Ship of Fools - questions about dual Axel's and tires

OneOfHam · 10-01-2019, 09:40 AM

Hello, this is going to be the build thread for my bus, I'll update it when I get more information or as plans u fold or whatever but for now, I'm going to use this page for questions about one of the main things I wanna do. Eventually. It needs other work first like the floors and the clutch, but I really want information on how I'd do this.

So I've been thinking for a while now how awesome dual axel trucks are, especially for off-road applications, in example like the big 5 ton military flatbeds and the good ol deuce and a half.

I have a decommissioned fire bus used for taking cut crews down the bad logging roads in national forests and whatnot. It's lifted up, and has a Detroit locker in the back. it's also a 34 footer and the missing 6 feet are out of the middle so it's got a decent wheel base as well.

Now this is just purely hypothetical, at least so far, but I was thinking if I split the distance of my rear axel, moved it, and added a second one with another locker, it'd both shorten my wheelbase further and make my back end stick out less. I also have room I think to comfortably add another 2 inches to the tires, and I'd like to do it for the added spacing underneath for off-road once again, but I don't know how much taller I can get without reaching critical mass as it were.

I already know that it's an ambitious, expensive, complicated idea, I'm just fishing for practical advice about how best to go about doing it, if I wanted to do it, and what I should expect to have to do. I like the idea and think it'd look cool as hell to boot, and I really like off-roading, it's part of the reason I got this bus in particular

musigenesis · 10-01-2019, 09:49 AM

I think this idea would work better if you used Photoshop.

brokedown · 10-01-2019, 10:10 AM

I guess the first question is: why? What are you trying to achieve with this modification? As you've admitted, it's not a trivial change. When big trucks have more axles it's for increasing its weight capacity. Short of filling your bus with water, you'd have a tough time hitting it's existing capacity. It won't really change the reality fo being a school bus if you try to go off-road, your front wheels will push into soft stuff and get you stuck as quickly with 2 drive axles as it does with 1.

OneOfHam · 10-01-2019, 10:22 AM

Well I've seen firsthand a few crazy off-road vehicles this year, straight mad Max inspired, and part of it is for aesthetic I will admit. But more than that, I've seen vehicle with double duallys Absolutely tear through some trails. Like I said it'll make my wheelbase both shorter and make my back end stick out less as well, plus more points of contact? It's not 4wd although if it'll really help I'd like to make the conversion anyways. I think front wheel drive and two sets of duallys will get me almost anywhere

OneOfHam · 10-01-2019, 10:27 AM

Well I've seen firsthand a few crazy off-road vehicles this year, straight mad Max inspired, and part of it is for aesthetic I will admit. But more than that, I've seen vehicle with double duallys Absolutely tear through some trails. Like I said it'll make my wheelbase both shorter and make my back end stick out less as well, plus more points of contact? It's not 4wd although if it'll really help I'd like to make the conversion anyways. I think front wheel drive and two sets of duallys will get me almost anywhere. It's not necessarily about weight, but just sheer off-road accessibility. Like I said, I've seen admittedly shorter vehicles like a 5 ton for instance absolutely tear up some extreme trails, and I'm not trying to take the bus anywhere too crazy, but it'll definitely help me get around I feel. But then again my opinion is based off of observation, not hands on experience, hence my questions here.

Booyah45828 · 10-01-2019, 10:51 AM

I'm with brokedown.

The only reason to add dual axles is to increase the weight capacity, and if you need dual axles, the frame is likely not strong enough for it.

Those 5 tons tear up trails because they're driving on every wheel. They would do just at well if they eliminated one of the axles in the rear.

The only way I could see it being better on trail stuff is for less tire compaction in the sand and soft soils. It would actually hurt traction in slick or icy conditions.

You have to realize, that in dual axle vehicles, the tires will scrub to some extent, which isn't really desirable either.

I think with the locker in the rear, you'd be surprised at how good you'll be for traction. I mean, it was good enough for the fire department on logging roads.

peteg59 · 10-01-2019, 11:05 AM

To add more moving, critical, mechanical parts to your drivetrain might be a colossal mistake.

Unless you totally rebuilt the dual rears there are now twice the moving parts that wear out and need correspondingly twice the corrective and preventative maintenance during their service life.

Never seen a dual axle powered rear bus like that. Some Crowns were dual axle rear, but the rear axle was not powered.

Would be different when done, but as already asked, why???

SolomonEagle · 10-01-2019, 11:47 AM

Buy a 6x6.. put yr bus body on it.. done!

brokedown · 10-01-2019, 12:13 PM

If you want something good at off-roading, get something based on the M35 6x6. Of course, it will top out around 50mph and you'll have to swap 3 different axles to change that!

https://en.wikipedia.org/wiki/M35_se...x6_cargo_truck

SolomonEagle · 10-01-2019, 12:27 PM

Quote:

Originally Posted by brokedown

If you want something good at off-roading, get something based on the M35 6x6. Of course, it will top out around 50mph and you'll have to swap 3 different axles to change that!

https://en.wikipedia.org/wiki/M35_se...x6_cargo_truck

Get the m939 5ton with the Cummins 8.3 and Allison 643!

OneOfHam · 10-01-2019, 05:37 PM

Ok so scratch that then I guess it just looked super badass in my head. Feasibility and practicality dictate no. Another question I have, is how complicated would it be to add a drive line and power my front wheels, and if at all possible on top of it, converting it to 4x4?

peteg59 · 10-01-2019, 05:51 PM

Just because most of us have never taken on such a project should not discourage you IF you have the $$ and stamina to take it on.
It would be interesting to witness such a transformation, no matter the practicality of the end result of the project!

Jolly Roger bus 223 · 10-01-2019, 06:05 PM

load of work
load of time to find the correct donor
load of money when you do find the correct and know works donor
money to get it to you
time to make it happen
money to make it happen
front end and rear end are probably going to be wider even with a close donor which means new spring perches
will the drive shaft line up
different drive shaft connections
differnt transmission output shafts
figure the proper angle of the dangle between the 2
find all that mess and buy all the pieces
find a damn good driveshaft shop. and ask for the recommened u-joints for your angles in the driveshaft from your driveshaft shop.
OH and you should know your driveshaft angle before you ever take it there shopand if they dont ask i would question there work?
next is and i am sure you know this and is why you want to go to such extreme is because it doesnt matter how many rear ends you have or front axles you have cause once you bury to your axles your done regardless of your body lift.
i know you mentioned taller tires but i grew up burying tractors and not for fun either.
one the grounds and the next its not?20\30,000 in a small foot print aint fun to get out of mud

Gilligans Land Yacht · 10-01-2019, 06:06 PM

Quick answer from a long time lurker. Many electric company bucket trucks run all wheel drive with a single rear axle. They can be had at auction, then swap parts under your bus. May have to swap motor and transmission, but there is no problem that enough time and money can't fix.

Jolly Roger bus 223 · 10-01-2019, 06:26 PM

Quote:

Originally Posted by peteg59

Just because most of us have never taken on such a project should not discourage you IF you have the $$ and stamina to take it on.
It would be interesting to witness such a transformation, no matter the practicality of the end result of the project!

i was busy posting while PETE was and i dream about an endeavor for my bus and the closest i have come is a linemans pole or service truck cause they are 4 wheel,highway geazr to a point and off road with a transmision that has a PTO that runs an onboard generator and hydraulics that could be repoursed for on board hydraulics like a jack leg at each wheel a lug wrench and whatever tool you want to make room for.
double axle 2 speed rear end with the right donor
alot heavier rating than a bus for rear ends and front and almost everything

Ronnie · 10-01-2019, 07:03 PM

A lot of work and money but can be done. 4 wheel drive that is. Certainly a coolness factor to it. But is it worth it from a practical stand point? I would have to say no unless you plan to go extreme off road, and then getting stuck without support vehicles could be a real problem. The locking rear is a real plus, I do have one in my bus. To be truthful sinking in soft ground/sand would worry me more, and once sunk you will need a really big wrecker, not just 4 wheel drive.

So coolness and a little more off road ability might be worth it to you, if so go for it. Otherwise be happy with it as is. Maybe bring some tire chains, that will do a lot in mud or snow.

ism minerals · 10-01-2019, 08:33 PM

Quote:

Originally Posted by Ronnie

A lot of work and money but can be done. 4 wheel drive that is. Certainly a coolness factor to it. But is it worth it from a practical stand point? I would have to say no unless you plan to go extreme off road, and then getting stuck without support vehicles could be a real problem. The locking rear is a real plus, I do have one in my bus. To be truthful sinking in soft ground/sand would worry me more, and once sunk you will need a really big wrecker, not just 4 wheel drive.

So coolness and a little more off road ability might be worth it to you, if so go for it. Otherwise be happy with it as is. Maybe bring some tire chains, that will do a lot in mud or snow.

I can tell you from experience getting heavy stuff stuck sucks with out the proper rescue equipment.

Brad_SwiftFur · 10-02-2019, 01:27 AM

Not mentioned is that with tandem rear axles, unless they have a lot of articulation, I've seen road tractors get "stuck" in rough gravel parking lots. Even with the "power divider" locked in, many still have open differentials and when you get opposite corners "high-sided", you end up with 4 tires spinning, the other 4 carrying the weight, and you're not going anywhere.

To solve/prevent this, you'll need locking differentials (at least one but both is better) and as mentioned above, unless you really need the extra weight carrying capacity, tandem axles will end up being more of a liability off road than a help.

Seriousracer · 10-02-2019, 08:17 AM

You probably won’t find any pass through axles with a locker in non military applications.

It would be cool

Follow your dream but like was siad before
It will be some work.

OneOfHam · 10-02-2019, 10:27 AM

Yeah it is something I wanna do eventually, and will, but maybe to a different bus and maybe after a few more years. This is my first bus and I'm just getting all the ideas out there and seeing what sticks, not unlike monkeys throwing **** at a wall.

Ok so next questions lol. What if I just added a drive line and made it awd?

Would that make it natively awd, or would it be on a rocker switch or something and I'd switch between rwd and awd?

Also, if I do this conversion only, would I hinder myself from making it 4x4 in the future? Should I buy a kit or something that supports 4wd as well as awd but not install it yet, just so that it's ready when I'm ready? Is this even a thing? Like I said, I'm brand new to this.

Also, I can comfortably add up to at least another 2 inches to my tires, but don't know what sort of center of gravity related issues I should expect, or the best way to counter them, aside from just weighing it down, obviously.

Thanks for the information this has been invaluable, love this forum.

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