Author Topic: A Beginner's First Engine (Single-acting Oscillator)  (Read 23705 times)

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9467
  • Surrey, UK
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #225 on: March 27, 2019, 07:41:27 AM »
I think an o ring will take up any deviations better than the yarn.

It's a trick of the photo or my eyes, when I just opened this thread again to see your message the surfaces looked quite grey and well tinned a few seconds later they looked more like bare brass  :headscratch:

Offline gary.a.ayres

  • Full Member
  • ****
  • Posts: 1297
  • Isle of Skye & sometimes France
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #226 on: March 27, 2019, 07:45:15 AM »
Yes, they were definitely grey with solder; no brass visible. Probably the one thing I got right yesterday   :)

I'll order some o-rings and some yarn anyway, to try both. Won't break the bank...

Cheers.

 :ThumbsUp:

Offline Gas_mantle

  • Full Member
  • ****
  • Posts: 1365
  • North Yorks - UK.
    • My Youtube channel
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #227 on: March 27, 2019, 08:35:22 AM »
I'm not entirely convinced that adding an O ring is the way forward, it seems to me that it could add extra friction that could be counterproductive in a single acting engine. As the engine is only under power on the downward stroke surely any benefit is lost fighting friction on the return stoke? I accept that the engine will run but my guess is you will lose power and find it may labour a bit.

It wont do any harm to try it but I'm inclined to think making a new piston is the way forward now  :(


Offline Jasonb

  • Full Member
  • *****
  • Posts: 9467
  • Surrey, UK
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #228 on: March 27, 2019, 09:19:56 AM »
Given that the bore is probably still out of round but just bigger I can't see the point in making a piston to fit that. Either bore out the cyl to a true round and make a new piston to fit or make a new one piece cylinder bored to fit the existing piston.

Yes any seal will add stiction.

Easy option is to try it with ring/yard and see how it goes.

Offline Ramon Wilson

  • Full Member
  • ****
  • Posts: 1942
  • Suffolk in the UK
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #229 on: March 27, 2019, 10:17:32 AM »
Commiserations on this latest set back Gary but you have learnt quite a bit I would think ::) I remember things like this going wrong in my early days only too well. I was once told "You need to slow down in order to speed up" Couldn't see the logic in that at first but once the penny dropped things began to happen in a much more satisfying manner.

Given all that's gone wrong I would say you are now 'chasing your tail'. Things do sometimes go wrong and attempts to put them right can quickly lead you down a path not envisaged at the outset.  Maybe time to take a step back and consider starting over again on a completely new cylinder learning from all that's gone awry so far. Whatever way you go about any repair on this one it's just that now - a compromise - fixing something that's gone wrong, gone wrong, gone wrong, so to speak. There comes a point when it's simply best to start again as whatever you do will be trying to overcome previous problems and in all probability inducing new ones. Peters point about friction is a perfect example.

I would think that given your highly commendable approach to sorting things you can safely say you've given it a good shot but move forwards and start afresh on new parts. Hope you'll take this as well meant advice :)

Soldering - any form of 'extra metal' will act as a heat sink so you need to keep things in contact with as little as possible. A little brass rivet or two just acting as locating dowels would hold your plate in situ. For soft soldering I use a hand held gas torch if overall heat is required - set to give a soft flame not a roar. Heat the parts slowly - watch for the flux to melt and run and then touch the solder on. The part should be just hot enough for the solder to melt and sit there in a puddle - a quick wipe with that fluxed paper will quickly smear the solder evenly over the area - just keep the heat gently applied to keep the solder in a fluid state until the solder is well spread over the face then leave to cool naturally. Treat any high points as mentioned before and flux both faces before bringing together. You have found another potential for disaster in your attempts - that of brass being easily distorted by the slightest pressure once heated to around red heat. That likelihood is definitely something to be aware of when silver soldering but should not be of any concern when soft soldering as the temperature should be nowhere near.

You can ascertain what level of temp needed by taking a piece of scrap brass, clean the face and flux it then support it across your hearth bricks with minimal contact so that you can heat from underneath. Cut a nib of solder wire and lay it on the face then apply the heat gently from below - not directly on the face. As the metal increases in temperature you will soon see the point when the metal temp induces the solder to melt - that will give you a good idea of just how little heat - relative to silver soldering - is required.

Whatever way you go Gary - best of luck - hope you will not see this as anything other than what it is  :)

Regards - Tug

"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Online crueby

  • Full Member
  • *****
  • Posts: 18559
  • Rochester NY
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #230 on: March 27, 2019, 11:10:50 AM »
Tug, great description on the soldering.  :ThumbsUp:

Online crueby

  • Full Member
  • *****
  • Posts: 18559
  • Rochester NY
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #231 on: March 27, 2019, 11:58:05 AM »
Gary, here is a shot of the different torches that have accumulated in my shop over the years. The first I picked up (and still use a lot) is the little black one with the red knob - refillable butane, use it a lot for both soft soldering and for silver soldering small parts. It would be plenty for the size of your cylinder for soft or hard soldering.

The rest I only use for high temperature silver soldering. Bigger yellow one on right is a MAPP gas torch, good for slightly bigger parts. The Sievert system, fed from a 20 pound propane grill tank with Seivert regulator, on the left, with the box o tips, is good for everything from small frames up to large boilers.
The flux you use varies with the solder - low temp solder only works in the temp range for low temp/soft solders. The high temp flux for hard soldering only works in the 1100-1400F range. Below that it does nothing, above it burns off and does nothing.
 :cheers:

Offline gary.a.ayres

  • Full Member
  • ****
  • Posts: 1297
  • Isle of Skye & sometimes France
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #232 on: March 27, 2019, 12:31:51 PM »
Given that the bore is probably still out of round but just bigger I can't see the point in making a piston to fit that. Either bore out the cyl to a true round and make a new piston to fit or make a new one piece cylinder bored to fit the existing piston.

Yes any seal will add stiction.

Easy option is to try it with ring/yard and see how it goes.

Yes... @Jason and Peter: my first step will be to try out the existing cylinder with a silicone ring and with graphite yarn, to see how it goes (rings and yarn are both ordered). There's very little to lose in trying it. If it doesn't work, or works but in too compromised a way, then I'll have to make a new cylinder as it's the cylinder that's the problem. If I do this, I'll either revert to the original design and thread the pivot hole with a square-ground tap to make sure it bottoms properly and doesn't strip again, or I'll solder on a plate before boring the cylinder, not after.

I can't rebore the existing cylinder as the screw holes for the cap are too close to the bore, and quite deep so further boring would most probably break into them.

Making a new cylinder would be quite easy; making it to fit the piston (rather than the other way round) probably less so, but clearly it's doable and will be good practice.

@ Tug - thank you for both your detailed advice on soldering and your sharing your wisdom on the philosophy that underpins this work (which is very important).

@ Chris - I have a couple of other torches too - will have a think about which ones best suit different applications. Cheers.

Thanks for your support, all. Just amazing!   :ThumbsUp:


Offline b.lindsey

  • Global Moderator
  • Full Member
  • *****
  • Posts: 13860
  • Dallas, NC, USA
    • Workbench-Miniatures
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #233 on: March 27, 2019, 01:06:27 PM »
Gary, thanks to you for posting all of these trials and tribulations and thanks to others for providing suggestions as well. I know I can and need to learn more about soldering both soft and hard so all of this is really helpful!!

Bill
« Last Edit: March 28, 2019, 01:24:04 AM by b.lindsey »

Offline gary.a.ayres

  • Full Member
  • ****
  • Posts: 1297
  • Isle of Skye & sometimes France
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #234 on: March 27, 2019, 10:23:24 PM »
Bill -

I'm glad that some good has come out of this for you as well as for me.

One thing I notice with building engines is that mistakes can be very quickly reframed as learning opportunities.

BTW I will try the existing setup with the silicone ring and graphite yarn to see how it works, but am more inclined now just to remake the cylinder.

This small wobbler has become something of a marathon project, but it takes the time it takes, and the money spent on materials isn't really spent on one small engine, but on a lot of learning.

Cheers,

gary

Offline gary.a.ayres

  • Full Member
  • ****
  • Posts: 1297
  • Isle of Skye & sometimes France
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #235 on: April 01, 2019, 10:05:43 AM »
Following my ludicrous foray into soft soldering land, I trial fitted the modified cylinder to the engine, only to find that the excessive heat had mangled it beyond recognition and rendered it fit only for the brass recycling bin. So... I made another cylinder. This time I was able to fit the composite crank pin, as suggested by Ramon, and mill a recess in the middle section to allow better contact between the port face and the wear plate, as suggested by Peter. Also at Peter's suggestion I changed the position of the bore, shifting it away from the port face in order to leave more metal to take a drilled and tapped holed for the pivot. There was only room to shift the bore by 1 millimetre but as we all  know that can make a big difference. In order to do this I had to drill and ream the bore in the mill as the position specified in the plans arises from the offset caused by the port face when the part is held in a 3-jaw chuck. I used the mill because I don't yet have a 4-jaw. With hindsight, shifting the bore out like this seems an obvious solution, but it would never have occurred to me. Maybe it will come with experience! Meanwhile, thanks Peter and Tug. I then took extra care with drilling and tapping the pivot hole, drilling first with a 3.3 mm tapping drill, then squaring off the bottom of the hole with the same drill with the point ground off, then using the usual three M4 taps before bottoming the thread with a plug tap ground square at the end. This all worked well. Cheers to Jason and a couple of others for educating me about grinding the ends off taps.

 

The video below shows the engine (finished, apart from a shine up and the walnut base) running on the boiler driven by a pressurizing kerosene stove. The video is also relevant to my boiler thread so I'll post it there too:

<a href="https://www.youtube.com/watch?v=FN4fvsMWZL8" target="_blank">http://www.youtube.com/watch?v=FN4fvsMWZL8</a>

As for learning how to soft solder properly, well, that's another day's work.   ;) 

Offline bent

  • Full Member
  • ****
  • Posts: 790
  • Wet side of Washington State, USA
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #236 on: April 01, 2019, 04:32:25 PM »
Atta boy!  Looks like a runner, and you've fixed the leaks.  :cheers:

Offline gary.a.ayres

  • Full Member
  • ****
  • Posts: 1297
  • Isle of Skye & sometimes France
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #237 on: April 01, 2019, 05:53:52 PM »
Cheers Bent    :cheers:

Offline Admiral_dk

  • Full Member
  • *****
  • Posts: 3752
  • Søften - Denmark
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #238 on: April 01, 2019, 06:14:30 PM »
Congratulations on your achievement - succes on all accounts in the end  :cheers:

Offline gary.a.ayres

  • Full Member
  • ****
  • Posts: 1297
  • Isle of Skye & sometimes France
Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #239 on: April 01, 2019, 06:55:16 PM »
Thank you, Admiral_dk!

 :cheers:

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal