Author Topic: A Simple Uniflow Engine  (Read 45816 times)

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #300 on: January 17, 2021, 11:04:32 AM »
Hi Zephyrin -

Thanks for your honest view.

I appreciate that you may be correct.

However, I intend to persevere for the time being. Even before making the piston the possibility of having to remove some of its mass has been in my mind. It should be possible to do so by cutting one or more holes or slots which could also have the effect of reducing surface drag. The only criteria would be that it would not interfere with the exhaust action and that it would still have the length and rigidity to avoid the need for a crosshead guide. I accept that this may or may not be enough to make a difference, but there's only one way to find out...

Enlarging the exhaust ports (there are currently 2) or - more likely - drilling extra ones is no problem and is already on my 'to do' list.

My aim is to run the engine on steam rather than air (if it will run at all), and a flash steam boiler could be an option though the one I have started (in another thread) may possibly need a bigger coil to have a chance of running this.

Your point about a larger intake advance: in my position as a rank beginner I don't know what this means, so clearly I'll have to look into that. All guidance is welcome!

I'm not ignoring what you are saying, but having come this far it would be wrong to give up at this point or I would always wonder... so I'll carry on until every option has been explored. If at that point it won't run, even on flash steam, then at least I'll have learned a heck of a lot and will then have quite a few pre-made parts to use in future projects...

 :ThumbsUp:


Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #301 on: January 17, 2021, 10:46:48 PM »
 :cartwheel:

<a href="https://www.youtube.com/watch?v=YPQMvaLH0Sk" target="_blank">http://www.youtube.com/watch?v=YPQMvaLH0Sk</a>

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #302 on: January 17, 2021, 11:28:02 PM »
 :pinkelephant:

Well, I wasn't expecting that!

It ran for a good two minutes or more, and when it finally petered out I did not get the feeling that it reflected issues in the engine per se. My sense is that either my budget compressor was having trouble keeping up, and/or the temporary pin was changing length due to just being threaded into the piston with nothing to lock it. Or both. However, if any of you think it may be otherwise, please feel free to say.

There are clearly changes and refinements to be made from this point on, but I think I can say the engine runs...

I made only two changes. Following MJM's advice I cut some grooves in the piston:



These made a significant difference - the piston ran more freely and with some thick steam oil in the grooves there was hardly any air leaking from the exhaust ports. I was a little worried because I had used my only remaining decent parting off tool to cut these grooves and they are not far short of 3mm wide. I thought maybe I had overdone it but it would seem not. Later, I may experiment with some graphite yarn in the grooves but for now this is good.

The other change was made in response to a point made above by Jason, who wondered if the valve was getting enough lift. So I lengthened the valve by unscrewing it then making a spacer from brass which was tapped with a thread to match the valve. This made the valve 2 or 3 mm longer and gave the ball that much extra travel:







What I did not do was reverse the cylinder, enlarge or add to the ports or remove metal from the piston to make it lighter. some of these things can be considered again a bit further down the line.

There will be many refinements and changes to make (including I suspect seriously enlarging the brass flywheels with steel rims so I can put that lathe chuck back on the lathe where it belongs).

Following another point made by MJM, I noticed that the crankshaft was indeed taking some punishment so in keeping with his suggestion I'm going to move the flywheels outboard of the frame to reduce the length of the centre section of the shaft. This will probably look better anyway, given that the frame as it presently is looks very wide. I don't think the crankshaft got bent in this run. I certainly hope it didn't but even if it did, making a new one at this point wouldn't seem like that much of a big deal now that this looks like it's going somewhere.

I may not have a lot of shop time this week, as I'll be busy with work, but at least I know that when I do get back to it I'll be moving on to a new - and very interesting - stage of the build.

Thanks so much for all your advice and encouragement so far.

 :LittleAngel:

Offline crueby

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Re: A Simple Uniflow Engine
« Reply #303 on: January 17, 2021, 11:47:05 PM »
Awesome!!!    :whoohoo: :pinkelephant: :cartwheel:

If it indeed is the pin unscrewing (one way or the other), at least that is an easy adjustment. For things like that I like to install it with a drop of blue loctite, which will allow it to be adjusted while keeping enough friction on it to keep it from moving again. Unless there is room on the top of the piston for a lock nut without the nut hitting the end of the cylinder? That would be even easier.

Great that it got going, now you know its just fine tuning!   :ThumbsUp: :ThumbsUp:

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #304 on: January 17, 2021, 11:59:44 PM »
Cheers Chris!   :cheers:

I have some blue loctite and was wondering if it might work in that way... and alternatively I haven't checked yet to see if there's room for a locknut but I suspect there probably is.

In any case, I can come back to that later, as now I know it runs the next step is to dismantle the test rig and work towards the final setup. Still quite a lot of work to go, but it will be happy work now that  he 'will it even run?' anxiety has passed.

Can't wait to run it on steam when the time comes...

 :ThumbsUp: :ThumbsUp: :ThumbsUp:


Offline propforward

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Re: A Simple Uniflow Engine
« Reply #305 on: January 18, 2021, 12:04:20 AM »
That's great Gary! What a great runner too - a joy to see it romping along!  :NotWorthy:

I'll enjoy watching progress as you fine tune it.  :ThumbsUp:
Stuart

Forging ahead regardless.

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #306 on: January 18, 2021, 12:06:00 AM »
Thank you Stuart!

 :LittleAngel:

Online Kim

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Re: A Simple Uniflow Engine
« Reply #307 on: January 18, 2021, 05:28:48 AM »
Congratulations, Gary!  It really runs well!  :ThumbsUp: :popcorn:
Kim

Offline MJM460

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Re: A Simple Uniflow Engine
« Reply #308 on: January 18, 2021, 06:01:06 AM »
Hi Gary, congratulations, a great result.

As you say, now the fine tuning.  But first sit back and enjoy the success.  Great to know that there is nothing really wrong, and those first adjustments were successful.

Unfortunately I now see why everyone is talking about disappearing videos.  As already said, options are limited on an iPad despite regularly taking my tablets on time every time.

MJM460

The more I learn, the more I find that I still have to learn!

Offline Zephyrin

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Re: A Simple Uniflow Engine
« Reply #309 on: January 18, 2021, 07:29:41 AM »
congratulations, bravo for your perseverance !
the flywheel looks hefty too !

Offline Jasonb

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Re: A Simple Uniflow Engine
« Reply #310 on: January 18, 2021, 07:39:39 AM »
Well that will save me having to try and sort out the poor original design for you :) Things can only get better now.

I'd asked Gary to send me the drawing so I could give him the angles that the inlet and exhaust open and close at but the drawing gives no length for the conrod so it's guess work as to how close the piston gets to the head and therefor how much it has to compress any remaining air/steam. At the other end there is no way of knowing when the exhaust starts to get uncovered.

Video here for those still having problems viewing

Offline MJM460

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Re: A Simple Uniflow Engine
« Reply #311 on: January 18, 2021, 08:35:11 AM »
Hi Jason, thanks for posting that link.  Great to see it running nicely.

MJM460
The more I learn, the more I find that I still have to learn!

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #312 on: January 18, 2021, 09:20:34 AM »
Thank you all - much appreciated.

@ Zephyrin - yes! The lathe chuck will disappear and I'll be rummaging in the scrap bin at the local machine shop looking for a couple of steel discs to beef up the existing flywheels.

@ Jason - yes, I guess it saves you a job! But many thanks for the offer anyway, and for posting the link to the video.

@ MJM - as you are probably aware, it'd due to a privacy setting in your own browser, as pointed out by Kim above.

It occurs to me that another reason for the engine stopping after 2 minutes or so could be because of the grooves losing steam oil steam over that period of time and causing a loss of pressure. If so, that would point to further work on the piston/cylinder. However, I'll come back to that later if it remains an issue. Having more work to do on specific areas feels much less onerous now that I know the engine will run.

 :ThumbsUp: :ThumbsUp: :ThumbsUp: :ThumbsUp:

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #313 on: January 18, 2021, 11:41:41 PM »
And so beginneth this very eve the dismantlement of the test rig, in anticipation of the first steps upon the still long road towards the engine in its finished form. No pix.


Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #314 on: January 19, 2021, 11:44:29 PM »
Dismantling the test rig:



Now, following a point made by MJM about how the long central section of the crankshaft could be liable to bending under the force from the connecting rod, it did occur to me that the crankshaft took quite a pounding when the engine was running. So this is the new configuration:



I also think it looks better - the narrower frame will make the engine look leaner and meaner, and it also makes much more sense to have the pulleys outboard of the frame so that the whole thing doesn't need to be dismantled every time I want to put on or take off a belt.

The bad news is that the crankshaft is indeed bent. Stuck it in the lathe chuck and the runout was clearly visible. To be honest, I think it was bent before the test run, and that I was in denial mode at the time. It may or may not have been bent a little more by the test run but that's academic. So... I'll just have to make a new one. I may even make two in parallel; one loctited and the other silver soldered, and see how I get on. The prospect isn't too daunting at this stage, to be honest. But not yet! I now plan to get on and work towards the finished engine - the replacement crankshaft can be made as one of the last jobs of the build.

Onwards and (hopefully) upwards!

 

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