Propeller or jet to push an in-line skater?

[John Doe[_4_]]

How far-fetched is the idea, to use a propeller or jet engine
(radio controlled type?) to push an in-line skater? How does
aircraft takeoff thrust compare to using a conventional motor and
wheel to push oneself along the ground? What sort of incline would
be achievable at say a skater weight of about 160 pounds? I think
the rolling resistance can be assumed to be zero or maybe the same
as a small aircraft.

Anybody know about Everglades/marsh air powered boats? Maybe I
should do a little research on that one.

One thing for sure, if there ever is such a thing as a jetpack, it
will very easily push an in-line skater before it will lift a
person off of the ground.

Thanks.





--
(Crossposted, please feel free to remove the other group)

[Brian Whatcott]

On 7/21/2010 7:57 PM, John Doe wrote:
> How far-fetched is the idea, to use a propeller or jet engine
> (radio controlled type?) to push an in-line skater? How does
> aircraft takeoff thrust compare to using a conventional motor and
> wheel to push oneself along the ground? What sort of incline would
> be achievable at say a skater weight of about 160 pounds? I think
> the rolling resistance can be assumed to be zero or maybe the same
> as a small aircraft.
>
> Anybody know about Everglades/marsh air powered boats? Maybe I
> should do a little research on that one.
>
> One thing for sure, if there ever is such a thing as a jetpack, it
> will very easily push an in-line skater before it will lift a
> person off of the ground.
>
> Thanks.
>
>
>
>
>
Jet thrust stays pretty constant with speed.
But Horse Power increases with speed for constant thrust.

Which is a fancy way of saying jets are inefficient at slow speeds,
but efficient at high speeds.
Anyway, think about 5 to 10 pounds of thrust per horse power at skating
speeds.

Brian W

[Orval Fairbairn[_2_]]

In article >,
brian whatcott > wrote:

> On 7/21/2010 7:57 PM, John Doe wrote:
> > How far-fetched is the idea, to use a propeller or jet engine
> > (radio controlled type?) to push an in-line skater? How does
> > aircraft takeoff thrust compare to using a conventional motor and
> > wheel to push oneself along the ground? What sort of incline would
> > be achievable at say a skater weight of about 160 pounds? I think
> > the rolling resistance can be assumed to be zero or maybe the same
> > as a small aircraft.
> >
> > Anybody know about Everglades/marsh air powered boats? Maybe I
> > should do a little research on that one.
> >
> > One thing for sure, if there ever is such a thing as a jetpack, it
> > will very easily push an in-line skater before it will lift a
> > person off of the ground.
> >
> > Thanks.
> >
> >
> >
> >
> >
> Jet thrust stays pretty constant with speed.
> But Horse Power increases with speed for constant thrust.
>
> Which is a fancy way of saying jets are inefficient at slow speeds,
> but efficient at high speeds.
> Anyway, think about 5 to 10 pounds of thrust per horse power at skating
> speeds.
>
> Brian W

The model airplane guys have a very small (about 15" long, 5" dia)
turbojet that they use on scale jet R/C planes. It costs about $3000 US.

--
Remove _'s from email address to talk to me.

[John Doe[_4_]]

Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:

....

> The model airplane guys have a very small (about 15" long, 5"
> dia) turbojet that they use on scale jet R/C planes. It costs
> about $3000 US.

How much for maintenance and fuel? Is it louder than a gas powered
weedeater? Just curious.

[cavelamb[_2_]]

John Doe wrote:
> Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:
>
> ...
>
>> The model airplane guys have a very small (about 15" long, 5"
>> dia) turbojet that they use on scale jet R/C planes. It costs
>> about $3000 US.
>
> How much for maintenance and fuel?

It burns a quart of fuel in a minute or minute and a half.

Is it louder than a gas powered
> weedeater? Just curious.

Deafening.

100,000 RPM with every harmonic ever invented.



--

Richard Lamb

[Dan[_12_]]

cavelamb wrote:
> John Doe wrote:
>> Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:
>> ...
>>> The model airplane guys have a very small (about 15" long, 5"
>>> dia) turbojet that they use on scale jet R/C planes. It costs
>>> about $3000 US.
>>
>> How much for maintenance and fuel?
>
> It burns a quart of fuel in a minute or minute and a half.
>
> Is it louder than a gas powered
>> weedeater? Just curious.
>
> Deafening.
>
> 100,000 RPM with every harmonic ever invented.
>

I think they missed the lower sub harmonics, but who can hear over
that racket?

Dan, U.S. Air Force, retired

[John Doe[_4_]]

Dan > wrote:

> cavelamb wrote:
>> John Doe wrote:
>>> Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:

>>>> The model airplane guys have a very small (about 15" long, 5"
>>>> dia) turbojet that they use on scale jet R/C planes. It costs
>>>> about $3000 US.
>>>
>>> How much for maintenance and fuel?
>>
>> It burns a quart of fuel in a minute or minute and a half.
>>
>>> Is it louder than a gas powered weedeater? Just curious.
>>
>> Deafening.
>>
>> 100,000 RPM with every harmonic ever invented.
>
> I think they missed the lower sub harmonics, but who can hear
> over that racket?
>
> Dan, U.S. Air Force, retired

http://www.youtube.com/watch?v=FxT5Hybnz6o&feature=related

Some backpack fan powered paragliding. Looks like so
much fun, but dangerous.





--
Thanks to the replies.

[Eunometic]

On Jul 22, 10:57*am, John Doe > wrote:
> How far-fetched is the idea, to use a propeller or jet engine
> (radio controlled type?) to push an in-line skater?

Not far fetched, just very pointless.

Simply decide if you want digits chopped of by propellor or scorched
of by model jet engine after loosing control and suffering concusion.

It should be a few laughs if the dudsons peform it or jackass does it.

[John Doe[_4_]]

Eunometic <eunometic yahoo.com.au> wrote:

> John Doe <j... usenetlove.invalid> wrote:

>> How far-fetched is the idea, to use a propeller or jet engine
>> (radio controlled type?) to push an in-line skater?
>
> Not far fetched, just very pointless.

Pointless, like Google Groups access to UseNet.

> Simply decide if you want digits chopped of by propellor or
> scorched of by model jet engine after loosing control and
> suffering concusion.
>
> It should be a few laughs if the dudsons peform it or jackass
> does it.

Have you ever designed and built anything? Anything to show? No,
of course not. Because your imagination suffers.

In fact, it has been done (by a guy from Australia for one, BTW).
There are videos of others testing it there too.
--



























See also Google Groups

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> From: Eunometic <eunometic yahoo.com.au>
> Newsgroups: rec.aviation.military,rec.aviation.homebuilt
> Subject: Re: Propeller or jet to push an in-line skater?
> Date: Wed, 21 Jul 2010 21:32:25 -0700 (PDT)
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>

[Garry O]

"John Doe" > wrote in message
...
> Dan > wrote:
>
>> cavelamb wrote:
>>> John Doe wrote:
>>>> Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:
>
>>>>> The model airplane guys have a very small (about 15" long, 5"
>>>>> dia) turbojet that they use on scale jet R/C planes. It costs
>>>>> about $3000 US.
>>>>
>>>> How much for maintenance and fuel?
>>>
>>> It burns a quart of fuel in a minute or minute and a half.
>>>
>>>> Is it louder than a gas powered weedeater? Just curious.
>>>
>>> Deafening.
>>>
>>> 100,000 RPM with every harmonic ever invented.
>>
>> I think they missed the lower sub harmonics, but who can hear
>> over that racket?
>>
>> Dan, U.S. Air Force, retired
>
> http://www.youtube.com/watch?v=FxT5Hybnz6o&feature=related
>
> Some backpack fan powered paragliding. Looks like so
> much fun, but dangerous.
>
>
>
>
>
> --
> Thanks to the replies.

I would imagine less dangerous than trying to in-line skate with one of
those things on :-)

--
Remember Altitude is more important than Attitude

[Keith Willshaw[_5_]]

"Garry O" > wrote in message
u...
> "John Doe" > wrote in message
> ...
>> Dan > wrote:
>>
>>> cavelamb wrote:
>>>> John Doe wrote:
>>>>> Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:
>>
>>>>>> The model airplane guys have a very small (about 15" long, 5"
>>>>>> dia) turbojet that they use on scale jet R/C planes. It costs
>>>>>> about $3000 US.
>>>>>
>>>>> How much for maintenance and fuel?
>>>>
>>>> It burns a quart of fuel in a minute or minute and a half.
>>>>
>>>>> Is it louder than a gas powered weedeater? Just curious.
>>>>
>>>> Deafening.
>>>>
>>>> 100,000 RPM with every harmonic ever invented.
>>>
>>> I think they missed the lower sub harmonics, but who can hear
>>> over that racket?
>>>
>>> Dan, U.S. Air Force, retired
>>
>> http://www.youtube.com/watch?v=FxT5Hybnz6o&feature=related
>>
>> Some backpack fan powered paragliding. Looks like so
>> much fun, but dangerous.
>>
>>
>>
>>
>>
>> --
>> Thanks to the replies.
>
> I would imagine less dangerous than trying to in-line skate with one of
> those things on :-)
>

There was a rocket powered roller skater back in the 70's

http://www.the-rocketman.com/capt-rollerball.html

Keith

[Jim Yanik]

"Garry O" > wrote in
u:

> "John Doe" > wrote in message
> ...
>> Dan > wrote:
>>
>>> cavelamb wrote:
>>>> John Doe wrote:
>>>>> Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:
>>
>>>>>> The model airplane guys have a very small (about 15" long, 5"
>>>>>> dia) turbojet that they use on scale jet R/C planes. It costs
>>>>>> about $3000 US.
>>>>>
>>>>> How much for maintenance and fuel?
>>>>
>>>> It burns a quart of fuel in a minute or minute and a half.
>>>>
>>>>> Is it louder than a gas powered weedeater? Just curious.
>>>>
>>>> Deafening.
>>>>
>>>> 100,000 RPM with every harmonic ever invented.
>>>
>>> I think they missed the lower sub harmonics, but who can hear
>>> over that racket?
>>>
>>> Dan, U.S. Air Force, retired
>>
>> http://www.youtube.com/watch?v=FxT5Hybnz6o&feature=related
>>
>> Some backpack fan powered paragliding. Looks like so
>> much fun, but dangerous.
>>
>>
>>
>>
>>
>> --
>> Thanks to the replies.
>
> I would imagine less dangerous than trying to in-line skate with one of
> those things on :-)
>

this powered-skater thing reminds me of the rocket-powered street luge.
(used Aerotech APCP rocket motors.)

--
Jim Yanik
jyanik
at
localnet
dot com

[Dean]

On Jul 22, 8:49*am, Jim Yanik > wrote:
> "Garry O" > wrote .au:
>
>
>
> > "John Doe" > wrote in message
> ...
> >> Dan > wrote:
>
> >>> cavelamb wrote:
> >>>> John Doe wrote:
> >>>>> Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:
>
> >>>>>> The model airplane guys have a very small (about 15" long, 5"
> >>>>>> dia) turbojet that they use on scale jet R/C planes. It costs
> >>>>>> about $3000 US.
>
> >>>>> How much for maintenance and fuel?
>
> >>>> It burns a quart of fuel in a minute or minute and a half.
>
> >>>>> Is it louder than a gas powered weedeater? Just curious.
>
> >>>> Deafening.
>
> >>>> 100,000 RPM with every harmonic ever invented.
>
> >>> I think they missed the lower sub harmonics, but who can hear
> >>> over that racket?
>
> >>> Dan, U.S. Air Force, retired
>
> >>http://www.youtube.com/watch?v=FxT5Hybnz6o&feature=related
>
> >> Some backpack fan powered paragliding. Looks like so
> >> much fun, but dangerous.
>
> >> --
> >> Thanks to the replies.
>
> > I would imagine less dangerous than trying to in-line skate with one of
> > those things on :-)
>
> this powered-skater thing reminds me of the rocket-powered street luge.
> (used Aerotech APCP rocket motors.)
>
> --
> Jim Yanik
> jyanik
> at
> localnet
> dot com

The whole concept sounds like a qualification entry for a Darwin
Award.

Dean

[Jim Wilkins]

On Jul 21, 8:57*pm, John Doe > wrote:
> How far-fetched is the idea, to use a propeller or jet engine
> (radio controlled type?) to push an in-line skater? ...

Diesel engines with treads:
http://blog.modernmechanix.com/mags/qf/c/PopularScience/6-1936/med_tread_skates.jpg

jsw

[John Doe[_4_]]

Dean <damarkley gmail.com> wrote:

> Jim Yanik > wrote:
>> "Garry O" > wrote
>> > "John Doe" > wrote
>> >> Dan > wrote:
>> >>> cavelamb wrote:
>> >>>> John Doe wrote:
>> >>>>> Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:
>>
>> >>>>>> The model airplane guys have a very small (about 15"
>> >>>>>> long, 5" dia) turbojet that they use on scale jet R/C
>> >>>>>> planes. It costs about $3000 US.
>>
>> >>>>> How much for maintenance and fuel?
>>
>> >>>> It burns a quart of fuel in a minute or minute and a half.
>>
>> >>>>> Is it louder than a gas powered weedeater? Just curious.
>>
>> >>>> Deafening.
>>
>> >>>> 100,000 RPM with every harmonic ever invented.
>>
>> >>> I think they missed the lower sub harmonics, but who can
>> >>> hear over that racket?

>> >> http://www.youtube.com/watch?v=FxT5Hybnz6o&feature=related
>>
>> >> Some backpack fan powered paragliding. Looks like so much
>> >> fun, but dangerous.

>> > I would imagine less dangerous than trying to in-line skate
>> > with one of those things on :-)

It would be a riot, somewhere around 250 cc I guess, apparently
more than necessary. Also maybe too heavy.

>> this powered-skater thing reminds me of the rocket-powered
>> street luge. (used Aerotech APCP rocket motors.)

> The whole concept sounds like a qualification entry for a Darwin
> Award.

I have many years experience inline street skating, and designing
and building stuff. Street skating, on narrow or uneven sidewalks,
up and down curbs, and on rough streets presents a unique
opportunity for invention. Sail powered skating would be good if
not for the restriction of movement, that is similar to ordinary
pushing. Propeller powered skating is attractive because of
surface traction difficulties. There would be no need to pull
something, like a push stick, up a curb. Flexibility in motion is
a great asset of rough street skating, and propeller power would
allow for excellent freedom of motion. I mainly need to know how
propeller power compares to ordinary motor and wheel against the
ground propulsion.
--





















See also Google Groups

>
> Dean
>

[John Doe[_4_]]

Jim Wilkins > wrote:

> John Doe > wrote:

>> How far-fetched is the idea, to use a propeller or jet engine
>> (radio controlled type?) to push an in-line skater? ...
>
> Diesel engines with treads:
> http://blog.modernmechanix.com/mags/qf/c/PopularScience/6-1936/med_tread_skates.jpg

Thanks for the picture. Sloping upwards in front would help too.
I have mentioned that possibility with my big front wheel skates,
but had not seen any attempt like that. Skating over rough terrain
has many possibilities.

http://www.flickr.com/photos/27532210@N04/3056505603/
--































>
> jsw

[cavelamb[_2_]]

John Doe wrote:
> Dean <damarkley gmail.com> wrote:
>
>> Jim Yanik > wrote:
>>> "Garry O" > wrote
>>>> "John Doe" > wrote
>>>>> Dan > wrote:
>>>>>> cavelamb wrote:
>>>>>>> John Doe wrote:
>>>>>>>> Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:
>>>>>>>>> The model airplane guys have a very small (about 15"
>>>>>>>>> long, 5" dia) turbojet that they use on scale jet R/C
>>>>>>>>> planes. It costs about $3000 US.
>>>>>>>> How much for maintenance and fuel?
>>>>>>> It burns a quart of fuel in a minute or minute and a half.
>>>>>>>> Is it louder than a gas powered weedeater? Just curious.
>>>>>>> Deafening.
>>>>>>> 100,000 RPM with every harmonic ever invented.
>>>>>> I think they missed the lower sub harmonics, but who can
>>>>>> hear over that racket?
>
>>>>> http://www.youtube.com/watch?v=FxT5Hybnz6o&feature=related
>>>>> Some backpack fan powered paragliding. Looks like so much
>>>>> fun, but dangerous.
>
>>>> I would imagine less dangerous than trying to in-line skate
>>>> with one of those things on :-)
>
> It would be a riot, somewhere around 250 cc I guess, apparently
> more than necessary. Also maybe too heavy.
>
>>> this powered-skater thing reminds me of the rocket-powered
>>> street luge. (used Aerotech APCP rocket motors.)
>
>> The whole concept sounds like a qualification entry for a Darwin
>> Award.
>
> I have many years experience inline street skating, and designing
> and building stuff. Street skating, on narrow or uneven sidewalks,
> up and down curbs, and on rough streets presents a unique
> opportunity for invention. Sail powered skating would be good if
> not for the restriction of movement, that is similar to ordinary
> pushing. Propeller powered skating is attractive because of
> surface traction difficulties. There would be no need to pull
> something, like a push stick, up a curb. Flexibility in motion is
> a great asset of rough street skating, and propeller power would
> allow for excellent freedom of motion. I mainly need to know how
> propeller power compares to ordinary motor and wheel against the
> ground propulsion.


since you have experience in designing and building stuff, why not
just and do and report back.

If you can...

Dean nailed it.


--

Richard Lamb

[John Doe[_4_]]

cavelamb <cavelamb earthlink.net> wrote:

> John Doe wrote:
>> Dean <damarkley gmail.com> wrote:
>>> Jim Yanik <jya... abuse.gov> wrote:
>>>> "Garry O" <ifuneedituwillge... home.com> wrote
>>>>> "John Doe" <j... usenetlove.invalid> wrote
>>>>>> Dan <B24... aol.com> wrote:
>>>>>>> cavelamb wrote:
>>>>>>>> John Doe wrote:
>>>>>>>>> Orval Fairbairn <o_r_fairbairn earth_link.net> wrote:

>>>>>>>>>> The model airplane guys have a very small (about 15"
>>>>>>>>>> long, 5" dia) turbojet that they use on scale jet R/C
>>>>>>>>>> planes. It costs about $3000 US.

>>>>>>>>> How much for maintenance and fuel?

>>>>>>>> It burns a quart of fuel in a minute or minute and a half.

>>>>>>>>> Is it louder than a gas powered weedeater? Just curious.

>>>>>>>> Deafening.
>>>>>>>> 100,000 RPM with every harmonic ever invented.

>>>>>>> I think they missed the lower sub harmonics, but who can
>>>>>>> hear over that racket?
>>
>>>>>> http://www.youtube.com/watch?v=FxT5Hybnz6o&feature=related
>>>>>> Some backpack fan powered paragliding. Looks like so much
>>>>>> fun, but dangerous.
>>
>>>>> I would imagine less dangerous than trying to in-line skate
>>>>> with one of those things on :-)
>>
>> It would be a riot, somewhere around 250 cc I guess, apparently
>> more than necessary. Also maybe too heavy.
>>
>>>> this powered-skater thing reminds me of the rocket-powered
>>>> street luge. (used Aerotech APCP rocket motors.)
>>
>>> The whole concept sounds like a qualification entry for a Darwin
>>> Award.
>>
>> I have many years experience inline street skating, and designing
>> and building stuff. Street skating, on narrow or uneven sidewalks,
>> up and down curbs, and on rough streets presents a unique
>> opportunity for invention. Sail powered skating would be good if
>> not for the restriction of movement, that is similar to ordinary
>> pushing. Propeller powered skating is attractive because of
>> surface traction difficulties. There would be no need to pull
>> something, like a push stick, up a curb. Flexibility in motion is
>> a great asset of rough street skating, and propeller power would
>> allow for excellent freedom of motion. I mainly need to know how
>> propeller power compares to ordinary motor and wheel against the
>> ground propulsion.
>
>
> since you have experience in designing and building stuff, why not
> just and do and report back.

Possible, but I would post the results in the skating group.

> If you can...

Apparently you are choosing to troll before reading.
It has already been done, and tested.

> Dean nailed it.

Says a silly troll?

Simply saying someone/something is "stupid" is the lamest insult
known to mankind.
--























>
>
> --
>
> Richard Lamb
>
>
>
>

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[Jim Wilkins]

On Jul 22, 9:31*am, Dean > wrote:
> ...
>
> The whole concept sounds like a qualification entry for a Darwin
> Award.
>
> Dean

The perpetrator of the car embedded in the cliff posted the full story
once on rec.crafts.metalworking. No one was injured, the rocket car
was rolling unmanned down an old mining railroad at maybe 60 MPH and
when their crude brakes failed it slid into the tunnel entrance, which
collapsed on it. The skid marks at the corner are from when they
bugged out afterwards, they are actually from driving full-throttle
onto the pavement from the sand. They had plowed the sand off the
tracks and it probably blew back and hid them before the wrecker
arrived.

jsw

[John Clear]

In article >,
John Doe > wrote:
>How far-fetched is the idea, to use a propeller or jet engine
>(radio controlled type?) to push an in-line skater? How does
>aircraft takeoff thrust compare to using a conventional motor and
>wheel to push oneself along the ground? What sort of incline would
>be achievable at say a skater weight of about 160 pounds? I think
>the rolling resistance can be assumed to be zero or maybe the same
>as a small aircraft.

Years ago (maybe late 1990s) one of those 'whacky invention' type
TV shows featured a guy with jet engines mounted on the tails of
his skis. No need for a chair lift, he'd just ski uphill.

So it has been done, just make sure your life insurance is paid up.

John
--
John Clear - http://www.clear-prop.org/

[cavelamb[_2_]]

I'm trolling?
LOL!

Bye now...

[John Doe[_4_]]

usenet jac.users.panix.com (John Clear) wrote:

> John Doe <jdoe usenetlove.invalid> wrote:

>> How far-fetched is the idea, to use a propeller or jet engine
>> (radio controlled type?) to push an in-line skater? How does
>> aircraft takeoff thrust compare to using a conventional motor
>> and wheel to push oneself along the ground? What sort of
>> incline would be achievable at say a skater weight of about 160
>> pounds? I think the rolling resistance can be assumed to be
>> zero or maybe the same as a small aircraft.
>
> Years ago (maybe late 1990s) one of those 'whacky invention'
> type TV shows featured a guy with jet engines mounted on the
> tails of his skis. No need for a chair lift, he'd just ski
> uphill.

Inline skating is like a combination of different sports,
including skiing. One unique difference is that in-line skating
requires man-made terrain.

> So it has been done, just make sure your life insurance is paid
> up.

If you wear lots of protective gear and consider the risks, safety
should not be a concern. On TV, you see skaters and cyclists who
do not wear protective gear, apparently many people enjoy seeing
the accidents, but I just change the channel. Carelessly riding
a large displacement motorcycle years ago makes anything I do now
days pale in comparison. This

Still researching the issue, but by the lack of detailed comment,
I get the impression that propeller power is nowhere near
efficient as conventional motor and wheel on the ground
propulsion. That is the question.
--























>
> John
> --
> John Clear - jac panix.com http://www.clear-prop.org/
>
>
>

[John Doe[_4_]]

cavelamb <cavelamb earthlink.net> wrote:

> I'm trolling?

Or just babbling.

> LOL!

"There is someone in my head but it's not me... la la la"

Safety depends on how a device is used. And then there is the fact
that an unbuilt device poses no safety risk whatsoever. A
thoughtful person might consider the possibility of others reading
without being cautious, but how is that a concern when you are
talking about building something.
--
























>
> Bye now...

[cavelamb[_2_]]

Just babbling...

Look up gyroscopic precession - torque induced.

Might also consider tip speeds, and what happens when props
contact things...


Oh, and just on a hunch, I've removed Free.usenet group.

John Doe wrote:
> cavelamb <cavelamb earthlink.net> wrote:
>
>> I'm trolling?
>
> Or just babbling.
>
>> LOL!
>
> "There is someone in my head but it's not me... la la la"
>
> Safety depends on how a device is used. And then there is the fact
> that an unbuilt device poses no safety risk whatsoever. A
> thoughtful person might consider the possibility of others reading
> without being cautious, but how is that a concern when you are
> talking about building something.


--

Richard Lamb

[John Doe[_4_]]

cavelamb <cavelamb earthlink.net> wrote:

> Just babbling...
>
> Look up gyroscopic precession - torque induced.
>
> Might also consider tip speeds, and what happens when props
> contact things...

So put a cage around it. That is what the example from Australia
does.

But seriously. A sixth grader could figure out that one.
--

























>
>
> Oh, and just on a hunch, I've removed Free.usenet group.
>
> John Doe wrote:
>> cavelamb <cavelamb earthlink.net> wrote:
>>
>>> I'm trolling?
>>
>> Or just babbling.
>>
>>> LOL!
>>
>> "There is someone in my head but it's not me... la la la"
>>
>> Safety depends on how a device is used. And then there is the fact
>> that an unbuilt device poses no safety risk whatsoever. A
>> thoughtful person might consider the possibility of others reading
>> without being cautious, but how is that a concern when you are
>> talking about building something.
>
>
> --
>
> Richard Lamb
>
>
>
>

> Path: news.astraweb.com!border5.newsrouter.astraweb.com! news.glorb.com!news2.glorb.com!Xl.tags.giganews.co m!border1.nntp.dca.giganews.com!nntp.giganews.com! local2.nntp.dca.giganews.com!nntp.earthlink.com!ne ws.earthlink.com.POSTED!not-for-mail
> NNTP-Posting-Date: Thu, 22 Jul 2010 20:34:56 -0500
> Date: Thu, 22 Jul 2010 20:34:31 -0500
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> Subject: Re: Propeller or jet to push an in-line skater?
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[cavelamb[_2_]]

John Doe wrote:
> cavelamb <cavelamb earthlink.net> wrote:
>
>> Just babbling...
>>
>> Look up gyroscopic precession - torque induced.
>>
>> Might also consider tip speeds, and what happens when props
>> contact things...
>
> So put a cage around it. That is what the example from Australia
> does.
>
> But seriously. A sixth grader could figure out that one.

And the precession?


--

Richard Lamb

[John Doe[_4_]]

cavelamb <cavelamb earthlink.net> wrote:

> John Doe wrote:
>> cavelamb <cavelamb earthlink.net> wrote:
>>
>>> Just babbling...
>>>
>>> Look up gyroscopic precession - torque induced.
>>>
>>> Might also consider tip speeds, and what happens when props
>>> contact things...
>>
>> So put a cage around it. That is what the example from Australia
>> does.
>>
>> But seriously. A sixth grader could figure out that one.
>
> And the precession?

There are dozens of paragliding videos on YouTube using a backpack
propeller. Let me know if you see any evidence of that.

[Keith Willshaw[_1_]]

"John Doe" > wrote in message
...
> usenet jac.users.panix.com (John Clear) wrote:
>
>> John Doe <jdoe usenetlove.invalid> wrote:
>
>>> How far-fetched is the idea, to use a propeller or jet engine
>>> (radio controlled type?) to push an in-line skater? How does
>>> aircraft takeoff thrust compare to using a conventional motor
>>> and wheel to push oneself along the ground? What sort of
>>> incline would be achievable at say a skater weight of about 160
>>> pounds? I think the rolling resistance can be assumed to be
>>> zero or maybe the same as a small aircraft.
>>
>> Years ago (maybe late 1990s) one of those 'whacky invention'
>> type TV shows featured a guy with jet engines mounted on the
>> tails of his skis. No need for a chair lift, he'd just ski
>> uphill.
>
> Inline skating is like a combination of different sports,
> including skiing. One unique difference is that in-line skating
> requires man-made terrain.
>
>> So it has been done, just make sure your life insurance is paid
>> up.
>
> If you wear lots of protective gear and consider the risks, safety
> should not be a concern. On TV, you see skaters and cyclists who
> do not wear protective gear, apparently many people enjoy seeing
> the accidents, but I just change the channel. Carelessly riding
> a large displacement motorcycle years ago makes anything I do now
> days pale in comparison. This
>
> Still researching the issue, but by the lack of detailed comment,
> I get the impression that propeller power is nowhere near
> efficient as conventional motor and wheel on the ground
> propulsion. That is the question.
> --

No that is the answer.

Keith

[Giles Ayling]

On 23/07/2010 09:01, Keith Willshaw wrote:
>
>
> "John Doe" > wrote in message
> ...
>> usenet jac.users.panix.com (John Clear) wrote:
>>
>>> John Doe <jdoe usenetlove.invalid> wrote:
>>
>>>> How far-fetched is the idea, to use a propeller or jet engine
>>>> (radio controlled type?) to push an in-line skater? How does
>>>> aircraft takeoff thrust compare to using a conventional motor
>>>> and wheel to push oneself along the ground? What sort of
>>>> incline would be achievable at say a skater weight of about 160
>>>> pounds? I think the rolling resistance can be assumed to be
>>>> zero or maybe the same as a small aircraft.
>>>
>>> Years ago (maybe late 1990s) one of those 'whacky invention'
>>> type TV shows featured a guy with jet engines mounted on the
>>> tails of his skis. No need for a chair lift, he'd just ski
>>> uphill.
>>
>> Inline skating is like a combination of different sports,
>> including skiing. One unique difference is that in-line skating
>> requires man-made terrain.
>>
>>> So it has been done, just make sure your life insurance is paid
>>> up.
>>
>> If you wear lots of protective gear and consider the risks, safety
>> should not be a concern. On TV, you see skaters and cyclists who
>> do not wear protective gear, apparently many people enjoy seeing
>> the accidents, but I just change the channel. Carelessly riding
>> a large displacement motorcycle years ago makes anything I do now
>> days pale in comparison. This
>>
>> Still researching the issue, but by the lack of detailed comment,
>> I get the impression that propeller power is nowhere near
>> efficient as conventional motor and wheel on the ground
>> propulsion. That is the question.
>> --
>
> No that is the answer.
>
> Keith
>
Jet / Propellor / rubber band. It doesnt mallet what the power supply is.

Work out where the center of thrust/pull is - Probably if on a skater
approx 1.2metres up.

When the skater hit a bump to large for the front to quickly rise over,
the skater kisses the ground.

Think water skiing - It is a challenge to get up o the skiis, and then
the second you relax, and let the ski dig it, you are in the water

[John Doe[_4_]]

Giles Ayling <giles tvp.ltd.uk> wrote:

> Keith Willshaw wrote:
>> "John Doe" > wrote in message

....

>>> I get the impression that propeller power is nowhere near
>>> efficient as conventional motor and wheel on the ground
>>> propulsion. That is the question.

>> No that is the answer.

> Jet / Propellor / rubber band. It doesnt mallet what the power
> supply is.

Are you using speech recognition? Or were you drunk?
Just curious.

> Work out where the center of thrust/pull is - Probably if on a
> skater approx 1.2metres up.
>
> When the skater hit a bump to large for the front to quickly
> rise over, the skater kisses the ground.

Skating is extremely flexible. One way to cope is to step over the
obstacle. Another way is by keeping your weight on your rear
wheels. And yet another way to cope with larger obstacles is
called "scissoring". And of course you can do stuff in
combination. If none of the above works, when you hit a bump that
radically slows one skate, you can quickly put all of your weight
on the other skate and simultaneously steer inwards with that good
skate to maintain your balance. You learn to do that stuff without
thinking.

But, coincidentally, large unexpected obstacles is exactly why I
made big front wheel skates, a 140 mm front wheel with 80 mm
trailing wheels. Love them and use them for rough street skating
regularly.

http://www.flickr.com/photos/27532210@N04/3056505603/
http://www.flickr.com/photos/27532210 N04/3056505603/




By the way... If anyone here (young enough to run or at least to
remember doing fun things) has never heard of "powered
paragliding", check it out! It is (lighter than) ultra light
powered flight. Amazing stuff IMO. Dozens of videos on YouTube.
--

























>
> Think water skiing - It is a challenge to get up o the skiis, and then
> the second you relax, and let the ski dig it, you are in the water
>
>

[Jim Yanik]

(John Clear) wrote in
:

> In article >,
> John Doe > wrote:
>>How far-fetched is the idea, to use a propeller or jet engine
>>(radio controlled type?) to push an in-line skater? How does
>>aircraft takeoff thrust compare to using a conventional motor and
>>wheel to push oneself along the ground? What sort of incline would
>>be achievable at say a skater weight of about 160 pounds? I think
>>the rolling resistance can be assumed to be zero or maybe the same
>>as a small aircraft.
>
> Years ago (maybe late 1990s) one of those 'whacky invention' type
> TV shows featured a guy with jet engines mounted on the tails of
> his skis. No need for a chair lift, he'd just ski uphill.
>
> So it has been done, just make sure your life insurance is paid up.
>
> John

how did he -not- fall on his behind?
get on some skates,tie a rope to your ankles,and have someone tow you,and
see if you can stay upright.
You need the center of pressure to be in the center of your mass.

--
Jim Yanik
jyanik
at
localnet
dot com

[John Doe[_4_]]

Jim Yanik > wrote:

> (John Clear) wrote in
>> John Doe > wrote:

>>> How far-fetched is the idea, to use a propeller or jet engine
>>> (radio controlled type?) to push an in-line skater? How does
>>> aircraft takeoff thrust compare to using a conventional motor
>>> and wheel to push oneself along the ground? What sort of
>>> incline would be achievable at say a skater weight of about
>>> 160 pounds? I think the rolling resistance can be assumed to
>>> be zero or maybe the same as a small aircraft.
>>
>> Years ago (maybe late 1990s) one of those 'whacky invention'
>> type TV shows featured a guy with jet engines mounted on the
>> tails of his skis. No need for a chair lift, he'd just ski
>> uphill.
>>
>> So it has been done, just make sure your life insurance is paid
>> up.

> how did he -not- fall on his behind? get on some skates,tie a
> rope to your ankles,and have someone tow you,and see if you can
> stay upright. You need the center of pressure to be in the
> center of your mass.

Ideally, Yes. Also, putting a motor on skates weighs it down and
destroys most of the quality of skating. However, I have put a
motor on my skates, powering the center two wheels on one skate,
and it worked very well propulsion wise. The problem was with the
weight and the motor being too close to the ground.

[David E. Powell]

On Jul 21, 8:57*pm, John Doe > wrote:
> How far-fetched is the idea, to use a propeller or jet engine
> (radio controlled type?) to push an in-line skater? How does
> aircraft takeoff thrust compare to using a conventional motor and
> wheel to push oneself along the ground? What sort of incline would
> be achievable at say a skater weight of about 160 pounds? I think
> the rolling resistance can be assumed to be zero or maybe the same
> as a small aircraft.
>
> Anybody know about Everglades/marsh air powered boats? Maybe I
> should do a little research on that one.
>
> One thing for sure, if there ever is such a thing as a jetpack, it
> will very easily push an in-line skater before it will lift a
> person off of the ground.
>
> Thanks.
>
> --
> (Crossposted, please feel free to remove the other group)

One thing is for sure it can't be too high or low relative to center
of gravity.

[John Doe[_4_]]

"David E. Powell" <David_Powell3006 msn.com> wrote:

> One thing is for sure it can't be too high or low relative to
> center of gravity.

That may be less critical than you think. Propeller propulsion
would be the freest form since it would not depend on the ground,
the full benefit of skating depends on freedom of movement. Push
stick based propulsion (a bulky prototype is currently being used
here) is stable, even when being pushed from knee level. I get a
third wheel effect, and stroking with my legs is not required.
Pushing/stroking is a HUGE source of instability while inline
street skating.