mech stuff

[AK]

ok. here's what i think is needed:
1. wooden board 2*4 : 300 approx
2. 2 DC motors(same as those used by shubham): 1000 each (second hand were 500 each)
3. wheels: 250 for 4
4. batteries: 3 needed, 200 each approx( not sure about this one)
5. misc gears, remote and stuff: 1000 bucks

Akshat Kaul

[siddharth munjal]

are u guys gonna use wood for the cosntruction.i thnk ts a bad idea.u should use some kind of graphite materials or some kind of plastic....it should be light and give it the required strength.Wood is easy to work on .....but not a nice material to use.

[Arjun Sarwal]

hi Siddharth
thanks for the useful information
but could you please elaborate a little on why you suggest so?
somthing from your experience tells you so probably..share your experience please

On 8/17/06, siddharth munjal <siddhart...@gmail.com> wrote:

are u guys gonna use wood for the cosntruction.i thnk ts a bad idea.u should use some kind of graphite materials or some kind of plastic....it should be light and give it the required strength.Wood is easy to work on .....but not a nice material to use.

--
http://www.geocities.com/arjunsarwal85

[siddharth munjal]

ok
all im saying is..

that wood is not a nice material to work with

see if u wont extreme workability....then polycarbonate(i think) will do...its a soft material...but has decent strength ...can carry quite a bit of wheight...spply thick sheets

strength...u can use that material...hmm....acrylic...verry brittle but yet very strong.....
or maybe that material u(arjun) used for tht internet controlled robo

see metal...some lightweight thing....with nice strength will be another nice option...but will be tuffff to work with..so NO-NO

there'll be millions of materials we can work with ...but we need to know the finer details of the robo before that

well if the kinda weight the robo has to carry is decided....then the material can be decided more effectively

and + im no1 to comment ...my experience is limited...we can ask parampreet for suggestions....and better still..consult PRK sir....i can talk to him if any of u want me to

siddharth

[Parampreet Bhasin]

hey sid

i think wat u r sayin is pretty true...

i ll elaborate on the pros and cons of most materials i've used:

wood: cracks pretty often and de cracks keep widening....major prb is the screwin and unscrewin of nuts and bolts actually breaks all the internal tapping. even the cuttin  and stuff is tough

acrylic:

pros: plastic hence lightweight and excellent strength

cons:cant be joined wid regular adhesives but only wid chloroform etc. which used in excessive qty can actually reduce the strength of joint. so if u go ahead wid this do use mechanical joints like screws etc.

another prb is the cuttin ...its not dat easy

polyproplene:

well can be joined wid regular adhesives where moderate strength joints are needed....for other s i prefer mechanical joints. also the strength is pretty gud.

cons: price a lil higher and also not widely available.
i hope de above info was helpful...tc

param
 

--
Love me the most when I deserve it the least,
coz that is when I need it the most

[arjun sarwal]

Thanks param for the useful info
Polypropylene thus seems like a good choice,
but a major point of concern is that for  larger values of weight, would we get suitably strong peices of polypropylene??
For example if there are about 4 lead acid batteries(12V,7AH) on the robot, and it is a huge frame, then would polypropylene be suitable?
also, please elaborate on metallic materials as possible options for the frame

Regards

[Parampreet Bhasin]

now dats de way i wud like ques to be put....straight to de pt

luk there are very few vendors havin polyproplene but they kno it's strength vs thickness ratio...tell them the area required and the weight and theyll tell u how much shud be the thickness..

considerin dat the frame wud be big and heavy i wud suggest u shud go for metallic materials. second hand iron sheets are common and not a bad alternative as they are as gud in strength as new ones..tell me if u want any other info....well am i still a part of it???

 

[Arjun Sarwal]

First of all , anybody who contributes is a part of it. So as long as you contribute in whatever way that you can, you are a part of it.

Coming to the question of materials,
Going by the weight required to be carried on board and the fact that it is required for the vehicle to be rugged, metal is scoring more points in my opinion.

What we would require is more information of
a) Thickness/grade of metal required (refer specifications given below)
b) places selling the required metal
c) approximate costs of the same(required for submitting the proposal)

the following parts would comprise the bulk of the weight to be beared by the frame-->

-batteries (12V 7AH) -approx 4 but better to keep room for 6
-DC motors - two and appropriate belt-gear mechanism
-suspension system
-onboard motherboard and processor (hardly any weight)
-cameras,gps units and other electronics hardware modules (hardly any weight)



regards
Arjun

ps- if param you can spare abt 3-4 hrs on deciding the basic shape,structure of the robot that would be quite useful

--
http://www.geocities.com/arjunsarwal85

[siddharth munjal]

1)in my prev mail i said"poly carbonate"...lol..i meant polyprop obviously...i thik its a great material to work with
2)r u talkin abt the bike waalaa lead acid battreries...i dont think u wud need those...and they r heavy...and cumborsome...if we could bend the budget a bit... there r awesome batteries(expensiove ones) avaoible in lajpat rai...rechargable...Li ion i guess..which can be used...lighter ...much lighter..and take less space too..
3)the suspension is gonna be tricky...since the vehicle is all terrain.. it hink it shud be discussed wid PRK sir!

sid

[Arjun Sarwal]

Hi
Could you please give a rough estimate of the costs of the batteries(Li-ion) please

Thanks

--
http://www.geocities.com/arjunsarwal85

[siddharth munjal]

see ...theyll be expensive...a 24v...i dunno abt the amperage...for approx 2000  2500 ..a.rnd that much i guess...and the amerage i guess will be sufficient...have to go to lajpat rai market to check:)
sid

[Karan Jain]

hey sid, what is the difference in the weights of the normal battery
and this one....
batteries are the having maximum weight among all things.
See money is an important factor, specially in the beginning.
So what we can do is, we can use say 2 lead-acid batteries in the
beginning....to drive all the motors. Their code can be stored in say
an ATMega 8 microcontrolle initially.
first consideration is making the ATV. in the second stage we could
put all the electronic components, even the mother board. Then, when
we get some more money, we can buy those better batteries and put them
on.

[Arjun Sarwal]

Yes
I tend to agree with this approach.
This will ensure that work starts asap.
So  I think construction of mechanical frame, mounting of batteries and motors seems to be the task at hand; and must be implemented immediately.
Therefore, requirement of mech ppl is of utmost importance at the moment.

--
http://www.geocities.com/arjunsarwal85

[siddharth munjal]

yeah i think u shud strt working wasap
but guys do consider params idea bt the batteries...he sayd theres a shop in lajpat rai which will make customized batteries for ya...which is pretty cool!!
sid

[Parampreet Bhasin]

well i dont agree wid de approach...wel i think u shud make a normal robo wid all de above mentioned features and simultaneously mech wrk shud go on.....becoz makin an ATV is pretty tough and it may not succeed its objective of all de terrains.but still u can mount de entire stuff on any robowars robo and make it wrk atleast. so dat in the future applications u can mention ATV

[Arjun Sarwal]

ok
we had discussed this in one of our meetings, and had come to the conclusion that the proejct is not exactly ATV- all terrrain vehicle; but 'Multi Terrain Vehicle'
our task would not be to be able to tackle a lot of terrains but plain,inclined,rocky areas shoud do well...

--
http://www.geocities.com/arjunsarwal85

[AK]

friends romans countrymen and other assorted individuals

the total budget available for the mech part of the project is around 2k. as is pretty clear from the previous statement, a full fledged atv is not req. any further suggestions shud be made keeping this in mind.

now coming to wood: its cheap, its easily available and its WORKABLE. you can drill it. u can stick it. if nothing else is available, u can nail it. its light and it lasts longer than ur interest does which is about as long as it has to last. polypropylene cracks. its not as easy to drill and its def not as easy to get as wood.

to make things quite clear, the design i had in mind was a rectangular  wood base with two motors and 4 wheels mounted on the bottom. thats it. if someone has a more rigorous treatment in mind, pls give design details and cost estimates.

Akshat Kaul

[jaid...@gmail.com]

Hi

Things seem to be in limbo here.

As Arjun pointed out, we are not making an ATV, what we aim to make is
something that can handle moderately rough terrains, maybe even mild
inclines. A "multi terrain" vehicle, if you will.

A conservative estimate of the money we can get at this point for the
mechanical fabrication part is < 2k (excluding the batteries). So all
suggestions should be made with this in mind.

The two major points of contention seem to be -

1. Batteries - Siddharth has pointed out that Lithium ion cells are
lighter and more efficient than the regular lead acid kind, but much
more expensive. Now, since the space and weight requirements of the Li
cell are much less than those of the lead acid cell, if we were to go
ahead with the cheaper lead acid ones in mind, the Li ones could be
easily worked in, if we manage to get the money for them.

2. Material - wood vs Metal vs Polypropylene. I have no idea about
this.

We cannot get money/start work until there is a consensus on these
issues. What is your suggestion?, should we meet on Monday?

Jaideep