The McOnie Oscillating Engine

[Jo]

Stuart, The flywheel on this engine is only 8" so you should find it no problem  .

jo

[Stuart]

Thanks  Jo

Stuart

[Dunstaneloi]

Hello Ramon. I'm working on my McOnie's and have the baseplate, frames and pedestal blocks completed apart from the bearing bushes. Now comes the crankshaft and was thinking of making it your way as the method using the flame cut plate is not very good. What tolerance did you use for the clearance between the shafts, crank pin, and the webs in order for the Loctite to work properly ?
I take it that you have finished yours, a picture would be much appreciated. Can I contact you directly by email for any further queries ?

Mike Malleson.

[Jo]

Hi Mike,

Would you like to make an introductory post in the introduction section so the members know a little about you. I am sure after that someone who has made this engine will answer your questions.

Jo

[sco]

When I did the crank for my McOnie I made the shaft as close as possible fit in the webs as I could to maintain the alignment and then machined a very shallow hidden groove (~0.1mm deep) in the shaft for the loctite.  So you end up with two shoulders for the location and a trough for the glue.

Hope that makes sense,

Simon.

[Dunstaneloi]

Thanks Simon. I may be in contact again whenI make a start. I'm finding the project quite difficult as I'm not equipped for metric, so am constantly having to find tooling without having to take out a mortgage ?  Mike.

[sco]

Mike,

I can sympathise as on my current project I'm going the other way - plans are in imperial and I'm mostly making it in metric.  You can probably make it work in imperial as long as you pay attention to matching items so where it calls for a 6mm shaft in a 6mm reamed hole why not just make it 1/4 if that's the reamer you have?

Simon.

[Ramon Wilson]

Hello Ramon. I'm working on my McOnie's and have the baseplate, frames and pedestal blocks completed apart from the bearing bushes. Now comes the crankshaft and was thinking of making it your way as the method using the flame cut plate is not very good. What tolerance did you use for the clearance between the shafts, crank pin, and the webs in order for the Loctite to work properly ?
I take it that you have finished yours, a picture would be much appreciated. Can I contact you directly by email for any further queries ?Mike Malleson.

Hello Mike - Welcome to the forum. Regrettably my engine is still not finished though has progressed considerably since last posting. I am hoping to at least get the inlet side of things done so I can run it on air at this years Forncett ME Day in October.

It's a long time back since I made that crank but would have done the following. The holes are reamed in the webs and the spigots on the end of the two shafts are made a size for size fit - ie to match the hole diameter. This produces an interference fit which is not what is wanted for Loctite so the spigots are reduced carefully with a light filing until the webs just slide on. If the holes are blind as mine were file a very slight flat on to allow air/surplus loctite to escape. When pressed home the small area toward the shoulder of the spigot will give that interference fit and bring everything up nice and tight. The crank pin spigot is the same on one side and fitted to it's web but the other needs to be able to slide all the way up so that it makes everything 'easy' for when loctiting it in place on the vee blocks as shown.

Hope that makes sense. Should you have any further questions I'd be more than happy to answer them here - I have no objection to email but time is limited and besides,what ever your questions are they may help someone else with similar problems.

With regards to the metric/imperial situation I have always found it's best to work in whatever your measuring kit is based on. Personally I use metric throughout but have two sets of measuring kit. It's much easier to change the dimensions on the drawing beforehand to 'what you want to work in' than to keep changing as and when. I either round up or down and take it from there as set for the project. Fastenings excepted - I still use BA wherever possible.

Hope that helps - Tug

[Jo]

Regrettably my engine is still not finished though has progressed considerably since last posting. I am hoping to at least get the inlet side of things done so I can run it on air at this years Forncett ME Day in October.

Careful Tug:  I find its best not to admit to having not actually finished an engine or getting it running or else JBWelder will start gloating again 

Jo

[Stuart]

Mike it’s not a easy engine but by ekk do they run well when you get it setup hardest job for me was the valve gear with its slide and arcs to enable the articulation

Mine runs on less that 5 psi ( note I used soft packing ) about the same as my ME beam nearing completion both run nice and slow but of the two the McO is the slowest

Note I would have done a few bits differently not built up but hewn from solid now that I have a CNC mill as well to play with

But today the workshop gnome has run off with my cherished starrett 17aa centre pop had it years , yes I know they are cheap dut  not happy bunny

[sco]

Steam Guy Willy made a large section of the valve gear arc profile and was making the leftover available to other builders - I had a bit and posted back the remainder so there could be still some left.

You can see it on this page: http://www.modelenginemaker.com/index.php/topic,3870.240.html

Simon.

[Dunstaneloi]

Hi All. Thanks for all the kind and helpful replies. This sort of support is so valuable in an increasingly venal world where people are out for all they can get from you. I had the same support when building my 'Terrier' from a gentleman who became a great email friend, and who I met twice at ME Exhibitions, long may it last, he gave me aa lot of confidence.
 
Mike.

[Dunstaneloi]

Hello again Ramon.
Referring to your first post in which you described the crank webs, at what angle did you set them to machine the sloped sides to give that inward lean towards the crank pin ? Also, Do you have a supplier of good quality reamers that don't need a second mortgage to afford them ?

Regards, Mike.

[Ramon Wilson]

Short of checking I don't know at this exact point Mike - is it (the angle) not on the drawing? Do take note of leaving the small 'feet' on until the shafts are in place.

Reamers? Well there are several sources but for the smaller stuff (up to 1/2inch/12mm) but I favour Arc Euro chucking reamers for cost and quick service. I do have a considerable collection from over the years but when I do need to buy the odd one that's where I usually go. Haven't found anything wrong with them and, as said, well pleased with AE's service and pricing.

Jason, Jo, others may have other sources bearing in mind your caveat.

I'll take a look at mine later to see what the angle is

Regards - Tug

[Jasonb]

Last few Reamers I have bought have all come from ARC, both hand and machine. Only exception was a 3.0mm one by Osborn as ARC don't go that small which I think came via Rotagrip. I did also use the hand ones under power which seem to work fine if run quite slowly.

ARC's machine reamers will cut a fraction closer to nominal than the hand reamers as they are H7 but the hand are H8. The taper on the hand reamer can be used to advantage sometimes when a press fit is needed.

The angle is not on the drawing but a bit of simple trig should get you it soon enough