Help with finishing Wobbler engine

Hi I have been making a wobbler from Steves workshop web site and one of the last things on making it says find the extreme position of the cylinder and mark the port with drill through the exhaust port but the position of the port is on the drawing. I just wondered if I put the hole in to drawing will it work or is it better to mark with a drill and how critical is it. If anyone has made one your help would be appreciated just so I don't have to adjust the hole after drilling.

David

Edited By David George 1 on 03/04/2020 08:01:09

I’ve no idea, but the first thing that comes to mind is: Is there a difference between marking the points by the different methods? No issue if the result is the same?

I would guess that the practical, rather than theoretical approach may be for those that have not managed all the drawings dimensions accurarely?

I'd do it with the drill through the port. That's the way I did the only wobbler I built years ago. But if you drilled the holes in the upright using x y co-ords in a milling machine etc, and do the same with the cylinder, it should all line up -- in theory!. Mine was all done in plain drill press freehand so the drill in port method was safest.

Main thing is to not let the hole in the cylinder be big enough to connect to both ports at once or the steam will simply bypass. Other than that, I dont think it's real critical.

One way is to use a jig for drilling the ports.

For one such jig, have a look at Elmer's Fancy 2 oscillator (wobbler). The drawings can be downloaded from
http://www.john-tom.com/html/ElmersEngines.html
Download no.18 and the jig is shown in the drawings.

Dave
The Emerald Isle

I'm with Hopper and would drill through the hole in the port.

Advantages include:

• The hole will be aligned correctly whatever - no chance of the builder misreading the plan, or mis-setting the machine.
• Using the machine itself as a jig will correct any small dimensional variances that might have crept in. For example, some ways of measuring dimensions accumulate error.

In the golden age of manual manufacturing most close-tolerance mass-production work was done using jigs and fixtures to guide the operator. Rather than the operator and his machine being wonderful, all they had to do was follow the jig. The high-accuracy part of the job was making jigs, fixtures, and shop-floor go/no go gauges in a tool-room, where the advanced skills and equipment were concentrated. Toolroom lathes and jig-borers were expensive to buy and high maintenance, not used for rough work,

Though it would be bonkers to make a full set of jigs and fixtures for a single wobbler, I often use simple fixtures to hold and position work and basic jigs to identify hole positions and reference features. The 'jig' might be another part of the same project or a paper template, printed or hand-drawn and glued to the job. The purpose isn't chasing tenths, I do it because it avoids silly mistakes. (I make more silly mistakes than anything else in my workshop!)

Dave

All the oscillators I have made I have drilled each part separately using the DRO to set things out, if you did the same to position the two hole in the standard on the 10mm radius then OK to do the same. If you marked out and drilled then spotting will line things up better though only to one of the two holes.

At the end of the day you would have to be wildly off for it not to run, at the worse you may bet a slight restriction to the flow if not all the hole is being uncovered at full travel. That No1 Muncaster that I am describing at the moment has the holes slightly out of line as I felt it would be easier for those using manual methods to mark out whole mm rather than to 0.001mm and that runs well enough.

Edited By JasonB on 03/04/2020 10:11:59

It runs. I had to use the tyre inflator to test as I don't have a compressor.

https://youtu.be/5fGVVvSl7pE

Thanks for help.

David

Edited By David George 1 on 03/04/2020 11:50:41

Edited By JasonB on 03/04/2020 12:59:10

I am in the final stages building the same engine.

Don't think mine will look so fancy, well done on the build.