Daydream believer
Well-known member
So why are so many propellers on shafts on a taper?
Why are lead acid battery terminal posts
- Thread starter Graham_Wright
- Start date
coopec
N/A
Interesting question! (Never thought about it)
"Essentially, we have a tapered negative post and a tapered positive post that are slightly different sizes. So, the positive terminal is slightly larger than the negative terminal. This was built as a safety factor so that the cables couldn't be easily interchanged on vehicles."
Don't overlook proper battery terminal set up
Graham_Wright
Well-known member
Somewhat different! Something to do with rotation?
BabaYaga
Well-known member
Totally different. The traditional clamp is compressed around the tapered post with nothing (short of friction) to stop it from rising, while the prop is compressed onto the taper by the nut, which counters that movement.
PaulRainbow
Well-known member
The material that the fastening is made of (in the picture that you quote) is irrelevant. Current passes through the post, through the lug/s and along the copper wire, nothing has to pass through the washer and bolt/nut. The bolt could be made from non conductive material and it would still work just fine.
Graham_Wright
Well-known member
Yes it would but if the bolt conducts, an electrical path is provided both sides of the connecting lug.
PaulRainbow
Well-known member
If you say so.
Daydream believer
Well-known member
What about the screw that holds the cup type connecting piece to the pole. That fastens the connector down onto the post. I have, in the past, had to use a lever to force it upwards after the screw had been released
Rappey
Well-known member
Wow. You've all missed the obvious reason they are tapered - it's so you can beat them on with a hammer to get them tight !
Graham_Wright
Well-known member
Agreed but the polarising is to do with the diameters not the tapers.
BabaYaga
Well-known member
Yes, the screw creates a compressing force that fastens the clamp to the post. But because of the tapered shape of the components, there is also a sideways force created that pushes the clamp upwards, which decreases the clamping pressure.
NB I am not claiming that this is a big problem with the traditional soft and coarse materials used, lead and tinned brass. But as I indicated upthread, with smoother surfaces it becomes obvious that the basic concept is not sound.
For comparison, a slightly tapered hose tail would probably also work (because of the softness of the hose), but would it be a good idea?
Farmer Piles
Well-known member
Tapers grip and make good contact, hence them being used on prop shafts but also in machine tools. You can tap a prop, battery terminal, morse taper machine tool holder into place and most of the grip will be made by the surface contact within the taper. Also, you can tap, clamp or tighten a nut to make them really grip, but they will then also release more easily when need be. A cylindrical shape wouldn't achieve this.
justanothersailboat
Well-known member
I can't agree at all with the idea that a taper is not a sound connection. For a cylindrical socket to pass over a cylindrical post it must have clearance, then if it gets pinched down to fit by a bolt then it is warped off-cylindrical so it can only contact the cylindrical post along a few lines, not a large surface. THAT would not be a sound connection. A conical socket can fit onto a cylindrical post exactly (as long as the cone angles are the same) and should not even really need the bolt. In machine tools it is really common for a hard steel cone and a hard steel conical socket to be all you need to hold a tool in place, even a drill bit, with only a fairly light pressure to get the connection firm. The friction between two conical surfaces that are really in contact all over is enormous. Probably more so with soft lead ones that can deform to an exact fit and be thumped on with a hammer.
Pinching down a cone with a bolt, like battery terminals do, also deforms the cone and would make it a worse fit if you started tightening up the bolt before the cones were well in contact. In practice you don't do this so it probably doesn't. Yes in theory the cone converts a small % of the force to an outward thrust but the taper angle is so small that that force is sine of a small number and is really really small. If it doesn't grip, probably you have a part with a wrong or damaged taper angle
Has anyone really run into a problem of these things popping off the lead cones? I had the opposite problem - took some sweat and swearing to get them to move! Someone must have followed the hammer theory a bit too vigorously. It just takes a tap...
Pinching down a cone with a bolt, like battery terminals do, also deforms the cone and would make it a worse fit if you started tightening up the bolt before the cones were well in contact. In practice you don't do this so it probably doesn't. Yes in theory the cone converts a small % of the force to an outward thrust but the taper angle is so small that that force is sine of a small number and is really really small. If it doesn't grip, probably you have a part with a wrong or damaged taper angle
Has anyone really run into a problem of these things popping off the lead cones? I had the opposite problem - took some sweat and swearing to get them to move! Someone must have followed the hammer theory a bit too vigorously. It just takes a tap...
ean_p
Well-known member
They're tapered simply to make removal easier then it would be if they were cylindrical. Once the clamp is eased then any 'lift' totally frees the fitting. If cylindrical the clamp would need a significant release so to clear the terminal over its full length ( read height). As the clamps are themselves tapered to suit the post then there is no significant up trust caused by the tapered shape as there would be had the clamp been parallel and the post tapered. I think much of it started in the days of lead 'caps' that were mentioned by DB above in that they were pulled down onto the taper by a centre fixing through the top surface. The tapers giving good all round contact as the caps were pulled down. Cylindrical posts wouldn't have provided this. As the caps were replaced with more convenient clamps the tapers were retained as more functional as in above.
Capt Popeye
Well-known member
Well I understand that a Tapered connection is firmer than any parale connection , so guess Batteries have tapered posts ; they are also tighter than paralel posts
PaulRainbow
Well-known member
Curious why the "WOW" to post #11 ?
Drilling, tapping and fitting a stud is a valid method, often used for repairing damaged battery posts.
Making the post "square" only makes it the same as millions of Ford batteries.
Capt Popeye
Well-known member
Well my guess is that if the Taper are compatable , thats on the shaft and the prop , here should be no slack for the prop to move about on the shaft (osilate about) due to the rotation and great thrusts imposed
Maybe I should had posted both a WoW and a Smiley together ?
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Capt Popeye
Well-known member
Well my Wow is to to reflect the most sensible suggestion that you made
Credit to you kind Sir (PR)
Getting used to your Enginnering skills
Daydream believer
Well-known member
The No 2 morse taper in the tailstock of my lathe holds a Jacobs chuck. It is held by friction alone. No draw bar to tighten it. I just push it in & it grips. I can put a 15mm drill in it & it will drill into steel without slipping. The morse taper does not rotate The steel it is drilling does.Somewhat different! Something to do with rotation?
There is no woodruff key either
The same for my pillar drill, except in that case the quill rotates & the steel is clamped. But there is no nut to hold the taper. It is held purely by friction between the male & female parts
Gsailor
...
Good question. Tapered posts have often caused me problems.
The answers have been useful too.
Thanks
