Recent Posts

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1
From Kits/Castings / Re: Another Westbury Wyvern build
« Last post by Muddy Rutter on Today at 11:55:46 AM »
Looking good David and really useful to follow.

Nick
2
Tooling & Machines / Re: Leadscrew
« Last post by steamer on Today at 11:44:17 AM »
I always try and have the follower on the fresh cut material. But it is a 2 way thing. The chips can easily get in the way.
Its a pain, but running a vacuum cleaner to draw away the chips works really well.
I put my compound on an angle, Normally 30 deg, so that  the value on the cross slide, now becomes the diameter of the cut.
But it gets worse as you have to reset or bring into the job the steady.
I find that the Myford travelling steady often just gets in the way.
Sometimes it is also easier to cut a longer blank, to give room for the tools etc, and then set up and cut the excess off later when
the end detail is being finished,
It is small jobs like this that I think I should make up a roller box.
But like you have just persevered and made do with what was available at the time.
Neil

I leave my compound at 29, but the tool aligned.   They both get it done in my book
I don't want to turn this project into a tool making exercise...I just want to get it done.  So I'll leave the tooling crude...but effective.

The original screw is cut long, I suspect for the same reason...to have some travel for the follower rest before the tool gets to the TS center.  Mine is also.

Dave
3
Tooling & Machines / Re: Leadscrew
« Last post by steamer on Today at 11:28:59 AM »
This one was a challenge.....the tool clamp screw is 4-40.    0.354-10 LH ACME

http://www.modelenginemaker.com/index.php/topic,1192.msg15322.html#msg15322
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From Kits/Castings / Re: Another Westbury Wyvern build
« Last post by MJM460 on Today at 11:13:20 AM »
Great progress David.  The family is really coming together.

MJM460

5
From Plans / Re: Model Otto_Deutz
« Last post by gbritnell on Today at 11:05:44 AM »
Thanks so much for the reference. I think you'll find that once you have done a couple of parts the whole process becomes much easier. I find it very satisfying when a part appears from a block of metal.
gbritnell
6
From Kits/Castings / Re: Another Westbury Wyvern build
« Last post by deltatango on Today at 11:02:28 AM »
Having a nearly finished cylinder head it's time to make some of the bits to attached to it, this time the valves and housings. Like other people I've modified the design to have both valves in inserted seatings rather than have the exhaust seating directly in the alli of the head (probably left over from having the head cast in iron). These could both be the same from bronze bar stock but as I'd already paid for the inlet side casting I might as well machine this as a start. There was a lot of extra metal on the raw casting so no worries regarding finding the finished part inside it. Mounted in the 4-jaw I turned the valve seat end to fit the hole in the head:



which could then be held in a collet to rough down the other end:



and drill and bore this to take the valve spring:



The flange was filed to shape using a steel guide made from the drawing. The exhaust housing was very much the same apart from the M12x1.0 thread and a 5/8" hex milled on to give a spanner something to get hold of:



After the 45 degree seatings were machined (see later), the final operation on both parts was to put a 2 degree taper on the outer end to improve the appearance:



The two valves were turned back-to-back from stainless steel (grade unknown but it may not have been free-cutting!). SS is a poor conductor of heat and flood coolant was necessary for running down the stem to 1/8", first with a Crobalt bit in the Diamond Tool Holder, then finishing with a sharp carbide bit:




Getting the lathe set up to turn the valve seating faces was tricky as its necessary to machine the valve faces and the bronze seatings at the same setting. The top-slide was set over to 45 degrees and the lathe run in reverse to machine the valves:



I was concentrating hard to avoid mistakes on the bronze bits and forgot to take a picture - sorry! Before separating the two valves looked like:



The springs were supplied in the kit of bits from Hemingway, I made two spring collars and 5BA nuts from MS and at this stage the finished set of bits looked like:



The final nerve-racking op was to fit the bronze seatings into the head and drill through for the inlet and exhaust tracts. All went well and the bits all fit together:



and into the head:



Currently the family looks like:



David
7
Chatterbox / Re: Talking Thermodynamics
« Last post by MJM460 on Today at 11:01:16 AM »
Hi Pete, thanks for looking in and explaining that.

Hi Willy, sorry to hear that you are not fully back to your previous self, but it is good that you are at least making some progress.  Time on the allotment might be the medicine you need, along with some sunshine.

Basically the heat balance is slightly different when starting a cold engine that it is for a hot engine.  When those glow plug engines are cold there is not enough heat of compression to get to ignition point.  Once they are running, as Pete says there is excess heat available and the compression ratio is enough.  Really the thermodynamics is the same in each case.  The little compression ignition or Diesel engines have a higher compression ratio so they can start on compression heat alone from cold.

On larger size engines, many little marine Diesel engines are fitted with glow plugs and operating these before attempting to start the engine makes them start a lot easier in my experience.  Similarly, my car is a diesel, and I notice the start sequence involves running glow plugs for a short  period before it starts.  All computer controlled of course.  I believe a similar principle is used even for quite large engines.  But these are really beyond my experience.  Perhaps some of the marine engineers on the forum will come in and tell us all more about them.  I think the same might apply to Diesel engines in construction machinery. 

The differences between all these systems basically revolves around how much heat is required to get those first few pops each start.

Hi simplyloco, thanks for looking in.  Yes, those are the pumps used on farms that I was referring to in the earlier post.  Thanks for looking that out and posting. 

Wasteful of course is not a strict technical term.  The second law of thermodynamics means that you cannot use all the energy in the water to pump it all back to the height at which it started, some of that energy is “lost”.  However the water is not lost, that part not pumped continues it’s merry way down hill, and is appreciated by those downstream, and no matter how well they are set up some always continues.  I believe that if well set up, there is not the obvious spillage evident in that video, though I never had much to do with them.  The limitations not only mean the water cannot all be returned to the original height, you probably can’t pump it all to any height using the ram pump, though you can move it all up some of the way simply by containing it in a pipe.  The difference with the ram is that some water must be passed through to establish the velocity that the device suddenly stops so the change of momentum develops the pressure.  It is using the kinetic energy, and can develop enough pressure to raise some of the water above the initial height, thus converting kinetic energy to potential energy, and of course losing some in the process.  Each time the check valve closes, the flow stops, and has to be re-established by a bypass flow after the pressure pulse.  I just can’t remember what makes the check valve flip closed.

A simple pipe down the hill then up the other side is simply using the potential energy of the height, and can raise the water surface up to the original height under conditions of no flow, and all the flow to some smaller height, the difference in height being energy lost in overcoming friction in the pipe.  Obviously you would normally just use the pipe if you have access to the water at enough height, and accept the extra complexity of the ram if you need more pressure that resulting from the height at the point you have access to the water.

In both cases, the energy “loss” is not really lost, it simply is dissipated as heat, and can always be accounted for if you look hard enough.  And it may even be useable to some extent if you have a use for low temperature heat.  Though recovering the heat from friction in the pipe would be a challenge.

Now we just need more information on Willy’s heating system using water hammer.

Good to see the odd question coming through again.

MJM460

8
Tug -

thanks for all your good advice. I have the two fluxes shown for soft soldering:



I used the LA-CO last night. It's a thick paste. It seemed to be fine but Pete's post had me wondering so today I went out in search of a strong acid-based flux. I'm not sure whether the Baker's No 3 fluid fits the bill or not, but I see you have used it and will know that it's zinc chloride based.

Any thoughts from your good self or others on the relative merits of these two will be much appreciated. Until I hear anything, though, I'll test out the Baker's on some scrap brass.

Will bear in mind your other suggestions. The piano  wire seems like a 'sound' idea (sorry...) and I'll look at something equivalent after getting rid of the clamp and not looking for the material to glow dull red...
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Engines / Re: My first spark ignition engine
« Last post by gbritnell on Today at 10:57:19 AM »
Great looking engine! Do you know what issues you were having with the Hall transistors, other than burning out? Was the grounding not adequate!
gbritnell
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Engines / Re: My first spark ignition engine
« Last post by Tennessee Whiskey on Today at 10:54:59 AM »
What a beautiful picture to wake up to this morning. Stunning Tug. Can’t wait to see and hear it running

Whiskey
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