In article ,
Jaques d'Alltrades writes:
|
| I don't know what they claim, but a demonstration showed almost instant
| stopping - less than half a second, I'd say.
|
| That I would believe, but it is FAR too long.
|
| It's not exactly travelling at the speed of light^H^H^a bullet.

1' in 1/20th second is under 14 MPH. That is an extremely likely
speed for the business end to flip back if it hits an iron bar.

| Nonsense! Even the torsion of a big saw (like the 36" Pioneer I learned
| on) is tiddly when it stops, or when you accelerate from tick-over to
| full-chat. Even the torsion from my R80 (800cc) BMW is pretty puny when
| you gun it. The ratio of the weight of a chainsaw to the inertia of the
| moving parts (some of which will cancel each-other anyway) is small.

Not that small. I don't know what the weight of the chain is, but
it will probably be 4-8 oz for a 10 lb saw. At 2,500 RPM (and some
go higher), stopping in 1/20th of a second is about 3 foot-pounds.
Not a problem if you are expecting it, but quite enough to make
you lose your grip if you are not.

Your statement about gunning it is irrelevant, as I don't believe
that it goes from nothing to full speed in 1/20th second.

Alternatively, using some reasonable estimates of moments of inertia
(most of the mass is pretty well concentrated), 2500 RPM translates
into the top of the blade moving at about 10 feet/sec (EXCLUDING
any effect of hitting a bar). That is 1/10th second to travel a
foot.


Regards,
Nick Maclaren.

Nick Maclaren wrote:
In article ,
Jaques d'Alltrades writes:
[...moments of inertia an' 'at...]

Any road oop, they're dangerous.

--
Mike.

In article ,
"Mike Lyle" writes:
| Nick Maclaren wrote:
| In article ,
| Jaques d'Alltrades writes:
| [...moments of inertia an' 'at...]
|
| Any road oop, they're dangerous.

Or, at least, are when used inappropriately. Which is where we
came in. I would have little hesitation using one to cut up
logs on a sawbench, but baulk at anything beyond that, as I am
not strong enough in the arms. Others might be safe cutting
trees down and up, standing on the ground, but not up ladders.
And so on. Using them as hedge- and brush-cutters is definitely
a dangerous use.


Regards,
Nick Maclaren.

The message
from Jaques d'Alltrades contains these
words:


I don't know what they claim, but a demonstration showed almost instant
stopping - less than half a second, I'd say.

Oh..so are chainsaw kickback accidents a thing of the past, do you suppose?

Janet

The message
from (Nick Maclaren) contains these words:
In article ,
Jaques d'Alltrades writes:
|
| I don't know what they claim, but a demonstration showed almost
instant
| stopping - less than half a second, I'd say.
|
| That I would believe, but it is FAR too long.
|
| It's not exactly travelling at the speed of light^H^H^a bullet.

1' in 1/20th second is under 14 MPH. That is an extremely likely
speed for the business end to flip back if it hits an iron bar.

IME, from observation, not from it happening to me, the blade tends to
stop there and then, or the bar kick back an inch or two. True, that's
not in a hedge, but a hard thing's a hard thing. (Said the constable to
the actress, as he drew his truncheon.)

| Nonsense! Even the torsion of a big saw (like the 36" Pioneer I learned
| on) is tiddly when it stops, or when you accelerate from tick-over to
| full-chat. Even the torsion from my R80 (800cc) BMW is pretty puny when
| you gun it. The ratio of the weight of a chainsaw to the inertia of the
| moving parts (some of which will cancel each-other anyway) is small.

Not that small. I don't know what the weight of the chain is, but
it will probably be 4-8 oz for a 10 lb saw. At 2,500 RPM (and some
go higher), stopping in 1/20th of a second is about 3 foot-pounds.
Not a problem if you are expecting it, but quite enough to make
you lose your grip if you are not.

The effective momentum of a chain stopping suddenly is zero, as all the
forces cancel. The only 'kick' you'll get is if you are pressing towards
the job, in which case the 'kick' will be in line with the bar and
towards you. Any other torque will be produced by the rotating and
reciprocating parts of the engine, most of which will also cancel
each-other.

Your statement about gunning it is irrelevant, as I don't believe
that it goes from nothing to full speed in 1/20th second.

Alternatively, using some reasonable estimates of moments of inertia
(most of the mass is pretty well concentrated), 2500 RPM translates
into the top of the blade moving at about 10 feet/sec (EXCLUDING
any effect of hitting a bar). That is 1/10th second to travel a
foot.

Meanwhile, the rest of the chain is going the other way, or describing
an arc, cancelling any effect on the assembly if the chain stops dead.
Mind you, it might not cancel the effects on a few teeth...

--
Rusty
horrid dot squeak snailything zetnet point co full-stop uk
http://www.users.zetnet.co.uk/hi-fi/

The message
from (Nick Maclaren) contains these words:

Or, at least, are when used inappropriately. Which is where we
came in. I would have little hesitation using one to cut up
logs on a sawbench, but baulk at anything beyond that, as I am
not strong enough in the arms. Others might be safe cutting
trees down and up, standing on the ground, but not up ladders.
And so on. Using them as hedge- and brush-cutters is definitely
a dangerous use.

Have a look at

http://www.users.zetnet.co.uk/hi-fi/temp/elm.jpg

The bloke beyond the top of the ladder has a 36"-arm Pioneer up there...

--
Rusty
horrid dot squeak snailything zetnet point co full-stop uk
http://www.users.zetnet.co.uk/hi-fi/

The message
from Janet Baraclough contains these words:

The message
from Jaques d'Alltrades contains these
words:


I don't know what they claim, but a demonstration showed almost instant
stopping - less than half a second, I'd say.

Oh..so are chainsaw kickback accidents a thing of the past, do you
suppose?

No idea - never met one. But if they happen, no: there will be plenty of
old ones about which don't have the safety brake - we're still using the
36" Pie and Ear which we bought secondhand in the 1950s, and I don't
expect we are unique.

--
Rusty
horrid dot squeak snailything zetnet point co full-stop uk
http://www.users.zetnet.co.uk/hi-fi/

In article ,
Jaques d'Alltrades wrote:

Not that small. I don't know what the weight of the chain is, but
it will probably be 4-8 oz for a 10 lb saw. At 2,500 RPM (and some
go higher), stopping in 1/20th of a second is about 3 foot-pounds.
Not a problem if you are expecting it, but quite enough to make
you lose your grip if you are not.

The effective momentum of a chain stopping suddenly is zero, as all the
forces cancel. The only 'kick' you'll get is if you are pressing towards
the job, in which case the 'kick' will be in line with the bar and
towards you. Any other torque will be produced by the rotating and
reciprocating parts of the engine, most of which will also cancel
each-other.

There is a principle known as the conservation of angular momentum,
which you may have forgotten after all those years!

I was estimating the effect of the transfer of the momentum of the
chain to the saw as a whole. Yes, it is POSSIBLE that the design
is as perfectly balanced as the wonderful one-horse shay, but I
have my doubts.


Regards,
Nick Maclaren.

The message
from (Nick Maclaren) contains these words:

There is a principle known as the conservation of angular momentum,
which you may have forgotten after all those years!

Which is taken out on the teeth if the chain suddenly stops because of a
nail, etc.

That either results in bent or chipped teeth (on the chain), or a lot of heat.

--
Rusty
horrid dot squeak snailything zetnet point co full-stop uk
http://www.users.zetnet.co.uk/hi-fi/

On Thu, 20 Oct 2005 14:30:47 +0000, penance wrote:
WaltA Wrote:
I am self taught.

Then you are not competant (by industry standards).

I know !! That is why I could not replace my Danarm with a
chainsaw of my choice !
The regs were not in place when I bought the Danarm,

or maybe they were but my vendor didnt bother at that time ! ?
Do you know when the prohibition on top handled saws came in ?

On Thu, 20 Oct 2005 14:27:44 +0000, penance wrote:

WaltA Wrote:
I had to replace it with a much larger much more dangerous two-handed
Sthil:-(

Not at all, the larger the saw the safer,

I spy a small misunderstanding,
I meant that I was more dangerous with the bigger more powerful Sthil
because it meant that I could now tackle bigger trees (and some have
been really really big) without needing to call in "the man"

as it is less likely to kick
back if the wrong part of the bar is used,

I've never had a problem with kickback, even when hitting steel bands
buried in a conifer.

also 2 handed use helps to
reduce the chances.
Top handled saws are for a specific use and should stay that way.

Agreed. Not disputed. If you had said "specific user" then I would
have disputed. I used my danarm for specific uses

If we are going to ban the use of chainsaws by the incompetent
then I suggest that we should ban hedge trimmers as well, especially
the littler cheaper ones which your cheapskate average urban gardener
is probably going to buy, I mean, look at the damage those can do to
fingers; and to electric cables fed through windows and plugged into
non-rcb power sockets !!

Come to think on it, praps we should ban gardens for Mr/s J.Bull ?
Horribly hazardous !
Right, that's it, campaign in support of towerblocks with no opening
windows, nor balconies, for the proletariat !

On Thu, 20 Oct 2005 14:46:14 +0100, Jaques wrote:
(WaltA) contains these words:
Leaving aside, for the moment, the possibilities of nails, barbed
wire, remnants of other fencing wires etc. destroying chains
( yes, I agree a spare is handy)
but the business bits do blunt under normal operations anyway, and one
always has a round file to hand to do the sharpening oneself, as part
of normal operations. Tedious work, but not a loss of "the rest of the
day" ! It is work that can be done 'by eye' with the usual cuppa'
whilst contemplating the next bit of the job !
The serious 'getting the angles just-so' part of maintaining the chain
can be left till the next evening in the workshop.

Thoroughly agree, but the OP wanted to do the job 'now, if not sooner',

Yes
And that is another problem, haste and power tools are not compatible.
We have already determined that OP is not competent (by his own
admission, he cut through the cable, forg*dss*%k,) now he wants a
petrol driven thing !
Mindyou, I regular had to go mend the cable of my next-door
hedgetrimer extrodinair, but he survived to 93y of age ( which must
speak well for my repairs ! , or something !!)

OP wanted to clear , how many years of neglect was it (?) not just
hedges.
(A) you should see some of my (laurel & beech) hedges at 20 to 40ft
high, they need a chainsaw !
(B) you should see the scrub wot grows in the nether regions of my
'garden' after 10y !! We burn logs from it.

so to speak. I've been using the things since the mid to late 'fifties,
and without problems, but I've heard of plenty of people who haven't
been so lucky/careful.

Yes, some of our ancestors fell out of trees as well.
Sadly they seem to have managed to procreate first :-!) and their
progeny to become legislators

The message
from (WaltA) contains these words:

/chainsaw off/

Yes, some of our ancestors fell out of trees as well.
Sadly they seem to have managed to procreate first :-!) and their
progeny to become legislators

You don't think legislators grow on trees, do you?

--
Rusty
horrid dot squeak snailything zetnet point co full-stop uk
http://www.users.zetnet.co.uk/hi-fi/

From my bad memory i think it was around '97, just after i finished my training. Yes it was due to the EU legislation coming to the UK.

Sorry, i thought you meant the saw itself, not the job you might tackle with it.

When you say that you had a specific use for your top handled saw, was that using it from a rope an harness?

In article ,
Jaques d'Alltrades wrote:
The message
from (WaltA) contains these words:

/chainsaw off/

Yes, some of our ancestors fell out of trees as well.
Sadly they seem to have managed to procreate first :-!) and their
progeny to become legislators

You don't think legislators grow on trees, do you?

No, their reproductive habits are closer to those of viruses and
prions than any higher form of life. People start off as human
beings attempting to make some changes to benefit all or part of
humanity, and the contact with legislators turns them into more
of the same.


Regards,
Nick Maclaren.