Bed Pneumatic Lift

[Chuck Newman]

I need some mechanical design help from the mechanical wizzards here.  And thankfully, their are many here.  Over the years we have seen 2 or 3 different air cylinder designs that lifted the bed.  I know the standard method is manual lift with the assistance of charged cylinders, but Elva can't lift most and some are downright heavy for my low back.  And when I looked at those, I wasn't paying attention.

Since we will have air all the time via one of two electric compressors, can someone help with the following.  Our "short queen" will be 75" long from the driver side wall, perpendicular to the bus length.  The "pivot point" to raise the bed will be about 5" from the wall, making the lifting surface of 3/4" plywood 60" wide by 70" long.  The bed's box will be 16" tall from the floor.  We would like the bed to open from the foot to about 4.5 to 5 feet off the floor.  This is typical for most we have seen.  With that in mind:

1. Using two cylinders, one on each side of the bed, where should they be mounted (between the pivot point and foot of the bed) to give the required height while not inducing undue strain on the plywood?

2. What would be the optimum cylinder extension length or reach length to get the required height without incurring the national debt?

Thanks,

Chuck

[Dreamscape]

Chuck,

I'm not an engineer, but you might consider a regulator in the mix to control the speed. Check McMaster Carr for cylinders, they have about anything you need. It will help you determine what kind of clevis or attachment you need also. I have bought many things from them over the years and was always very happy with the service and shipping.

One more thing, you can put a muffler on the exhaust port of the valve, it should have a screw that you can adjust the flow to control speed when the cylinder is retracting.

http://www.mcmaster.com/#

Paul

[luvrbus]

Chuck, this the way mine works
My base is 15 inches high off the floor
The lift height is 63 inches from the floor not the top of the base
My lifts have 12 inches of travel (2)
The lift is mounted 43 inches from the hinge at the front of the bed on the floor
The top hinge is mounted 47 inches from the hinge to bed platform a piece of 1 inch plywood
Both the lift and the brackets have pivots I tried to mount the lifts completely vertical with a pivot on one end and it would tear the brackets off.
Finding a air cylinder that will work is going to be the problem most are about 21/2 inches or larger in diameter
I used electric lifts screw type made buy Drew Industries (happijac) so far they work hope this helps and the beds do get heavier with age trust me on that one and if you going to Oregon  before George passed away at Northwest RV surplus in Eugene he sold the lifts for 50 bucks a set I don't know what they charge now or if they are still in business  

Wrong about the price they were 150 bucks a set

good luck

[Busted Knuckle]

Or you could do like Cody is and make it a catapult so when he want's Libby to get up all he has to do is pull the lever! LOL!

Sorry I couldn't resist!
  BK 

[Chuck Newman]

Luvrbus,

Thank you for the Happijac info.  I went to their site at happijac.com and it appears all they are now making are the track type bed raise/lower mechanisms used in the toy haulers.  Wasn't Happijac a pick up camper electric jack manufacturer for years, or am I confusing them with someone else?  That happens frequently lately.

I did call Northwest RV Supply (as you know, used to be "Surplus"), and the lady I spoke to said they didn't have any, and she didn't seem to understand what I was talking about.  When Ron Craig's daughter sold RV Surplus in Chico, the guys who bought it changed it into a plain Jane RV store.  They went under in only a couple years or so -- before the economy drop off.  It was sad as they really had a large selection of surplus several years ago.  I hope Northwest RV Supply has not gone the same route.

Paul,

Many thanks for the McMaster-Carr tip.  When I worked in power generation we used them a lot, but they were not the easiest folks to work with.  Really tight with their catalogs considering the thousands of dollars went spent with them.  If the name now is just MCMaster maybe they have succumbed to the merger monster and are more receptive to making sales.  Their web site appears to be so.

Anyway, you made my day.  I had more selection of pneumatic cylinders than types of candy at a Seas store.  http://www.mcmaster.com/#cad-2d/=3axji1     
appeared to be the winner, but then I found one with a 24" stroke.  And both less than $70.00.  I'm at relatives in Sonora for the weekend, no printer, no reference material, etc.  I guess I'm lucky to have Internet access while the girls do their craft fair thing.  So when I get home Tuesday I'll do some serious study on their air cylinders.  Looks like I can have my cake and eat it.  Though I never understood the logic of that saying.

And Bryce, I can tell we share some of the same personality traits.               hehe

[wrench]

I need some mechanical design help from the mechanical wizzards here.  And thankfully, their are many here.  Over the years we have seen 2 or 3 different air cylinder designs that lifted the bed.  I know the standard method is manual lift with the assistance of charged cylinders, but Elva can't lift most and some are downright heavy for my low back.  And when I looked at those, I wasn't paying attention.

Since we will have air all the time via one of two electric compressors, can someone help with the following.  Our "short queen" will be 75" long from the driver side wall, perpendicular to the bus length.  The "pivot point" to raise the bed will be about 5" from the wall, making the lifting surface of 3/4" plywood 60" wide by 70" long.  The bed's box will be 16" tall from the floor.  We would like the bed to open from the foot to about 4.5 to 5 feet off the floor.  This is typical for most we have seen.  With that in mind:

1. Using two cylinders, one on each side of the bed, where should they be mounted (between the pivot point and foot of the bed) to give the required height while not inducing undue strain on the plywood?

2. What would be the optimum cylinder extension length or reach length to get the required height without incurring the national debt?

Thanks,

Chuck
       I don't know if this hallucination is helpfull! If using water pressure to lift, you would save on shock absorber.
           good luck      wrench

[06 Bill]

I think air lifts could be made from 2 Quality manual tire pumps. Long stroke plenty strong enough for  this app. 06 Bill

[TomC]

Would highly recommend using a 12v screw type lift.  It is what is used on the go fast boats on the engine covers, and can easily be used on the bed.  Air cylinders are too sloppy in operation to make them nice and smooth-can be too fast, go slow then suddenly pop up, or drop, etc.  Good Luck, TomC

[JackConrad]

We used 2  12 volt linear actuators. We purchased them on Ebay from a company called Fiorelli (SP?). They have many different actuators of different stroke lengths and lifting capacity. Jack

[Chuck Newman]

Thank you everyone for the ideas.  Lots to ponder.

Chuck

[Skykingrob]

Hey Chuck
Just an FYI about McMaster-Carr. I just tried to order several things from them Wednesday. When I was trying to place the order, the second thing the woman ask was what company I was with. I told her none, just a privatge individual doing my own work. She said "Sorry, we only sell to companies". I ask her if she was serious about not selling to indiviudals, she said "yes, company policy". Needless to say, I didn't get my items after spending hours on their web site finding just what I wanted. I hope your experience is different.

Rob
91 Prevost LeMirage XL

[Charles in SC]

I have bought from McMaster a number of times on line and never had a problem. I am an individual.