1/3 Scale Ford 289 Hi-Po

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A few small parts later, and I had a functional water pump. The impeller was machined from Delrin and pressed onto a 3/16" shaft. Its one thou interference fit wasn't tight enough to keep it from slipping under load and so it had to be pinned. The shaft runs in a pair of 3/8" sealed ball bearings separated by a half inch spacer. It's sealed by a pair of silicone o-rings located on the shaft below the rear bearing. For good measure and lubrication while dry running, the o-rings were coated with silicone grease. Drag on the spinning impeller was kept to a minimum by insuring its two thrust surfaces were free of grease. The pulley mounting flange was secured to the shaft with a grub screw tightened against a machined flat. Axial thrust is limited by the impeller itself spinning between the backing plate and an integral thrust bearing machined into the pump body.

At least two varieties of impellers could be found on the small block Ford. A six vane stamped steel impeller was the factory's cost effective solution. A 'high performance' cast aluminum version was also available from the aftermarket. One difference between the two is that the stock impeller has straight vanes while the aftermarket version has curved vanes. Out of curiosity I decided to machine versions of each and compare their relative performances in a crude test bench. For some reason, maybe because it was fun, I made spares of both impellers.

The coolant outlet tubes double as dowels to locate the water pump and timing cover to the block. They fit snugly inside the pump's backing plate, but their orientation inside the pump body is very important. Both ends of the tubes were identically beveled so their orientations in the pump sub-assembly can be verified. The dowels are sealed by the pump and cover gaskets.

The outlet tubes were fashioned from quarter inch aluminum hobby tubing, but with a wall thickness of only .014" they are rather fragile. I was concerned that over time they might become stuck inside their close-fitting surroundings and create problems for later disassembly. Anodizing or nickel plating would reduce the long term effects of their wet environment, but based upon previous experience I had concerns about making reliable electrical connections to them during plating, Instead, I settled on an alodine dip but just in case I also made an extra pair.

The pump and its impellers were tested as those were in my Offy build. The pump's input was fed from a water reservoir approximating the expected volume and input/output hose locations of a radiator. The pump's output hoses dump into a 1500 ml beaker. With a drill spinning the pump, the time required to empty the reservoir into the beaker was measured. In a second test, the output hoses were raised above the water level in the reservoir until the flow stopped giving the maximum water column supported by the pump. This number was converted to a rough head pressure measurement.

My best Offy results were used as a baseline for comparison since that pump worked well in actual operation with the engine's 3 cubic inch coolant capacity. At 1300 rpm it flowed an average 15 SCIM (std. cubic inches per minute) and was capable of .32 psi head pressure.

The stock six vane impeller running in the HI-PO's pump body was tested first. It produced the same .32 psi head pressure, but flowed a whopping 115 average SCIM. I expected some improvement over the Offy's pump because of the V-8's larger scale and dual outputs, but the 7.5X improvement was a pleasant surprise. The test was repeated several times with consistent results.

The curved vane disk impeller was tested next. It was the clear winner producing .43 psi and flowing an average 170 SCIM. Since the Hi-Po's estimated coolant capacity is 8.5 cubic inches, this pump should work well assuming the actual flow rate achievable in the engine is any where near the pump's capability.
Another positive result was that after the few days of testing there were no noticeable leaks. I did discover though that I'd made the inlet barb from steel instead of stainless when the water in the beaker began developing a brownish tinge.

I had planned to start on the crankshaft next, but will instead begin work on the bell housing. It would be nice to finish up the major parts requiring marathon machining sessions before the summer heat sets in, but to be honest I don't like making crankshafts and I'm probably procrastinating. In any event, I haven't yet created a model for the bell housing, and so it looks like I'm headed back to SolidWorks for a while. - Terry

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An electric starter with ring gear engagement has been a nice-to-have feature of this engine since the beginning of its build. The starter will be an integral part of the bell housing, and so a candidate was needed before getting too deep into the design of the bell housing.

My quarter scale Merlin and Knucklehead engines have electric starters, but I wasn't able to come up with a ring gear version for my Inline 6 due to its smallish (one-fifth) scale. The largest dc brush motor that looked appropriate on that engine was a size 390, but testing showed insufficient cranking torque especially around its anemic 4:1 ring gear ratio.

The HiPo's larger scale provides more opportunity, and modeling showed even a size 775 motor looking at home on it. This same size motor performed well on my Merlin, and I guesstimated the HiPo's cranking requirements to be similar. Cranking current measurements on the Merlin combined with the starter motor's performance curves were used to create a spec for the HiPo starter. These waveforms during cranking showed the Merlin's starter delivering some .26 ft-lb torque @ 5000 rpm during starting. With its 10:1 starter gear ratio, the actual crankshaft torque worked out be 2.6 ft-lb at 500 rpm (.2 hp or 150 mechanical watts). Tests were never performed,however, to investigate a reduction in cranking speed using a higher gear ratio. I chose this same 2.6 ft-lb crankshaft torque requirement for the HiPo but with a target rpm between 200 and 600 rpm.

It looks like the largest diameter flywheel that will fit inside the HiPo's bell housing is 4.375" which is good for 140 teeth on a 32 DP ring gear. A 12 tooth pinion will provide a nearly 12:1 gear ratio. Two issues come up though. First, the oil pan will prevent a 775's pinion from engaging the ring gear and so an idler gear must be added. The biggest issue is that a one-way clutch must be inserted somewhere between the crankshaft and the starter motor to prevent the starter from being over speeded. For example, with a 12:1 gear ratio, a 5 krpm running engine will try to spin the starter at 60 krpm.

After a lot of head scratching and modeling, I decided to integrate the clutch into the flywheel itself. The plan is to press a 1" diameter sprag clutch into the flywheel that will run on a hardened sleeve keyed to the crankshaft. The hardened sleeve will also have a hex socket integrated into its rear end to allow the engine to be drill started if necessary. A consequence of this design is that most of the flywheel's inertia will be dumped from the crankshaft just after starting but, I'm not convinced a well-running V8 needs much flywheel anyway. The Conley engines which used a similar scheme didn't seem to suffer from lack of flywheel inertia, but they did wind up with very impressive throttle responses.

A 550 size motor will also fit inside the available space in case my starting torque requirements turn out to be less than expected, and so I've ordered 12 and 21 'turn' RC motors to experiment with. (I just hate the way these things are spec'd.) Since I really didn't feel like dealing with the starter just yet, most of my time recently was spent procrastinating. But with the starter ground work now laid I think it's safe to finally get on with the bell housing. - Terry

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An electric starter with ring gear engagement has been a nice-to-have feature of this engine since the beginning of its build. The starter will be an integral part of the bell housing, and so a candidate was needed before getting too deep into the design of the bell housing.

My quarter scale Merlin and Knucklehead engines have electric starters, but I wasn't able to come up with a ring gear version for my Inline 6 due to its smallish (one-fifth) scale. The largest dc brush motor that looked appropriate on that engine was a size 390, but testing showed insufficient cranking torque especially around its anemic 4:1 ring gear ratio.

The HiPo's larger scale provides more opportunity, and modeling showed even a size 775 motor looking at home on it. This same size motor performed well on my Merlin, and I guesstimated the HiPo's cranking requirements to be similar. Cranking current measurements on the Merlin combined with the starter motor's performance curves were used to create a spec for the HiPo starter. These waveforms during cranking showed the Merlin's starter delivering some .26 ft-lb torque @ 5000 rpm during starting. With its 10:1 starter gear ratio, the actual crankshaft torque worked out be 2.6 ft-lb at 500 rpm (.2 hp or 150 mechanical watts). Tests were never performed,however, to investigate a reduction in cranking speed using a higher gear ratio. I chose this same 2.6 ft-lb crankshaft torque requirement for the HiPo but with a target rpm between 200 and 600 rpm.

It looks like the largest diameter flywheel that will fit inside the HiPo's bell housing is 4.375" which is good for 140 teeth on a 32 DP ring gear. A 12 tooth pinion will provide a nearly 12:1 gear ratio. Two issues come up though. First, the oil pan will prevent a 775's pinion from engaging the ring gear and so an idler gear must be added. The biggest issue is that a one-way clutch must be inserted somewhere between the crankshaft and the starter motor to prevent the starter from being over speeded. For example, with a 12:1 gear ratio, a 5 krpm running engine will try to spin the starter at 60 krpm.

After a lot of head scratching and modeling, I decided to integrate the clutch into the flywheel itself. The plan is to press a 1" diameter sprag clutch into the flywheel that will run on a hardened sleeve keyed to the crankshaft. The hardened sleeve will also have a hex socket integrated into its rear end to allow the engine to be drill started if necessary. A consequence of this design is that most of the flywheel's inertia will be dumped from the crankshaft just after starting but, I'm not convinced a well-running V8 needs much flywheel anyway. The Conley engines which used a similar scheme didn't seem to suffer from lack of flywheel inertia but instead wound up with very impressive throttle responses.

A 550 size motor will also fit inside the available space in case my starting torque requirements turn out to be less than expected, and so I've ordered 12 and 21 'turn' RC motors to experiment with. (I just hate the way these things are spec'd.) Since I really didn't feel like dealing with the starter just yet, most of my recent time was spent procrastinating. But with the starter ground work now laid I think it's safe to finally get on with the bell housing. - Terry

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I would think that the mass of the harmonic balancer should at least partially offset the inertia loss in flywheel disengagement. This is an excellent write up on your proposed starter system!

John W
 
Interesting solution. Don't know how much room you have axially, but could you squeeze in a thin flywheel beside the gear? Perhaps it could occupy some of the annular space in the recessed face of the gear.
Charles,
Yes, that's the reason the flywheel was turned down just under the ring gear. I can press a flange onto the the crankshaft sleeve and then bolt a secondary flywheel to it if necessary. - Terry
 
What, no "working" starter Bendix? Oh well - maybe next engine? Still VERY impressive!

When's it going to go VROOM-VROOM without you having to supply the sound effects?
 
The bell housing was designed around models of the already completed block and 775 motor adapter. The hope is that the adapter will absorb minor changes to the starter as its design is finalized. If it turns out that a 550 size motor will work after all, only a new adapter will be required. An additional constraint on the bell housing's design was that it could be finish machined from one side of the workpiece using a 3/8" ball end mill.

There were several bell housings available for the small block Ford. Under the constraints I was working and after my traditional battles with SolidWorks' filleting tool, I ended up with something that was more or less an average of a couple of the full-size versions. The biggest disappointment with my final result is that I wasn't able to duplicate the rear end of the HiPo's starter flange. Its swept conical shape wasn't a problem but getting SolidWorks to blend it smoothly into the rest of the existing model was a battle I lost. After several frustrating days of starting the design over (and over) I gave up, and the end result is shown in the photos. George though was able to handcraft an accurate copy of the original.

The workpiece was band sawed from my dwindling stick of 7075 before being squared up to the bell housing's hefty (6" x 7") outside dimensions. An extra 1/8" stock was left on one end for vice-holding during the final exterior machining operations.
The bell housing's interior was machined first with most of the excess stock being removed with a 1/2" roughing cutter. It was then finished with 1/4" and 1/2" ball cutters for a total interior machining time of about four hours.

The exterior was roughed in using a 1/2" cutter and finished with a long 3/8" ball cutter. Before machining, the interior was packed with modeling clay to help dampen workpiece vibrations as its wall thickness approached its finished value. The more complicated exterior surface required nearly twice as much machining time. The final operation was to bolt the nearly finished bell housing to a fixture plate for removal of the 1/8" work-holding stock. Eighty percent of the ten pound workpiece wound up in chips.

The completed bell housing was bead blasted and will later be dust coated with Gun Kote gray. After an oven cure this very thin coating will seal the outside surface from grease and oil but maintain the look and feel of a bare cast aluminum.

The finished bell housing completes the kit of machined 'castings' for this engine. The next step will be to work on the starter while procrastinating over the dreaded crankshaft. - Terry

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so this is what you can do with SolidWorks and a Tormach, very impressive, am hoping to be able to do similarly well with Fusion360 and a Tormach, would you want to talk me out of Fusion360 ? to what extent would using Fusion360 make interacting with you and George Britnell more difficult ?
 
so this is what you can do with SolidWorks and a Tormach, very impressive, am hoping to be able to do similarly well with Fusion360 and a Tormach, would you want to talk me out of Fusion360 ? to what extent would using Fusion360 make interacting with you and George Britnell more difficult ?
I really have no CAD/CAM experience except with 2007 and 2010 SolidWorks and 2007 Sprutcam which is what I started with 20 some years ago, and it seems I'm still learning about. So, I can't speak to any other software. I do know that George also uses SolidWorks, but I don't know about its ability to reliably interchange files between other CAD programs. Good Luck. - Terry
 
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A 3/4" disk of 4-1/2" diameter Stressproof arrived from Speedy Metals in time to start work on the flywheel/ring gear. Its sawed ends were faced flat, and a 1.3125" hole was bored through its center for a one-way clutch. This hole's exact diameter was important for a couple reasons. A too-small hole risks damage to the bearing while being pressed, and a too-large hole can allow the clutch to slip. The manufacturer's recommended hole size should be used rather than a shop measurement of the bearing's o.d. The flimsy outer shell of a large diameter sprag bearing is designed to assume the contour of the hole it's pressed into, and out of the box it may not even appear round.

A lot of material had to be removed from the disk to create the gear blank, and both the mill and lathe were used. A shop-made mandrel and a set-true chuck kept the blank's o.d. concentric with its center hole.

The 138 teeth on the 32 DP gear required four hours of cutting time on my Tormach. I've heard of builders cutting the .067" deep roots in single passes, but I used three. Normally, I'd have walked away from a four hour operation and allowed the machine to work alone in the dark. Instead, I hung around to listen for cutting noise changes that might signal a cutter becoming dull.

My particular bearing has a roll-strengthened end that's intended for the face of the press ram. Care is needed to insure this end of the bearing is installed through the correct side of the flywheel required for proper lock-up direction. It's easy to get confused, and the bearing can be damaged if it has to be removed. My past success rate over some half dozen bearings hasn't been 100%. A simple shop-made insertion tool reduced the chances of bearing collapse during the pressing operation.

The clutch's inner race was machined from drill rod. It's i.d. was broached for a key that will lock it to the crankshaft while the one-way clutch is allowed to spin freely on its hardened o.d. A hex socket was machined into the rear end of the race as a backup for starting the engine with a drill. Unfortunately, the sleeve's construction photos were lost in a corrupted memory card.

The next steps will include finalizing and machining the motor adapter(s). - Terry

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First up for the finished ring gear was a sanity check of its center-to-center spacing when meshed with a commercial gear of the same DP. An advantage of using 32 DP is that it's a popular gear pitch used in some Traxxas RC stuff, and a handful of pinion gears can be purchased for $10 from a number of Amazon sellers. Measurements using an 18 tooth pinion selected for an idler was very close to expected.

A simple plate with a pressed-in flywheel shaft needed to make these measurements without a bell housing evolved into a complex fixture capable of testing a complete motor assembly including its output torque. Accumulated runout from the flywheel, hardened clutch sleeve, and dummy shaft measured at the ring gear's tooth tips in this fixture was a disappointing but usable .0035".

Along the way I realized I hadn't provided a way to keep the flywheel from walking off the crankshaft sleeve. The solution was to hard press a machined flange onto the sleeve to limit the flywheel's aft thrust. A secondary flywheel can be later attached to this flange if running is shown to benefit from some of the free-wheeling flywheel's inertia being added back to the crankshaft. On the other hand, if the electric starter is totally abandoned, the main flywheel can be easily locked to the crankshaft with a couple bolts through the flange.

Although I had some previous data showing the torque of the Nichibo 775-8511FDAS and John Deere motors were similar, I wanted to make better measurements since the difference in their prices is nearly 10X. To be fair, the John Deere motor is available only as a component in a starter assembly most of which ended up in my odds&ends drawer.

Nearly identical adapters designed for 12 tooth pinion and 18 tooth idler gears were machined for each motor. The only difference between them is the spacing between the pinion and the idler gears, and it took a couple scrapped parts to get this just right. Although the mating bendix gear in the John Deere starter assembly is 32 DP, its motor pinion appears to have been cut for a slightly different DP for some reason. It required a different spacing than the true 32 DP pinion on the Nichibo.

A shop-made tool was used to keep the idler shafts straight while they were being pressed into their adapter plates, but both needed tweaking afterwards. The one thou interference fit used for the 1/8" steel idler shafts in the 1/8" aluminum adapter bases was probably too snug and would have benefitted from a half-thou-under reamer had I had one.

Before evaluating the motors, a final fit check was made of each finished motor assembly installed in the bell housing and the flywheel spinning in the block. A test rod running in the inner and outer main (ball) bearings simulated the crankshaft so the fit of the ring gear to each starter assembly could be verified. Got to admit I was happy the fit in the bell housing matched the one in the test fixture.

After making a temporary pulley for the crankshaft flange, I'll finally be able to get on with my little science fair project. Torque measurements will be made using the motors to wind up weights suspended from the pulley. Each motor's usable torque can then be determined by progressively increasing the weight while monitoring the motors' rpm and current draws. - Terry

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The only difference between them is the spacing between the pinion and the idler gears, and it took a couple scrapped parts to get this just right. Although the mating bendix gear in the John Deere starter assembly is 32 DP, its motor pinion appears to have been cut for a slightly different DP for some reason. It required a different spacing than the true 32 DP pinion on the Nichibo.
Probably 'addendum modification'. A 12 tooth gear will have undercut teeth unless addendum modification is applied. It allows a stronger tooth form, but increases the pitch.
 
Probably 'addendum modification'. A 12 tooth gear will have undercut teeth unless addendum modification is applied. It allows a stronger tooth form, but increases the pitch.
Thanks, Charles. I'd never heard the term before (my copy of Ivan Law's book doesn't mention it), but after reading up on it I think you're right. My 12 tooth gear's addendum seems to have been increased to a DP of 42. - Terry
 
Were can i get the files for this engine would so like to resin print it
 
Terry
If I may ask are you putting some kind of a bendix starter drive on. So it will disengage after the engine starts???
 
Martynb1:

As of October of last year when I got my set of files from George, the procedure was to PM gbritnell about them. The files aren't free, but considering the amount of work that George put into developing them, they are VERY reasonable.

Don
 

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