Little and large - building 2 vertical steam engines.

[Jasonb]

This may help but you may need the Roundy, roundy" table,

http://www.modelenginemaker.com/index.php/topic,4438.msg87653.html#msg87653

[Gas_mantle]

Thanks Jason, I've partly done the bearings for the no4 while I think about how best to tackle the cylinder. When I've finished the bearings I'll study your photos and see if I think I can manage something better at the 2nd go.

I could do with more practice at the rotatey twisty table 

[Gas_mantle]

I didn't take any photos of the making of the no4 bearings as I used the same method as the 10v earlier

Without any 12mm rod to check the alignment this 10mm suggests everything will be ok.



My only slight concern is they may have a bit of the 'Legoland' look. I'll probably make humpback tops to soften the appearance a bit.

[Gas_mantle]

The more I look at the bearings the less happy I am 

They are far too boxy and Lego like, for now I think I'll get the crank made while I think of the way forward.

I'm open to suggestions if anyone has thoughts on how to soften the look and make them more realistic 

[Jasonb]

As per my PM reduce to 22mm square, thin flanges, round over the top half. This allows caps like a Stuart.

You could also do as your last message and turn the whole thing down and use an insert in the lower half flange could be all round or just rounded at the top

[Gas_mantle]

Thanks 

I really need to get some drawing software so I can do that kind of thing.

I'm looking at doing something like your suggestion but I'd like to have the end flanges fully circular if they will still cover the inner square portion.

[Jasonb]

Drawing software says you would need a 26.87mm dia flange to cover the rectangular hole

[Gas_mantle]

Thanks, that's a prime example why software would help. When you are just imagining things and trying to build from a plan in your head it doesn't always turn out right.

Looks like a job for the turny table tomorrow 

[Gas_mantle]

Although the no4 bearing blocks still need a bit more cosmetic work I decided to tackle the bottom cylinder cover and piston next. I did take a few photos of machining the cover but somehow seem to have deleted them before uploading to Flickr. Anyway it was a simple turning job from a casting I bought followed by cutting a M12 fine thread to accept the gland nut.

The 2 taps and the die I bought for the job were only cheap ones (I think I paid about £11) but I was quite impressed by look and feel of them and they did the job :-)



Although this thread is aimed at beginners it's difficult to know how much detail to show and when to be brief, I guess most beginners can turn a piston but I did take a few photo along the way. My initial intention was to make the piston from cast iron but after a bit of advice and  a bit of thought I settled on aluminium. I've never used aluminium pistons before so we'll see how this performs on the hot stuff later but the lightness may be useful in high speed running ?

I like to turn the piston on the rod it will be coupled to, it is 7mm rod threaded at 2ba with a centre for stability.



Creeping up on the final diameter it's a nice close fit 



I think it may have been in Brians Oscillator build thread that the subject of graphite yarn piston rings briefly came up so for the benefit of those who have never tried it this is how I do it. The yarn for this piston is ¹/₈" sq so with a parting tool I just gradually cut a piston groove until the yarn will just fit width ways but to a depth that it sits wider than the diameter very slightly.

Here I am getting close to the size of groove I want



A bit deeper then cut to length and this looks about right



Soaking the yarn in oil and packing it down it's possible to get a good seal around the piston, the ring is in place here and a couple of loose strands / graphite can be seen. It is a good seal though and slides smoothly in the bore 



I'm now at this stage





With the covers in place I'm happy with the suction effect so hopefully the finished engine will have a bit of oomph 

[zeeprogrammer]

Although this thread is aimed at beginners it's difficult to know how much detail to show and when to be brief, I guess most beginners can turn a piston but I did take a few photo along the way.

I think detail and discussion is good regardless whether it's aimed at a beginner or not.
Beginners read a lot.

And I learned a few things from this post. 

[Gas_mantle]

Thanks Carl, it's good to know you are still following along 

I've largely got the crosshead made and would like to machine out the vertical slots in the trunk guide next (my guide is a fabricated one as hasn't got the slots cut yet).

As it would normally have been a cast item the plans I have don't show the slot dimensions. Admittedly the dimensions aren't critical but I'd like my engine to look very similar to the original if possible so if anyone has a No4 they can measure I'd be grateful.

Many thanks 

[john mills]

The slot on mine is 3/4" wide there is 5/16 + of metal or 5/16" thick of metal at both ends .

[Gas_mantle]

The slot on mine is 3/4" wide there is 5/16 + of metal or 5/16" thick of metal at both ends .

That's great thanks John 

I have a 16mm mill so that should give me something very close and keep the semi circular ends to the slots.

19mm would be better but I don't think my milling set up will take larger than 16mm but to preserve the radiused ends to the slots with an under sized cutter will be a pain.

[john mills]

you could use a simple boring bar with a tool set to bore 3/4"at the ends

[Gas_mantle]

you could use a simple boring bar with a tool set to bore 3/4"at the ends

I have a boring head and rarely use it so kinda forgot I have it but you've got me thinking that it ought to do this sort of job perfectly.

Cheers