shortbus4x4
Expedition Leader
Do you sell them?
pivoting frames and mounting campers
- Thread starter lehel1
- Start date
Hi Ramdough. Well, all but the lock outs/hydraulic system are built. I have the two outer pivots no more than 100mm from the rear hanger of the front springs about 400mm behind the cab, keeping the cab and body faces in a fairly similar plane at all times. I have two central pivots, the first is located on the rear springs front hanger cross member and the second on the rear spring rear hanger cross member. These are all tack welded to the body and are yet to be fully welded. I've since added another central pivot at the very rear of the truck. All pivot points are on the center line of the chassis. I have then twisted the truck chassis (rear lh dual wheels 400mm off the ground) to the point where the lower lockers just touch the body to check that it all worked without any of the tack welds going bang, which it did. To double check what you mentioned about binding, I then unbolted and removed each locking bolt in the pivots and tapped each pin with the hammer to see how much load they were under. To my surprise they would tap out with ease and have minimal to no load on them. I must have got something right!Re the hydraulic setup, I have gone away from this due to weight, the time involved and cost to do it. I now plan to utilize 2 (poss 4) stumpy 100mm x 100mm coil springs between the body and chassis these will be sat with no or minimal tension when the truck is flat, and will only be compressed as the chassis twists. Here's a pic of the chassis twisted and the body straight. it was in this position that the pins would tap out.
View attachment 575883
The guy from UNICAT actually describes Sitecs system, but calling it a 3-point... I guess you could view a 4-point as a 3-point with a mirror axis. The thing we can take from the UNICAT live stream is that you can add as many central points as you wish (theoretically), as long as they are all located on the central pivot axis of the chassis.
They surely do have proven track record!
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Victorian
Approved Vendor : Total Composites
I watched it too... Funny to see my old boss talk about stuff we repeated soo many time in the shop when I was working there. When it comes to subframes, they really know what they are talking about. I'm not aware of any frames/mounts ever failing coming from that shop. On the other hand, we had several rigs from other well know manufacturers show up with big structural failures! I have seen this on several North American made ones too...
Generally speaking, subframe design and builds are still a specialty in North America with not many that have a proven track record. Best places are currently: Overland Adventure Trucks in Olympia WA , Acela Trucks in Belgrad MT and ITB in Surrey BC. Only Overland Adventure trucks is selling and manufacturing them as a stand alone item.
Alloy
Well-known member
Did you choose 50mm to keep the OA height down?
Sitec
Adventurer
Hi Alloy. Not really, though doing it the way I have has assisted in keeping the overall height at 3.55m. I have the pivot points in the center of the rail as I think that's where they need to be, and the 50mm chassis rail to body rail travel is at 50mm as the pivot center to rail distance is about half what the pivot point to edge of body is, and I only wanted a 100mm travel gap between the body... Much more and it would have looked odd from outside. Hope that makes sense.. I have also gone with a 100mm clearance gap between the habitation box and the chassis, so that if for any reason my 5 point system does not work as intended, I can slide a piece of 100 x 50 RHS in between the chassis and box and quickly make it 'rail on rail' without major mods... Lets hope it all works eh!
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Sitec
Adventurer
Spot on. The only drawback with the way I have done it is that by having the outer support pivot points of the 4 point system at the front then means that the travel between body and chassis at the rear is huge... (hold a ruler at one end and twist it at the other). If the outer support pivots are mid mounted (as normally found), then travel is halved at each end. The advantage of my system is that movement between the cab and habitation box is minimal as the outer support pivots are at the front. As I'm not after huge twist, but looking to share the twist load between the chassis and suspension as my habitation box is very strong, I am allowing a percentage of chassis twist, but letting the leaf springs do the rest.
That sounds interesting! and you know the positives and the downsides. I have actually thought about this a lot through several years. I have read just about all the discussions, theories and real-world experience. I started a project on a Volvo TGB just because the frame is rigid. but two kids later, it was too small even before it was finished.
So we bought a Mercedes LAF 1113B, much larger, but with a flexible chassis. Ok, it's not that big, approx. 7.5m/24.5ft. So I want to make it a fully integrated, so we can utilize the cab space while camping. I know this goes againt all canon here, but that's what we want.
So I'm trying to design a subframe that´s a bit unusual:
Up front there will be two heavy LORD cab mounts, which will support the front weight and control the front both vertically and horizontally.
These will also keep the subframe and chassis in alignment up front, so controls (gearshift, gas pedal etc.) will not be affected by movement.
Approx. above the rear axle there will be a Watts linkage which will control the rear side to side, but allow chassis flex and vertical displacement.
Behind the rear axle there will be an airbag on each side. These will support the weight of the subframe in the rear. On-road these will be inflated and controlled individually. Off-road they will be connected to allow air from one to go to the other. This way they will allow the chassis to flex.
I believe this should work, and have run FEA on the subframe. A bonus will be isolating the box from the chassis vibrations.
Please look it over and give me all your thoughts both positive and negative, as long as they are constructive!
PS: the yellow shadows are an interference block I have used to make sure I did not design anything that would interfere with the chassis while flexing...
T
mog
Kodiak Buckaroo
Nothing against LORD mounts (we used them quite a bit in aviation applications), but there have been some less than stellar results in the overland/expo applications.
Is this a Unimog failure or a GXV failure? (Pic included)
I recently resumed my search for a towing/travel rig for my boat and still kinda sitting on the fence between an ER and GXV. I saw this update on a blog I follow and was a bit concerned. My question is this: was this a failure of the Unimog or the GXV? If its the Unimog, i'm not overly concerned...
www.expeditionportal.com
Alloy
Well-known member
Hi Alloy. Not really, though doing it the way I have has assisted in keeping the overall height at 3.55m. I have the pivot points in the center of the rail as I think that's where they need to be,
You mean horizontally and vertically?
and the 50mm chassis rail to body rail travel is at 50mm as the pivot center to rail distance is about half what the pivot point to edge of body is, and I only wanted a 100mm travel gap between the body... Much more and it would have looked odd from outside.
You mean too large of air gap between the chassis rail and the body rail?
Hope that makes sense.. I have also gone with a 100mm clearance gap between the habitation box and the chassis,
Now you've got me wondering.........habitation box?
Nice stone retaining wall by the way!
so that if for any reason my 5 point system does not work as intended, I can slide a piece of 100 x 50 RHS in between the chassis and box and quickly make it 'rail on rail' without major mods... Lets hope it all works eh!
Thanks and of course! I have read the accounts of the Unfortunate Unimog. LORD actually describes how these mounts can be “safetied” using a big washer, just like i.e. a standard Landcruiser body mount, and I plan on doing just that.Nothing against LORD mounts (we used them quite a bit in aviation applications), but there have been some less than stellar results in the overland/expo applications.
Perhaps as BAH in that thread pointed out, having a large enough washer to 'captive' the mount if the rubber portion fails?Is this a Unimog failure or a GXV failure? (Pic included)
I recently resumed my search for a towing/travel rig for my boat and still kinda sitting on the fence between an ER and GXV. I saw this update on a blog I follow and was a bit concerned. My question is this: was this a failure of the Unimog or the GXV? If its the Unimog, i'm not overly concerned...
If I can find a supplier, I plan on using J-21159-9, they have a rated static axial load of 11.39kN/2.560lb and according to a LORD representative should handle 5-8 times that momentarily. The only thing I’m not sure about is their ability to isolate the actual vibrations from chassis and engine.
Alloy
Well-known member
Nothing against LORD mounts (we used them quite a bit in aviation applications), but there have been some less than stellar results in the overland/expo applications.
Perhaps as BAH in that thread pointed out, having a large enough washer to 'captive' the mount if the rubber portion fails?Is this a Unimog failure or a GXV failure? (Pic included)
I recently resumed my search for a towing/travel rig for my boat and still kinda sitting on the fence between an ER and GXV. I saw this update on a blog I follow and was a bit concerned. My question is this: was this a failure of the Unimog or the GXV? If its the Unimog, i'm not overly concerned...
I've seen lots of rubber/neoprene fail. The material does not have a good cycle life. Happens allot with suspension components from a company called Moryde International. Their components have to be inspected yearly.
Sitec
Adventurer
I wouldn't be worried too much about vibration form the engine and chassis... There's very little that will stop the shake rattle and roll found on corrugated dirt roads! There's always going to be a certain amount of vibration. Looking at your drawings, in theory if you have your front and rear pivots in the center line of the chassis, then you shouldn't need the complexity of connecting arms like you have drawn in... A simple pivot and greasable bush would surfice. Then, as the 4 'points' are rigid, but can only flex in the direction required, you could do away with the Lord rubber things (that look like oversized tractor cab mounts), and replace them with 4 decent shock absorbers to allow the travel required while giving a dampening effect and not a restrictive effect found by the Lord system... Just my thoughts.
filippomasoni
New member
I know pivoting frames are used a lot on big trucks, and for good reason but what about small pickups like a Ford Ranger?
I'm planning the build of a camper on a flatbed (with back wheel cutouts for having a low as the possible center of gravity). The vehicle will be a Ford Ranger chassis cab (single cab sold without the bed). The flatbed will be about 2.5m long x 1.9m wide x 1.9m tall (8.2ft x 6.2ft x 6.2ft). The fully laden weight of the camper (with everything inside) will be about 6-700kg (1500lb). I'm in Italy and we don't have the choice of bigger heavy-duty trucks like you in the US, so I'm trying to build a hard side camper with all the comfort for long expeditions, but maintaining a small size (with no more overhand than the stock bed) not to make the small pickup unstable in offroad.
Since the frame is much shorter than big trucks I don't think it will have so much flex to need a real 3 or 4 point pivoting frame, but maybe mounting with captured springs can give some help to articulation? What do you guys think?
I'm planning the build of a camper on a flatbed (with back wheel cutouts for having a low as the possible center of gravity). The vehicle will be a Ford Ranger chassis cab (single cab sold without the bed). The flatbed will be about 2.5m long x 1.9m wide x 1.9m tall (8.2ft x 6.2ft x 6.2ft). The fully laden weight of the camper (with everything inside) will be about 6-700kg (1500lb). I'm in Italy and we don't have the choice of bigger heavy-duty trucks like you in the US, so I'm trying to build a hard side camper with all the comfort for long expeditions, but maintaining a small size (with no more overhand than the stock bed) not to make the small pickup unstable in offroad.
Since the frame is much shorter than big trucks I don't think it will have so much flex to need a real 3 or 4 point pivoting frame, but maybe mounting with captured springs can give some help to articulation? What do you guys think?