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Member postings for Stub Mandrel

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

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Thread: Gear milling
14/02/2010 18:04:29
Hi Tom,
 
Those cutters look enviably good. I keep thinking of making a 'Eureka' but your buttons don't look like they were designed for one.
 
What method did you use to relieve them?
 
Neil
 

Thread: Perpetual Motion
14/02/2010 17:37:29
I don't think there's anything wrong with the concept of perpetual motion. Newton pointed out that a body will remain at rest or in a state of continuous motion unless acted on  by an external force.
 
All you need to do is reduce frictional and other losses to zero - in other words a closed system is a perpetual motion machine. The electrons whizzing around a superconducting magnet are effectively in perpetual motion.
 
Of course the real problem is the 'closed system' bit, even if one of these brave siouls achieved perpetual motion, they still can't get energy for nothing - they start taking it out and the machine slows down.
 
More interesting is the possibility of generating energy at a quantum level - Maxwell's demon anyone?
 
Neil
Thread: broken tap
13/02/2010 22:59:59
Thanks Ian,
 
Neil
Thread: Hand Crane
13/02/2010 22:58:09
The plot thickens!
 
I was wondering about J S LEE - I it doesn't look right on the base so I took a close look at this:

Get in close and it says  "J.SLEE" google Slee Earlestown and you turn up a plenty of links to a 19C manufacturer. So the info plate is wrong!
 
Thanks for your description Ian, I think a second decent sized pulley belongs at the top of the pillar now. I have been reading 'Machinery's Handbook' and a rope strong enough for 15cwt  would need a big pulley too. My money os on 5/8" or 1/2" rope and two 12" pulleys now.
 
Thanks both,
 
neil
Thread: Gear milling
11/02/2010 22:16:28
I've made single-point cutters using Ivan Law's method. They worked 100%:
 
Tom Walshaw (Tubal Cain)  was a sceptic and took the approach of hand-filling a cutter to match another gear of the same pitch and similar number of teeth. When I needed a 63-tooth changewheel for metric screwcutting on my lathe, I tried this using a 60-tooth changewheel as a pattern. the result was excellent IMHO:
(unsharpened but hardened cutter filed from 1/8 gauge plate)

All you need for gearcutting success is the patience to understand the instructions, do the calculations and take your time with the cutting.
 
 
Neil
Thread: broken tap
11/02/2010 21:49:45
I read a tip that you can use a solution of alum salts to eat away taps broken in aluminium. Not much help for mild steel, I know, but it's a problem I've had.
 
Unfortunately these days the chemists don't sell chemicals anymore. Does anyone know a source for alum salts?
 
Neil
Thread: Stuart Turner Sun Engine
11/02/2010 21:44:13
Posted by Alan Worland on 10/02/2010 23:29:19:
You can keep your ducks - I'm having my boat in the bath!
Bathtime went well, engine runs like a dream, tied to the taps I was able to run full power at 45 psi and with the burner turned up the pressure was rising.

ROFL! 
 
Brings to mind an old Chuck cartoon where he starts up a boat in the bath and creates a tidal wave!
 
Your 'tied to the taps tip' should be reprinted in ME, I hope Dave spots it!
 
Post a pic of your boat once you get it out on the water.
 
Neil
 
Thread: Turbine Blades
11/02/2010 21:38:31
Hello James,
 
You've picked an interesting challenge. When you start, take photos of each stage for us to see!
 
The following is all guesswork, but reflects the design of an amazingly effective small plastic ducted fan I have.

Water flowing constrained to a tube is effectively incompressible, but there is no spill of the edges, like with a free prop. An ideal blade will still need a greater pitch  near the hub than at the periphery, but the pitch can remain constant along the blade (i.e.you don't need curved blades like a prop). If the turbine is designed so the hub is quite large (say 1/3 to 1/2 total diameter) and the width of the blades short (i.e. use 12 narrow blades rather than 3 wide ones), then I'm sure you could get away with many straight blades. If you accept a less than perfect root profile, such as that generated by a bull-nose cutter going across at an angle, I reckon it would work.
 
I made a radial water pump rotor from aluminium alloy, but it wasn't too effective because of the size of the gap at the edges is too big. I guess the same would apply to a turbine.
 
You can either try suck it and see, or do some maths based on the volume of water and rpm required.
 
Good luck, and don';t forget to report back!
Thread: Hand Crane
11/02/2010 21:23:50
Martin, that's an amazing photo, the wooden beam is extraordinary!
 
I'll have to add that pic to my 'future models' file
 
It's rather bigger than mine - you can see it has two sets of gears instead of one and the handles are quite low down by comparison (or the crane is bigger and they are the same height, if you get what I mean). I'd guess the cable drum at right is about 4' diameter.
 
I see what you and Ian mean about rollers.
 
Regards
 
Neil
Thread: Stuart Turner Sun Engine
10/02/2010 21:59:12
Sounds great!
 
I have heard that the oil in some full size closed-sump steam engines was in fact more like a mousse of oil and water. Take care you don't get bacterial corrosion if it's left to settle out.
 
Neil
Thread: Hand Crane
10/02/2010 21:55:46
Hi Martin
 
There is a plate at the base of the crane giving a brief history. I thought the name was J Slee, but the plate says it is J S Lee.
 
I googled for ("J S Lee" earlestown Lancashire), and it came up with 2 hits - a list of Irishmen and a crane at Fradley junction

Hi Ian,
 
I won't lose anything by trying your suggestion - if there isn't room, I just add a pulley instead.I will try and take l look at the elsemere crane.
 
I'd be interested to see some pics of the water turbine or other Kiwi engineering.
 
Thanks both,
 
Neil
09/02/2010 22:06:06
Hm - much food for thought. 15cwt is about 3/4 of a ton, taking a safety factor of at least 10 and the lesser typer of steel in Machinery would indicate 1/2" wire rope (the groove in the pulley would take a larger rope, but the fixing loop on the drum suggests smaller.
 
A calculation for pressure on drums or sheaves in Machinery is
 
P=2*Tension/(sheave dia x rope dia)
 
With a 12"  sheave and a 1/2" rope and 15cwt tension I make the pressure 550lbs. The safe limits given for cast iron with different types of wire rope vary from 300 to 800lbs.
 
With the winding drum itself being 8" diameter, this suggests a wire rope at least 3/4" diameter for safe running, and there's no way you could get away with a small roller at the top if it was cast iron or ordinary steel.
 
For manilla rope you would need 1" dia for a 3/4 ton SWL, perhaps that's the answer, but a tight fit in the loop on the winding drum.
 
I'm leaning towards adding a second 12" pulley on some sort of added frame.
 

Neil
 
 
09/02/2010 21:52:05
I have got the late Dave Lammas' articles. He  had some nice models that were off the beaten track - I think his last one was a spring hammer. The crane articles are useful, but as you say he doesn't have the routing problem and neither do LBSC and Tubal Cain's small steam cranes.
 
It is hard to measure something that's on top of a 12 foot pole, but a 6" diameter roller would foul the top bearing, and a 4" diameter roller would not be large enough for the rope/cable to clear the bearing. You might just get away with a 5" roller, but that's a tight  bend. I shall go away and consult my old Machinery's Handbook to see what would be a suitable rope and wire cable for 15 cwt SWL, and what radius it would bend to.
Thread: Slow loading pages.
08/02/2010 21:14:57
Half an hour later , and suddenly everything is flying!
 
Neil
Thread: Hand Crane
08/02/2010 21:13:06
Hi Niloch,
 
Nothing as grand as that! It's a small wharfside crane that was restored about 20 years ago:

The cable run has to come from the drum up and over the pillar:
 

The cable drum is here (note the fixing loop and ratchet - the brake is fitted to a replacement for a broken lug on the ratchet dog, the brake should mount on two studs that would position it to work on the - missing- winding handle).

But this is the obstacle the cable has to get over - no room for a decent size pulley?

My thought - the bar across to the jib looks wrong, if the pivot was mounted the other way around it could provide a mounting point for a pulley support:

That's the evidence! An ideas?
 
Thanks
 
Neil
 
 

Thread: Slow loading pages.
08/02/2010 20:38:40
Firefox and XP here too, but still slow. I notice Kwil was online 9:00 am, I was at 9:00pm.
 
Could be contention issues, locally or at the server?
 
Neil
Thread: Hand Crane
07/02/2010 22:00:14
I've nearly finished drawings for a hand crane that can be found at Fradley Junction. It is built around a double fram hanging on a tall central pillar. The winch drum is on one side of the pillar and the jib is on the other. This means the cable had to go up, over the top of the pillar and across to the end of the jib.
 
There is only room for a small pulley, not large enough to guide the cable away from the top  bearing. Also, I imagine any pulley up there would need to be similar in diameter to the winch drum (8") and the jib pulley (12"). I'm imagining a second large pulley stood off from teh top of the frame above the winch. I'm also assuming a wire cable, not a rope for this 15 cwt (about 750kg) crane.
 
Is anyone familiar with this type of crane? Would it have had a rope or a wire cable? Any suggestions how it would be routed over the top?
 
Thanks in anticipation for any suggestions!
 
Neil
 
 
 
Thread: Slow loading pages.
07/02/2010 21:45:26
I've only been on line regularly for a few weeks. The site can be tortuously slow, especially at weekends. I reckon over a minute to lead a page.
 
Connection here is fairly slow - aboput 1.3 Mbs - but not THAT slow.
 
I think that the site may be a victim of its own popularity.
 
Neil
 
For what it's worth, it took 63 seconds for the original, unedited, version of that commment to load and the page to refresh.

Edited By Neil on 07/02/2010 21:47:33

Thread: Spindle Speed
06/02/2010 22:14:26
I built a tachometer, largely because I wanted to get into AVR microcontrollers and it looked like a good starting place. It does have one really good use, that I haven't seen mentioned elsewhere.
 
With a fairly small, low powered machine (mini lathe), one can keep an eye to how much the revs drop when you put on a cut. It's surprising how much you can increase the depth of cut/feedrate before the revs drop more than a few percent, and it's a much kinder approach than waiting for it to stall, start labouring or popping fuses.
 
FWIW I also replace the fuse with a circuit breaker.
 
Neil
 

 
Thread: Tachometer design
06/02/2010 22:06:08
Fair point on the gear sensors, but I wanted something that made one pulse per rotation, as I was timing one pules, rather than counting pulses in a tiome period. Same view, but looking down the other end of the telescope!
 
To be honest, I think half the reward of designing something like this is trying the various options - if they weren't valid options then we wouldn't have so many parts to choose from.
 
I think my bias for a magnetic sensor has more to do with the elevated oil and dirt levels around my lathe - I'm not sure a reflective marker would remain refelctive too long with me around
 
When you do your article you could consider giving examples of different sensor types and their pros and cons.
 
Neil
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