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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: Rina and T&K drawings
28/10/2010 11:06:42
What a great job you have made of the drawings John, and so quick! I note that in another posting, you have advocated the use of 3D over 2D because one can easily generate 2D drawings from the 3D. Maybe I need to go back to Tech next year to do the 3D extension to the 2D course I did this year. One never stops learning.
 
Elsewhere, I mentioned that in converting Rina to metric, I have made some changes. Two of these relate to the valve train and to my  aversion to tightening threads to achieve a specific orientation. They are:
 
Fixing the Cam Mounting Shaft (Fig 17) with a capscrew from the inside of the frame. There is room to do this and it means that Fig 17 can be correctly oriented and the screw also correctly tightened.
 
At the other end the Rocker Bearing Mount incorporates one of the head bolts. The same considerations in regard to bolt tension and mount orientation apply. I propose a separate bit like a right angle bracket attached under the push bar mounting on the head, and providing a separate mounting for the Rocker Bearing Mount. The head bolt is then separate and can be tensioned correctly.
 
Your comments on these changes would be appreciated. They could save me reworking these elements when I get into the project (which should be early next year)
 
Jim
 
Thread: Continuing Articles
18/10/2010 08:08:28
Are you familiar with the drawings of M.C.Escher? He has done some wonderful woodcuts along similar lines.
Jim
 
Thread: Rina and T&K drawings
17/10/2010 20:17:44
Thanks David, that was quick.
Cam base circle to top of lobe determines the lift. In retrospect, I guess I could figure it out since a lift of (valve diameter)/4 will give an opening equal to the area of the port ie. maximum required opening. I just didn't stop to think at the time.
Jim
 
Thread: Hints and tips
17/10/2010 07:23:49
For picking up swarf:
 
I was using a magnet in a plastic bag but the bag kept developing holes.
 
Then I realised that I have a magnet that I can turn on and off. So now I use my magnetic DTI stand: turn it on, wave over floor, take to bin, turn it off.
 
It is not showing any ill effects from this but, if it does, then I will buy a new one for the DTI.
 
Meanwhile, it works in both roles and it has a nice handle that saves me bending too far to pick up the swarf.
 
JIm
 
Thread: Rina and T&K drawings
17/10/2010 07:18:22
Thanks John for more excellent advice. Much appreciated.
 
David,
Two things:
1. Could we have a name change for this thread from Rena to Rina or a link please. The search engine does not pick up the incorrect name,
2. We seem to be missing a dimension for the cam base circle in Fig 16.
 
Regards
Jim
 
17/10/2010 01:41:30
Thank you John, that is good advice. I have been trying a bit of that and it works well. In fact, I prefer it to the marking out method when I can use it. Holes are particularly troublesome - no matter how I try (even feeling for the lines), I can't seem to get them exact. Coordinate milling is much better despite having to accommodate the backlash.
 
I take your point in regard to gear spacing. On my current (and first) engine, I "fudged" it by making the shaft slightly eccentric so the spacing is adjustable. Not sure if that is good practice but it seemed to be one way around my skill limitations.
 
The other reason for making dimensions to 0.5 mm resolution is that the drawing looks better. And if there is no reason to specify a dimension to 0.2 or 0.1 mm, why bother.
 
Thanks again. This thread and the forum in general makes subscribing worthwhile.
 
Jim
 
Thread: Hints and tips
17/10/2010 01:23:19
Dishwashing is good AND you get Brownie points
Thread: Rina and T&K drawings
16/10/2010 21:59:28
I am (rather slowly) working on drawings for a metric version for my own use because I don't have any imperial tooling. In doing so, I have had to massage most of the dimensions so that they come out with 0.5 mm resolution because that is as fine as I can mark out. 
 
I am a newbie at this and just hope it works when it is built.
 
Jim
 
Thread: Hints and tips
15/10/2010 06:27:04

To make life easier when setting work in a four jaw chuck, I made a second, small chuck key as shown in the photo. I use this one in my right hand at the back of the chuck in conjunction with the normal key at the front.>>

 It lets me keep pressure on the work and speeds the process.

 Jim 

Thread: Continuing Articles
15/10/2010 04:22:47
And as for Rina, we get a miserable 2 pages every second issue. Very  poor. I was patient when I thought it was because David was laid up but even then it should have been farmed out in the interests of the readers.
Thread: Cutting Aluminum Sheet/Plate
20/07/2010 04:30:12
Yes Sid, you can cut aluminium using a carbide tipped saw used for wood. I have cut 12 mm aluminium on my saw bench using a 216mm 60T blade with 10 degree positive rake with no troubles. And I did it before I read (somewhere) that you need to use a lubricant so it was all done dry.
 
I also found a blade called a Diamond (brand name) Multicutter. This is a 100mm diameter carbide tipped blade for cutting aluminium, PVC and Fibreglass at up to 7000RPM. I have fitted it to the slitting saw arbor in my milling machine and used it to cut 12mm aluminium. It gives a great surface finish. And it is fast - just slow enough to let the chips clear the teeth. And it cost $15.
 
On saw bench, I now have another blade. It is a MetalSonic Part No MSB1602040 160mm 40T blade that will cut steel, aluminium, plastics, wood (solid, ply and MDF) even with nails in it much faster than anything else I have seen. I have used it to cut 6mm mild steel both cross cut and ripping. I have not be brave enough to fit this monster to the slitting saw arbor but would like to hear from anyone who tries it - it should work.
 
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