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Member postings for Steve Withnell

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

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Thread: electronics
18/09/2011 13:39:51
Any books good on the design of the input stages to power / mos FET type devices?
 
I'm at the stage where I can almost grasp the device characteristics charts in the datasheets, but not well enough to do the input design...
 
 
 
Regards
 
Steve
 
 
Thread: Nemetts 15cc engine
17/09/2011 19:40:47
Hey Roy - you avoiding the cylinder head? I can see all the parts getting done, except the head!
 
Steve
 
 
Thread: Running my Stuart S50 on air
17/09/2011 16:54:38
Posted by Geoff Theasby on 17/09/2011 15:38:24:
Hi Duncan,
 
I have an S50, a Stuart beam engine and a 7A, all fed with 4mm plastic piping from the local car accessories shop.
 
Regards
Geoff Theasby
 
Wouldn't it be easier to buy yourself a compressor?
 
Sorry couldn't resist

17/09/2011 14:27:52
Hi Duncan,
 
Make sure you keep the internal moving parts lubricated, you either need to get some oil fed into the air supply or only run it for short periods (a few minutes I think) between manually getting some oil into the cylinder. Even run on steam, lubricators are used to get oil droplets into the steam supply.
 
 
 
Steve
Thread: chester comet
11/09/2011 22:00:47
Isn't the Comet a Sieg C6 and Arceurotrade sell a QCTP for it...
 
Steve
Thread: Content
07/09/2011 20:59:39
I have to disagree.
 
1957 ME
Black & White printing only
Only 2 photo's of machining set up's out of 24 issues
"Event" photo's low grade b/w to the extent that detail is completely lost beyond the immediate foreground
Some issues look like boating mags rather than ME.
LSBC and Mr Westbury producing high standard drawings
 
2011 ME
High quality 4 colour printing throughout
Page layouts I guess (David?) 25% bigger and better laid out too
The bigger size means materially bigger drawings and photo's and far more detail to aid understanding.
Routine documenting of machining setups

Price equivalence, roughly the same.I wonder which mag Mr Westbury would have chosen for his 60cc Gas Engine?
 
A good example is the Nemett 15S article. The layout and large detailed setup photo's made the engine far more accessible to novices than would have been the case in the 1957 ME's and less Nemett's would have been built.
 
Content then as now relies on good contributions and the quality of the current ME is an excellent vehicle for those contributions.
 
Steve
 
 
 
06/09/2011 18:38:45
Posted by chris stephens on 05/09/2011 23:05:47:
Hi Steve,
Try and get hold of some MEs from the late forties or early fifties, then you will know how.
chriStephens

Funny thing that. I spent part of last evening in the den looking at a stack of 1957 ME's. Amazing what the world was like without TV and a UK manufacturing base that produced loads of skilled (ie time served) people. A lot of interesting stuff in the mags, but you cannot seriously compare the production quality? " They don't build 'em like that anymore", - damn good job too!

 
Steve
 
 
05/09/2011 20:30:04
I thought the content of todays ME was very well balanced with IC, Loco, stationary steam and a clock article. Struggling to see how you can do better than that.
 
Steve
 
 
 
 
Thread: Fitting a backgear to a variable speed lathe.
04/09/2011 17:10:57
 
 
Here you go - low speed the belt runs from the lay shaft pulley to the spindle and high speed is a belt direct from the motor shaft pulley to the spindle pulley.
 

This is the new pulley I made for the motor shaft. The grooved part was done with a 5/8 tap held in the toolpost, so really easy to get the grooves "right" (idea copyright John Stevenson). This is a good match to the spec of a Contitech Poly V belt. Mine has run for years now and it's showing no signs of abuse at all.
 
The tensioner needed a mod to work with the new arrangement, but again simple stuff (you can see the slotted plate I made to re-mount the original tensioner wheel).
 
 The outcome of this effort is that I have a lathe which has good torque from 40 - 2500rpm,  instead of circa  150 - 2000rpm.
 
Steve

Edited By Steve Withnell on 04/09/2011 17:13:38

04/09/2011 16:23:35
Hi Pailo,
 
Sort of did this on my Sieg C6, not a "back gear" but added an extra ratio to give me torque at the bottom end - it was easy to do on Sieg, but part of that was down to ArcEurotrade being excellent on spares provisioning.
 
The Sieg C6 was in two versions, a conventional six speed belt drive and a variable 0-2000rpm known as the C6B.
 
ArcEurotrade got me the C6 components so I could add the conventional belt drive back into my C6B! Bit of a cheat really but it's made my C6B very versatile.
 
I think the photos are in my albums on this site, if not I can soon do that.
 
Steve
Thread: Nemetts 15cc engine
04/09/2011 14:46:58
One thing I do remember from the build which I did forget, was that Nemett recommended the use of a split pin to retain the prop nut as he'd had his prototype backfire and kick the prop off. I simply used a nyloc nut. I didn't experience the engine kicking back on the few occasions I ran the engine, so maybe the timing on mine was slightly off.
04/09/2011 14:42:01
Hi Roy,
 
Don't think the glow plug version needs the breather, I didn't accidentally omit it and I'd never made an engine before, so I will have stuck to Nemett's article to the letter as I had no experience to rely upon. I did put a couple of drops of oil in the cam housing before I started it up and after that there was plenty of oily smoke every where!
 
You are doing a cracking job of this - you can't avoid the head much longer! Just keep measuring twice, checking twice and cutting once and it will come out just fine!
 
Steve
30/08/2011 21:06:33
I must admit the head was the one component that had me worried. In the end the only thing I screwed up was milling the locating square on the top, everything else was just a load of patience and keep re-reading Nemett's article on the build. One thing to watch is avoiding clamping marks on the head, I'm a bugger for not taking care in that department!
 
The Cams didn't turn out too difficult, but I did have a DRO on the mill Z-feed by then, it would have been impossible on my Warco mill as the mechanical readout is hopeless for close tolerance stuff. In the article Nemett uses loctite to fix the cams, I was a bit doubtful but they have held tight no problem.
 
The scalloped effect you described sounds just like the issue I had, but adjusting the top slide gibs fixed it for me.
 
 
30/08/2011 18:40:12
I'm impressed at the rate you are getting on with the build! Took me about 18 months to build the Nemett!
 
You've also got a nice smooth taper on the front crankcase half - mine has a sartorial corduroy finish, as I didn't have the gibs adjusted quite right! It's very uniform, so I could claim it was deliberate!
 
Do post the video of it running, it's a great noise -
 
Steve
Thread: MT3 Standards
29/08/2011 18:08:53
5 Inch Chuck. The primary issue was that the business end of the cutter has two large profiles machined out to take the tips, not too obvious in the photo, which meant I needed to get down the throat of the chuck to get a good grip and the throat was just not big enough. Grinder was faster than setting up on the lathe anyway.
 
 
29/08/2011 17:48:33
Wouldn't fit in the lathe chuck, a nats wotsit too big, so I circumised it on the grinder and now it fits like a glove.
 
 
 
 
 
29/08/2011 17:05:53
Good point Jason. Just measured the tapers again based on a datum which is the diameter of the bottom of the taper socket on the machine. This makes the Glanze taper an actual 9mm longer than the others.
 
I'll take John's advice and have at it with a decent carbide tip tool.
 
Steve
 
 
29/08/2011 15:04:24
The two chucks at the top have a taper 77mm long. The top one is an autolock type from Warco, the other chuck an ER32 type from Arceurotrade. The Glanze mill has a taper 89mm long which exceeds the 3-1/16 quoted above by some way. The parallel section is not threaded, so that can go without a problem. Depending on how hard the taper is, I could turn the first 10mm of the taper parallel and then it will fit no problem.
 
 
 
Steve
 
 
 

29/08/2011 08:49:35
Thanks guys. I'll take a photo and overlay the dimensions. There is plenty of meat in the Warco Mill, at time of manufacture it would not of been an issue to produce a longer socket).
 
The drawbar thread appears to go pretty deep into the taper so, shouldn't an issue to "adjust" it.
 
Steve
28/08/2011 23:51:55
Last year I treated myself to a Glanze 32mm endmill, the type with the carbide inserts.
 
Got a job for it this afternoon, to my disdain, it won't fit in my Warco Mill spindle!
 
I've never had this problem before, and I have a fair amount of MT3 tooling accumulated over the past few years.
 
On examination, the taper on the endmill is quite a bit longer, c10mm than my other MT3 tools. Pretty sure I can turn off the offending length, but the question I have is - Is there no defined standard for MT3 tooling (I not just the taper but the complete fitting)?
 
 
 
 
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