Double scissor jack for trailer ramp?

All,

I have a new (to me) glider and trailer. Good rig, but like most things,
capable of improvement.

The ramp that extends from the back of the trailer for assembly has a
single, car style scissor (spare tire) jack for raising and lowering the
fuselage. It rocks back and forth a bit too much, and that makes it a bit
too unstable for my taste.

I see other trailers with a double scissor jack that are clearly more
stable, and would like to go that direction. Can't find any info on Our
Friend the Internet about how to do that, though.

Can anyone point me in the right direction?

Are there any of these, new or used, available? (Yes, I know I could order
one from Cobra or Komet, but would like to save that for a last resort.
Looking for something here in USA, if possible.)

Any spares from trailers no longer in use?

Making one of these is acceptable, but would like some advice on types of
jacks to get, how to connect them, etc.

Thanks in advance for your advice,
Bullwinkle

Bullwinkle wrote:

I have a new (to me) glider and trailer. Good rig, but like most things,
capable of improvement.

The ramp that extends from the back of the trailer for assembly has a
single, car style scissor (spare tire) jack for raising and lowering the
fuselage. It rocks back and forth a bit too much, and that makes it a bit
too unstable for my taste.

One of our club trailers had a pair of scissor jacks, but they were old
and one eventually stripped its thread. We replaced it with a single
jack that was already at the club. That works OK but, as you say, its
less stable.

The problem is to find a (pair of) jacks with narrow enough spans to fit
side by side within the width of the tail ramp. None of the screw jacks
I could find in car places were narrow enough and the hydraulic jacks
were all too tall. However, I did do some research and found a source of
suitably small screw jacks, though not until after the ramp had been
repaired.

The jacks you need were made for British sports cars. They are narrow
because they were kept inside the spare wheel. They are still made: find
one of the specialists who supply parts for Triumph or MG sports cars
should be able to sell you suitable jacks for a reasonable price.

The jacks are set to the same height and welded into the ramp's rear U
channel and ground support after lining them up the same way and using a
sleeve to join the screws together.

--
martin@ | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot

I used a couple of Honda Civic scissor jacks.
They are light weight and compact.
When collapsed the jack ideally should have the screw stick out of
the threaded thrust bearing just a bit (as oppose to being flush).
This allows a fork to be welded on to connect a shaft, without interfering
with the threaded portion of the jack. If the welding interferes with the
thread you will not be able to collapse the jack completely.
In any case, if you get a couple of jacks you will see what is needed
and what needs to be done.
Udo




Friend the Internet about how to do that, though.

Can anyone point me in the right direction?

Are there any of these, new or used, available? (Yes, I know I could order
one from Cobra or Komet, but would like to save that for a last resort.
Looking for something here in USA, if possible.)

Any spares from trailers no longer in use?

Making one of these is acceptable, but would like some advice on types of
jacks to get, how to connect them, etc.

Thanks in advance for your advice,
Bullwinkle

Make certain the jack lifting pad moves in a straight vertical motion.
Some scissor jacks let the lift pad translate as it moves vertically.

Gale Winnett

When you say "back and forth", I think of "side to side". If that is right,
attach small chains at each end (side) so that when the ramp is raised high
enough to allow lowering the main wheel, these chains become taught. Cheap
and easy!

Bob (RS)

"Bullwinkle" wrote in message
...
All,

I have a new (to me) glider and trailer. Good rig, but like most things,
capable of improvement.

The ramp that extends from the back of the trailer for assembly has a
single, car style scissor (spare tire) jack for raising and lowering the
fuselage. It rocks back and forth a bit too much, and that makes it a bit
too unstable for my taste.

Thanks to all for your suggestions (including Todd, who I am sure was joking
about the procedure below ).

I think I know how to proceed now.

Bullwinkle

On 1/16/06 8:59 AM, in article ,
"T o d d P a t t i s t" wrote:

Bullwinkle wrote:

I see other trailers with a double scissor jack ...
Are there any of these, new or used, available?

Some people like the Cobra hydraulic jack enough that
they've retrofitted one to their trailer and then have an
old double scissor to get rid of.

I suggest the following - Find a likely prospect with glider
and trailer. Wait until his attention is elsewhere, then
with glider supported in his fuselage dolly and wings on,
retract his gear, put his tail dolly on and lower the double
scissors fuselage dolly jack as far as you can. When he
returns, point out that his gear is up. He will be unable
to extend it until he lifts his fuselage. The double
scissors has very little mechanical advantage from the low
retracted position and raising wings plus fuselage from very
low, particularly with the tail dolly holding the tail high
is extremely difficult. As the pilot struggles, make a few
judicious comments about the improved hydraulic jack system.

Leaning on the wing while he cranks, adding water ballast to
his wings, lead ballast under his seat cushion or putting
sand in the jack bearings may improve results.

I've dealt with single and double scissors jacks on Cobra/Komet
trailers for about 25 years. As Todd points out, they have nearly zero
mechanical advantage when fully lowered. The hydraulic jack alternative
eliminates this problem but, based on all the complaints I've heard,
introduces others (e.g., leaks).

The most intriguing solution I've seen is replacing the scissors jacks
with vertical screw jacks with Acme (square shouldered) threads. The
mechanical advantage is the same no matter the height of the jack. I
know Komet offers this as an alternative because I actually trial
fitted one to my Cobra trailer before deciding not to pay the cost to
upgrade. Cobra may offer it as well.

I haven't checked into U.S. sources (new or used) but if I were
undertaking a rebuilding project, I'd definitely consider this
alternative. The biggest obstacles would appear to be (1) that the
jacks are vertical so they have to be set on either side of the
fuselage and (2) it may be more difficult to drive them simultaneously
than with the two-scissors-jack approach where one jack drives the
other.

Chip Bearden
ASW 24 "JB"

I purchased two regular scissor jacks for mine and slaved them
together. About $10 each at:

http://www.toolshopusa.com

I have been intrigued with trying a leveling jack:

http://www.pplmotorhomes.com/parts/r...ling-jacks.htm

Tim

I saw an interesting jack yesterday at Harbor Freight.. It was a
hydraulic scissor jack. Looked like it might be stable enough that you
could use just one in the middle. I tried to find it online just now
and can't locate it. When I go back out there, I will look at it
closer..



Larry

"01" USA

Here is a link to one that looks like the one I saw at Harbor Freight.



http://www.autobarn.net/mvp22lbhydsc.html



YMMV,



Larry





"01-- Zero One" wrote in message
:

I saw an interesting jack yesterday at Harbor Freight.. It was a
hydraulic scissor jack. Looked like it might be stable enough that you
could use just one in the middle. I tried to find it online just now
and can't locate it. When I go back out there, I will look at it
closer..



Larry

"01" USA