System for levelling a motorhome

[Dr. David Kirkby]

A friend of mine has bought a 21-seater coach with the idea of
converting this into a motor home. Although it is a bit over the top
(OTT) in my opinion, he wants a system that can

a) Stabilise the vehicle when parked so that wind does not cause it to
move on the suspension. i.e remove the effect of the springs in the
suspension.

b) Level the vehicle if parked on terrain with an incline.

He has asked me if I can design him a system to do this. He is quite
capable of adding hydraulic rams to do the mechanicle work, as he has
excellent mechanical skills and has built a kit-car and done other
related items. However, he has asked me to design a control system to
do this. He wants to push one button and it all work. I'm an
electronics engineer, with quite a bit of experience of using A/D's,
D/A's and microcontrollers.

He intends adding two sensors that can check if the vehicle is level
in two orthogonal (at right angle) directions.

I'd like some advice/guidance from anyone with knowledge of how such
systems might work - I belive they are available at a high price.
Someone has pointed out to me the turret on militrary tanks keeps in
one direction, despite the fact the tank moves on uneven terrain.

My thoughts to date have been

1) Determine from the angle sensors which of the 4 corners the coach
needs to be raised. Lower a ram in the corner most needing raising
until such time as it in contact with the ground with say a 1 degree
correction in the angle of the coach.

2) Raise the corner that requires the second most degree of correction
until there has been a 1 degree change in the coaches angle.

3) Do likewise for the second and third corners.

At this point each ram should be touching the road surface.

Then repeat the procedure, after which the coach should be level.

Another idea is the dead opposite of this.

a) Raise the corner of the motorhome that is already highest, so
making the motorhome in a worst position than originally. Then do this
for the second worst corner. and to this for each corner. This seems
more robust as an algorithm, but needs longer rams, which cost more.

I have nagging doubts about all these.

Do I need pressure sensors to be certain the rams are indeed touching
the surface on which this is parked ? What happens if the surface is
not very hard, and gives a certain amount? What effect would wind have
on this ?

I don't want to completly lift the motorhome, but likewise I do need
to be able to remove some of the give in the suspension.

Dave kirkby

 

[Will Sill]

I see where [email protected] (Dr.
David Kirkby) inquired:

A friend of mine has bought a 21-seater coach with the idea of
converting this into a motor home. Although it is a bit over the top
(OTT) in my opinion, he wants a system that can

a) Stabilise the vehicle when parked so that wind does not cause it to
move on the suspension. i.e remove the effect of the springs in the
suspension.

b) Level the vehicle if parked on terrain with an incline.

He has asked me if I can design him a system to do this.

You're not going to like my answer, but here it is: You should tell
your friend that you don't know how to do it, and that he need to
hire someone with a clue to engineer what he wants.

Will Sill

 

[Chris Bryant]

A friend of mine has bought a 21-seater coach with the idea of converting
this into a motor home. Although it is a bit over the top (OTT) in my
opinion, he wants a system that can

a) Stabilise the vehicle when parked so that wind does not cause it to
move on the suspension. i.e remove the effect of the springs in the
suspension.

b) Level the vehicle if parked on terrain with an incline.

He intends adding two sensors that can check if the vehicle is level in
two orthogonal (at right angle) directions.

I'd like some advice/guidance from anyone with knowledge of how such
systems might work - I belive they are available at a high price. Someone
has pointed out to me the turret on militrary tanks keeps in one
direction, despite the fact the tank moves on uneven terrain.

I believe the military units are a whole different ball of wax-
gyroscopically stabilized, rather than leveling, but reading on...

My thoughts to date have been

1) Determine from the angle sensors which of the 4 corners the coach
needs to be raised. Lower a ram in the corner most needing raising until
such time as it in contact with the ground with say a 1 degree
correction in the angle of the coach.

2) Raise the corner that requires the second most degree of correction
until there has been a 1 degree change in the coaches angle.

3) Do likewise for the second and third corners.

At this point each ram should be touching the road surface.

Then repeat the procedure, after which the coach should be level.

Another idea is the dead opposite of this.

First- while commercial systems are indeed expensive, I have doubts that a
system can be prototyped much cheaper. The leader in this type system is
HWH- http://www.hwhcorp.com/ - they have a bunch of downloadable
information on the website.

Their automatic system first lowers the front and rear jacks until they
touch the ground (I *think* they have pressure sensors to do this), then
it will activate the jacks in pairs (to keep from twisting the frame),
raising the lowest point- I'm not sure of the algorithm used, but I think
their sensors do not measure degree of out of level, but rather pick on of
the low spots (front to back, or side to side), level that way, then level
the other direction- IOW, if the right front corner is low, it will raise
the right side until side to side is level, then raise the front, 'til
front to back is level.

 

[Bob Thomas]

A friend of mine has bought a 21-seater coach with the idea of
converting this into a motor home. Although it is a bit over the top
(OTT) in my opinion, he wants a system that can

a) Stabilise the vehicle when parked so that wind does not cause it to
move on the suspension. i.e remove the effect of the springs in the
suspension.

b) Level the vehicle if parked on terrain with an incline.

He has asked me if I can design him a system to do this. He is quite
capable of adding hydraulic rams to do the mechanicle work, as he has
excellent mechanical skills and has built a kit-car and done other
related items. However, he has asked me to design a control system to
do this. He wants to push one button and it all work. I'm an
electronics engineer, with quite a bit of experience of using A/D's,
D/A's and microcontrollers.

He intends adding two sensors that can check if the vehicle is level
in two orthogonal (at right angle) directions.

I'd like some advice/guidance from anyone with knowledge of how such
systems might work - I belive they are available at a high price.
Someone has pointed out to me the turret on militrary tanks keeps in
one direction, despite the fact the tank moves on uneven terrain.

My thoughts to date have been

1) Determine from the angle sensors which of the 4 corners the coach
needs to be raised. Lower a ram in the corner most needing raising
until such time as it in contact with the ground with say a 1 degree
correction in the angle of the coach.

2) Raise the corner that requires the second most degree of correction
until there has been a 1 degree change in the coaches angle.

3) Do likewise for the second and third corners.

At this point each ram should be touching the road surface.

Then repeat the procedure, after which the coach should be level.

Another idea is the dead opposite of this.

a) Raise the corner of the motorhome that is already highest, so
making the motorhome in a worst position than originally. Then do this
for the second worst corner. and to this for each corner. This seems
more robust as an algorithm, but needs longer rams, which cost more.

I have nagging doubts about all these.

Do I need pressure sensors to be certain the rams are indeed touching
the surface on which this is parked ? What happens if the surface is
not very hard, and gives a certain amount? What effect would wind have
on this ?

I don't want to completly lift the motorhome, but likewise I do need
to be able to remove some of the give in the suspension.

First, you are reinventing the wheel here. There are systems out there.
You could probably get your hands on the design.

One important thing you've left out. It is possible to overstress and bend
the frame with these "rams". Most manufacturers have stopped allowing
individual rams to activate but, rather, only allow pairs to function. Just
a point to remember.

cheers

bob

 

[John Woodgate]

I read in sci.electronics.design that Dr. David Kirkby <see_my_signature
[email protected]> wrote (in <c99d2c79.0402270549.3789f98
[email protected]>) about 'System for levelling a motorhome', on Fri,
27 Feb 2004:

My thoughts to date have been

1) Determine from the angle sensors which of the 4 corners the coach
needs to be raised. Lower a ram in the corner most needing raising until
such time as it in contact with the ground with say a 1 degree
correction in the angle of the coach.

With four points of support, you can get 'rocking' - like a table with a
twisted top or legs of slightly different lengths. With only three
points, you cannot get rocking, and the level adjustments don't
interact. See 'milking stool'. (;-)

 

[RAM^3]

I read in sci.electronics.design that Dr. David Kirkby <see_my_signature
[email protected]> wrote (in <c99d2c79.0402270549.3789f98
[email protected]>) about 'System for levelling a motorhome', on Fri,
27 Feb 2004:

With four points of support, you can get 'rocking' - like a table with a
twisted top or legs of slightly different lengths. With only three
points, you cannot get rocking, and the level adjustments don't
interact. See 'milking stool'. (;-)

One "minor" problem: where to put the third support.

FWIW, the 4-corner systems are readily available from a number of
manufacturers (and have been for over a decade),

 

[Frank Bemelman]

I read in sci.electronics.design that Dr. David Kirkby <see_my_signature
[email protected]> wrote (in <c99d2c79.0402270549.3789f98
[email protected]>) about 'System for levelling a motorhome', on Fri,
27 Feb 2004:

With four points of support, you can get 'rocking' - like a table with a
twisted top or legs of slightly different lengths. With only three
points, you cannot get rocking, and the level adjustments don't
interact. See 'milking stool'. (;-)

Farmer's milking stools have only one leg. The seat is tied to their
ass, and they sit on it, using their own two legs as well of course,
so in fact it's still 3 legs at work

 

[Rene Tschaggelar]

A friend of mine has bought a 21-seater coach with the idea of
converting this into a motor home. Although it is a bit over the top
(OTT) in my opinion, he wants a system that can

I'd call that way over the top (WOTT).

a) Stabilise the vehicle when parked so that wind does not cause it to
move on the suspension. i.e remove the effect of the springs in the
suspension.

Put some bricks or some wooden 4 by 4 underneath.

b) Level the vehicle if parked on terrain with an incline.

He has asked me if I can design him a system to do this. He is quite
capable of adding hydraulic rams to do the mechanicle work, as he has
excellent mechanical skills and has built a kit-car and done other
related items. However, he has asked me to design a control system to
do this. He wants to push one button and it all work. I'm an
electronics engineer, with quite a bit of experience of using A/D's,
D/A's and microcontrollers.

He intends adding two sensors that can check if the vehicle is level
in two orthogonal (at right angle) directions.

A safety point: when the sensor becomes disconnected or the
sensor becomes loose, the jacks will try to compensate for that.
Tricky. A possible liablity case too.

[ snip]

I have nagging doubts about all these.

me too.

Do I need pressure sensors to be certain the rams are indeed touching
the surface on which this is parked ? What happens if the surface is
not very hard, and gives a certain amount? What effect would wind have
on this ?

It becomes complicated ...

I don't want to completly lift the motorhome, but likewise I do need
to be able to remove some of the give in the suspension.

But it'd be possible with it.

Rene

 

[Fred Bloggs]

I see where [email protected] (Dr.
David Kirkby) inquired:




You're not going to like my answer, but here it is: You should tell
your friend that you don't know how to do it, and that he need to
hire someone with a clue to engineer what he wants.

Will Sill

*I* like your answer- succinct, practical and realistic- ask an EE and
you end up with GPS controlled magnetic levitation and fuzzy logic
before you know it-ask an ME and you get a working system- why the heck
would this operation need to be automated anyway?- is it being installed
on tundra or something.

 

[John Woodgate]

I read in sci.electronics.design that RAM^3 <[email protected]>

One "minor" problem: where to put the third support.

Left as an exercise for the student, of course. You just look at the
underframe to find a suitable point in the middle at the front or back.

 

[EEng]

One "minor" problem: where to put the third support.

FWIW, the 4-corner systems are readily available from a number of
manufacturers (and have been for over a decade),

So have the 3 point systems.

 

[Stan Birch]

Such measures are seldom needed on medium duty rigs, since the
suspension generally is so stiff, that wind et al, isn't a significant
factor. On our 18,000 lb Ford chassis, we've never recognized a need
for any kind of stabilizer.

For less than 1% of the cost of hydraulic jacks, a few boards from yer
local lumber company will accomplish the same purpose.

 

[John Woodgate]

I read in sci.electronics.design that Stan Birch <[email protected]>

Such measures are seldom needed on medium duty rigs, since the
suspension generally is so stiff, that wind et al, isn't a significant
factor. On our 18,000 lb Ford chassis, we've never recognized a need for
any kind of stabilizer.

Up to what wind speed?

 

[Roger Gt]

"Dr. David Kirkby"
message : A friend of mine has bought a 21-seater coach with the idea of
: converting this into a motor home. Although it is a bit over the
top
: (OTT) in my opinion, he wants a system that can
:
: a) Stabilize the vehicle when parked so that wind does not cause
it to
: move on the suspension. i.e remove the effect of the springs in
the
: suspension.
:
: b) Level the vehicle if parked on terrain with an incline.
:
Just stiffen the suspension and use chocks for leveling.
Air boost shocks will take a lot of flex out and provide some
lift.
While the entire task can be done. There seems no point.

 

[Alan Balmer]

Farmer's milking stools have only one leg. The seat is tied to their
ass, and they sit on it, using their own two legs as well of course,
so in fact it's still 3 legs at work

Not in my neck of the woods. I grew up on the farm, and our milking
stools had three legs. Same with the neighbors. Never saw a one-legged
one.

 

[Frank Bemelman]

Not in my neck of the woods. I grew up on the farm, and our milking
stools had three legs. Same with the neighbors. Never saw a one-legged
one.

Here in the Netherlands the farmers used 1 legged stools. Not anymore
of course, it's all milking machines and even milking robots these days.

 

[Rheilly Phoull]

A friend of mine has bought a 21-seater coach with the idea of
converting this into a motor home. Although it is a bit over the top
(OTT) in my opinion, he wants a system that can

a) Stabilise the vehicle when parked so that wind does not cause it to
move on the suspension. i.e remove the effect of the springs in the
suspension.

b) Level the vehicle if parked on terrain with an incline.

He has asked me if I can design him a system to do this. He is quite
capable of adding hydraulic rams to do the mechanicle work, as he has
excellent mechanical skills and has built a kit-car and done other
related items. However, he has asked me to design a control system to
do this. He wants to push one button and it all work. I'm an
electronics engineer, with quite a bit of experience of using A/D's,
D/A's and microcontrollers.

He intends adding two sensors that can check if the vehicle is level
in two orthogonal (at right angle) directions.

I'd like some advice/guidance from anyone with knowledge of how such
systems might work - I belive they are available at a high price.
Someone has pointed out to me the turret on militrary tanks keeps in
one direction, despite the fact the tank moves on uneven terrain.

My thoughts to date have been

1) Determine from the angle sensors which of the 4 corners the coach
needs to be raised. Lower a ram in the corner most needing raising
until such time as it in contact with the ground with say a 1 degree
correction in the angle of the coach.

2) Raise the corner that requires the second most degree of correction
until there has been a 1 degree change in the coaches angle.

3) Do likewise for the second and third corners.

At this point each ram should be touching the road surface.

Then repeat the procedure, after which the coach should be level.

Another idea is the dead opposite of this.

a) Raise the corner of the motorhome that is already highest, so
making the motorhome in a worst position than originally. Then do this
for the second worst corner. and to this for each corner. This seems
more robust as an algorithm, but needs longer rams, which cost more.

I have nagging doubts about all these.

Do I need pressure sensors to be certain the rams are indeed touching
the surface on which this is parked ? What happens if the surface is
not very hard, and gives a certain amount? What effect would wind have
on this ?

I don't want to completly lift the motorhome, but likewise I do need
to be able to remove some of the give in the suspension.

Dave kirkby

One of the lads here in Oz has come up with a system, no electronics as I
understand. AFAIK the rams are all fed from a common reservoir and thus
each moves until it hits the deck and I guess a coupla pounds are then added
to take the load.

 

[Genome]

Dave kirkby

First off, go to

http://www.bigconcreteblocksRus.com

and give them the general dimensions of your motor home.

Then contact

http://www.us.gov.army

and request a big helicopter.

Job done.

DNA

 

[thehatter]

Here are to groups about bus conversion:
http://groups.yahoo.com/group/schoolbusconversionuts/
http://www.yahoogroups.com/group/fotr

There are some others that are related to specific bus types but they might
be able to help, do a search in yahoo groups for < RTS > < MCI > <Bus> you
find some help in one of those.

At the schoolbus site, is a guy named Ben Rosander who has written several
book on the subject.

Good Luck,
Byrd

 

[Don]

Farmer's milking stools have only one leg. The seat is tied to their
ass, and they sit on it, using their own two legs as well of course,
so in fact it's still 3 legs at work

I thought one legged stools had been outlawed by OSHA. If not, they
should be. They're dangerous.

Don