How to choose a caterpillar platform on aliexpress?

Question

Arduino

Good afternoon,
I am considering buying a caterpillar platform on aliexpress (11.11 discounts), the following criteria:
1. There must be not a single copy, that is, something more or less standardized
2. Separate parts must be sold so that you can replace it in case of exit from building
3. High clearance)
4. I want to shove raspberries into it for control / camera, plus an arduino for capturing on several servos, plus power for a couple of hours, if possible

. While I chose the TS100 platform, it costs about 6k, I see different manufacturers, the dimensions are 275x190, but this is at the extreme points, how much the central useful platform size is not known. The first link is to alishka, but you can just dial TS100

Questions on the merits:
1. I don't understand if there are replacement parts for this model. That is, I see a scattering of rollers, all sorts of springs. But I don't understand if they fit this model or not. Okay, I can find the same parts if it's a breakdown. But I see a slightly different type on some models, something like shock absorbers, is it possible to somehow understand whether they will fit this platform or not
2. There are some motors that are unknown to me. Who worked with this, will there be any problems connecting them to a raspberry or an arduino, or will it be necessary to take other motors right away?
3. I see on some of the larger models that the motors are mounted through a gear system. I don't know what it's called correctly. Looks like a gearbox. Searched according to henglong gearbox engine box picture. If this is still a gearbox, then it is needed for reliability, as I understand it? Plus an increase in power due to a decrease in speed? Should I take it right away? Will it fit my chosen model? I also see all sorts of different planetary gearboxes on this topic. Is this all necessary or not?
4. I see separately sold iron tracks. I don’t understand why they are needed, because they are heavier than plastic ones. As for reliability, it seems to me that in models there are no such loads that plastic cannot cope. In any case, if, suddenly, I want to change plastic to iron, how do I know if they will fit this model? I can't determine at all. The answer "buy and attach" does not suit me, these tracks cost 2k, expensive for "just attach"
5. Next in size is a platform with four tracks. At the same time, as far as I understand, all 4 tracks have a drive wheel, that is, it is necessary to synchronize work on one side of the platform. Also, the front tracks do not turn, that is, the steering mechanics remains the same as with two tracks. It's more complicated, I don't understand why such platforms exist?
5. Prices generally bite, 6+k for similar models, and if you look at some bigger model, for example , the price is 20k, plus delivery 18k, what kind of game?

Well, in general, a general question, tell me where to find a community or people interested in this topic? It's just that in groups about robotics, raspberries or arduino, a bunch of other projects are discussed. To write in a personal to the guys from YouTube who post this is such an option

Answer 1

I must say right away that I am not an expert on traveling robots. So it's just a side view. On questions:
1) And nobody knows it. Maybe there is. Or as an option today is, but tomorrow will not be. If it were a constructor from some Tamiya, then we could count on spare parts. And a Chinese friend today rivets cars, tomorrow he sews panama hats. I would choose a platform with which spare parts are sold in the same store. And immediately took at least something in stock.
2) Almost any motors are not connected directly to microcontrollers. Only through the driver. So, those that are, are no worse than others.
3) Motors almost always turn wheels / tracks through gearboxes. Motors on the selected platform already with a gearbox in one housing. So these motors do not need anything extra.
4) Iron is stronger, more durable. Someone at home will ride on the carpet, and someone on the stones. Which ones are suitable - see item 1. Only if they are sold from the same seller - you can ask him. The rest is a lottery.
5) You did not give a link to the 4-track, so we are only guessing. There may be options for how it is arranged. Stupidly dividing the caterpillar into two does not make much sense. But designs are possible that provide greater cross-country ability of the model. And yes, you need to synchronize the tracks even if there are only two of them (right and left), otherwise it won’t go straight due to imperfection.
6) Come on 20k, here is 200k :) https://aliexpress.ru/item/33050725092.html
Pricing is like that ... So they take it! Here is one option. These designs are quite simple, you can see everything from the pictures. You can make and assemble yourself, and only buy caterpillars, shafts, motors.