Lorry's rolling cab

[balsamiq]

Hello there!
I am bulding a 4wd unimog style truck from scratch for a 1/10th scale chassis I bought some time ago. I need some advice with something;
I’m trying to replicate the truck’s dimensions as closely as possible. That means, I don’t want to raise the current bodywork too much to avoid touching the wheels on it’s maximum swing angle.
The truck looks more or less like this;

The rear box already allows enough travel space for the wheels when swinging, but the front axle doesn't…. I need somehow to increase the mudguard height at least for a centimeter. So I thought, It would be cool to let the front cab tilt sideways a bit when necessary, by attaching it to the frame using an axle, and a couple of springs to center it in position.
Is that a thing? Is there anyone who has done it before?
I’ve been doing some research, but the only thing I can find are servo powered tilting kits for semi-trailer tractor cabs, and doesn’t help me to solve some of the conceptual problems I’m facing; like, keep the cab from swinging excessively, or anticipate the cab tilting to avoid the tire touching it in order to start rolling...
Here’s a quick draft of what I am talking about;

Any thoughts?

 

[ferp420]

thats a comin issue and there are.some.comin fixes but there all compromises
1 cut fenters
2 limit suspention traval and or run the front suspention in drooop
3 smaller tires
4.just let the tires rub your not flexed out all.the time so it wont hurt much lol
5 try a narrower offset so the wheels tuck
im sure there are other options.too

on to the cab tilting idea im not gona say it wont work im sure if you spend enuff money and can.fabricate all the stuff needed to make it happen then it could work
just mounting the cab on zprings would make it look like a bobbel head going down the trail
if the cab is mounted to the axle.some how the cab would.be moving with the axle and rock back and forth as you drive
you could control the cab tilting with a servo somehow
in my opinion the hard part.would.be keeping the cab from floping around all the time and making the truck unstable

it would be interesting to see.for.sure

 

[mikemcE]

Real semi cabs float on the chassis.
What you trying would not work 1:1 as the linkages would have issues.

Not sure how to work thru realistically


Hang up and Drive

 

[OnTheTrail]

You can perhaps add an oil dampened shock (remove the spring if you already have springs otherwise) to the cab to stop the bouncing.

 

[OnTheTrail]

Not the same thing but an example of a tilting cab.

https://i.ytimg.com/vi/y70JfKQWfIc/maxresdefault.jpg

 

[balsamiq]

thats a comin issue and there are.some.comin fixes but there all compromises
1 cut fenters
2 limit suspention traval and or run the front suspention in drooop
3 smaller tires
4.just let the tires rub your not flexed out all.the time so it wont hurt much lol
5 try a narrower offset so the wheels tuck
im sure there are other options.too

on to the cab tilting idea im not gona say it wont work im sure if you spend enuff money and can.fabricate all the stuff needed to make it happen then it could work
just mounting the cab on zprings would make it look like a bobbel head going down the trail
if the cab is mounted to the axle.some how the cab would.be moving with the axle and rock back and forth as you drive
you could control the cab tilting with a servo somehow
in my opinion the hard part.would.be keeping the cab from floping around all the time and making the truck unstable

it would be interesting to see.for.sure

yep, Suggestions 2 3 and 4 are viable in case I don't succeed with the cab modifications first...
Actually, I am using smaller tires to sort the problem out, but it seems it's wearing small boots, if you know what I mean :wink:

Real semi cabs float on the chassis.
What you trying would not work 1:1 as the linkages would have issues.

Not sure how to work thru realistically

I see... I know it will be rather complicated to replicate a natural movement like that. I hope that looking for a single-plane roll instead of a complete hovering above the chassis would be simpler... Well, it's worth a try! I already have the attachments I did first to fix the cab on the chassis, so I case that doesn’t work, I’ll lose nothing more than some styrene

You can perhaps add an oil dampened shock (remove the spring if you already have springs otherwise) to the cab to stop the bouncing.

That’s actually a good approach! I think I’ll try that to sort the excessive bubbling problem.

 

[balsamiq]

Here’s a brief update regarding the project;

I took OnTheTrail’s approach; I bought 2 extra oil-dampened shocks, and mounted a chassis base where it is all supported. The mounting point was actually the original battery compartment, which is perfect to fit my setup since it has several holes meant to be used for screws and whatnot.
The cab is being held by 2 main anchor points at the transversal axle installed in the chassis, which are placed 10cm (4~ inches) apart from each other. This allows the cab to tilt.
After some iterations, here’s the setup it fits the best to both chassis and bodywork i what a spring/shock-absorbers position concerns;

Both shocks are sitting at 50% of its travel, so they can either compress and decompress without topping out. I’ve tried by filling both of the shocks with oil, but it gets too stiff, so I’ve just kept one of them doing that function, while the other is only acting as a spring to keep the cab centered.

The maximum travel of the entire cab side to side gives me more space than I originally needed. Now the question is, how will it handle offroad?

Cons of this project;
- The spring pre-load has to be adjusted if there’s any weight distribution change (like, taking off/putting in the driver figure from its place), or compensate for that weight change instead.
- More parts, mean more problems… I knew that long before starting planning everything up, but hey! if it were easy, we wouldn't be here
Pros of this project;
- Looks cool AF.
- There are not many rigs out there with this thing. (perhaps for a reason.. we’ll see...)

It is still a WIP feature; Next step is to attach the entire cab to the tilting support and finish with the cab’s interior.

 

[ferp420]

so how dose it move with the axle is it conected to it some how

 

[balsamiq]

so how dose it move with the axle is it conected to it some how

wel...
I haven't really figured that out yet.
My intention was, for now, to mount everything and see how it handles with a basic setup, and proceed to fix the "parallel axle movement" at some point further on.

I have a couple of ideas in mind tho, but I need to have everything in place to test those solutions, and check what pros and cons would have every approach.

 

[ferp420]

in my opinion this set up will make it more top heavy and when the cab tilts.its gona throw your center of gravity way off making it so tippy that any advantage you get will be waisted cause the truck will just tip over instead of rub the tire
but damb atleast your thinking ive never seen anything like this before so i hope im wrong
if you had some kind of computer controls you could use servos to adjust everything and keep it stable but even that wont help with tire rub

 

[OnTheTrail]

I'd look at putting a fixed "bump" rod from the top of the axle upward so that the only time the bump rod touches the cab is when and only when the cab needs to move slightly out of the way of the tire.

 

[mikemcE]

I'd look at putting a fixed "bump" rod from the top of the axle upward so that the only time the bump rod touches the cab is when and only when the cab needs to move slightly out of the way of the tire.

And a limit strap to prevent “launching”


Hang up and Drive

 

[Gula]

Mount the cab using these: https://www.ebay.com/itm/M3-M4-M5-M...p2349624.m2548.l6249&mkrid=706-127636-26712-0

I just got a couple for a Tonka winnebago build. I know, only 10 years late.

You could mount it with just 2 to get the wobble your after.

 

[balsamiq]

Mount the cab using these: https://www.ebay.com/itm/M3-M4-M5-M...p2349624.m2548.l6249&mkrid=706-127636-26712-0

I just got a couple for a Tonka winnebago build. I know, only 10 years late.

You could mount it with just 2 to get the wobble your after.

This looks exactly what I would have had to use in the first place ¬¬ I can’t believe I haven’t thought of it… Where were you three weeks ago? XD

I’ll keep it in mind in case the oil-shocks approach gets over complicated. Anti-vibration rubbers are easy to install, take little space and in the case I had to detach the cab, with only two screws is way easier/faster...

I'd look at putting a fixed "bump" rod from the top of the axle upward so that the only time the bump rod touches the cab is when and only when the cab needs to move slightly out of the way of the tire.

It is actually what I thought… but I have a couple of doubts about it, that will be sorted once I have the cab mounted (yeah… I haven’t done it yet... ) I have to make sure this rod doesn’t touch anything other than the cab in any other possible position while the axle is traveling. The other way I have in mind is to replace the pushing rod for a pulling string from the opposite side of the axle. In any case, it requires some testing.

 

[mash914]

If you could figure out a way to mount the bottom of the "cab shock" to the links, further toward the chassis mount, you could have a way to...encourage less movement of the cab relative to the axle.

For example, I'm not saying that there would be room, but if you could replace the front lower links with something like the rear lower links from the gatekeeper, you could mount the bottom of the cab shock to the middle of the link, and the normal shock still on the axle.

The geometry would, by definition, lift the cab less than the axle. You could adjust how much it affects it by relative locations and cab shock stiffness, stuff like that.

 

[Gula]

"Where were you three weeks ago? XD"

Probably in here,, browsing. Yeah,, I've got a couple og tricks left up my sleeve. a very neat way to mount the cab. I find it very over complicated functionally though.. What happens if one side of the mechanism fails?