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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: Is it time to give up?
29/01/2012 03:31:22
I love it Tel, that cartoon says it all. I need a BIG copy in my workshop. Thanks.
 
Jim
 
Thread: Milling - difficult to gauge exact cut
29/01/2012 03:26:21
Hi Wolfie,
 
If you don't have a DRO, you can make a little one from a digital tyre tread depth gauge as shown here:
 
You just need to be careful to keep it square to the direction of travel.
 
Jim
Thread: Rina and T&K drawings
29/01/2012 03:21:12
Hi Norman,
 
I don't have a clear picture of the way you are proposing to tighten the collet - will you thread the outside of the crankshaft, drill and tap the end of the crankshaft to take a screw (like a slitting saw arbor) or use screws through the collet into the flywheel?
 
As a result of my procrastination and faffing about, I have not started on the flywheels which are, as yet, disks of cast iron.
 
Because I rather like the look of solid flywheels, my intention is to simply bore them leaving the rim. And to provide a starting point, I will bore the hole for the crankshaft.
 
Since I was always going to bolt the bosses to the flywheel, it was a relatively simple exercise to design the bosses in two parts with a taper as shown in the photos uploaded to my Rino album. The ignition side has a driving dog to accept a starting bit rather like an old fashioned crank handle.
 
One other thing: I wonder if you really need the circlip or if a simple mark on the crankshaft would suffice. I suppose it depends on the way you tighten the collet.
 
BTW the weather was superb, the Honda survived the Rally and there was a beautiful Venom there that made me think of you. When the photos go up on the website, I will post a link.
 
Jim
 
28/01/2012 06:46:35
Thank you John, now all I have to do is to remember that when (and hopefully if) I strip the engine down.
 
First up is the Triumph which started making very unhappy noises in the primary chain case. Luckily, I heard it before the chain emerged from its hiding place. So the Honda is getting a run.
 
Sorry Norman, that is getting further off topic.
 
Jim
 
25/01/2012 20:59:49
Nice to know that you are following John, off topic or not.
 
But as the owner of both a Tiriumph twin and a CB350, I can identify with your comments.
 
And going even further off topic, our Annual Rally starts today (I am riding the Triumph) and the weather forecast is for 28 degrees and chance of rain.
 
Jim
 
Thread: Finding the centre again
23/01/2012 10:04:53
I'm not laughing Ed, I think that is quite brilliant. Simple, effective and useful. Thank you for sharing.
 
Jim
 
Thread: Rina and T&K drawings
23/01/2012 04:25:04
Jeff: A question for you
 
Did you use standard roll pins like these?
 
 
Do you think these groove pins would be better?
 
 
Sorry, that's two questions
 
Jim
23/01/2012 01:33:49
Aaah! Not you too Norman? John Somers (www.start-model-engineering.co.uk) gives me a hard time about the DVD player going backwards. We had a conversation one evening in which we each checked to see which way the water went down the plug hole. The result was inconclusive.
 
But I made him an Elmers Tiny upside down as a gift on one of my visits.
 
I like the phrase "abused the privilege" for tidying up after the glue has set. And I will also be more kind to the next one.
 
I don't suppose there is any chance that I will see you at the Harrogate ME Exhibition?
 
Jim
 
Thread: Finding the centre again
22/01/2012 20:10:39
That is a good one Lee, and even better because you don't need to fold the paper; just use the centre where the compass points marked it..
 
Stick the paper circle on with a bit of spit and centre punch the compass mark.
 
Jim
 
Thread: Rina and T&K drawings
22/01/2012 20:01:18
Norman,
 
That's really bad luck and I sympathise with you. I have been distracted and have not yet commenced the new crankshaft for my engine. One of the things I have been looking at is methods of mounting the flywheels.
 
Some of the experts over on the HMEM forum favour tapered locking centres of various types because they permit the flywheel to be precisely located and accurately bored to prevent wobble. So I am messing around with designs instead of getting on with the job.
 
Did you try straightening the crankshaft? On a previous engine I found some distortion after silver soldering it so I put it in the lathe and wacked it with a hammer and block of wood until it clocked true.
 
On the current one, I did all the things that Jeff suggests and I left it for about a week to harden in Australian summer temperatures before drilling and pinning. But I might have been a bit premature with the turning after pinning. Perhaps only 3 or 4 days.
 
I have ordered the taper reamers for the taper pins but now I cannot find a supplier of taper pins who is willing to sell me less than a couple of hundred. So I now either have to make my own or change the design to copy Jeff's example.
 
Jeff: I am really pleased to hear that it is possible to use Loctite. I know that Metal Butcher has used it successfully on his Upshur Farm Engines and you have confirmed that it does work on your engines. Of course, the pins will help.
 
Ah well, we press on.
 
Jim
21/01/2012 19:19:47
Hi Norman,
 
I am still following with interest.
 
You do need a condensor (capacitor) in the circuit; its function is to suppress the spark at the points which would otherwise destroy the points in no time.
 
Keep up the good work, I am looking forward to the photos/video of this engine in full song.
 
Jim
 
Thread: Loctite
15/01/2012 05:24:36
I don't think it is a good idea to keep Loctite in the refigerator. The specifications for optimal storage are 8C to 21C and the product sheets say that storage below 8C or above 28C may adversely affect the product properties.
 
I stored mine in the the workshop (beer) fridge. I recently built up a crankshaft using 609 and straight dowels with attention to gaps and cleaning and curing time and it came loose when I put it in the lathe to cleanup. I know that others have used it successfully for this purpose and have assumed that the low temperature caused the problem.
 
I have tossed out all the stuff from the fridge and replaced it with fresh (muttering about the cost all the time). I am now about to try again using 638 which appears to be the strongest.
 
This time I will also use taper pins (if I can find somebody to sell less than 100).
 
For what it is worth.
 
Jim
 
Thread: Rina and T&K drawings
12/01/2012 21:02:39
Hi John, I wondered where you had got to. I really must thank you for introducing me to Alibre which is just magic.
 
 
And also, of course, to the Rina files that you sent me. They gave me a good starting point and a reference. In typical fashion, I drew everything from scratch when converting from imperial Rina to metric Rino but there were many occasions on which I referred to your files to see how you did something.
 
In regard to submissions and postings, you might get more joy from the MadModder or HMEM websites. Have a look.
 
And as for "ordinary Andrew": Two Burrells and a H&M sounds about right. Like you, I reasoned that building two or more is simple since the setup time is shared. So I set out to build four of PutPutMan's Tiny four stroke engines. Despite using jigs and stops and Alibre modelling, I generated scrap at an alarming rate. Heads in particular were mounting up to the point where I considered fishing as an alternative so I could use the sinkers.
 
I am sure that a lot of us would be interested in the build log of your projects. Have you considered sharing the ride?
 
Cheers
JIm
 
 
 
Thread: Basic geometry question
10/01/2012 22:12:25
Buy 6000, sell the rest on eBay and get your money back.
 
Jim
 
Thread: Rina and T&K drawings
10/01/2012 22:06:56
Back again; I was just about to put up the jpeg when visitors arrived. So I will do it now.
 
I am going to try the crankshaft again, this time with fresh Loctite. Reading all the specifications for Loctite (read the manual?) it seems to me that 638 is the strongest so that is what I will try. And although Metal Butcher used parallel pins, I intend to use taper pins. I have ordered the reamer, now just need to find somewhere that will sell me the pins in sensible quantities.
 
So here goes for the jpeg
 
Jim
 
 
10/01/2012 02:33:46
Hi Andrew, the Burrell looks like the sort of project that would keep an ordinary person occupied for quite a while but the list of machines in your workshop leads me to believe that you are not the usual sort of "ordinary" person.
 
Modelling the assembly is fun. Even so, I still miss things but that is one of the limitations of PE - not having the checks available in expert. The other drawback (for me) is that I keep getting good ideas that I try on the model. It is still good fun, and that is what I am doing this for. But it does slow the production of the finished article.
 
It was the clutch Norman, that was the bit I thought was a bit masochistic. Not from personal experience, just from hearing others in the Club discussing it quietly amongst themselves. They would never openly admit that Velos are anything but perfect. I can understand why a 1957 Venom remains in your possession. It is a work of art, particularly as you built it yourself. People who collect statues and paintings (done by others) don't understand but that is because they are ignorant.
 
And "printscreen"!!! Never thought of that. It works a treat. I will put up the photo shortly.
 
Jim
 
Thread: Hot Air Engines
10/01/2012 01:51:48
I'm hangin' in there waiting for the answer. And for photos, videos (of the engine, not of you bounding down the street wrapped in a towel).
 
Jim
 
Thread: Rina and T&K drawings
08/01/2012 21:53:54
Hi Norman,
 
I wondered about your preference for points and coils until I came to the word "Velocette". That explained it. A lovely machine for the afficionado or masochist.
 
So how about a photo or at least some details.
 
My Rina took one step backwards this morning. I have not been happy silver soldering crankshafts so I copied one that Metal Butcher did with Loctite on his Upshurs here: http://www.homemodelenginemachinist.com/index.php?topic=11257.30 but when I put it in the lathe to clean it up, it came loose. So I either have to silver solder one or try again on the assumption that my Loctite was a bit old or had been too cold (I keep them in a fridge but I have just found that storage below 8C can affect the performance).
 
Andrew: I think the reason you can create .jpg and I can't is that I am using the PE version. But I like your mechanism, what is it?
 
Jim
 
08/01/2012 03:26:28
Hi Norman,
 
The ignition is another thing that I have changed. I intend to use the same arrangement that I have used on my two previous engines. It is based on an RCEXL CDI similar to the one recommended at the end of the ME articles.
 
Instead of all the cutouts around the 40T gear, I have cut a channel into the side plate on the other side as shown in the photo in my album. The channel will contain the hall effect device and the wiring leading to it.
 
The magnet will be glued into a ring attached to the crankshaft by a grubscrew to allow it to be rotated to adjust the timing.
 
The CDI and a battery box containing 4xAA rechargeable cells are attached to the underside of the base plate. Sorry I can't show you on this forum because I can only upload jpg files and Alibre CAD produces pdf. Maybe if we used HMEM we could do it.
 
Anyway, that works for the other engines. Of course it will fire every stroke but that is no problem, the same thing happens on my Triumph.
 
If you would like the pdf, send me an email and I will reply to it.
 
And I note that you intend to use petrol. I have built the gas demand valve but I don't think I will use it. Instead, I will use one of Jan Ridders' vapour carbs. They are simple and they work ok.
 
Jim
07/01/2012 22:57:36
Well done Norman, you are way in front of me. I have struck one of those mental blocks exacerbated by having too many projects. The result is that I spend all my time swapping projects and none actually getting something done.
 
In multi-tasking operating systems (like Windows) it is called "thrashing" - a very apt term. So I need either to close some jobs or increase the time-slice allowed for each.
 
I am also making a few changes (apart from the metric conversion) to accommodate my limited skills and material on hand. Latest change is to a roller cam follower which might end up in the scrap bin along with quite a few other ideas that seemed good at the time.
 
But it keeps the days apart and is more interesting than watching the TV.
 
If you are playing with the governor springs, I guess we are getting close to cigars all round. Please keep me informed.
 
Jim
 
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