Nerd's Webster build

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Nerd1000

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So my first proper dip into model engines begins! The ubiquitous Webster engine. I'm sorry to say that I haven't yet finished any parts, so perhaps I'm getting ahead of myself in starting a build log, but things are fresh in my mind and I'm feeling enthusiastic so it's a good time to write.

I decided to start with the cylinder head, so it's over to my little Atlas horizontal mill to square up the stock...
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The slab milling cutter makes fairly easy work of facing blocks like this, though with only 1/4 of a horsepower nothing happens fast on the Atlas.

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It's a pity I didn't start this project sooner, as we're making lots of nice Christmas tinsel!

Next we need to mill the shoulder in the side, so the slab mill is replaced by a 10mm side and face cutter.
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The Atlas has power feed so I can get nice action shots like this from time to time.

I finished up by drilling and tapping the hole in the bottom surface. As small AF fasteners and taps are uncommon here in Brisbane I've decided to replace them with metric ones where possible, in this case M5. Soon after completing this operation my girlfriend grew tired of practicing her cast net throwing skills on the lawn and asked to make a trip down to the river for a practical test... So the remaining drilling operations (and pictures thereof) will happen later.

Ciao!
 

ZebDog

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watched a couple of vids of this engine on YouTube.
looking forward to seeing this little chap come to life
 

Nerd1000

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Last weekend we went into covid lockdown for three days, and whilst I only just got around to posting in the aftermath of that it did give me plenty of shop time. Onward to the good stuff:

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The Webster head has a lot of holes to drill and in some cases tap. I picked up the edges of the part with an edgefinder and offset the appropriate distances by counting turns of the mill handles...
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Spotted...
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And drilled to depth in each case. These drillings included a pilot for the spark plug hole, which would be important for boring the cylinder socket later. Another challenge was the counterbore for the spark plug seat. I didn't have an appropriate cutter, or so I thought until I realised that the diameter of my dovetail cutter was about right for the job.
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As they say, if it's stupid but it works... I'm still stupid, as I put the counterbore on the wrong side! No harm done as that area will be machined away anyway, just had to set back up the other way around and re-do.
With the milling and drilling operations done, I set the head up on the lathe to bore the cylinder socket.
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Thanks to legendary Pratt Burnerd quality control my 4-jaw doesn't have a matched set of jaws, so the part was seated on a pair of parallels against the chuck body. I then clocked in on the pilot hole for the plug with a dead centre. Machining started by drilling 9mm for the M10x1 spark plug thread that will eventually go in there (when I've made the appropriate tap...). I then bored the socket for the cylinder.

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And with that, the head is done for now. Next up, the cylinder!
 

Nerd1000

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The cylinder of course is more work for the Sheraton lathe. Here's my starting point, a chunk of 40mm continuous cast ductile iron I bought for some previous projects.
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As you may have noticed, I already turned the steady rest journal. Doing things this way avoids making a cut on the coldsaw, which while faster than a bandsaw is obnoxiously noisy when cutting anything heavier than RHS.

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The bar was faced and pilot drilled to depth, then a 20mm twist drill removed the bulk of the material from the bore. This particular drill gives nothing but trouble no matter what I do with it, but we eventually got it done.
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I used an insert boring bar to finish the bore to size (0.874") and cut a chamfer on the end of the bore. This chamfer is intended to ease insertion of the rings, but it also allowed me to support the bore with a live centre while profiling the OD.
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Here you can see the cooling fins being cut. I diverged from the plans a bit by cutting 1.5mm fins. To finish profiling the cylinder was parted off and re-chucked on the already completed end. My 3 Jaw is a 'Griptru' type so I was able to clock this in quite accurately. The head end was then turned, and finished to a close fit with the cylinder head socket using a fine mill file. This completed the lathe work on the cylinder. Next I had to add some holes for the head bolts, cylinder oiler and the valve block. For this, I devised a cunning plan...
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A stud borrowed from the mill clamp kit and some washers were sufficient to hold the cylinder in the head. I picked up existing holes with the pointy end of the edge finder where relevant, otherwise the straight end was used to find reference surfaces for the hole locations. The holes were tapped when needed.

The last step on the cylinder was to finish the bore. For this I used a brake cylinder hone.


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This is the first time I honed a cylinder of any sort, and I'm fairly happy with the results. A crosshatch pattern appeared quickly, and the tool marks from machining soon vanished, leaving the bore still a little undersized. With that, the cylinder was done. Next will be the piston and gudgeon pin.
 

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aconnor

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Good luck with your build, I assume you must be in SEQ to get locked down for the three days.
 

Nerd1000

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Wow, way too long since I updated this. I've been working on the engine, but super disorganised about documenting the build.
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As you can see, we've got a piston (with rings) frame, flywheel, crankshaft, conrod (not happy with it, will remake), rocker, the valve cages, valves, spring retainers and the exhaust valve spring (I'll wind the inlet valve spring once I get some thinner wire).
A close-up of the valves:
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As for the piston rings, I recalculated their size to 0.8mm width and depth. Hopefully this is a better fit to the bore than the original design. The setscrew fixed piston pin has been replaced by a fully floating one with brass pads to avoid marring the bore.
 

ZebDog

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Nice to see your still working on your Webster build and progress being made keep up the work.
 

Nerd1000

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Another brief update. This weekend I made the cam gearing blanks (a fairly straightforward turning job) and a simple tool holder for running 6mm round tool blanks in the mill. I'm sure you can all see where this is going...
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I ground the gear cutter from a broken 6mm endmill using a printout as a reference. A quick and dirty Arbor made from 10mm silver steel allowed me to mount the blank in my Atlas indexing head using a MT2 collet, finally proving that MT collets aren't entirely useless. I 3d printed a 48T index gear to use as a template.

Here's the final result:
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I have a strong suspicion that I got the tooth profile wrong, but so long as it meshes and runs ok in the engine I'm happy. You'll note this gear is made of aluminium, I have some 2011 T3 left over from when I made a camera adaptor for my partner's telescope, and it was just begging to be used. My dad (a mechanical engineer) assures me that a steel pinion will ruin an aluminium gear in no time, so the pinion will be made from bronze to afford a better match to the gear.
 

Nerd1000

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Ok so the pinion is made, no pics at the moment unfortunately because I spent far too long on it and was late for uni. The gears mesh, but they're in no way smooth- hopefully they'll run in a bit with use, but I think we'll always have some gear whine from this engine. Need to figure out a better way of shaping my cutters, or else buy commercial ones on future projects.
 

Nerd1000

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Some nice progress this weekend. First of all I made the cam, seen here with the cam gear and the flywheel/pinion.
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I shaped the cam with files using a paper template, and finished by polishing the outer surface so it doesn't grind down the aluminium rocker. Not the most precise way of making a cam but it should be good enough. I made the camshaft and assembled the cam onto the engine with the rocker to test the motion: it appears to have around 110 degrees of duration as intended.

Continuing the valve train theme, I next made the valve blocks.
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Apologies for the fuzzy photo, the phone always had trouble focusing on shiny stuff. More of the same here, drilling hole patterns :/
To my dismay, when I pressed in the valve cages they didn't go flush with the faces of the blocks (probably because I counterbored with an endmill) so I counterbored the middle block as well to clear them. Next I assembled the blocks and faced the surface that will mate with the cylinder head. I then lapped the valves with 600 grit silicon carbide grinding media I got from our lapidary kit, mixed with oil to make a paste.

Here's the valve assembly mocked up on the engine:
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I did a quick compression test by covering the spark plug hole with my finger and turning the crank. It was immediately obvious that the inlet valve wasn't sealing (I could hear air hissing out of it) so I covered its port and tried again. The engine in this state could push my fingers off the ports on the compression stroke, pull a decent amount of suction on the induction stroke and even 'spring' back when released, so I'm hopeful that with some more lapping and a sparkplug we'll have enough compression to run.
 

Nerd1000

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I've made up the various spacers, set the timing and pinned the flywheel to the crank. With the addition of the oil cups we now only need a carb and an an ignition system. I'll probably also make an exhaust with a simple muffler, as I plan for the gears and cam to be grease lubricated.
 

minh-thanh

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Hi

Just curiosity, did you try to test the suction and compression of the cylinder and piston + rings ? I usually check them by hand because I want to make sure they're okay
 

Nerd1000

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Yes I did. I can produce a far bit of suction from the piston in the cylinder by covering the spark plug hole and intake port. As for compression, if I cover the plug hole the engine will 'bounce' off compression when flicked over, but I'm not strong enough to keep my finger sealed over the hole on a full compression stroke so some air escapes. Still waiting for a spark plug so I can test this better.
 

Nerd1000

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I think so. Brian's experience in the piston rings thread does worry me, in particular I'm not certain that compression will still be good when the engine has run a bit and got rid of some of the oil on the cylinder walls. Hopefully this will be balanced by running in, and I'm planning to add some 2-stroke oil to the fuel to try to keep the upper ring wet.

Another thing I've noticed is that after turning the engine over a bit the oil pushed out from the bottom of the cylinder is very clearly full of cast iron particles. This is evidence of the rings wearing in to the bore, and I'm hoping that most of those wear particles are from the asperities in the cylinder wall rather than the rings themselves. Looking at the material data sheets my ductile iron cylinder should be slightly softer than the grey iron rings, which should encourage that. But all remains to be seen.
 

werowance

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my webster did the same thing on the gray/black sludge oil from the cylinder with some extremely fine sparkles in it. it actually still makes the same sludge oil but i dont see the sparkles in it any more. i used store bought rings from the company the plans say to buy them from on mine.
 

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