and we can see the video.
K2
Another mechanical masterpiece is coming !!!
Mighty pretty Terry!
John W
John W
My dad used to always say to add some ground pepper to the water if there were any small leaks as the pepper would get trapped in the hole and swell up thereby sealing it. Never tried it myself but he seemed to think it worked.
Hi Perko: Hot Stuff! But I dislike "sludge inducers", that usually produce unwanted sludge in places that cause other problems. So I rather prefer "proper" sealing techniques, like vacuum impregnation of porous castings with resin, etc. Professionally done, the chemistry of the resins is selected for lifetime durability at the service temperatures involved. Better still, is "no leaks".
Seriously, a dab of vaseline will stop a bleeding boxer or rugby player from dripping blood - all be it temporarily! But there is no way you would want anything less than a "proper" medical elastoplast and healing after the match. Likewise, "bodge!" sealants on engines, etc... I have used rad-seal on leaking radiators, sometimes for a couple of years, but have had it "wash away" from the flush when changing the coolant at 3-year service intervals (necessary to refresh the anti-corrosive properties of the solution). A replacement radiator was the proper solution to the leak. I have even done a "zinc alloy" solder repair to an aircon radiator, that lasted 4 or 5 years before corrosion caused it to leak again. So I consider this a temporary fix. On castings, I have seen fatigue cracks (in my job) and they were often "dirty" from some leak preventative gunge... which had no mechanical properties to prevent the casting form cracking further and failing at an embarrassing moment.
Take care with pepper. It is an acid, so may react badly with some metals and liquids, or encourage electrolytic corrosion somewhere you don't want.
K2
Seriously, a dab of vaseline will stop a bleeding boxer or rugby player from dripping blood - all be it temporarily! But there is no way you would want anything less than a "proper" medical elastoplast and healing after the match. Likewise, "bodge!" sealants on engines, etc... I have used rad-seal on leaking radiators, sometimes for a couple of years, but have had it "wash away" from the flush when changing the coolant at 3-year service intervals (necessary to refresh the anti-corrosive properties of the solution). A replacement radiator was the proper solution to the leak. I have even done a "zinc alloy" solder repair to an aircon radiator, that lasted 4 or 5 years before corrosion caused it to leak again. So I consider this a temporary fix. On castings, I have seen fatigue cracks (in my job) and they were often "dirty" from some leak preventative gunge... which had no mechanical properties to prevent the casting form cracking further and failing at an embarrassing moment.
Take care with pepper. It is an acid, so may react badly with some metals and liquids, or encourage electrolytic corrosion somewhere you don't want.
K2
Thanks for that. As I said, pepper was not something I was inclined to try, I prefer the 'fix it properly' method too.
The carburetor and its 'fixins' should be the final parts for this build. George designed a carburetor specifically for this engine, and I wanted to stick to its internals as closely as possible. The recirculating fuel loop I want to use though will require the addition of a fuel bowl.
My fuel loops are complicated by their constant displacement gear pumps which were originally intended to fuel up RC planes. Adding a simple speed control to their drive motor doesn't reduce the flow enough to reliably work in my application. Keeping the bowl filled without overrunning its drain requires the motor to run at a speed too close to zero. In the past I've used a .020" restriction in the pump's output line in order to raise the head pressure and force an internal leak through the pump's gears. This restriction which had to be placed well away from the carb in order to avoid a jet spray inside the bowl, raised the operating point of the motor for a more consistent rpm.
For the Inline 6, I experimented with a more elegant solution - a 'splitter' that returned a portion of the pump's output to the tank before it reached the bowl. The splitter required its own return-to-tank line which I was willing to add if the splitter could have be hidden in the floor of the bowl. It turned out that its performance while so close to the bowl was limited. Building the splitter into its own enclosure well outside the bowl improved things, but I didn't like the extra chunk of hardware. The splitter really belongs inside the fuel tank, but I was long past redesigning the tank. In the end, I went back to using a restrictor.
Some experimenting was also needed to optimize the shape and size of the fuel bowl. A tiny bowl with a pressurized inlet, negative pressure outlet, and gravity fed drain provides some challenges. The drain tube height inside the bowl establishes its steady-state fuel level which I want to be 1/8" below the spray bar. But, unless an accounting is made for surface tension across the drain's input, the actual level can be very different and inconsistently high. Another issue is that a maelstrom can be generated between a tiny bowl's inlet and drain, and this can affect fuel flow to the needle valve.
After a week or so, I had a tested bowl design that I was happy with, and I began the design of the carb body. The bowl was integrated into a body that used George's internals as well as the existing mounting pad on the intake manifold. The mount proved particularly troublesome, and the carb's installation will require some heroic effort with a tiny crowfoot fashioned from a 5/32" open end wrench.
Machining of the carb body began with a block of aluminum squared up to body's outside finished dimensions. Its six faces were carefully machined in as many setups. Despite two power brown-outs during machining and a couple operator errors that forced some design changes along the way, I was able to continually rescue the original workpiece and finally hold the finished carb body in my hands. The body was bead blasted, dipped in NaOH, and then alodine'd for a poor man's gold iridite like appearance.
The carb body was a fun side project that included a few 'firsts' for me. I don't think I've before put so much machining into such a small chunk of metal. I only recently discovered SolidWork's Text functionality, and I used it instead of my CAM software to add the engraving to the front of the carb. Another 'first' was the waterline machining operation using a 1/32" end mill that it required. Now, it's on to the 'fixins'. - Terry
My fuel loops are complicated by their constant displacement gear pumps which were originally intended to fuel up RC planes. Adding a simple speed control to their drive motor doesn't reduce the flow enough to reliably work in my application. Keeping the bowl filled without overrunning its drain requires the motor to run at a speed too close to zero. In the past I've used a .020" restriction in the pump's output line in order to raise the head pressure and force an internal leak through the pump's gears. This restriction which had to be placed well away from the carb in order to avoid a jet spray inside the bowl, raised the operating point of the motor for a more consistent rpm.
For the Inline 6, I experimented with a more elegant solution - a 'splitter' that returned a portion of the pump's output to the tank before it reached the bowl. The splitter required its own return-to-tank line which I was willing to add if the splitter could have be hidden in the floor of the bowl. It turned out that its performance while so close to the bowl was limited. Building the splitter into its own enclosure well outside the bowl improved things, but I didn't like the extra chunk of hardware. The splitter really belongs inside the fuel tank, but I was long past redesigning the tank. In the end, I went back to using a restrictor.
Some experimenting was also needed to optimize the shape and size of the fuel bowl. A tiny bowl with a pressurized inlet, negative pressure outlet, and gravity fed drain provides some challenges. The drain tube height inside the bowl establishes its steady-state fuel level which I want to be 1/8" below the spray bar. But, unless an accounting is made for surface tension across the drain's input, the actual level can be very different and inconsistently high. Another issue is that a maelstrom can be generated between a tiny bowl's inlet and drain, and this can affect fuel flow to the needle valve.
After a week or so, I had a tested bowl design that I was happy with, and I began the design of the carb body. The bowl was integrated into a body that used George's internals as well as the existing mounting pad on the intake manifold. The mount proved particularly troublesome, and the carb's installation will require some heroic effort with a tiny crowfoot fashioned from a 5/32" open end wrench.
Machining of the carb body began with a block of aluminum squared up to body's outside finished dimensions. Its six faces were carefully machined in as many setups. Despite two power brown-outs during machining and a couple operator errors that forced some design changes along the way, I was able to continually rescue the original workpiece and finally hold the finished carb body in my hands. The body was bead blasted, dipped in NaOH, and then alodine'd for a poor man's gold iridite like appearance.
The carb body was a fun side project that included a few 'firsts' for me. I don't think I've before put so much machining into such a small chunk of metal. I only recently discovered SolidWork's Text functionality, and I used it instead of my CAM software to add the engraving to the front of the carb. Another 'first' was the waterline machining operation using a 1/32" end mill that it required. Now, it's on to the 'fixins'. - Terry
Terry,
Your parts look amazing, like they were die cast. How much hand finishing do you do before bead blasting?
Your parts look amazing, like they were die cast. How much hand finishing do you do before bead blasting?
Actually, none. I'm willing to spend the time to let the machine do it. I've learned it's best to keep my hands away from the parts if I can. - Terry
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