Scotty's Webster

[scottyp]

So I finally have some progress on my Webster so I thought I'd start a post to keep me motivated. I built a few basic steamers and a NGEZ maybe 10 years ago with "OK" results and have had the Webster 4 stroke in mind for quite a while. The kids are older and I have since gained more milling experience and patience so I figure I should step it up a little. I have ambitions of a Tiny Inline 4 and a Demon, but let's start here right? Anyway, here are the basics so far. The valves seal up nice and the piston came out good. I had some oversize rod and milled some flats on it to hold it for the milling cuts. I'll either sleeve this cylinder (which I sort of made as practice and it fits really well) or make a new steel one, we'll see. The carb is from a .15 RC engine. More to come...

 

[scottyp]

Finished up the con-rod and piston. Now I need to order some metals for the spinny parts.

 

[scottyp]

OK - I liberated a piece of steel and made a new cylinder, should work a little better.

 

[a41capt]

Looking good! I’m in the middle of a Webster also and just slightly ahead of you in the parts count.

JohnW

 

[awake]

Scotty, you are doing wonderful work, and well on your way!

 

[scottyp]

Thanks guys, I had the day off today and my wife was working so I could do what I wanted today (just kidding honey) . I cranked out a crankshaft, it turned out nice and square. While I am waiting for my bushing materials I made a couple from a chunk of delrin to find out that things fit pretty well and the gears mesh nicely also.

The shaft and pin were a good and tight press. Should I pin them also?

 

[Cogsy]

I would, just for safety, although there's arguments against it also. I relied on a press fit for a single, vertical I built from Brian Rupnows design (my choice, I can't remember if the plans advise pinning) and when I had a valve retaining clip fly off the engine locked up suddenly. The quick stop bent the valve which caused the issue and also moved the crank to web in 2 axes. I corrected the crank easily enough but it wouldn't have happened if it was pinned. On the other hand, if it couldn't twist and slide where it did, it may have bent or broken something else so I really don't know if it would have helped.

Being that it's rare for an engine to just stop dead like mine did, but much more common to backfire and impart a bit extra force on the crank fits, I'd probably pin it and it'll likely never cause you any trouble.

 

[a41capt]

Thanks guys, I had the day off today and my wife was working so I could do what I wanted today (just kidding honey) . I cranked out a crankshaft, it turned out nice and square. While I am waiting for my bushing materials I made a couple from a chunk of delrin to find out that things fit pretty well and the gears mesh nicely also.

The shaft and pin were a good and tight press. Should I pin them also?

Like Cogsy mentioned, I had a roll pinned crank on my Ford Kitchen Sink engine when it backfired (don’t ask me how such a low compression engine can develop a big backfire!), and it sheared the roll pin. I turned a tight fitting solid pin to replace the roll pin and green loctited it in!

On my Webster, I turned a one piece crank out of 1/2” HRS so I wouldn’t have that problem with my second engine. Live and learn!

John

 

[scottyp]

I pinned my crankshaft and made a rocker arm. I think I'll make the exhaust cam next and get it all adjusted (and put better washers and spacers on it). I haven't really done much milling on steel, it went surprisingly easy. It is coming along though.

 

[scottyp]

Well, I had some time and I finished the Exhaust and Ignition cams and things are looking good. Now I just need to figure out a flywheel that I can turn out w/ my mini lathe, (yes, I need a find a deal on a bigger better lathe). And my list of engines that I would like to do just keeps growing...Thanks for the support, I like it here.

 

[awake]

You are getting close!

My thoughts on a flywheel on the minilathe, FWIW: yes, certainly challenging, but plenty of folks here have done it, so it must be do-able! One of the keys will be whether you can get the chuck jaws around the blank and still clear everything. It will also help if the material is relatively easy to machine - aluminum is maybe too light for a flywheel (??), but good grey cast iron machines nicely, or 12L leaded steel.

You didn't ask, so feel free to ignore the rest of the post, but in case it is helpful, here's how I would do it. I'll be interested to see what other approaches others may suggest.

Mount the blank in the chuck, and taking light cuts, face one side until it cleans up flat. If you plan to do any contouring, do that as well to this side. (But take it slow - it's hard enough to do this on my full-sized lathe, and watch out for the blank shifting under the heavy cutting pressures - you may need to re-face the part after contouring.) Drill out the center hole undersize, then bore it to final size. (Or you could ream, but I tend to trust boring more to get dead-on straight and concentric - just make sure to allow for spring passes so that the bore is straight and not tapered.)

Remove the blank and put a scrap piece in the chuck. Turn a "spigot" on it to a nice sliding fit in the bore. With the finished face towards the chuck, secure the blank on the spigot using high-strength Loctite. Yeah, the blue stuff likely won't hold. Alternatively you could make an expanding mandrel, or tap for a screw to help hold the part. Let the Loctite thoroughly set up (overnight), then begin taking light cuts to clean up the rim, face, and if desired, contour.

Finally, remove the spigot and flywheel from the lathe and use a heat gun to heat it up until you can press the spigot out. Clean up with some scotch brite, and voila - a flywheel!

 

[Nikhil Bhale]

I have worked on large marine two stroke diesel engine of 30,000 to 60,000 bhp. The crankshaft are made by shrink fitting the crank web on the journal.
I do not know if this method is used in model making or if it is not feasible on a small scale..

Here is a reference
marinediesels.co.uk The Two Stroke Crosshead Diesel Engine Semi built crankshaft and

http://www.marinediesels.info/2_stroke_engine_parts/Other_info/semi_built_crankshaft.htm
Rgrds
Nikhil

 

[werowance]

one other way on the fly wheel which i dont recomend if your chuck will actually expand enough to hold the OD of the flywheel stock - but if it wont then what you can do is find and center punch the center of the stock and drill / ream the hole to match your crank shaft - or even better is you can over size drill and ream the hole then later on make a sleeve to bring it back down to the crankshaft size, then mount the stock on a smaller arbor that will fit in your chuck. but you have to take ease shallow cuts - no hogging or the arbor will bend on you. its also best if you do not let the flywheel stock hang out past your chuck, in other words when the flywheel stock is mounted on arbor, shove arbor and flywheel stock all the way back into the chuck until the stock is up against the face of the cuck snugly. this way it wont flex as much on you.

this method will allow you to do the outside and inside of the flywheel at one time. then flip around to get the other side / inside. once all is complete you can then remove the flywheel from the arbor and the center hub should be enough for you to rechuck to without the arbor so you can face off the center hub which previously could not be faced because of the arbor.

this is sort of the method i used on my webster when drilling the larger holes in the fly wheel - which if you have seen my build log you will see that it got away from me and slipped on my arbor when doing that because i forgot to tighten up the nut on the end of the homeade arbor.

 

[werowance]

oh, and if you are looking for flywheel stock, i made the mistake of buying a "mystery" piece of steel on ebay and it turned out to be tool steel which the more i worked on it the harder it got. so if you want easy cutting steel you might want to look for 12L14 or 1215 (1215 doesnt have the L but to me cuts every bit as easy as 12L14 and 1215 was cheaper when i bought it) and if you can afford brass then that will be even easier

 

[scottyp]

Thanks for the ideas guys - it will be a little while, my "shop" has been turned into a graduation party.

Wero - I did actually follow your build and is was good.

 

[scottyp]

Do you suppose that there is a flywheel inside of that chunk of laser cut 1" steel plate?

 

[aka9950202]

I used a weight lifting plate to make the flywheel. The piece of steel would be spot on for your flywheel.

Looking forward to a video of it running soon.

Cheers,
Andrew in Melbourne

 

[Sprocket]

Or a wicked heavy hockey puck...

 

[ALEX1952]

I've used a cast weight lifting plate before and it had some big hard spots which made it a pig to machine, not saying they are all the same but beware.

 

[scottyp]

Well, look at that, there was a flywheel in there...All I had to do was remove everything that wasn't flywheel.