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Member postings for Jim Greethead

Here is a list of all the postings Jim Greethead has made in our forums. Click on a thread name to jump to the thread.

Thread: Morse Taper Removal
15/12/2011 19:33:19
Hi John Coleman 1
Just looked at your system and I like the idea of the captive nut (although I don't think I am capable of threading the end of the spindle on my machine).
But if you replaced the top nut with a handwheel, could you not do away with the spanners?
Just grip the chuck at the bottom and tighten the handwheel to install, and reverse to remove.
Just a thought
15/12/2011 19:14:21
Hi Peter G Shaw,
Like you, I have worried for years about the shock load imposed on the bearings by the whacking process.
But then as I lay in the twilight zone between sleeping and waking this morning I realised: the bearings in a mill/drill don't constrain the quill in the vertical direction so they don't get any shock load.
The shock load is actually taken by the rack that controls the vertical movement of the quill in the drilling mode.
And that rack can be offloaded by clamping the quill. This puts the load on the head itself. And if the Z axis is clamped, the shock load goes all the way to the floor.
Now I am happy
15/12/2011 05:02:38
I tried it, and it works. So far it is only a lashup using a bit of threaded rod, an aluminium disk from the "come in handy" box and a lump of steel for the hammer. But it does the job.
And now it just needs to be tidied up (when I have time)
Here is the URL to the YouTube video of it.
14/12/2011 23:03:38
Thanks Tel, you have set me thinking ...
On my mill, the drawbar has a nut on top. I wonder if I could make a new drawbar in which the nut is replaced by a knurled cylinder for hand tightening (aluminium to minimise the moment of inertia so it does not unscrew) and top it with a small slide hammer for removal.
If it works, it will save bending down for the lump hammer. I have heard that middle age is where nothing less than a dollar is worth bending down for, and I am well past that.
14/12/2011 22:03:49
Ah - I think I might have been overdoing it (if a job's worth doing, it's worth overdoing).
I am always concerned that the drawbar will unscrew. I have found it loose a couple of times but that might be due to AADD (adult attention deficit disorder).
Even tightening 1/16 turn means that it will still need to be whacked but maybe with a smaller hammer.
Is there any clever method that does not involve a hammer?
Thread: Rina and T&K drawings
14/11/2011 07:13:50
Thanks Jason,
Now we are cooking with gas (so to speak). I understand the demand regulator and I like the idea of making a block to run several engines. That will come later. The one shown is similar to one that I got from Model Engine Builder using the Tecumseh kit which seems very popular and which included the jets. I have already constructed the demand regulator and carby shown with the RINA drawingsand it is much smaller so I will start with that one (if it works and if it seals properly).
I was smiled upon by an normally malevolent spirit which guided me to the GasMate BBQ spares when I was looking for something else in the hardware store. And there I found a 2.75kpa (1.45 psi) regulator with POL fitting to go on a LPG bottle. Just the thing. I won't need to make a fuel tank, just connect to the big bottle. But thanks for the offer of a design. Testing something I made to 300 psi was a bit of a worry so I am please to avoid it.
Forest Classics (I had not previously heard of them) seem to have the fittings as you suggested.
And your HMEM build of the IHC Famous gave me a big injection of humility. I still have heaps to learn and I learned a lot from your photos. Great work and thanks for sharing.
13/11/2011 07:59:36
Thanks Jason, those fittings look quite the thing don't they. And what is the engine? It looks a good one too.
Rina is supposed to be gas powered and therein lies the problem. We got the drawings for the gas carby (and another beautiful one in Alibre from John Olsen) and I have made that. But there is no indication of the fittings, fuel or tank for the gas supply.
If I can't find a solution, I will convert it to one of Jan Ridders' vapour carbys which, I suppose are a form of gas carby with the gas being the vapour under ambient pressure which dispenses with the demand valve section. And I will certainly use Coleman fuel as I do in the Debbie two stroke
Thread: Jan Ridders Pressure-controlled Two-stroke engine
13/11/2011 00:13:23
Thank you John, it is nice to have the video where the paint is not too badly chipped and the shiny bits are still shiny. But I wish it would run as smoothly as yours.
You are right Mark, the unleaded stuff won't work in the old motorcycles either. I tried Premium but it left a horrible residue so I am using Coleman fuel (aka Shellite here in Australia).
It won't run with any extra air either which sent me looking for air leaks particularly around the bottom seal. But I have good compression at both ends of the piston travel. But having just re-read the earlier posts, I might try the suggestion from Dick Parsons and try some soapy water (or kid's bubble mix). You never know. Thanks Dick, sorry I missed you earlier in the year when I came through Hungary.
Thread: Rina and T&K drawings
12/11/2011 21:46:01
I have finally completed the drawings for a metric version of Jim Service's RINA with a few simplifications to accommodate my limited skills (I hope Jim will forgive me) and now I have commenced construction.
But I still have (at least) one problem: I can't find any information about the type of fuel (gas) used, or the construction of the fuel tank or the connection from the carburettor to the tank. Could someone please point me in the right direction?
Thanks to the good advice from John Olsen, I have completed the drawings in Alibre - certainly the quickest, easiest and cheapest way to produce 2D drawings and you get 3D images and assemblies into the bargain. My copies of AutoCAD, DesignCAD and TurboCAD are now only used to retrieve drawings that I made in the past.
I am happy to provide copies of my drawings to anyone who asks for them (I hope I can do that without doing anything illegal). You can have them in Alibre, .pdf or .dxf.
As I work my way through, I am finding some dimensions missing but you are welcome to them as they are if you are in a hurry or later on (after Xmas at least) if you want the corrected set with the errors minimised (they are never absolutely correct).
Thread: Jan Ridders Pressure-controlled Two-stroke engine
12/11/2011 21:31:24
In case anyone was wondering, I did finally get around to painting my version of Jan's engine and you can see it here:
It is still rather sensitive to fuel level but at least it runs. The screw that needs constant adjusting in the video is a form of throttle - it adjusts the maximum lift of the ball valve which I have relocated in the bit going into the fuel tank.
Thanks again to all of you who gave me advice and encouragement along the way. Without your assistance, it would have been just another doorstop.
Thread: Accessing the digital MEW using an e-reader
14/06/2011 14:33:59
A good thought. I have just purchased a Kindle as a book reader and the same idea crossed my mind.
But I don't want an i Pad at great expense because the keyboard is on the screen and I can't touch type on it. Also, it seems that I can't connect an external keyboard or even a USB drive; so that's out.
On the other hand, Kindle does not have colour which limits its ability as a magazine reader.
And lastly, while Ireally do want to dispense with the hard copy of the magazines, the digital editions are really not very good. Hopefully the publishers of the magazine will do a bit of homework and link into some modern technology that protects their investment while giving us a quality product.
Thread: Jan Ridders Pressure-controlled Two-stroke engine
15/03/2011 09:38:15

At last, IT RUNS!!! And you can see it here
The problem was lack of compression which was diagnosed by my expert friend Win Coupland.
The solution was to make a new piston with a flat top and just a small cutaway for the transfer port. I actually designed it to comply with the parameters suggested by Dave Parkes in his articles on two stroke engines in ME. Transfer port opening 100 degrees, exhaust port 120 degrees and compression ratio 8:1.
I am not sure how close I got but it certainly has plenty of compression and lots of power. I think I need a throttle control like the one in John Somers' Pimento carburettor.
Many thanks to all of you who supported my efforts to get it running and who offered good advice. Your support was really important in keeping me going.
And now I have to make it pretty (but not until I have played with it some more).
04/03/2011 23:30:07
Well, I have made a bigger flywheel (disk 150 dia x 25 width) and put it all together and:
It still does not run. And of course Ian is right: the flywheel only stores energy and needs only enough inertia to maintain a certain minimum speed between pulses. Any larger (or heavier than needed) just adds to the bearing friction and to the load on the engine.
From trying it and thinking about the result and thinking about Ian's comments, I have learned something about flywheels. So I suppose some good has come from it.
Jeff - I took your advice about the ignition timing which translates to about 11 degrees BTDC (I have to outsmart the electrickery) and I think it improved the power output. Maybe I need to take the rest of your advice and dive into the spare parts box for an old Bonneville coil and capacitor. We shall see.
Now I am waiting to see how John gets on with the Pimento Jar carburettor.
04/03/2011 23:14:54
Thank you for your kind words and continuing encouragement as I struggle with your lovely engine. Yours works beautifully, and the Belgian students have made theirs work with the small flywheel so the design is good.
Despite the frustrations, I am enjoying building these small engines but I could not do so without you and other people designing the engines and making the plans available. I am grateful to you for all the work you do.
Maybe I will get the engine to run, maybe not. Making it and trying to get it to run is the interesting part. Of course, having a finished engine that runs is good too.
02/03/2011 18:15:49

I think I have found the solution.
Debra would not stay in the box because I have been convinced all along that the solution is so obvious that I could not see it. So I kept taking it out for one more try.
When a friend came over to play with the engine, something was said that convinces me that the problem is:
I have been trying to cure the four cycling and misfiring. But when I looked again at Jan's video, I noticed that his Debbie four cycles and misfires as well. So I have been looking in the wrong place. The difference is that Jan's engine has a larger flywheel to keep it running between the power pulses. A rough estimate is that Jan's flywheel has about 4 times the moment of inertia of the smaller one.
I may be wrong again but the diagnosis fits all the known facts. This does not make it right but it is a good start.
And now I can't wait to get to the shops to buy a lump of metal to make a larger flywheel.
28/02/2011 00:49:16
So that's it. I am now giving up on this engine. I have tried everything I can think of and it still misfires and won't run.
The problem is not friction because it misfires when driven by the drill.
It is not being driven too fast because it misfires at all speeds.
It is not the ball valve because it misfires with Jan's original arrangement (on John Somers' engine) and with Jan's arrangement on mine and with a poppet valve instead of the ball valve.
It is not the fuel because it misfires on petrol and on Coleman fuel,
It is not the exhaust because putting a vacuum cleaner on the port to extract the burnt gases made no difference.
It is not gas contaminating the incoming mixture because the non-return valve made no difference.
It is not spark quality because it uses an RCEXL CDI system and we can see the spark in the Colortune video.
It is not mixture because we can see it firing on rich, correct and lean mixtures.
It is not compression ratio because I have tried different piston locations.
So I now join the others in this Forum who have given up without getting Debbie (or Sabrina which is similar) going.
But I will put it in a box, at least until I need to rat it for bits, in the hope that someone will solve the problem and put it on this Forum.
28/02/2011 00:32:44
I have now tried the engine with a poppet valve at the transfer port to prevent cylinder gases getting into the transfer passage and contaminating (poisoning) the incoming mixture.
Video of the test is here.
It made no difference. The engine still misfires.
When looking at the captured video, I noticed what appears to be condensation in the transfer tube. Further testing indicates that it appears to be oil from the bottom of the cylinder, picked up by the mixture and then deposited on the walls of the tube.
I don't think this is fuel condensing out of the mixture and thus changing the ratio because heating everything with a hot air gun made no difference, and it was 30 degrees in my workshop anyway so additional heat was hardly needed.
That, plus the fact that the mixture remained rich as shown on the Colortune test part.
Thread: Chemi Blacking
24/02/2011 19:52:54
I am using Blackfast - a room temperature process for iron, steel and zinc. Mine came from John Lines in Queensland (Australia) whose email address is john@
The kit came with the chemicals, sealable containers in which to use and keep the diluted chemicals already labelled, comprehensive and clear instructions (the process is simple) and product safety data sheets for each of the chemicals.
The chap who recommended it to me has had his for about 5 years and it still works.
It works for me.
Thread: Jan Ridders Pressure-controlled Two-stroke engine
23/02/2011 21:27:50
Hi Jan,
Yes, I think something like that is happening. I have the piston just a bit lower - about 1.5mm below the exhaust port. That is where the transfer port is completely uncovered on my engine.
But just in case the exhaust gases are not being completely expelled, I put a vacuum cleaner on the exhaust port to extract them. It made no difference.
I also reduced the volume of the expansion chamber (just put tube in its place) to increase the pressure and velocity of the mixture as it is injected into the cylinder to assist scavenging. That made difference either (except that the extra pressure blew the tube off after a while).
My cylinder would look upside down to you because I am in the southern hemisphere where everything is upside down (as John Somers keeps reminding me) but it is the right way up for me.
I have now designed another poppet valve to go on the transfer port to stop any gases being drawn back into the expansion chamber. The next job is to build it and see what happens.
This is a very interesting problem.
22/02/2011 11:29:17
I have done some more work and here is the result:
Jim: I tested it again with the CM6 plug head and it made no difference.
Jens: With the head off, I get a very distinct "poof" from the transfer port. There is a general smell of Coleman fuel.
Jan: Your mention of two strokes misfiring led me to wonder if the cranking speed was too high for the (effective) throttle opening thus causing four-cycling like motorcycles do when the throttle is closed. After extensive tests, particularly at lower cranking speeds, I have concluded that this is not the cause of the problem.
To see if the ball valve really is the cause of the misfiring, I have replaced it with a poppet valve. I can see this valve operating. And it makes no difference. The valve and the tests are on YouTube and if TerryD's advice is correct, you should find it here. Thanks Terry, it worked.
So I am not sure where to look now. The problem is not friction (because it is misfiring when cranked) and not the ball valve (because it is still there when the poppet valve is substituted for the ball valve).
I am wondering if, when it fires, it blows the next incoming charge back or contaminates it in some way. The only way I can think of to test this is to put another non-return valve right at the transfer port on the cylinder where the mixture in injected.
Any advice anyone? I am running out of ideas.
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