Stretching frame on a single

[haddixj]

Hi I'm in the planning phase of what I hope will be my last motorhome. I have looked through most of the builds but have trouble finding detail on how you guys stretched the frame. What metal? Is it boxed? I am looking to build a single axle truck that has a 20' box on it as the living space. I plan to tow a 30' stacker trailer that should be about 15k loaded. Also I live in ca and have looked over the rules for converting to rv and it doesn't seem to bad. So what do you guys think? Fwiw I built my tube chasis race car and understand frames being square and axle placement. Thanks for any help to guys can offer
Jason

[Bob86ZZ4]

Sounds like it should be pretty doable. I've seen some guys over on the Escapees HDT forum that have similar setups. I think they use C channel to extend the frame back to where they put their 5th wheel hitch. If you're doing a bumper pull trailer you might not even have to extend the frame, depending how long the frame is on your truck. My truck is a single drive axle with a 26' box and it's got a 295" wheelbase. But, the box extends pretty far behind the rear axle. There is a section in that HDT forum that has a lot of info regarding truck frames and hitches and stuff. Most of them just use the truck to pull their 5th wheels and build big decks for cars or cycles or such. But I think some of that info might be of help here. Keep us posted and put up lots of pictures of your build. That seems to be one of the things lacking around here. Lots of projects get started with pics and then we don't hear much. I think they get their trucks done and take off down the road with huge smiles on their faces.

[Gordy]

If I was stretching the frame between or after the rear axle, I would find a donor truck (junkyard) and use the frame sections from it. Dragonslayer has an ongoing post about his build that you can check out. Renegade, Haulmark and other builders want double frame rails but Showhauler and NRC can use a single by the way they manufacture the floor and wall section, which help reinforce the frame. Good luck on your project.

[haddixj]

Do you guys have any pics of how the other companys are doing it? It seems from what I have found class 8 trucks arent available with a long wheelbase. By that I mean I want to have a 20' box after the cab. I was thinking of using the same size C channel to extend the frame then getting a samller size C channel that will fit in the existing C channel and basically box it in like



I have seen where people just add a new section of frame and seems like they just weld a fish plate <> where the frame is added but that seems like it wouldnt last.

Also I have seen plenty of class 7 trucks that are exactly what I want in a chassis just the engine is a smaller cat or cummins at only 250/300 HP. I think that will hurt the milage and the point of doing this. I want a big truck for safety/power and reliabilty.

[haddixj]

Bob I saw that you tow a race trailer around how does the truck handle it with that much overhang? I am going with a bumper pull trailer. Do you ever wish you had twin drive axles? Also do you know your gross weight?

[Dragonslayer140]

I Think the thread Gordy was referring to is "Frame stretching" by Kenn, Unfortunately my build is still on the drawing board, and is at least a year away from becoming real... although since I work in the engineering field I will probably redesign it six more times before I actually start. Kenn is doing a great job of documenting his build though and a lot of good ideas can be gained from him.

Dave

[haddixj]

I just read his build thread and found that he has a 243" wheelbase tractor. That would work for me. I have no problem or concerns stretching the frame after the axles I was worried about doing t before the axles. Kenn's thread is everything I want to do and the older Pete's are reasonable to find. Are most of the tractors with sleepers and twin screws that big of a wheel base? If so that would be perfect. I read that after they remove the front axle then they end up with 270" or so. My project is still in the planning stage also. I am looking through all the forums I can find to figure out how the frame is built and what wall tubing. Seems 2x2 is common I have seen 3/16" being used for the wall. What about roofs? I see people saying aluminum is the best but where do you get 1 piece that is that big ? Can you buy the bullnose corners from a trailer place?

Sorry for all the questions this is just something I found out that I can build and afford.

[Dragonslayer140]

Tractors come in quite a few wheel bases, over the road units usually will have the longer frames due to big sleepers, In my opinion its always best if you do not have to cut and stretch a frame, and adding frame rails after the drivers is pretty easy and not to much money to have a frame shop handle it if you do not want to do it yourself. 2x2x3/16 tubing is going to be pretty heavy (runs 4.3 lbs per foot) and expensive. I am planning on using 1-1/2" for the walls with some heavier tube at the corners and around the roof for added shear strength. Seems like the most popular roof materials are aluminum, rubber (EPDM), and fiberglass. Each has definite good and bad traits. Personally I tend to lean toward 60mil EPDM rubber, installed properly is a good 20+ year roof. The company I work for builds mobile office trailers, and we have hundreds of units out there and the rubber has hold up the best, and is easy to patch. It is easy to install and seal. Aluminum is also a good choice and is available in sheets or in a full length roll.

[haddixj]

Being an engineer what wall 1 1/2" would you run? I agree that would be heavy. And for the corners would you run 2" or just thicker 11/2"? Would you mind sharing you plan such as material specs for the floor And the walls and roof? Thanks

[Dragonslayer140]

Currently I am leaning toward 11ga for studs and general framing, I have not made a decision on the corner posts yet, but am thinking of building a L shaped composite post from 3 studs, that way the corner is not thicker than the rest of the wall. I plan to frame my interior walls with steel tubing also so they become an integral part of the overall box assembly. The biggest concern for me on the construction is to eliminate as much moisture as possible from the vehicle. Steel studs will transmit the cold through the wall and create condensation, i will be adding a thin layer of rigid insulation board over the entire wall before i sheet the inside. I plan on using 7/16 osb or 1/2" exterior grade sheathing over that. The exterior rated glue in these products creates a moisture barrier if all the panel seams and penetrations are sealed. Same construction for roof and floor, except thicker T&G ply for the floor. All walls and ceiling cavities will be filled with expanding foam insulation after all electrical conduits and piping is installed. Underside of the floor will be 26ga galvanized sheet metal, and I am trying to decide if it will be undercoated or perhaps spray on bedliner material. outer siding i am not sure on yet, but probably .060 aluminum with VHB tape to insulate it against the steel studs and prevent electrolysis. Heating will be provided by a diesel fired boiler with radiant floor heat, and a basement heat pump for cooling. moisture buildup will be greatly reduced by using a air to air heat exchanger. I want to keep as much off the top of the truck as possible as I am already going to be plenty tall. I still have some serious design challenges to squeeze what I want into the rig, but as what I want is not mainstream I will not find a rig from one of the standard builders that meets my needs.

Dave

[haddixj]

So we're you going to put the 26 guage between the ground and the t&g floor? How far were you going to space the studs. Also what is your plans for the floor framing? Like width and materials. Thank
Jason

[Dragonslayer140]

Jason, My plan is to use 4" structural C channel for the two main rails and for the perimeter of the floor. 4" structural channel crossmembers will be coped in at 8 foot centers along the floor, 4" light 11ga gauge channel joists at 16" centers will infill between the heavy crossmembers. With the floor upside down, I will sheet the whole underside with the 26ga galv. using VHB tape and either Tek screws or Hilti fasteners as a secondary fastening method. Then will flip the floor back over and put on the truck frame. Before floor is installed onto truck I will build the basement storage, and skirting much the same way as Kenn has on his project. All of the partition walls in the storage compartments will be diagonally braced and will have removable cross braces underneath (so i can service the drivelines and running gear when needed.) These will help to transfer some of the forces from the weight of the walls and roof load back to the frame reducing loads on the floor joists. Then I can frame the walls flat on the floor deck and stand them into place much as you would when building a house. the roof will be framed last on top of the deck using the walls as a template to keep it square and the correct size, then hoisted up into place and welded. After that I can spray foam the floor joist cavities and install my plywood sub floor. I am choosing channel for the roof and floor joists because its open side allows for the spray foam to fill the void and create less cold pockets, also cheaper..lol. trying to use diagonal bracing and lighter materials to reduce weight and still retain the needed strength. I will be doing all my building out in the weather unless i get lucky and find a good deal on shop space to rent until the rig is water tight.
Dave

[hot rod]

I am also in the planning stages of building my toter, the chassis is bought and here, and parts and plans are accumulating.

I found the top corners at a surplus yard just up the street from Bontrager's (can't remember the name, but it is just up the street), they had the cast aluminum corners for the front and back, as well as the extruded aluminum trim for the top, and lengths of rounded stainless to match for the front corners and top front. Basically will look like a nice flat roof race car trailer which will work good for me because it will match what I am towing. You're gonna need to plan a trip to Elkhart before you get too deep into the build, there are just some things you can't get anywhere else. For example that trim is in 20' lengths so you can't ship it and your local rv/trailer shop would rake you over the coals. There are a bunch of surplus stores there, plan on taking a big list and spending a full day or 2 there. I got a bundle of 10 new matching cargo compartment doors (framed with hardware, just screw them in) for $100 for all, and a nice new entry door with screen door for $90, you get the idea.

I, like most builders, I think tend to over-think, over-build, and over-engineer, and end up with too much weight and spend too much money. While it certainly can't hurt to build with bigger tubing with thicker walls, it is just overkill and weighs too much. Which you'll hate every time you fill up, and every time you get on a grade. Every extra pound takes power and fuel to lug around the country. My older Pace trailer (back when they were good, before they sold out) is built with the old fashioned hat posts in the walls and 1x1.5 square tubing in the roof and 2" angle iron for the top of the walls. The thing is 10+ years old, gets loaded to 20,000+ on a regular basis, totet all over the country, and still looks like new. And I guarantee that 40' trailer takes more flex than a 20' box on a class 8 frame. I've been trailer shopping the last few months and the hat posts are still common for the walls, and 1" tubing the first step up (which I don't care for) and 1x1.5 on the better trailers. So I'm thinking that 1.5" square in the lightest thickness you can find is more than adequate for strength, and is wide enough to make sheeting inside and outside easy. I do like the idea of heavier corners and perimeter, and Dragonslayer's idea of triple corners would make sheeting the inside simple, you'd have something to screw to on both walls which is something I wondered about. Actually, you could probably just use 2 posts there, so you could use rounded sheet metal on the outside for a cleaner look. Figure your side and end walls so the posts match up corner to corner and weld the seam all the way up. Anyway, don't over-build the size/thickness of your steel, you're getting your strength from the complete structure, not the individual tubing.

[haddixj]

Yea I agree with trying to build it without lugging to much weight around. I have a 24' enclosed now and it only has 1" box on the sides and roof so your right 1 1/2" should be plenty with the same for the roof. I live in ca so there is no way I can make it to Indiana.y plan is to buy a class a rv and strip it for the interior, generator, inverter, windows, maybe the bathroom if it is nice. Also I will get all the tanks from the donor. I have seen decent Ones for 7k or so. So if I can get a truck for 10-12k I would be right on budget. I figure I can get it done for 30k hopefully. That will leave me 13k for building the box and any other little things I may need. I leaning towards a peterbuilt now probably pre 98 to try and avoid smog in ca. Are the older Pete's still decent on mpg? I think they went to electronic motors by 97. Seems most have a Detroit in them.

[#90-GTSC]

These details are very interesting. Whether building one's own, shopping for a used T/C, or event a factory built motorhome or trailer ... you guys are making me think about things I would not have thought about.

Regarding the studs in the outside walls. It appears everyone is using rectangular tubing. One of the posters talked about moisture and condensation which is an important concern. Is anyone using or has anyone considered using channel vs rectangular tubing for the studs and event the floor and roof? Less weight, one less piece of steel to transmit cold (and contribute to the condensation problem), and another cavity opened up for foam insulation. Added benefits would be probably cheaper, easier to route plumbing and wiring.

I'm not an engineer. I don't know if using channel versus rectangular tubing results in a woefully inadequate structure ... or if using as much steel as is used and welding (or securely bolting everything on top of a Class 8 chassis to begin is more than adequate.

Looking forward to the comments and debate.

Dick

[#90-GTSC]

These details are very interesting. Whether building one's own, shopping for a used T/C, or event a factory built motorhome or trailer ... you guys are making me think about things I would not have thought about.

Regarding the studs in the outside walls. It appears everyone is using rectangular tubing. One of the posters talked about moisture and condensation which is an important concern. Is anyone using or has anyone considered using channel (same dimension and gauage) vs rectangular tubing for the studs and even the floor and roof? Less weight, one less piece of steel to transmit cold (and contribute to the condensation problem), and more cavities opened up for foam insulation. Added benefits would be probably cheaper, easier to route plumbing and wiring.

I'm not an engineer. I don't know if using channel versus rectangular tubing results in a woefully inadequate structure ... or if using as much steel as is used and welding (and/or securely bolting) everything on top of a Class 8 chassis to begin with is more than adequate.

Looking forward to the comments and debate.

Dick

[blizzardND]

Originally Posted by haddixj

Yea I agree with trying to build it without lugging to much weight around. I have a 24' enclosed now and it only has 1" box on the sides and roof so your right 1 1/2" should be plenty with the same for the roof. I live in ca so there is no way I can make it to Indiana.y plan is to buy a class a rv and strip it for the interior, generator, inverter, windows, maybe the bathroom if it is nice. Also I will get all the tanks from the donor. I have seen decent Ones for 7k or so. So if I can get a truck for 10-12k I would be right on budget. I figure I can get it done for 30k hopefully. That will leave me 13k for building the box and any other little things I may need. I leaning towards a peterbuilt now probably pre 98 to try and avoid smog in ca. Are the older Pete's still decent on mpg? I think they went to electronic motors by 97. Seems most have a Detroit in them.

I don't mean to be a Debby Downer, but you are using the same budget that I started my build with, your VHT tape alone will cost you 1500, the little things add up so fast. I think we spent 3-4K at Menards alone. The 060 aluminum is over 110 dollars a sheet. Steel is $pendy. I figured in the beginning my 15K truck and 30K to build a 22' box. I have nearly 90K in it using many used parts from Elkhart.

But you have me hooked, what are your special requirements that there wouldn't be a similar used model for sale on Racing Junk?

blizz

[haddixj]

what i have seen on RJ in class 8 is over 100k and they are way to long. I am looking for something that is about 32' long bumper to bumper so I can tow a 28' stacker and remain under the length limit. I have looked into MDT and they seem ok but I might as well just do a P pumped cummins like in my f350. what kinda weight do you tow with your setup? What kinda mileage? From what I read people seem to be unhappy with them. I would rather have a big truck that will get around the same mileage as a mdt and be safer. I also enjoy building stuff. From what I have seen if I did some rough calcs on 2x2 steel that was about 7k and that was .25 that I had priced out for another build, if I can do 1 1/2x thin walled which should be half the cost and build the box like a heavy duty enclosed trailer sheet the outside with plywood then skin it with AL sheet. For the interior I will get an older Class A and use all of it. That will save me on the little things inside. Generator will be used as well as inverter. I found nicer older ones for less then 8k. I will build in stages one I start the outside I wont stop until its weather tight. My main concern is what I will do for the roof. I'm not sure how much someone would charge me to do a rubber roof on it.

oh I forgot to ask what is the VHT tape? is that the butyle tape for sticking down the siding? Is it me or does that seem sketchy? I know rivets will hold. I am not into making it a show winner or anything just looking for an RV that I can take camping or tow 15k plus and not be worried when stopping or if i will make it up the hill.

[Dragonslayer140]

The VHB tape is an extremely sticky double side tape used by body builders to fasten sheet siding to framing and itself. It comes in two thicknesses a thin on for sheet to sheet lap joints and a thicker one for sticking the sheets to the framing. Properly installed and you will destroy the sheet metal trying to peel it off. There are very detailed directions on how to prepare the metal and covering the installation, if not followed you will have joints coming apart. The tape also provided a barrier and thermal break between the aluminum and steel. There are several threads on this site that discuss the differences between using tape and or screws. Big thing to remember is the alum siding expands quite a bit and can and will produce some waves and wrinkles in the summer heat. the preformed metal studs and joists are quite strong, both the C shape and the Z shape are stronger than they appear, but only in one direction. they rely on the sheathing/siding products to give them lateral strength. I have designed many mobile office buildings for the modular industry with 11 ga. Z shaped joists and rafters. These support far more snow and internal loading requirements than a motor home will need. Aside from lower weight and cost, you get about 10% less voids in your insulation due to being able to insulate the framing cavities. It is still wise to use structural steel at the corners and framing around doors and large windows. the price of steel is very high and they charge a premium for the tubing. One would be very wise to listen to Blizz's advice on budget. you are combining RV with Big truck nothing for either of these is inexpensive. at my work we have to estimate materials for all types of buildings, and its still surprising what gets overlooked. If you can find something that meets your needs already built you will probably be money ahead, and far easier to finance. i have been looking for a good rig close enough to what I want that I could tear out the inside and remodel, but so far no luck. It does not help that I want a classic KW or Pete conventional with manual transmission. Most conversions are Volvo/Freightliner with the automatics. As far as the rubber roof, that is a easy project that you should not have any problem with doing your self. I have done two of my own RV's for a very reasonable price (less than $600 for my 30' class C.) First thing is to avoid any RV place for sourcing your materials. If you happen to have an ABC roofing dealer near you, they usually carry the Mule-Hide EPDM roofing (either .45 or .60 mil.), just order it about a foot or so longer and wider than your rig. They also have the water based glue to fasten it to the decking. Cover the whole roof, then cut out the openings for the vents and such, and fasten them down over the rubber. Eternabond micro seal tape then goes over all the joints and around vents. (This stuff sticks to anything in any weather forever..lol)

Dave

[blizzardND]

my Rumrunner gets 10-11mpg although it only weighs 19K and I don't tow more than an open 16' trailer

Racing junk has many trucks under 60K that would pull your trailer

you could not replace /build this truck for 80 grand:

1997 C7500 13' Toterhome For Sale


Volvos have great turning raduis, this truck will turn tighter than a dually pickup
Volvo Toterhome and Pace 40 ft. race trailer For Sale

this freightliner only has 200K you'd never wear it out, engine might be small for your stacker though.

You should get anothe 200 thous. miles on this big bad boy
Toterhome, Truck conversion, Race Hauler For Sale

needs water added, lots of truck for the money.
1988 Peterbilt Toterhome For Sale

blizz