Jack vs Gantry-shell lift

[gronlampa]

Hello all!

Aside from being able to use the gantrys to flip the frame etc., what other reasons would I go that route over jacks?

It seems like jacks would be a lot cheaper and not that difficult.

What am I missing?

[cwf]

Gantry can lift through the roof 'skylights'/vents. make sure you have some interior bracing after removing the interior skins...

There are lots of threads on here about this...

besides... if 'lifted', via gantry, you can move stuff underneath without the concern of knocking over a jack or jack stand.

[rugjenkins]

It's personal preference. I used gantries and would use them every time for a full monty. They are inexpensive to make and harbour frieght sells cheap chain hoists. Many say to brace from side to side. I just used a 2x6 the length of the roof vents. Lifted shell no problem and bolted it directly to my driveway for 2 years. The shell is pretty tough. Btw the shell is now bolted to the new frame 😄.

The gantries are very versatile. You can use them for serval purposes.

[HiJoeSilver]

Gantrys!!!
I tried the jack method lifting the shell and it was a nightmare, unbelievably difficult, and stressful. Actually ended up dropping the rear a few inches. Not pretty or fun. To easy for something to tip on one of the jacks which aren't all that stable to begin with, then consider that the shell weight is not distributed evenly and things can get very touchy.
When it came time to put it back on I hired a crane and lifted through the vents as you would a gantry. Still not perfect but much easier and less stressful.
Gantrys let you control the lift better, easier to keep the lift even. Only time I might consider jacks would be on a very small trailer.
Gantries can also be used for platforms to work on trailer and trailer roof, ac, vents, solar etc. without having to get on the roof.

[Belegedhel]

I don't see the gantries as being expensive. If you do the jacking method, you are going to have to build bracing inside the trailer to jack against, plus get saw horses or the equivalent to rest the shell on while pulling the frame out. At the end of the day, I doubt there is much difference in cost. By the way, like many others, I lifted with a gantry and did not use any bracing inside the shell--all went fine.

I got a lot of use out of my gantries. Must have flipped my frame over a dozen times during the process of repairing the frame itself, wire-brushing it, painting it, installing the tanks with the frame upside down, and finally putting the bellypan in place. Trying to put a brand new bellypan in place from underneath the frame would be an absolute nightmare. After my shell was back on the frame, I added a few 2x4s to my gantries to create scaffolding over the roof of the trailer. I then did some roof repair, resealed and installed some vents, removed the original AC, patched the mess left behind, and finally installed the new unit. All of this goes much easier if you are walking around on a platform, not worrying about scratching/denting your roof.

good luck!

[gronlampa]

Thanks all!

Gantries it is!

Your replies helped me think things through a bit. I will be doing some of the frame work off site and was having a hard time figuring the logisitics.

Gantires are the solution.

I see no reason why they can't be broken down and attached to the frame for transport to the workshop where I will be doing most of the repairs.

[gronlampa]

Does anyone out there have plans for a wooden gantry?

[Belegedhel]

Post number 14 of the thread below has plans for the standard wooden gantries. The only thing I would suggest for an improvement is to use a 4x6 as the weight bearing member across the top. I used 4x4s just like in the plans, and noticed more deflection than I really liked while lifting and flipping my frame. The 4x4s should be more than enough for the job, and I have yet to hear of anyone having a catastrophic failure, but a little over-engineering wouldn't hurt.

http://www.airforums.com/forums/f36/...on-115765.html

good luck!

[DavidF]

I agree with Belegedhel. I just built and used 2 gantries per the plans. Simple and not very expensive, even with the chain hoists. I used 4x6's for the top beams and they work great. I made one 12 ft. wide and one 10 feet wide so I could get them close together if necessary. Also used 5/8 in. bolts for the main joints. I have cleaned up the frame and am now painting it with silver Por-15. You can get it on eBay for $36/Qt. with free shipping. Have fun...

[AlbertaBound]

i used the jack method on my 28' as i had everything to do it. jacked the back up 4 inches to slide a 10' 4x4 through under a rib. blocked up the 4x4. lifted and blocked the front the same. pulled out the frame. took about an hour. building gantries just seemed like a waste of time/money for something i would use once. but then again i have access to a forklift for flipping the frame and replacing a/c, etc.