Author Topic: A Simple Uniflow Engine  (Read 16594 times)

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #330 on: February 07, 2021, 12:08:45 AM »
Thanks Chris.

Yeah, I thought that it would be that kind of process.

I reckon the round holes will be ok for this engine, though you never know - I might decide to give it a go...

Offline crueby

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Re: A Simple Uniflow Engine
« Reply #331 on: February 07, 2021, 12:30:02 AM »
Thanks Chris.

Yeah, I thought that it would be that kind of process.

I reckon the round holes will be ok for this engine, though you never know - I might decide to give it a go...
Good technique to practice on some scrap first.   :cheers:

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #332 on: February 07, 2021, 10:11:53 AM »

Good technique to practice on some scrap first.   :cheers:

Absolutely! But thinking more about it, I reckon round holes will do for this one...

 :cheers:

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #333 on: February 09, 2021, 12:26:07 AM »
Deja vu time.

Started working on the replacement crankshaft. The previous one was out of true because - if I remember rightly - I caught the end of it with a lathe tool.

Not that I really want to be repeating steps, but needs must. I chose two nice straight 12 inch pieces of 12mm precision ground mild steel, one for the shaft and one for the journal. The one for the journal will be kept long initially to test the parallelism of the holes in the webs, i.e. if the two bars are parallel when the webs are in situ then the holes are too (sorry - I'm sure you're well aware of that).

The photo below is of centre-drilling a small cone-shaped hole in the end of what will be the crankshaft to enable tailstock support at a later stage. It's not something you haven't seen a million times before but I find myself liking the photo for the motion blur on the end of the shaft and the lovely green colour of the cutting oil...



Two pieces of rectangular EN3B steel were then cut for the webs. I was thinking of maybe silver soldering this crankshaft, but have decided to just use Loctite and pins again rather than venture into unknown territory at this stage. Silver soldering a crankshaft is hopefully something I'll have plenty of opportunities to try in the future.

 

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #334 on: February 09, 2021, 10:12:05 PM »
A little more progress on the crankshaft remake this evening.

Blanks for the webs milled square, superglued together and left in the vice for tomorrow and a final truing up, rounding of the corners, and drilling and reaming the holes for the crankshaft and journal.

I won't bore you with a photo of two small rectangles of steel held in a vice, but basically I'm making this new crankshaft the same way as I made to old one (page 6 of this thread).

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #335 on: February 15, 2021, 11:33:21 PM »
While giving the loctite on the new crankshaft extra time to set due to the cold, damp weather, I turned my attention to other things. This photo shows the approximate positions of the cylinder support pillars and the cylinder cross-braces:



Note that the cross-braces are higher than the centre line of the cylinder to increase the stability of the structure. The black flecks inside the cylinder are just bits of sawdust from another project - I swept up what I could, but after a certain point it's diminishing returns, especially after the sawdust gets oily and gets everywhere! The height of the cross braces was marked on the end of the cylinder.

The positions of the support pillars and cross-braces were then marked out on the cylinder using the surface plate and height gauge. The picture below shows the cylinder upside down, with the support pillars roughly in position:



The support pillars and cross-braces will all be drilled through with clearance holes for long M6 screws which will pass through the bottom and sides of the engine frame, through the pillars/braces, and into blind tapped holes in the cylinder wall. Lining all this up will be a challenge - I think transfer screws will be used for much of it. I then had to pause on this step because I'm waiting for the M6 screws (plus a drill and tap) to arrive in the post. A gratuitous shot of my bench showing the state of play follows:



I then started on a new flywheel. I'm pretty sure that the original brass flywheels are too light to run the engine. On the test rig I only got it going after I put my 4-jaw self-centring chuck on the end of the crankshaft. It may or may not be that one of the original flywheels still has a part to play, but clearly something heavier is needed. I had originally intended for this engine to be symmetrical, with twin flywheels, but that would have necessitated a trip to the local machine shop to rummage in the scrap bin and we are now back in lockdown here so I decided to use what I already have.

I surreptitiously borrowed the kitchen scales and weighed the 4-jaw chuck, which came in at 4 kilos:



It may be that the new flywheel doesn't have to be quite as heavy as that, but it gave me somewhere to start. I found a disc of EN8 steel which I have had for ages - it weighed 3.7 kilos. Some of this will be lost in machining, so I also selected a smaller piece of some other kind of steel, which weighs 1 kilo. If necessary, the two pieces can be combined in some way:



The good thing about the piece of EN8 is that it already has a spigot on it which made it very easy to mount in the 3-jaw chuck:



The plan is to face one side and even up the perimeter in the 3-jaw, then drill and ream it 12mm and turn the other side on a short mandrel made of the same diameter of steel as the crankshaft. This is as far as I got before calling it a night:



Cheers,

gary

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #336 on: February 17, 2021, 11:47:37 PM »
As the second application of loctite continued to set on the new crankshaft, I carried on with the new flywheel:



Fortunately the piece of EN8 that I'm using came with a pre-machined boss on each side, and even the shallower of the two allowed me to hold it in the 3-jaw, so I was able to take the initial cuts on both faces plus the edge:



The plan is to use the other, smaller piece of steel to make an extended boss on the flywheel:



I'll attach it via a circle of M6 cap head screws with the holes counterbored for the heads. If the whole arrangement is too heavy it will be easy enough to reduce the weight by turning down, facing and/or drilling a circle of holes. I'll be very lucky if I don't have to do some final truing up on a mandrel to eliminate wobble. The trouble with that is that it tends to invite chatter.

Finally, a quick mock-up just to give an idea of the look of the flywheel mounted on the engine:



This will enable me to make final decisions from an aesthetic point of view about what shape the frame will be. In fact I'll probably just stick with my original template but I didn't want to commit until I had an idea of how big the final flywheel would be.

Offline crueby

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Re: A Simple Uniflow Engine
« Reply #337 on: February 17, 2021, 11:53:03 PM »
 :ThumbsUp: :popcorn: :popcorn:

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #338 on: February 17, 2021, 11:55:59 PM »
 :ThumbsUp:

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #339 on: February 18, 2021, 11:37:38 PM »
Here are the basic forms of the main part of the new flywheel and its boss:



They are sitting in front of the milling vice which is holding a hexagonal ER32 collet block which I was thinking of using to drill a 6-hole bolt circle with the collet holding a 'superglue arbour' because the rotary table with chuck didn't leave enough room in the mill. However, I have decided instead to use the DRO to make the bolt circle to enable more stable workholding and to stick to the original idea of five-hole patterns as a feature of this engine. I have never used the DRO for this before so it will be a learning experience for me.

The plan is to make a circle of clearance holes in the main wheel for M6 cap head screws. These will be counterbored so that the screw heads will be just below the surface of the wheel. A matching pattern of blind holes will be drilled in the boss and tapped M6. This will allow the main wheel and the boss to be bolted together. The assembly will then be chucked in the lathe and the diameter of the boss reduced to match the existing raised section on the main wheel. After that, further machining can be done to reduce the weight if required.

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #340 on: February 22, 2021, 10:51:05 PM »
Having thought about it I decided that M6 may be too flimsy for the screws which will hold the two parts of the flywheel together, so I rummaged through my 'miscellaneous' box (well, through one of them) and found five M10 stainless cap head screws:



Nice and chunky!

Now, as this was my first time using the DRO to make a pitch circle, just to be on the safe side I put a marker pen into the drill chuck and marked out the hole positions with it using the DRO:



This looked good to me, so I went round again with a small centre drill to make marks that would be insoluble in cutting oil  :) . Unnecessary really, but better safe than sorry:



The holes were then drilled using a larger centre drill and three drill bits to take them up to size. I found it more efficient to leave the table in position and swap the drills for one hole at a time than to go round all of the holes with each bit before swapping them:



A test fit of the screws:



The holes will be counterbored and the screw heads will sit 2mm beneath the surface of the wheel. However, I have in my possession neither a counterbore nor an endmill of  an appropriate size, so I am waiting for the mail before continuing with this part. Although the DRO would let me break down the setup, use the mill for something else and then set up again, I'd rather leave it undisturbed.

I appreciate that the content of this post may be old hat to many of you, but this was a first for me and I found using the DRO to make a pitch circle to be an absolute dream.

I am converted...


Offline crueby

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Re: A Simple Uniflow Engine
« Reply #341 on: February 23, 2021, 12:15:03 AM »
Came out well!  And I agree, leave the setup till all the operations are done, always best.


 :popcorn: :popcorn: :popcorn:

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #342 on: February 23, 2021, 10:25:21 AM »
Thanks Chris.

Hope that counterbore arrives soon!

Offline propforward

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Re: A Simple Uniflow Engine
« Reply #343 on: February 23, 2021, 11:24:58 AM »
Looking good Gary. Itís maddening waiting for a tool when you want to just crack on - but I admire your patience. Definitely best to leave the part set up. Nice job as always.
Stuart

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #344 on: February 25, 2021, 12:26:10 AM »
Thanks Stuart.

Yes, it can be frustrating, but this week I seem to have plenty of other things to do, so as long as the post isn't too slow it will be ok. Am looking forward to continuing with it though - this flywheel is quite fun so far.

 :ThumbsUp: