Building A Billabong Engine

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Hi Gabby,
No mate, the thread hasn't ended I'm just a bit slow with updates and I'll probably still be working on this engine in five years time the way things are going.
I don't think the castings are commercially available, Len had enough made for the engines he built himself and he sold a few sets of castings but I don't think he has had any more made.
There is a youtube clip of the first engine Len built running here:


Well it's been a while since I've posted any updates but this build is still progressing albeit at a glacial rate. Working on other projects and having to travel a lot for work doesn't help but I have managed to inch the Billabong engine along a little bit.

To fabricate the crankshaft I wanted to try a slightly different approach so as to avoid having to cut out the remnant section of the main shaft from between the webs after everything is assembled. My plan for doing this meant making a couple of additional components to facilitate the assembly process. The first, an aligning pin machined to be a close sliding fit in crank web bores for the main shaft and the second a 1.5” disk exactly 0.625” thick to match the distance between the webs at the crank pin.

The main crank shaft and crank pin were machined from 1” 1045 CRS. The crank pin was machined to 0.750” for the big end then down to a press fit on each end to go into the webs. The main shaft was machined down to 0.875” as one section before parting off and centre drilling the end that had been held in the chuck. The shaft was then cut into two equal lengths and one end of each was machined to be a press fit for a length that matched the thickness of each web.

Machining the main crank shaft to 7/8” diameter.

The crank main shaft machined to size and marked ready to cut in half.

Crank shaft components marked up ready for assembly and the additional assembly aids.
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First step in the assembly was to press the crank pin into the first web. The press fit was fairly tight so the hydraulic press came in handy for this. Some newspaper folded a few times was used to protect the crank web surface.

Pressing the crank pin into the first web.

Crank pin installed in first web.

With the crank pin in the first web the aligning pin, which is a close sliding fit, was inserted into the main shaft bore and the second web fitted over it and aligned with the crank pin.

Crank web aligning pin in use.

Pressing second web onto crank pin.

The 5/8” disk was placed between the webs opposite the crank pin and the whole thing pressed together.

Crank pin and webs assembled.

In order to ensure that the webs and crank pin remained securely positioned, pins were installed rather than relying on the press fit alone. Each web was drilled through the centre of the crank pin and an 8mm pin, machined to a slight interference fit, was pressed in.

Setup to drill the webs for crank pin securing pins.

Crank pin securing pins installed.

The pins were left protruding about 0.250” on either side and then belted with a hammer to peen them slightly. This peening expanded them into the holes which not only served to ensure the pins stayed in place but meant they would be virtually invisible when machined flush.

Securing pins after peening.

After peening, the protruding pins were machined down to within a couple of thou of the web then draw filed flush.

Setup used to mill down the securing pins.

After a polish with emery cloth the location of the pins was virtually invisible.

The completed web and crank pin assembly.

Web assembly ready for main shafts to be inserted.

With the web assembly complete it was time to press the main shafts in to complete the crank assembly. The aligning pin was removed and the 0.625” disk positioned so it was beneath the holes for the main shafts. The disk served two purposes, the first to support the webs so the crank pin would not be bent when pressing in the main shafts and the second to act as a stop so the shafts could not be pressed in so far that they protruded into the space between the webs. The first shaft was pressed into position and the assembly flipped 180⁰ before pressing home the second shaft.

Pressing main shafts into web assembly.

The assembled crank shaft

As with the crank pin, the main shafts were also pinned. The webs were cross drilled through the main shafts again using 8mm light press fit pins.


Main shaft securing pins ready to press home.

After pressing them in, the pins were also peened. Because of the awkward position of the pins they were a bit tricky to support and while peening I managed to hammer my thumb and score a nice black nail in the process.

Securing pins after peening.

Using the mill in horizontal mode, the protruding sections were milled down nearly flush using a side and face cutter then finished with some draw filing and emery cloth.

The completed crank shaft assembly.

All up I’m pretty happy with how it came out, the only thing left to do is cut the key ways but I will do this after it has been mounted in the main bearings and I can work out how far along the shaft they need to be cut.


The completed crank shaft assembly.

I mounted the completed shaft between centres on the lathe and rotating it by hand there was about .005” total runout. I marked the high spots and a few tweaks in the press with the shaft supported on hardwood blocks at each end and I got that down to just under .001”.

The completed crank set up between centres in the lathe to check the runout.
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Very, very, nice work. I know this engine is your own design and it is really an awesome piece of work so far but do you have a set of drawings to share with the group here? I would love to attempt to build this engine.

Thank you,
Jim in Pa, USA
Thanks for the kind comments gents.
Hi Jim, the engine was actually designed by a mate of mine and there are no drawings as such, the details are all in his head. He only ever had a few sets of the castings made and although I believe he did sell a couple of sets they were never commercially available.
Hi Gabby,
No mate, the thread hasn't ended I'm just a bit slow with updates and I'll probably still be working on this engine in five years time the way things are going.
I don't think the castings are commercially available, Len had enough made for the engines he built himself and he sold a few sets of castings but I don't think he has had any more made.
There is a youtube clip of the first engine Len built running here:



That link is not working. Is there another?
With the crank shaft more or less done it’s time to make somewhere to mount it. This meant the next job was to bore the main bearings. I wanted the main bearings of this engine to be of the cast white metal variety so the bearing housings will be bored out to 1.125” which allows for the bearing to be bored to 7/8” leaving 1/8” of babbitt material all round for the bearing itself.

The bearing caps were secured onto the crankcase casting and the centre location of the main bearings marked out. The crankcase was mounted on the mill table then aligned and centred with the horizontal spindle ready for boring operation. A slot drill was used to produce a small flat which would prevent a drill from wandering when starting. The pilot hole was spotted with a centre drill then a 6mm stub drill was used to go right through. The pilot hole was then opened up using a 1/2” stub drill then a 5/8” MT2 drill bit.


Ready to drill the first pilot hole through the casting with a 6mm stub drill.

The pilot hole was increased first using a 1/2” stub drill then with a 5/8” MT2 drill.

With the first bearing pilot hole opened up to 5/8” the pilot hole for the second bearing was drilled. A 100mm ER11 chuck was mounted in the spindle to reach through the casting and hold the slot drill, centre drill and 6mm stub drill before going straight through with the 5/8” MT2 drill to finish the pilot hole.


Centre drill mounted in an ER11 chuck to spot the pilot hole.

The 5/8” MT2 drill ready to finish the second pilot hole.

It was at this point I discovered two flaws in my setup of mounting the crankcase flat on the mill table and using the horizontal spindle for the boring.

The first was that the casting had moved slightly under the load of drilling the second pilot hole meaning it was no longer correctly aligned with the first bearing or the cylinder mounting face. This was not a huge problem as there was still plenty of material left and this could be easily rectified during the final boring operation. I should have mounted a positive stop behind the casting to prevent this from happening, but the thought did not occur to me at the time.

The second problem was a bit of a show stopper for this setup though as there was not quite enough room to mount the boring head in the horizontal spindle and still have clearance for the extended boring bar to machine the first bearing. I could have used a shorter bar for the first bearing then used the longer bar for the second one, but the long bar is solid carbide so it’s very rigid and I preferred to do both bearings in the same pass.

It’s at times like this that I really love my Thiel mill because I can remove the universal table and mount work directly to the X axis slide. After a bit of juggling, the crankcase was mounted to the X axis vertical surface and aligned to the vertical spindle making sure to include a positive stop under the case this time. I also left the parallel used to align the casting in the correct plane in place and used a DTI to monitor if any movement occurred during the boring operation.


Crankcase casting mounted directly to the vertical X axis slide.

Another view of the crankcase mounted on the mill showing the positive stops, the parallel and DTI.

Action shot of the boring operation, this is about three quarters through the second bearing housing.

The second off centre pilot was bored back in line and the rest of the boring progressed with no further issues until the main bearing housings were at the required 1.125”. The outer sides of the crankcase were then faced flat to a diameter of 1.675” to remove the pattern draft and make the sides of the crankcase parallel around the bearings.
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The main bearing housings needed some anchor points to prevent the babbitt from moving. Using a 6mm end mill two keys were milled on either side of the crankcase and one on either side of the bearing caps. The 100mm ER11 chuck came in handy again for this operation.


Cutting the babbit anchors into the crankcase.

The finished babbit anchors.

View of the anchor positions with the bearing assembled.

The inner sides of the crankcase were also faced to 1.675” to remove the pattern draft, mainly so the components of the bearing mould & core would sit flat and parallel against the crankcase.


View of the setup for facing the inner side of the bearing housings.
With the bearing housings bored and keyed everything was now ready to pour the actual bearings but finding a source of babbitt was not as easy as I at first thought it would be. I visited a couple of different bearing shops with no luck and it was only when contacted BRS Bearing Remetalling Services in Doveton (Victoria, Australia) that I managed to find some. They agreed to sell me a kilo for $50.00 but when I called in to pick it up they gave me a chunk weighing closer to two kilo which should be enough to last me a long time.

Due to the size of the bearings I didn’t want to pour the two halves as solid plugs of Babbitt. I made up a mould / core fixture that would allow the bearings to be poured with a 0.625” void to keep the wall thickness to 0.250” which I hoped would prevent any shrinkage problems.

One end of the fixture is an interchangeable threaded bush which is clamped in the bearing not being poured to centre the core assembly. The 0.625” core has two flat wings that separate the two halves of the bearing and a disk which forms the base of the mould. The two semicircular pieces are clamped onto the protruding wings to form a riser dam which feeds the mould as the babbitt cools to reduce shrinkage.


The bearing mould / core fixture.

The areas of the core / mould fixture that will be in contact with the babbitt were blackened over some burning kero to act as a release agent preventing the babbitt from adhering. A 1.125” bush was fitted on the fixture and it was installed on the crankcase and clamped in place with a piece of aluminium shim under the bearing cap. The cap of the bearing to be poured was clamped down over the wings of the fixture and the disk tightened up against the inside edge to seal the bottom of the mould before the riser pieces were clamped into place. The last step was to plug the oil hole in the bearing cap to prevent the babbitt from escaping through it, for this I used an aluminium pop rivet which just so happened to be the right size. The crankcase was then positioned on its side and chocked from beneath to sit level and it was ready to pour the bearing.


The bearing mould / core fixture before fitting the bearing caps.

And clamped by the bearing cap for the first bearing.

Everything in place (except the rivet) ready to pour the first bearing.
I’m using a tin based babbitt with a pouring temperature of around 430⁰C. While the low melting point makes working with babbitt fairly easy it is important to be careful with the temperature. Obviously, if the metal is too cold it may start to set half way through the pour resulting in an unusable bearing. However, if it is allowed to get too hot or left in the molten state for too long, the metallurgical properties can change as lower melting point metals burn off. A laser thermometer is probably the best way to monitor the temperature but I don’t have one so I relied on a more primitive method. A small piece of pine (I used an icy-pole stick) immersed in the molten babbitt for a few seconds will just start to blacken if the temperature is correct. If the stick doesn’t blacken it’s not hot enough, if it ignites it’s too hot. Not as accurate as a thermometer but by all accounts a valid method and it worked ok for me.

Preheating the bearing housing before pouring is an important step as pouring the molten babbitt into a cold shell will result in any number of failures due to the babbitt cooling too quickly. The metal may start to set before the pour is finished resulting in a short pour or an uneven bearing substrate. The bearing may shrink away from the housing and not be retained properly allowing movement. I used an LPG torch with a fairly large burner to preheat the crank case before pouring each bearing. The crankcase was heated until the area around the bearing was hot enough to sizzle when touched with a wet finger. Ideally it should probably have been a bit hotter but given the size of the casting this was about the best I could practically do given the torch I was using.


Preheating the crankcase (this was actually before pouring the second bearing).

My melting pot, made from a piece of 1.5” steel pipe with some 12mm threaded rod for a handle, was pre charged with a few of chunks of babbitt cut from the larger ingot and the same LPG torch was used for the melt.


Melting the babbitt.

How the test stick should look when temperature is within range.

The LPG torch was swapped back and forth a few times between the crankcase and the pot to make sure everything was at the right temperature and the babbitt was given a gentle stir to ensure even consistency before completing the pour. Each half of the bearing is done as a single continuous pour. I poured the crankcase half first, immediately followed by the bearing cap half. The trick is not to let the first pour overflow into the second half and with hindsight I should have made the wings on the core a bit longer to match the height of the riser ring but in the end it all worked out ok.


Action shot of the first bearing pour.

View of the completed pour after it had set.

After the pour everything was left to sit while the bearing cooled. In theory I should probably have pre tinned the bearing housing to guarantee the shells adhere to the walls but I thought I would just do the pour and see how things went. After around twenty minutes I disassembled everything to inspect the pour and was pretty happy with the result. The babbitt had flowed nicely, filled the anchor keys and not pulled away from the sides of the housing. There was no discernible movement of the shells within the bearing cap or the crank case housings so all was good.


The freshly poured bearing cap.

The crankcase babbitt shells.

With the first shell a success it was a on to the second one. The same setup was used with a 0.625” bush on the mould / core fixture allowing it to be clamped in the first bearing. Everything else was a repetition of the first pour and the result was pretty much the same.


The second completed pour.

View of the two crankcase bearing shells.
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With the babbitt pours successfully done the next job was to trim the risers off. The plan was to use a slitting saw but I wanted to be sure the bearing shells wouldn’t move during the process so an improvised clamp was made up to ensure the shells stayed in place during the cut.


View of the strap clamp in use.

Action shot trimming the risers.

View of the bearing with the riser trimmed back.

And from above.

Before the bearings could be bored to size I needed to make some shims to go between the crankcase and bearings caps to allow for adjustment to compensate for wear over time. I used two 0.0015” shims, one 0.002”, one 0.003” and one 0.004” shim on each bearing cap stud. Cutting the shims to the correct size was easy enough, I just used a sharp set of tin snips. To put in the holes, a small jig was made to clamp a stack of five shims in a tight pile between a guide hole that allowed the shims to be drilled using an 8mm slot drill.


A few shims along with the jig for drilling the holes, the shim thickness was marked with permanent marker.

The shims stacked on each stud.

View of the bearing cap installed with the shims in place.

With the caps shimmed the bearings were now ready to be bored to size using pretty much the same setup as that used to bore the bearing housings. The use of a sharp, high positive rake HSS tool is usually recommended to machine babbitt but I wanted to stick with the solid carbide boring bar so I used a polished high positive rake aluminium insert. Running at 210 RPM this produced a nice finish in the babbitt which machines very easily as you might expect.


Mill setup for boring bearing shells.

To get the bearings to the required 0.875” required the removal of around 0.125” of material. A couple of initial cuts were made to get the bearings circular in shape before a reference measurement was taken to calculate exactly how much more material needed to be removed. A couple of heavier cuts were made to bring the bearings to 0.833” ready for a couple of finishing cuts to get to the final size.

The facing stop on the UPA-4 can be used in conjunction with gauge blocks to make very accurate adjustments, this is particularly useful when working to an imperial size with a metric boring head.

Fist measure the bore and calculate the depth of cut needed to bring the bore to the final required size, in this case (0.875-0.833)/2 = 0.021”. I wanted to make two cuts to reach the final size, one of 0.018” and a finishing cut of 0.003”.

Assemble a stack of gauge blocks to a total ending in the amount required for the cut. In this case I made a stack from the following blocks: 0.100 + 0.110 + 0.080 + 0.100, giving a total of 0.418”, the two 0.100 being wear blocks.

Place the stack between the stop plate and pin of the UPA-4 and clamp the stop plate to reference the position of the boring head.


Initial gauge block stack in place between the stop plate and pin of the UPA-4 boring head.

Assemble a second stack of gauge blocks smaller than the initial stack by the amount the head needs to be adjusted, in this case 0.400” (0.100 + 0.200 + 0.100), then adjust the boring head until this stack is a sliding fit between the stop plate and pin. The boring head will now take a cut of exactly the difference between the two gauge block stacks, which in this case was 0.018”.


Boring head adjusted to size of second gauge block stack.

Using this method removes the possibility of errors caused by misreading the adjustment scale or from backlash in the boring head adjusting screw. The procedure was then repeated to set the boring head to make the final 0.003” cut and the bearings were bored to exactly 0.875”.


A view of the 0.018” cut showing the surface finish.

The outer flange of each bearing was faced off using the UPA-4 and a 45⁰ chamfer cut on the outer bearing edge. The bearing caps were then removed and the oiler holes drilled through the bearing and slightly countersunk.


Setup for facing off the outer flange of the bearing shells.

A view of the bearing cap bored to final size and ready for fitting with the crankshaft.
With the main bearings bored to size it was time to fit the crank shaft and finally see something come together. A couple of spots of bluing compound were applied to the crank shaft before assembly to give an indication of any high spots that required scraping. With the bearings assembled, the crank was able to be rotated with some slight binding. Some binding on the initial fit is a good thing because this means only a little scraping is required to bring the bearing to the required fit. If the shaft had been a loose fit then some shims would have to be removed and more substantial scraping performed to fit everything correctly.


The crank shaft fitted for bluing.

The bearings were disassembled and the points that were binding were clearly indicated by the locations where the blue had transferred to the bearing shells.


The bearings disassembled after a bluing cycle.

The blue areas indicate the high spots.

The high spots were scraped back using a three lobe bearing scraper and everything reassembled and the process repeated until the crank rotated freely and the blue transferred evenly across the bearing surface.



The three lobe scraper used to scrape the bearings.

The bluing pattern after the bearings have been scraped to fit.

And the crankcase.

The last step was to add some grooves to distribute oil evenly around the crank shaft. I went with cross pattern oil groves which were first marked in using a texta before a Dremel fitted with a 3mm carbide ball burr was used to cut them in. The groves were cut freehand and I was aiming for a depth of around 1/32”. Being soft, the babbitt cut very easily so I had the Dremel rotating at the second slowest speed and had to be careful to keep the tool moving to prevent it from digging in. As can be seen, a couple of the grooves came out a bit wonky but they should do the job. Last step was to chamfer the edges of the grooves using a scraper ground from a hacksaw blade.



View of the oil grooves cut into each bearing shell.

A couple of drops of oil were placed in the bottom of the crankcase shells before fitting the crankshaft. A couple more drops were put on top of the crankshaft before assembling the bearing caps then a bit more was added through the oiler holes. The crankshaft rotates very smoothly and has virtually no measurable vertical play so I’m very happy with how these bearings have come out.


The completed main bearings.

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