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01-31-2019, 10:30 AM
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#15
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Senior Member
Join Date: Jun 2000
Location: Martinez, CA. USA
Posts: 354
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Quote:
Originally Posted by grindstone01
Granted I do not have a DP. But do the lift jacks and suspension fail that often? I have seen DP's parked w/tires lifted off the ground for a month and longer. I agree it's probably still not safe to crawl under, but hopefully the jack failure risk is a pretty low occurance.
Gary's post from above makes sense to me!
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They only need to fail once to ruin your day.
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01-31-2019, 10:36 AM
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#16
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Registered User
Join Date: Oct 2017
Posts: 4,985
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Quote:
Originally Posted by Fyrflie
They only need to fail once to ruin your day.
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Based on that thought, I'd better stay in bed for the rest of my life.
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01-31-2019, 10:37 AM
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#17
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Community Administrator
Tiffin Owners Club
Join Date: Sep 2013
Location: DFW, Texas
Posts: 21,267
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No, I do not trust the jacks as reliable as they are. All it takes is the one in a million failure and you are done. If you are going to work on the coach, build a set of these ramps. They raise the coach six inches and gives plenty of room to work underneath whether the air suspension is up or down.
__________________
2017 Phaeton 40IH XSH Maroon Coral - Power Glide Chassis with IFS
Previous '15 Tiffin Allegro RED 38QRA and '06 Itasca Sunrise 35A
'16 Jeep JKU Wrangler Sahara or '08 Honda Goldwing
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01-31-2019, 10:48 AM
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#18
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Senior Member
Join Date: Jul 2014
Posts: 35,349
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Hydraulic jack failure is rare but can happen, at any moment.
If your working under the lifted MH and knock a fitting off or cut a hose, down it comes.
I worked in two heavy equipment shops for 35 years and never saw a sudden jack failure but we all still used stands or blocks to hold the load. We all did take some oil baths and had some crushed fingers from hydraulic failures of some kind or another.
Even with my floor jack, while doing car brakes, I always push the removed tire under the car body, in case the jack comes down.
If I had MH jacks, I would scrounge up 4 peices of 1/4 thick aluminum angle. They can be cut to length and easily tied against the jack piston when fully extended. That's what we used on pay loader bucket, lift cylinders, if the arms needed to be raised and supported for access.
You don't need to let them support the load, just know that they can, if things go south.
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01-31-2019, 11:07 AM
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#19
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Moderator Emeritus
Monaco Owners Club Texas Boomers Club
Join Date: Nov 2015
Location: Central Texas
Posts: 13,426
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If I don't need the wheels to be off the ground, I drive the coach on to two 2X10s stacked on top of each other. Then I place a jack stand made of laminated layers of 3/8 plywood under each jack pad and lower the suspension until the motor home is sitting on the plywood jack stands.
__________________
Dennis and Katherine
2000 Monaco Dynasty
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01-31-2019, 11:22 AM
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#20
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Senior Member
Tiffin Owners Club
Join Date: Aug 2016
Location: Bastrop Texas
Posts: 1,343
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I would second Gary's comment If I can get under it with air down then it is safe in my mind and the added work space is nice. Second, Failure of the jacks would be just about as likely as getting zapped by lightning. I do however understand those who have a fear of a lot of things.
__________________
2000 Allegro Bus 35R 3126 Cat 300 Allison 3060MD 6 speed
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01-31-2019, 11:48 AM
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#21
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Registered User
Join Date: Oct 2016
Posts: 2,078
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On most of the larger DP's there is a valve underneath that if you push it lets the air down very fast so you have to be aware of that if leaving the air bags inflated
Hydraulic failures should be slower but they are faster than you might think
If you were employed by someone with insurance you would be required to block up whatever you had raised that had wheels off the ground
Simply common sense
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01-31-2019, 11:58 AM
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#22
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Senior Member
Join Date: Jan 2011
Location: Wandering below the Gnat Line
Posts: 1,995
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My MH blew a jack hose a couple of years ago. That corner came down RIGHT THAT INSTANT and bounced. I think it would be unsurvivable.
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-jbh-
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01-31-2019, 12:05 PM
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#23
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Senior Member
Monaco Owners Club Workhorse Chassis Owner
Join Date: Aug 2002
Location: Clovis, CA, USA
Posts: 13,103
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No I don't trust my levelers. I use two jackstands that I know will support my RV.
How do I know you may ask...I forgot to remove the stands one day and dropped the front end on them. They held fine.
Over the years I've read several newspaper articles where guys have been killed or trapped underneath their cars. I don't want to be a news article.
__________________
2004 Monaco La Palma 36DBD, W22, 8.1, 7.1 MPG
2000 LEXUS RX300 FWD 22MPG 4020 LBS
Criticism is easier than Craftsmanship
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01-31-2019, 12:06 PM
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#24
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Senior Member
Join Date: Aug 2001
Location: North America somewhere
Posts: 30,655
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Quote:
Originally Posted by lwmcguire
Never,
Wood cribbing or metal jacks
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I'd never bet my life on a hydraulic hose never rupturing. Two years ago a mechanic did not use cribbing or jack-stands, he died from suffocation when the MH lost air pressure to the suspension and pinned him underneath.
__________________
2000 Winnebago Ultimate Freedom USQ40JD , ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;Good Sam Life member,FMCA. " My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy
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01-31-2019, 12:26 PM
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#25
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Registered User
Join Date: Apr 2018
Posts: 1,459
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Quote:
Originally Posted by Gary RVRoamer
I'm a bit more pragmatic. If I can fit under without raising it on the jacks, i.e. it wouldn't crush me when down, then I don't worry about raising it on the jacks for more work room and easier access. That's for working on things that don't involve suspension and such, e.g. changing oil filter or stringing a wire. I have some rules too, e.g. nobody, especially kids & dogs, inside the coach where they might hit the air dump or jacks switch.
My coach generally sits high enough I can slide under the frame rails and body sides, but several inches more makes life a whole lot easier.
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Watch for bounce. My not kill but the impact can make it hard to crawl even if the load is not on you.
As a teenager, I had a VW fall and pin me. I could push up enough to breath, but can't move while holding it up...
Quote:
Originally Posted by twinboat
Hydraulic jack failure is rare but can happen, at any moment.
If your working under the lifted MH and knock a fitting off or cut a hose, down it comes.
If I had MH jacks, I would scrounge up 4 peices of 1/4 thick aluminum angle. They can be cut to length and easily tied against the jack piston when fully extended. That's what we used on pay loader bucket, lift cylinders, if the arms needed to be raised and supported for access.
You don't need to let them support the load, just know that they can, if things go south.
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For a vertical jack, I would want the brace to be 'C' shaped, and have some sort of strap to hold it in place...
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01-31-2019, 02:23 PM
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#26
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Senior Member
Join Date: Sep 2018
Posts: 1,944
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Hydraulic systems designed to have people under the working gear (like cranes), or for that matter, on the working gear (like man lifts and elevators) have additional valving that MH stabilizers do not have. Like flow fuses (to guard against hose burst) or load-holding valves (piloted counterbalance or pilot check valves to prevent motion not driven by the engine), usually in cavities machined right into the cylinder. And additional valves downstream of the load-holding valve(s). Truck crane outriggers, and hydraulic boom cylinders on cranes and manlifts (including scissor lifts) use such valving, with cylinders and mounting structures designed for that loading. Motor coaches do not.
Dump trucks and track and wheel loaders use struts to back up the hydraulics when working under the working gear (truck body or bucket in the air). Machines like that are not designed to have someone under the moving bits, supported only by hydraulics.
I've investigated construction accidents caused by hydraulic failures, including fatal accidents, and that's with machinery with far more redundant systems specifically designed for lifting personnel or having personnel underneath.
Please don't get under there with the typically marginal (at best) hydraulics or pneumatics as the only support. That stuff is fine for what it was designed to do, but not for supporting a lifted load with someone underneath. A few seconds to place heavy jack stands or wooden cribbing can save your life in the unlikely, but too often occurring (if reports of hose failures on this board are true), event of hose or structural cylinder/frame/connection failure.
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01-31-2019, 04:53 PM
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#28
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Senior Member
Join Date: Jan 2013
Location: Muskoka Ontario Canada
Posts: 3,142
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Quote:
Originally Posted by Lt Dan
No, I do not trust the jacks as reliable as they are. All it takes is the one in a million failure and you are done. If you are going to work on the coach, build a set of these ramps. They raise the coach six inches and gives plenty of room to work underneath whether the air suspension is up or down.
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I like this idea. If I dump the air on my DP, there are many places I cant get to underneath. If I was in one of these places, and an air line blew or such, I would be in trouble. I would think on these blocks, you would be safe pretty much anywhere.
__________________
2000 coachmen santara 370 5.9 cummins isb
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