Date: Sun, 12 Apr 2009 23:07:19 -0500
Reply-To: John Rodgers <inua@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: John Rodgers <inua@CHARTER.NET>
Subject: Re: Only ONE drive wheel?
In-Reply-To: <02ed01c9bbe4$a66934a0$6401a8c0@PROSPERITY>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Scott,
For me there is a lot of crossover between vans and aeroplanes - but,
lest we get to far astray, here is one for Vans,
Ever get stuck in a hole?
If you can find a log (not rotten) about 4 inches in dia. or a piece of
stout pipe of similar diameter, or a wagonwheel jack - anything you can
lay down crossways in front to the tire, you are on our way to getting
out of the hole. You also need a hank of rope, sufficient to wrap around
the tire. Now dig under the tire, and wrap the rope around the tire
several turns, with the bitter end (sailor talk for loose end) running
around the circumference of the tire - over the top, down the back,
thence under the tire, and up to the log lying front of the tire. Tie
the Bitter End to the log. Now, with someone pulling the other loose
end of the rope up tight, put the van in Granny Gear and apply the
power. As the wheel begins to turn, the rope will tighten around the
tire and the tire will pull up against the log and the wheel will lift
out of the hole and up over the log onto solid ground.
I have done this more times than I care to count. It works. Try it.
Regards,
John Rodgers
88 GL Driver
Scott Daniel - Turbovans wrote:
> awesome John......
> not too VC so we can't say too much here.
> But that's why the P-38 Lightening has counter-rotating props.
>
> I hadn't ever thought that tail draggers never have variable pitch
> props ,
> if that's what you said.
> If I had to guess on a test, I'd guess that there are taildragger
> aircraft
> with variable pitch props.
> I can't imagine a P-51 Mustang having a constant pitch prop - just
> doesn't
> sound right.
>
> thanks for the good words too, on the one wheel drive thing.
>
> the way I learned the saying is.,....................... 'Flying is hours
> and hours of boredom punctuated by moments of sheer terror."
> your redentition is probably more correct.
>
> let's see.............( VC )
> " Driving a Vanagon is hours and hours of pure pleasure,
> intersped with periods of sometimes challenging repair and rescue. "
>
> needs some work to get it more elegant/poetic .
>
> Scott
>
>
>
> ----- Original Message -----
>
> From: "John Rodgers" <inua@charter.net>
> To: "Scott Daniel - Turbovans" <scottdaniel@TURBOVANS.COM>
> Cc: <vanagon@GERRY.VANAGON.COM>
> Sent: Sunday, April 12, 2009 7:17 PM
> Subject: Re: Only ONE drive wheel?
>
>
>> Scott,
>>
>> Very good description and insight into what happens with the standard
>> differential.
>>
>> Viva la Posi-trac!!!
>>
>> Nice "Tip's and Trick's" on how to get a "poor man's limited slip
>> differential". It's akin to letting some air out of the tires to
>> drive off
>> a sandy beach or get out of your home garage when to save money at home
>> you switched to bigger rims and tires only to discover you can't get
>> out
>> of your garage any more, or perhaps to go under a really low bridge.
>>
>> To expand on the aircraft propeller thing - whether single or
>> multi-engine
>> aircraft type - the crankshaft is for the most part horizontal to the
>> ground or the earths surface plane in aircraft with tricycle landing
>> gear.
>> On tail-draggers there is another element involved which I won't mention
>> here. In the tri-gear machines the blade angle on a propeller is the
>> same
>> on all blades, and all rotate in the same plane - 90 degrees to the
>> crankshaft - and 90 degrees to the relative plane of the earths surface.
>> However, when the pilot rotates the nose of the airplane skyward, the
>> angle of the propeller and the crankshaft changes relative to the earths
>> plane. Given that most modern American made aircraft engines rotate
>> to the
>> right as seen from the pilots seat, the propeller blade on the right
>> will
>> be going down while blades on the left will be going up. Because of the
>> change in the angle relative to the ground, the propeller blade on the
>> right going down takes a much bigger bite of the air, than the blade on
>> the left coming up. This produces much greater thrust on the right than
>> the left, and the airplane tries hard to turn left all through the climb
>> to altitude. The pilot is trained to overcome this and kept the airplane
>> under directional control, but it adds an additional load on him to take
>> care of the airplane. Additionally, the left turning tendency also tends
>> to drive the right wing forward faster, allowing the left wing to drop
>> back relative to the path of flight. The result is increased lift on the
>> right wing, and reduced lift on the left wing. With more lift on the
>> right
>> wing and less on the left, the airplane has a tendency to roll to the
>> left. So there you have it. Left turning, and left rolling, all of
>> which a
>> pilot is trained to control very precisely. But it can make for some
>> interesting moments under certain conditions. But it makes a pilots life
>> interesting to say the least. It is said that a pilots flying life is
>> filled with thousands of hours of relative boredom, interspersed with
>> moments of sheer terror!!! I'm here to tell you it is so true, so true!
>>
>> Engines, crankshafts, torque, left wheels lifting, right wheel getting a
>> better bite on the ground, rotating propellers getting a bigger bite on
>> the right and less on the other ---- it's all got it's similarities
>> - and
>> it all derived from the same physics. Vanagons and airplanes - who
>> would
>> have thought there could be such similarities.
>>
>> Regards.
>>
>> John Rodgers
>> 88 GL Driver
>>
>> Scott Daniel - Turbovans wrote:
>>> what you experienced is perfectly normal.
>>> let's see.........
>>> the differential in the rear end drives both wheels evenly............
>>> as long as the van is going straight, and there is equal and good
>>> traction
>>> for each rear wheel.
>>>
>>> so it drives both rear wheels..........but either rear wheel is free to
>>> turn
>>> more revolutions ( like the outside wheel would in a turn ) or just
>>> plan
>>> spin.
>>>
>>> saying that the right rear is 'the driven wheel' .......
>>> is not true in the hardest sense of the term.
>>> What is true, I believe is .........
>>> due to the direction of engine rotation ( especially true in a front
>>> engine
>>> rear drive car ) ....engine and drivetrain torque tends to lift one
>>> rear
>>> wheel, and push the other rear wheel downwards.
>>>
>>> yeah........just thinking about in my head - consider a front engine
>>> rear
>>> drive car .......engine rotates clockwise when viewed from the front of
>>> the
>>> engine ......or counterclockwise viewed from the driver's seat.
>>> Viewed
>>> from the driver's seat, the body of the car is trying to rotate
>>> opposite
>>> the direction of crankshaft rotation .........thus the left rear
>>> wheel is
>>> lifted slightly and the right rear is driven into the pavement more.
>>>
>>> this affect is also observable in single engine propeller aircraft, and
>>> in
>>> single prop boats too. The body of the vehicle tries to twist in the
>>> opposite direction of crankshaft rotation, and in a car that tends to
>>> drive
>>> one side of the vehicle more into the pavement. It's quite
>>> observable in
>>> big trucks too .......they really tilt when the jump on the gas
>>> ...........the tractor part with no trailer attached .........with all
>>> that
>>> torque the cab really wants to tilt under a heavy right foot on the go
>>> pedal.
>>>
>>> here's a trick......
>>> the 'poor man's limited slip rear differential ' ...........when you're
>>> stuck from one wheel spinning..............put the parking brake on
>>> half
>>> way, or even a little more.
>>> the idea is that by making the resistance to turning of both driven
>>> wheels
>>> roughly the same, drive will be transferred to both wheels,
>>> including the
>>> one not touching the ground, or slipping on ice etc.
>>> Scott
>>> www.turbovans.com
>>>
>>>
>>> ----- Original Message -----
>>> From: "Brian Doss" <doss88wkndr@ZOOMINTERNET.NET>
>>> To: <vanagon@GERRY.VANAGON.COM>
>>> Sent: Sunday, April 12, 2009 5:28 PM
>>> Subject: Only ONE drive wheel?
>>>
>>>
>>> I have an '88 GL with a manual transmission. I got it stuck backing
>>> into
>>> an
>>> uneven driveway yesterday. Just so happened that I was in a saddle on a
>>> hillside, with just enough torsion on the bus to lift the left rear
>>> wheel
>>> off the ground - and presto - no go. The left wheel spun happily in
>>> forward
>>> or reverse. What I can't understand is that I thought the right
>>> wheel was
>>> driven as well - why did it not receive any power? Does this mean
>>> something
>>> is wrong with my transmission?
>>>
>>> Thanks for any insight on the matter
>>>
>>>
>>> Brian Doss
>>> Butler, PA
>>> '88 Weekender, Queequeg
>>>
>>>
>>
>>
>
>
| 
