[offroad_maniac]

Attached here is a pic of M&M chassis having K-Member & Fuel tank attached.
The old jeep chassis were great in terms of simplicity & strength for that time & till. They are easy to paint from the inside as well so that Rust can be avoided , hence the longer life. This may not be possible with Modern Box section chassis.

1. BTW, Can anyone compare the similarity between chassis of below vehicles:
Bolero
Invader/ Stiker
MM550 NGCS

2. Are the Invader & Striker chassis same as MM550 NGCS

3. Is the thickness of Bolero chassis, same as Army NGCS?

4. Is there any difference in chassis thickness amongst various Bolero Model (Eg. Old GLX vs SLX vs DI vs Storm-VLX)

Please reply or PM

[SPIKE ARRESTOR]

@offroad maniac thank you for the pic, your pic clearly gives the answer, you can see 2 holes of the K member here, these are used for mounting the pintle hook, i believe there must be 2 more with welded nuts on the chassis (IIRC the hardware is 1/2" nut with 14 TPI), newer vehicles do not have the K member due to two reasons:-1. The rear cross member is different 2.The orientation of the exhaust pipe at the rear overhang area is different.
Answers to your questions-
1. Bolero, Inavder and MM540/550 are of different WB, there are similarities in a few cross members.
2. Invader and Striker chassis is completely different from MM550 NGCS. 3. All NGCS chassis have 115*60 mm sections with a thickness of 3.6 mm. 4. Chassis thickness as mentioned above is same for all bolero models (3.6mm) however other dimensions are different depending on the dress level offered. Hope this clarifies.

@Vinod is your Jeeps tailgate hinged at the left side (opening from right)?

Spike

P.S. Nice knowledge sharing session going on guys, keep them coming in

[Sutripta]

Originally Posted by SPIKE ARRESTOR

...cross bracing is done to improve the torsional rigidity of the chassis i am attaching a pic for this.

Spike

Hi,
How does MM measure torsional rigidity? End of chassis rails, or hubs? Reason why I'm asking is that we seem to be on totally different pages on torsional rigidity.

Regards
Sutripta

[SPIKE ARRESTOR]

Hi Sutripta,

Yes we do measure it, infact there is a test setup specifically for this. The chassis is kept stationary near the rear axle and a torque applied about the front axle, then dial gauges are placed to find the deflection of the chassis, this is done for both clockwise as well as anticlockwise moments, this is what i know.isn't it correct? please share your valuable thoughts on this

Spike

[offroad_maniac]

Originally Posted by SPIKE ARRESTOR

@offroad maniac thank you for the pic, your pic clearly gives the answer, you can see 2 holes of the K member here, these are used for mounting the pintle hook, i believe there must be 2 more with welded nuts on the chassis (IIRC the hardware is 1/2" nut with 14 TPI), newer vehicles do not have the K member due to two reasons:-1. The rear cross member is different 2.The orientation of the exhaust pipe at the rear overhang area is different.
Answers to your questions-
1. Bolero, Inavder and MM540/550 are of different WB, there are similarities in a few cross members.
2. Invader and Striker chassis is completely different from MM550 NGCS. 3. All NGCS chassis have 115*60 mm sections with a thickness of 3.6 mm. 4. Chassis thickness as mentioned above is same for all bolero models (3.6mm) however other dimensions are different depending on the dress level offered. Hope this clarifies.

@Vinod is your Jeeps tailgate hinged at the left side (opening from right)?

Spike

P.S. Nice knowledge sharing session going on guys, keep them coming in

Thanks Spike for the answers.
I think the main reason for K Member was to provide stiffness + to distribute stress uniformly during Towing operations. This is can be achieved through stiffness & strength of NGCS rails

[SPIKE ARRESTOR]

you have hit the nail on the head, that is exactly the main reason it was provided, also pintle hooks were mounted on an "Angle Plate" which acted like a washer and distributed the drawbar load to a greater area.

Spike

[Sutripta]

Originally Posted by SPIKE ARRESTOR

Hi Sutripta,

Yes we do measure it, infact there is a test setup specifically for this. The chassis is kept stationary near the rear axle and a torque applied about the front axle, then dial gauges are placed to find the deflection of the chassis, this is done for both clockwise as well as anticlockwise moments, this is what i know.isn't it correct? please share your valuable thoughts on this

Spike

Hi,
OK, we are on the same page. So how does X-bracing help in torsional rigidity. I mean any form of bracing will add some rigidity (along with weight) but these do not really address torsional rigidity. Or do they? What do your test results show. Also, do you just check static deflection, or also measure frequencies?

Regards
Sutripta

[SPIKE ARRESTOR]

@Sutripta cross bracing although adds to the weight but deflection of chassis in that area vastly improves, you can check this in a CAD/CAE simulation, i don't have test reports to prove this, static deflection and vibration frequencies are measured, also the road load data collected can be simulated through various test/simulation rigs.

Spike

[Sutripta]

Originally Posted by SPIKE ARRESTOR

@Sutripta cross bracing although adds to the weight but deflection of chassis in that area vastly improves, you can check this in a CAD/CAE simulation, i don't have test reports to prove this, static deflection and vibration frequencies are measured, also the road load data collected can be simulated through various test/simulation rigs.

Spike

Hi,
A number of thoughts. Most really off-topic.

First of all, preface every statement of mine with a AFAIK, and IMHO.

A simulation is only as good as its underlying model. Just because one can compute to ten decimal places does not mean it is relevant, or even correct. Normally one simulates because one cannot solve analytically. This also results in a model with simplifying assumptions. Which is why refining the models, and checking it against the actual is a never ending process. The simulator is just another tool, not god.

Having said that, the ladder frame, even with varying cross-sections etc. is fairly easy to model and simulate. Any structural analysis package worth half its salt should be able to handle it easily. Only question becomes the joints. Are these absolutely rigid, or like ball joints, or something in between. And how accurately does the model represent a real joint.

For torsional rigidity, one needs depth, something which is sorely lacking in a ladder frame. A X-brace adds huge strength in the plane (it prevents a rectangle from becoming a diamond), but little to torsional rigidity.

It will be interesting if you run some designs through your system, and let us know the results.

Regards
Sutripta

[SPIKE ARRESTOR]

@Sutripta well said, but when you say "Normally one simulates because one cannot solve analytically" i tend to disagree that, one tends to simulate only because it cannot be analyzed. Modern simulation tools are moving away from archaic methods of modelling a system and then applying boundary conditions to simplify complex mathematical functions inorder to achieve the results, this leads to lessen the co-relation between the CAD data and the actual product, at present real time road load data obtained is fed back during simulation to co-relate with actual test results on the vehicle, this reduces Product development cycle time considerably.

Spike

[Sutripta]

^^^
Hi,
Totally (Mods- need a smiley showing head scratching!)

However, rather than getting sidetracked into CAD/ CAM/ CAE, differential equations and boundary values, etc. etc. should stick to the topic under discussion:- chassis design.

It would be interesting if you could run the original CJ chassis through your CAE packages, tweak the designs using gut feel, run it through your system again, and share the results with us.

Regards
Sutripta

[SPIKE ARRESTOR]

Hi Sutripta, there was a typo in my post#55, i repeated the sentence "one tends to simulate only because it cannot be analyzed" , sorry for causing confusion

Spike

[ex670c]

Hi Guys,

I would request Sutripta and Spike to explain to the Lay man;

i) Torsional Rigidity

ii) Effect of Cross-Members (Tubular/X/K) on Chassis.

Regards,

Arka

[headers]

Originally Posted by SPIKE ARRESTOR

"Normally one simulates because one cannot solve analytically" i tend to disagree that, one tends to simulate only because it cannot be analyzed. ... this reduces Product development cycle time considerably.

A +1 to that. Also, factors such as cost, time, rework, etc get simplified with simulation.

[SPIKE ARRESTOR]

@Arka please do the honours, i will add whatever i know

Spike