Not sure. I do like the idea of the engine being self contained rather than needing a drill to turn it over. I'll see.

Rod

The crankcase is made from 4 bits of 1/4" ally plate. Front and back machined together, drilled and reamed for the crankshaft bushes

I made a bush from 1/2" PGMS to keep the plates aligned for further work

Milling the 21 degree angles for the cylinder seats (after cutting off most of the waste on the Lidl bandsaw)

Then hacking out the profile

and finishing with a 6mm slot drill and a 6mm ball end mill

The hole for the cylinder seat was step drilled in the pillar drill to 1" then transferred to the mill to use the boring head for final sizing

Then drilling the various holes

Tapping the holes on the side plates using the GHT pillar tool

I'm trying now to get a good join at the "ridge" so the side plates were fastened at the correct spacing to a base plate and the crankcase top plate angle machined in situ. With a bit of dead reckoning and a couple of swaps from side to side I was happy with the result

Cutting the "eaves" in situ as well

It's OK

More holes to make in the crankcase front for the cam housing and cam shaft. The spacing from the crankshaft to the camshaft will be slightly altered from the drawing because I will be using 0.8M gears instead of 32DP.

Rod

A digression on cams.

I've been slightly sceptical of the accuracy of the method that Randall Cox uses(and never really understood) to produce the cams (as shown in Jason's pictures) so I thought I would have a look at the process and compare it with the Manual Numerical Control method that is CamCalc. However, I must emphasise that the Cox method clearly works because there are many examples of running Hoglets.

I drew the Cox process (I loved my Spirograph when I was a kid). The large circles are the path of the cutter as it moves around the blank in 5 degree steps with the flank radius offset of 0.4" and a lift of 0.065"

A couple of points first: For a truly Harmonic cam the transitions between the base circle and the flank circle must share a radius, as must the transition between the flank circle and the nose circle. Although not given as a parameter in the Hoglet drawings, the CAD sketch shows that the action angle of the cam (the transition from base to flank) is 135 degrees. The nose circle is drawn as a tan, tan, tan circle to the the 2 flanks and the maximum lift line.

Using these parameters in CamCalc I get this:

The nose radius from CamCalc is a little larger than the Cox method shows (which is constructed by filing until it looks right). In CamCalc a sharper nose would be given by reducing the flank radius slightly.

The CamCalc method always seems a little laborious (not to say tedious) – take a cut, wind the handle,move the cutter height, take a cut, wind the handle, move the cutter height, take a cut… but the Cox method is no different really. I would use a 3 degree increment for this size of cam and Cox uses 5 degrees.

Conclusions: I like the Cox method, it has an elegant simplicity that does not require following a list of numbers. It is not quite as accurate as CamCalc in the nose area but for the sort of engines we make this is immaterial. For this particular engine there is a down side and that is that the cams must be machined in the vertical mode with the ensuing problems of rigidity with an interrupted flycut. With CamCalc the cam blank would be horizontal and the machining is a light cut with an end mill for each increment of rotation and no risk of interference from the boring bar on the subsequent cams.

I shall be using the Cox method for my Hoglet 'cause it's good enough and a different challenge and I like that.

Rod

Edited By Roderick Jenkins on 01/09/2022 11:49:46

Yes. Sadly, I dont think my Sherline mill with its maximum collet size of 1/4" is rigid enough to make the cam shaft in vertical mode with a woodruff cutter hanging 1 1/2" out of the chuck. If only Fusion let us have a 4th axis

I had thought about individual cams and cutting the gap between them so that they interlock at the correct orientation. But, the Cox method is new to me so it's always nice to try something novel.

Cheers

Rod

PS: I think the Cox method produces a smoother facet because the cutter has a smaller radius than CamCalc which is a straight line cut and therefore of infinite radius 

Edited By Roderick Jenkins on 01/09/2022 13:07:59

One thing I should mention is that I have enjoyed Andrew Whales' Hoglet videos on YouTube – very useful for envisioning the bits even if we choose different methods according to the kit we have available.

The cam housing is a complicated bit of carving

Need to bring out the Dore facer again to cut the space for the cam gear

The top of the housing is at 25 degrees and the cam follower holes at 23 and 29 degrees. The housing sits on a jig made from 2 bits of steel out of the oddments drawer Loctited together. I have marked every ten holes (1 degree) on the dividing plate with a Sharpie to help keep track of the rotation

Drilled 6mm and reamed 1/4". Fortuitously, the centre on my dividing head tailstock is 1/2", the same diamter as the relief for the cams to rotate in so I was able to provide a bit of support

The housing cover was squared up

Held by the cover to hack out some more swarf

Then trimmed

Forgot to take pictures of drilling and reaming the cam shaft hole and rounding the profile – kept getting distracted by the sounds of Merlin engines flying round the house

When I made the Crankcase front plate I drilled the smaller hole according to the drawing, forgetting that I needed to enlarge the dimension by 9 thou to cope with the slightly larger diameter gear caused by using a 0.8M rather than 32DP. So, squared it up

and re-centred

then drilled the holes and reamed in the correct (I hope) places

Just one more cosmetic oversight to trim

Phew. The cam shaft and crankshaft holes are oversized for bearings to be pressed in but they seem to line up, which is nice.

Thanks for looking in.

Rod

Edited By Roderick Jenkins on 04/09/2022 16:47:52

Cams. This is my setup.

For the top cam the table is at it's very lowest extent. A respectable cam set was produced though it was hard work. I try and avoid feeding a cut by raising the table ( I don't have a quill). 2 hours of moving the table up and down was painful on the wrist. Sadly, I got the orientation of the single cams reversed. I found it difficult to get my head around where the peak of the cam is using this method. The interrupted fly cut, together with the flexibility of the whole setup is not very restful either. I prefer CamCalc for the next try- much gentler.

3 degrees (half a turn) between each cut

The cams are made fro EN3B and case hardened. I am fortunate to a have a small stock of genuine Kasenit. The ends were covered in Tippex Rapid then the blank heated and dipped in the Kasenit before heating to bright red and quenching in water

The dappled grey is a good sign

A file skidded off nicely. The duff one (upper) and the good one polished with some wet and dry.

Rod