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Guys, let me jot down my understanding of various types of chassis commonly used on vehicles with ladder frame construction. I will describe various types of chassis commonly used today along with their pics, also i will try to explain various types of cross members commonly used today along with their pros and cons. Basically there are three types of chassis systems:-

1. Uniform cross section chassis
2. Variable cross section chassis
3. C in C chassis construction which is a mix of 1 and 2.

1.The first pic shows a tubular construction(circular):-This is mainly intended for low load applications with low structural rigidity,the advantage of it being it is light and easy to manufacture (as it is a type of
uniform cross section chassis)


2.The second pic shows a uniform cross section chassis:-This is used mainly for long members which are generally high load carrying, this is easy to manufacture with low tooling investments, the only disadvantage being this adds to weight as the tooling uses a uniform cross section even in places where a smaller cross section can suffice.


3.The third pic shows a variable cross section chassis:-this is required for long members which require good bending stiffness, this leads to a complex and expensive design but with reduced weight when compared to type 2 mentioned above.


4.The fourth pic shows a "C in C" construction which is used for long members which require high stiffness this necessitates lots of tooling with a sacrifice on dimensional tolerances, this gives an added advantage of reduced weight by using variable cross sectional long members (now you must have understood why Thar incorporates a C in C upto the engine mounting brackets.)


5.The fifth pic shows a rolled uniform section:- this is used for long members of pickups and trucks because it is easier to manufacture.


6.The sixth pic shows a formed variable section:-this is used for long members requiring high stiffness and rigidity the only disadvantage being it required high amount of tooling investments.


Next is the type of cross members, they are basically of two types open and closed.
1. Open cross member (pic 7):- These are basically required for torsional rigidity and give an advantage of reduced weight the only disadvantage being cost.


2.Closed cross member (pic 8):- this is a frugal version for obtaining torsional rigidity,the cost is lower so is the torsional rigidity when compared to open type cross members.


Gurus please correct me if i am wrong somewhere, also i would request other forum members to share any useful information
(if any) on this topic.

PS-Mods i dont know if this is right thread to discuss technical details of chassis, however i felt the need after seeing the responses in the thread related to C in C sections

Spike:)

Dear spike,
Thanks for the valuable info. clap:Majority of us here had impression that tubular chassis was tougher but it seems it is used for light weight and inexpensive construction.

Then can we safely conclude that Gurkha's chassis is not as strong as Thar's? If tubular chassis is not strong then why is force motors using it even on its pick up versions?


Tell me one thing, i read this somehere, Bolero strom/ Thar's chasis is a fusion between C in C and box section. Scorpio has complete C in c section.

Why was this path chosen? In the interests of cost?


@Arka- Manufacturers POV and consumers POV make up for win win situation in most passenger vehicle cases. Consumers are ready to pay for that extra cost for comfort and handling. Thats why solid axles are disappearing even in hardcore 4wd's. Dont be surprised if Army also opts for Thar once BSIV for Army vehicles kicks in. They just dont have choice at this price braket baba.:-)) We are not able to digest IFS, future generation 4wd's like AXe have all wheel independent suspension (without diff lock as std. equipment:Frustrati) and has a monocoupe chassis. So its like this unfortunately; Solid axle front and rear suspension=old world charm!

Vinod,

Thanks, i cannot comment about the gurkhas chassis unless i see it, can you post some underbody pics of this vehicle (if you have it), regarding chassis of Bolero storm/Thar only Behram Sir can tell you regarding this, what i can say is, it is possible because the rear track of Thar as mentioned in the brochures is same as boleros and manufacturers in the name of "standardisation" use a mix and match of two or more platforms. In this case only Mr.Thar can tell you what is in store, also it would be interesting to know the level of standardisation M&M have achieved through Thar.

Spike:)

Could you please explain the above in a bit more detail.

I dont think the answers/conclusions are as simple as that.

I think the operative terms are strength per weight, strength per cost (I couldn't think of a better phrase) and suitability/ acceptability for the job.
And cost has two components - fixed (tooling, manufacturing methods/ infrastructure) and variable (mainly variable). There is no such thing as no compromise engineering. The trick is in making the right calls.

The tube is an engineering marvel. Simple, elegant, frugal in use of material, when forces are uniform in all directions. When it is not so, it loses its charm. Thats why we land up with I beams, and C sections. If we now factor in that loading is not uniform along length, we can further refine the design, landing up with non uniform crosssections, which reduce material without sacrificing strength.

AFAIK, the biggest problem with ladder frames is torsional rigidity.

I might be totally wrong, and open to education!

Regards
Sutripta

the open type cross member is manufactured through hydroforming process whereas the closed type cross member is manufactured through extrusion process, the microstructure/grain properties (internal structure of metal) obtained through hydroforming are better hence providing better torsional rigidity.

OT- sorry for being a too technical

Spike:D

Hi,
Thanks for the explanation.

AFAIK, one can use any number of different methods for forming, hydroforming being one of them. But that is a manufacturing process, and we are talking design, and so I think somewhat besides the point. (And totally OT, isn't hydroforming an accepted method of making motorcycle silencers, which are essentially shaped tubes). I still am in the dark as to how the nature of a crossmember, open or closed, majorly affects torsional rigidity.

Not at all! Actually calls for celebration.

Regards
Sutripta

Dear Spike.. this is a nice thread.

All this time I only knew of C-section & box- section chassis types. (+ Force motor's tubular chassis)

SPIKE ARRESTOR,

Thanks! This is a superb thread!

Please be as technical as required - we will only learn more in the process.

Do keep the info coming.

cya
R

Quote:

Originally Posted by SPIKE ARRESTOR (Post 1694102) Thanks, i cannot comment about the gurkhas chassis unless i see it, can you post some underbody pics of this vehicle (if you have it),

cpics:

new a 4x4 gama chassis (similar to gurkha?:confused:)

That does not look like a gurkhas chassis, it looks like a pickups chassis

Spike

interesting discussion going on here.hey thanks spike for adding to my knowledge.ill keep a check for this thread.

Jeepster, why have you put your logo on Ramchandran's images? Do you know that he is a member here?

Spike, that chassis belongs to Judo, that is the LWB Gurkha.

See here: Judo

Samurai you are correctagree:,those outriggers look huge,that is one reason why they have been reinforced with huge gussets to counter shearing loads originating due to cantilever action

Spike

i didnt knew that he is member here.
(i downloaded them from anther web site)

about the logos , i just used them as i always do.stupid:
there were no bad intentions behind them.:Frustrati

All sections whether tubular, C sections or box sections can be equally tougher depending on the size, thickness of the material and type of material used. The size and shape of the long member are based on bending stiffness, torsional stiffness plus factor of safety added to it and packaging of vehicle aggregates as targeted in the design stage.



I think (need to confirm the same)the Scorpio and Bolero Long member vary in height along the length of the vehicle, which is a general practice. The height of the Long Member at various places along the length of the vehicle depends on the bending and torsion stresses in induced at that particular place. Such varying height long members can be either produced by Hyodro forming, but is expensive. The other method is by clubbing two separately formed components (example: C in C).



The chassis image shown (Gurkha) is Tubular one. It may be used for various reasons viz. The Long member seems to be too long and no press could have accommodate a die to form such a long Long Members. Hence a tubular Long Member is used which can be bent easily on pipe bending machine. This process is cheaper too.