Modifying Wheelbase

[soused moose]

I need to pick some of your brains here a little….

Here’s what I’m wondering about….
I want to cut approx ¾’s of my bus off ….slide the rear end forward, attach a new drive line etc.etc. And use it as a temporary tow rig.

I took a peek under my bus and noticed that the drive line was made up of two approx. 6 ft. long sections that have a universal joint in the middle.
I’m figuring that the joint in the middle is there to keep stress off the drive line if you hit a bump or something and the rig flexes up & down a bit.
Is that correct or is there another reason for that mid-point universal joint?

Where do you think it’s best to pick up a new drive-line ?
Am I going to have to have one built to fit ? (Manufactured)
Any phone numbers or websites to places you trust for this sort of thing would be greatly appreciated.

Next ,,,
Is there any actual formula that a person needs to take into account when you shorten the wheelbase of a rig?
I did a short web search, and all I could find was a lot of sites about changing wheelbases for sporting rigs or companies that produce dump trucks and the like.

Thanks so much,
Michael

[Jarlaxle]

The center bearing is due to the fact that a long driveshaft is very hard to balance--most trucks use one.

However, why not just start with a short bus?

[soused moose]

Jar Axle….
The reason I want to do this is I already have my bus….(the worlds most expensive Schoolie )
I live on an Island in Alaska where its hard to find small buses …so I want to use what I already have…
Thanks....
Michael

[J.B.]

HI Soused Moose , Here in the Pacific N.W. I have used Drivelines N.W. based in Seattle and various towns around this are with great success. If you can't find a website I will get you a phone #. On another note I am close to mounting the propane heater you sold me and the propane tanks.

Later, J.B.

[soused moose]

Hi JB….
Thanks for the info on Drivelines N.W. and good luck with your heater install…

At lunch yesterday (at my job) I called around to the few auto-mechanic shops here in Sitka to see if the could shorten up the wheelbase for me …and was told no.
I’m going to call the last one today. These guys work with heavy equipment…so there’s still hope.
I don’t have the tools , space or the knowledge to do a job like this right….so I’m going to have to fork up the cash and hope the mechanics know what their doing….

I’m finally getting started on our Trailer project…ordered 3-7000 lb Dexter trailer axle assemblies out of Seattle and they should get shipped up to me sometime next week…once I get notification their on the way .
I’ll order the wheels, tires etc. etc. from the same place…
It feels really good to start this project. I got the steel for the frame and a welder to weld it up in the works too…
This has been a long hard thing for me to figure out…I’m glad I’m finally getting down to doing it.

I’m really hoping I can use our bus …in a shortened version to tow with.
Even though I’ll be able to pull-out all the stuff I installed in Latcho Drom and use it in our trailer….I’d still like to keep the bus.
I’ve been chatting with a few guys through email who buy the big tractor trucks and convert them over to tow rigs for their big 5th wheel trailers …and they tell me that a Schoolie couldn’t tow a big trailer around.
There’s probably a little truth to this…. But at the same time I think there’s also a bit of snobbish anti-schoolie attitude going on too…so I guess I’ll have to find out about this for myself.

Michael & Millie

[J.B.]

Hi Guy's , I sure don't know why a lowly schoolie couldn't tow a trailer ? I know people down here that do it all of the time. If I can assist in any way let me know. I am going to tow one with my Crown.

J.B.

[soused moose]

I think given the hefty rear-end of schoolies….they should be able to tow a lot of stuff with no problems…
But , I’m not so sure about the size & weight of trailer I intend on building .
I figuring on something that measures out at around 38 feet long and will weigh at least 15,000 lbs when it’s finished.
So….my bus probably can pull something that big & heavy….but I’m wondering what my highway speed would be?
3-15 miles per hour????

Michael

[Skoolie BOBB]

I used to drive a truck carrying liquid oxygen to patients with respiratory problems. For some idiot reason, another drive wanted the wheel base shortened on one of our trucks. They took it to a company that puts truck bodies on frames and so on and it was done. It was my understanding that this was a common practice to modify the wheel base. In bad weather, driving that truck was like pushing a ball through the water with a stick.

But, will you have to modify the wheel wells? Sounds like a big, big project.

Herb in Utah--Flat nose Blue Bird

[soused moose]

It’s not really that big of a project Bob if you’ve got the right tools to work with.
Plus…I’m kind of used to working with steel and using saws to take sections out of our Bus so I could install the various bits and pieces…so it doesn’t spook me to cut the bus body off at all.
Having good tools really saves your butt for projects like this….
When I cut a section of the roof off so I could add on a second story for our daughters’ bedroom …on our Last School Bus conversion …I had terrible tools and not much knowledge on what I was doing.
I used a cheap $20.00 jigsaw & a hammer and chisel to do the work. I’m really surprised I still have a workable jaw from all the saw kickbacks I took in the face on that project.

But I don’t have the tools or the space to do the actual work on sliding the rear end and attaching the new drive line and such …so I’m going to have to find a local mechanic who’s able and willing to take on a job like this.
I’m not looking at any really drastic shortening up of the wheel base here…all I want to do is slide the rear end forward 3-4 ft. …which will give me a tow vehicle that’s large enough to carry some stuff in ….but not so large to make the combination of trailer & bus absurdly long.
Even if I was to leave the rear end where it is right now and just cut off the area of the bus behind the rear axles …I’d still be too big (length wise) for towing a large trailer.

There’s that guy who’s got some pics of his 5thwheelhauler over on the “other Site’…he left his rear axles in place and cut the back off the bus so he could tow a 5th wheel trailer around ….but because the bus is close to the same length as the trailer is …taking a corner with that thing is a bitch.
I don’t want to run into problems like that …and I don’t really see why a shorter version of our bus at around 18 feet is going to be hard to maneuver or control. (at least I hope not )
But I’ve got to do something here….
I ordered $3200.00 worth of axles , springs, wheels & tires which will arrive next week for our trailer project …plus I’m working on getting the steel together for the frame…so I’m committed to doing our new Rolling Home project….
I’d really like to use our Bus to tow the trailer with if at all possible…even though I can pull out all the stuff I installed in our bus to use in the trailer….The bus cost us $7000.00 here ….and after spending such an outrageous amount for a Schoolie (which I could never recoup by trying to sell her ) I really want to keep her.

Herb …the wheel wells on a Schoolie are just fabricated pieces that bus manufacturers install in a bus when they build one…that makes them removable . It’s not any easy part of the project, but it is doable. A person would have to a lot of cutting and refitting a new wheel well in their bus …for sure though.
But…I haven’t completely decided what type of body setup I’ll go for once the wheel base is shortened up.
Since our trailer is going to be an actual house with a peaked roof & wooden siding…I’m kind of thinking of cutting the bus body off right behind the drivers seat and just building a little house for the body that would match the look of the trailer…then building in new wheel wells would be a piece of cake.
I’d make them out of wood with galvanized steel inserts to keep the water from rotting out the wood.
Yup …Herb it’s a big project…but that’s why I like doing stuff like this.
It would be a lot cheaper for us to just buy a used motor home or trailer …which we’ve own and lived in a few times in our travels …but I always go back to buying a van or Schoolie to convert because I love building stuff.
I cant wait to start building the house part of our trailer…this is going to be a really fun project.!!!!
The nicest part will be good straight walls …which means I’m not going to have to make cabinets and walls to fit into a curved ceiling like a Schoolie has….that’s always been my least favorite part of doing a schoolie conversion.

[paul iossi]

I'm relatively new to the skoolie net, just long enuff to read thru the archives and mobilehomestead site very informative, interesting and thought provoking. It looks like my future includes a skoolie & trailer combo either a fullsize conversion bus and enclosed trailer or a shortened skoolie toter and a gooseneck enclosed trailerhouse with garage.
So much for my future, the past is equipment mechanic, welder, fabricater,that got lost in prototype engine development.

Anyhow to shorten your chassis is not difficult,just plan and measure carefully, decide how much you want to shorten the wheelbase, move the rear axle and suspension forward, shorten the driveshaft and cutoff the rear framerails and reinstall the bumper. Just bull work, the devil is in the details.

First consideration is that you need clearance to jacknife the trailer, max width 102" half of that = 51" plus _" clearance from the bodywork including overhang to the center of the kingpin, on a chassis this size you want the kingpin 1 or 2" ahead of the rear axle centerline so that the trailer weight is carried between the axles with the majority of it on the rear axle but some on the front to maintain balanced steering and braking.

Second= driveshaft length and u-joint angle, the factory has done the engineering on the maximum's so the easiest thing is to leave the rear shaft length alone and shorten or remove one of the intermediate pieces, if you can just remove 1 piece and get your wheel base you lucked out, if not then the next longest section gets adjusted to length and the crossmember and carrier bearing have to be moved accordingly. I think that I would not use a shaft less than 18 just from the ease of installation standpoint, someone has listed a westcoast driveline shop that can offer advice, the dynamics that effect driveshaft length are the torque twists the shaft and the distortion causes the shaft to whip resulting in catastrophic failure.

So it's time to measure and figure,draw some pictures and sleep on your plans.

Commitment; get the bus on a hard level surface, block the front tires, carefully remove the driveshaft after marking it with a permanent paint line lengthways so that it can be reassembled "in phase",disconnect and cap the brakelines. Measure and mark the frame for the new axle position"from the front of the spring hanger bracket to the new location" scribe your lines both sides front and rear hangers and the crossmember above the axle. Drill the rivets and chisel the heads off, jack the rear frame enuff to clear the suspension points 1" or so,move the axle forward by either rolling the tires or turning the driveshaft/pinion flange, lower the frame onto the suspension, align and clamp the spring brackets in place and drill new holes in the frame, bolt everything together with Gr8 nuts and bolts and hard washers on both sides, use a chemical lockwasher, try to find bolts with unthreaded shanks to penetrate the holes for the best alignment, move the crossmembers as required and reassemble the frame. cut off the offending frame overhang and install the bumper & taillights.

Brakes-I like brakes so if it was my rig, I would just replace the brakelines from the master cylinder to the flexhose @ the axle on general principal, bleed the hydraulic system, If it has air brakes shorten the air lines installing new hardware as required.

Shorten the driveshaft and install. disassemble driveshaft so that you are only handleing the section that needs to be shortened,clean well no dirt or loose rust, scribe a line lengthwise, measure the cutoff from the center of the weld at the yolk at the end with the smallest balance weights,wrap a stiff piece of paper around the driveshaft at the cut mark to get a square cut, scribe the line, cut with a cutoff wheel in the 4" grinder take your time accuracy really counts here, clean up the burs on the id with a file,do not chamfer the tube only remove the burs, now cut the tube off of the yoke, first mark the scribed alignment line with the cutoff wheel, go deep enuff in the yoke that you don't loose the mark, rethink: that slit thru the tube and into the yoke use a grinding wheel grind the weld flush with the OD and then carefully grind the until you can remove the tube, clean up the machined shoulder on the yoke probably 3/16" line upthe alingment marks, install the yoke, this will probably take some finessing since you don't have a lathe to help with alignment and pressing the assembly together, tack weld in at least 3 places after you are sure that everything is in alignment and square, have a helper turn the shaft as you weld it so that you get good penetration and even buildup.
Measure the location of the balance weights on the cutoff,remove them and install them on the newly shortened shaft, most imballance is in the yoke forging so you should be good to go, if you have a vibration go easy until you can get to a real driveline shop and get balanced.reassemble the driveline keeping every thing phased using the paint line and install in the chassis.

install your hitch and fab up a rear body

afterthought/disclamer--when shortening the driveshaft make sure that the welds are professional and high quality, preheat the forged flange and cool slowly do not quench, if you can have the shaft professionally shortened that is your best bet, the described proceedure will get you going in a pinch
frame length- leave 6"-12" behind the rear spring hangers for bumper and trailer hitch brackets, you probably want an 8' bed length minimum, but remember excessive overhang will cause turning interference with the trailer 48-51"from the trailer kingpin centerline is the absolute max length to be compatable with the standard 7' gooseneck length

[paul iossi]

OH yeah, I almost forgot you are going to want a good heavyduty 1/2" drill minimum, larger is even better and low rpm is advantagous, loop a piece of light 1/4" chain around the framerail and have a helper use a lever inserted in the loop to apply pressure on the drill while you align and aim it, it's a good team building, communication exercise that will really speed up the process and also save many aching muscles.

good luck

[paul iossi]

After going back and looking at the LATCHO DROM II site how is the rear body attached to the frame? Is it possable to unbolt it from the truck frame, jack it up and drive the bus out from under it? If so yuou could cut the body down to make your flatbed(cut off the top, cut the sides off above the wheel wells, remove the bus and shorten the frame, then trim the rear body so the wheelwells fit over the tires, install it back onto the bus, reattach the tiedowns to frame and then finish the top of the sides somehow. Inside the bed some joist brackets to drop in temporary crossmembers to carry longstuff will make you popular at the supply house/lumber yard, flat surface above the wheelwells and fifth wheel so someone can load you with a forklift or lay sheetgoods flat, good tiedown points would also be a good thing.
It also looks like your truck boxes could be installed ahead of the rear tires and either hung from the body or mounted on some angle iron L brackets bolted to the frame.

Your fifth wheel hitch should be bolted to the truck frame not the body

[soused moose]

Thanks Paul …
I wish I had the option to just un-bolt the back section and pull it off the frame. That certainly would make my life easier.
But there’s no place here on the island to get rid of the body (as is).
Our dump won’t take it…so I’ll have to whip out my hateful sawzall and cut her up into pieces the dump will take.

Since my little house is the size it is ….I’m not going to move the rear axle forward . I’ll leave it where it is and cut the frame back close to the axle hangers.
For the bed part I’m going for a frame of steel with pressure treated deck lumber for the trucks deck.
I’ve been checking out the MDT & HDT forums and have gotten some really good ideas for building my deck.
Thanks I had planned on hanging my boxes below the rear deck.

All of that has to wait for better weather ,were having some of the worst storms people have ever seen here ….so I decided no more foolish stuff like trying to work outside in bad weather.
What I am working on right now is running around town asking people if I can crawl under their trailers to take pics of their frame.
The steel I needed for the 20 foot main center frame section of our trailer project got delivered last week ..so I’m getting all my numbers right , because I want to have a welder put her together soon.
Bought a good chopsaw and drill press setup so I can do some of steel work myself which should save us some cash here …
Thanks again

Michael

[paul iossi]

Some of the commercially built 5th wheel sites have blowups of how their frame/floor systems are laid out, i'm not saying that that is gospel for construction but it's a good place to start.
I'm thinking that I'll recycle a mobile home frame and double up the crossmembers @ 2' max spacing. These frames are unbelievably flexable at the horizontal perimiter without a floor deck, the strength is in the verticle direction, and the diaphram /skin adds the rigidity.
Analogy; an enclosed semi trailer has no frame, it's strength is in the lengthwise rails and connecting diaphrams/skins, a flatbed trailer has a significant frame,with camber, and no sides.

[Elliot Naess]

Hey, Soused Moose; try cutting up the body with cut-off blades like your chop saw,
rather than the sawsall. Cutoff blades are available for skil saws and angle grinders.

[soused moose]

Thanks Paul , on our website we have links to some info on frame building/design. I’ve been researching this for a lot of years …the best resource I’ve found for seeing how a more conventional 5th wheel frame is put together is Stan Millers site. He took a very good series of pictures of his Automate 5th wheel being built.
http://www.stanmiller.info/pages/automate/am-intro.html

Another great Resource on this is Glen-L ….they have very good and very affordable plans for building a travel trailer or 5th wheel.
http://www.glen-l.com/campers/glenlrv.html


For awhile ,I thought about just buying a commercial flatbed trailer and building on that…then after a good bit of research , it hit me a School bus which is essentially a MDT truck has its limits to how much weight it can carry or pull.
What I’ve learned in my research on this is its very important to take into account how you’re going to tow your trailer around.
Since a commercial flatbed has its wheels located at the rear of the trailer …much more weight is placed on the hitch then you see with more conventional trailers, but they don’t care about that because they typically haul these trailers around with Heavy-duty trucks..
You can pick up other commercial trailers which have their running gear located in positions that don’t put so much weight on the hitch …but you’re still running into the reality that the frames were designed for a different application …so they’re either over-built or under-built.

The word over-built definitely applies to using a Mobile Homes frame.
A mobile Homes frame is made up of relatively ‘huge’ I-beams and never was designed to travel with. It was meant to be moved from the factory, to a sellers lot …then moved somewhere and set up for a semi-permanent dwelling.
So even if you pull the house off the mobile home and add some extra framing to stiffen it up …you’ll just wind up with a very heavy overbuilt built frame.
I don’t think you’d get very far trying to haul it around with a School bus or MDT truck …you’d need an HDT.

So this is why I’m going the more expensive route of building the frame from scratch . We’ll have a frame designed to be strong enough to carry the house ….but isn’t too heavy or over-built .An over-built frame would cut down on how much weight we could carry.
Will our bus be able to tow the weight our trailer most likely will be … I really don’t know?
It could turn out to be a situation where I’ll have to give the bus away and buy an old Mack logging truck.


…………………………………………†¦â€¦â€¦â€¦â€¦â€¦â€¦â€¦â€¦â€¦â€¦â€¦â€¦â€¦â€¦â€¦â€¦â €¦..
Thanks Eliot ….
I used a cut-off blade in my framing saw to take out the floor section and it worked great.
I am tempted to use that method to take the roof off. That’s the only place where I hate using my sawzall …the sides don’t bug me because you can lean into the saw and don’t have to worry much about kick-backs.

[the_experience03]

Ok...I'm a little lost on what your final plan is here (I'm still lost on the plans for my own bus), but a word of caution just from reading some of the posts. When you get the driveshaft shortened, you're going to have to be exremely careful about the angles from the carrier bearings. The angles are precisely measured for the factory suspension genometry and obviously moving the axle forward is going to mess up the hypotenuese (did I spell that even remotely correctly?) which happens to be the driveshaft length. The end result could be some pretty horrible vibrations, even from a perfectly balanced driveshaft. The solution could be one of three things as far as I see it....

1. Recalculate all carrier bearing angles and adjust as necessary. This is a whole lot of work

2. Run a constant velocity joint off the back end of the last carrier bearing. This is likely expensive, but easy

3. Eliminate the last carrier bearing and run a single piece driveshaft from the next rearmost carrier bearing. You still might have to mess with the carrier bearing angle and driveshaft whip will become an issue unless you use some thick wall tubing, but this is what the guys with lifted trucks tend to use most frequently.

[soused moose]

Because I built the house section larger than I originally thought I would … I’m going to leave the rear axle as is.
But thanks anyway … I appreciate the help and info.

[paul iossi]

Driveshafts, U-joints, carrier brgs. -- multipiece driveshafts are used to eliminate long driveshaft sections that torque-up, distort and then start to whip which creates an imbalance condition, the U-joint angle is kept at approximately 1 degree per joint untill you get to the last shaft where their are joints at both ends that are operating at the same angles and therefore canceling the harminics that are created when you exceed 1 degree of angle, also if you do not have some angle in a u-joint it will develope harmonics/vibration. Carrier bearings do just that they carry/support one end of each section of driveshaft until you get to the last piece with 2 U-joints that goes to the axle.
I hope that this helps clarify the previous post on wheelbase/driveline modification.


Soused Moose;
thanks for the websites and reply to my thoughts on frames etc I highly recommend that you get ahold of a steel company's full line catalog and reference book, it will list standard shapes and dimensions of steel along with weight per foot, I'm looking at 10" Ibeams @25.4 and 35 lbs/ft and then their is a 10" junior I beam @ 9 lbs/ft which is a lot stiffer than 1/4 X 6 X 2 @12.2 lbs/ft, upon closer inspection I think that you would find that mobile homes are built on jr I beams and if you set your triaxle suspension between 1/2 and 2/3 back on your frame it will balance well and pull like a dream. The majic formula for a 5th wheeler on a pick-up is 20-25% tongue weight on the truck, your MDT has a rear axle/suspension that is rated at approx 17,000lbs and is going to be real happy with 10k lbs or approximately 1/2 of your gross trailer wt.
Thats another opinion, for whatever it is worth. BTW how did you make out with welding lessons and congratulations on the chopsaw and drillpress.

Happy New Year

[soused moose]

Of course this is going to take some time , because I don’t have any money to be doing something like this …
Even so ,I figure I’ll mostly have the trailer frame completed by mid-late spring. . I already have all the Dexter axles , springs , hubs ,wheels tires etc.so that’s a done deal. …the only thing I need is more steel , which I’ve been getting from Metal supermarkets in Seattle who put this bunch on a barge and shipped it to us. ( we already have the 2-20ft sections of 2x10 in storage)


I’m using ¼ rectangular steel rather that Channel or I-beams , basically because after chatting with Stan Miller, that guy who took those pics of his 5th wheel being built … I figured since Automate is considered a top of the line manufacturer I’d stick with a sure thing.
For the center main frame I’m going for 2x10 main runners, with 2x8, 2x6 & 2x2 cross members …
If everything works out like it should, some time next week the welder will start putting it together, once he welds it up we’ll flip it over weld on the axle/spring hangers …put the running gear on and tow that section to storage.

Then I’ll get the steel for the rear frame section and the front, have him weld those sections up and store them until the weather gets better.

Then we’ll weld them to the main frame …pop on our great Trail pin box and there you go…
Once that’s done I’ll use the Chop-saw ( didn’t get here yet) to cut up the various angle-iron pieces we’ll need to have welded to the frame then call the welder up to install them.


I have emphysema so the welding class didn’t last as long as I would have liked…but I did learn how to use a cutting torch which was very cool and fun.