Author Topic: Cheapest prebuilt chassis  (Read 9652 times)

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Offline Half ShellTopic starter

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Cheapest prebuilt chassis
« on: November 15, 2007, 10:35:24 PM »
As I mentioned here:
http://www.societyofrobots.com/robotforum/index.php?topic=2368.0

I am in the process of making a robot kit as cheaply as possible for engineering students.

The idea is out of the box readiness. Using nothing but what's in the box you can create a robot, albeit simple. From those same parts, you can then spend your own time and money expanding it to create some cool and functional robots.

The chassis I am leading toward is one I've recently used and was decently impressed with:
http://www.trossenrobotics.com/store/p/3172-Robby-RP5-Chassis-Only.aspx
This has two 9 volt motors and comes with a battery holder (6 AAs).

This one has caught my eye though, but may be a bit too cheap on quality:
http://www.superdroidrobots.com/shop/item.asp?itemid=484&catid=68


I have been debating whether or not to merely provide pieces to a chassis and build one from scratch, but I want it to be simple as possible. Any help or suggestions would be great help!

Offline Ro-Bot-X

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Re: Cheapest prebuilt chassis
« Reply #1 on: November 16, 2007, 07:59:23 AM »
I wanted to manufacture such a kit, but I couldn't find a cheap motor source for it. That means under 6 dollars for 2 geared motors. But for the chassis is simple:

The cheapest method would be to have the PCB as the chassis of your robot. You can see a sample of that in Asuro robot, or my VCR robot. You can also use nuts and bolts to connect PCB modules like in Microbric Viper robot. You can solder PCB's at 90 degrees, cut and predrilled to mount servos.

You can also have one 3.8" piece of plastic as the chassis and screw on the sides the servo mounts and on top the electronics PCB. Possibilities are endless.
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Offline Steve Joblin

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Re: Cheapest prebuilt chassis
« Reply #2 on: November 16, 2007, 08:18:23 AM »

Offline Half ShellTopic starter

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Re: Cheapest prebuilt chassis
« Reply #3 on: November 16, 2007, 10:28:37 AM »
The BOE bot is way too pricy for this project- 100 dollars or under definately, the lower the better. I'm chiming in at 90 dollars right now for a complete IR sensor robot equipped robot with a chassis that's sturdy with two 9 volt motors built in.

As for building on the PCB - good for smaller robots but this is basically RC car size or bigger.

I am going to research finding mountable motors/gearboxes/wheel combos onto lexan or plastic and compare costs there.

Thanks for the help so far -keep the suggestions coming!

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Re: Cheapest prebuilt chassis
« Reply #4 on: November 16, 2007, 10:43:38 AM »
How about this?
http://www.pololu.com/products/pololu/0250/
(since you are buying in bulk, you could save a lot here)

Offline Half ShellTopic starter

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Re: Cheapest prebuilt chassis
« Reply #5 on: November 16, 2007, 11:57:54 AM »
Ooooh nice find. I saw those somewhere else for 30 but decided for that much the one I currenty had (Robby RP5) was much better. I have been eyeing the Tamaiya dual gearbox too for a possible make-it-yourself solution so I think I'll buy one and test it out for myself. Since the price still comes out to about the same (the chassis does not come with the kit, so I have to spend about 25 bucks a piece so 5 bucks saved overall) it will have to be of quality. Do you have experience with this model or did you just webcrawl for it?

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Re: Cheapest prebuilt chassis
« Reply #6 on: November 16, 2007, 12:35:07 PM »
Quote
Do you have experience with this model or did you just webcrawl for it?
I've never used that particular product, but its a very simply design I've seen used very often for ultra-cheap robots. I remember seeing a similar one around that used servos, but can't remember where . . .

Offline paulstreats

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Re: Cheapest prebuilt chassis
« Reply #7 on: November 16, 2007, 03:21:09 PM »
ive used this pololu set up before, the main problem is that its really too small, of course you can use more than one base seperated by risers to build upwards with, but this makes it unstable. Also when you have the base, gearbox and castor put together, the whole thing tilts backwards from the weight of the gearbox.
If you get one of the kits, you can see how to make your own base like this easily enough out of some kind offlat plastic, either making a biger base or just a cheaper version of that design.

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Re: Cheapest prebuilt chassis
« Reply #8 on: November 16, 2007, 03:35:21 PM »
paulstreats, yea, you are right. I'm looking at it now and its butt heavy . . .

The reason for this is that it allows for the center of rotation to be at the center of the robot . . . at the cost of being less stable . . .

If you put the batteries on top of the caster, it should balance.


Offline Half ShellTopic starter

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Re: Cheapest prebuilt chassis
« Reply #9 on: November 16, 2007, 09:47:14 PM »
I noticed the off center part and knew about the "building up" aspect, but I didn't know it became unstable fast. Thanks for the tip.

That base actually ends up costing the same as the Robby RP5 - the combo kit plus the plate (does not come with it) plus the battery pack to power the motors (microcontroller COULD power it, but the motors might pull too much current) adds up to 30 dollars as well.

Looking at this I realize that the Robby RP5 is the better deal - still turning within its own radius (or at least damned close from what I can tell). The base is stable to build out of and can easily become an RC car size robot with expansions. On top of that the insides can allow for an encoder to be attached and, if the batteries are replaced by a simple 9 volt, can leave room for electronics. It is actually the chassis to a much more complicated and more expensive robot kit.

After looking at this I'm wondering if Arduino is the right choice - maybe there is where I can cut my costs the most.

Offline HDL_CinC_Dragon

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Re: Cheapest prebuilt chassis
« Reply #10 on: November 16, 2007, 11:37:39 PM »
havnt read this thread too thoroughly. Very tired ATM but how about going with an erector set kind of setup? Just a bunch of rods and such with evenly space/dimensioned holes and a bunch of little bolts and premade 5v hobby motor brackets for mounting a motor where ever? that way its even MORE customizable/engineerable

what do you think?


-EDIT-
Or just give the guys some aluminum angle stock, some sheeting perhaps, and let em have at it :P
« Last Edit: November 16, 2007, 11:38:40 PM by HDL_CinC_Dragon »
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Offline Half ShellTopic starter

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Re: Cheapest prebuilt chassis
« Reply #11 on: November 17, 2007, 12:23:03 AM »
I actually did think of that - order some premade motors with gearboxes attached and buy some erector set parts to allow for base customization, much like a vex kit.

However, looking at costs right now it seems like this route would end up costing as much for less, or maybe even more. i'm still exploring this of course as an option but a complete prebuilt solution may be cheapest.

Offline maverick monk

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Re: Cheapest prebuilt chassis
« Reply #12 on: November 23, 2007, 08:51:47 PM »
As I mentioned here:
http://www.societyofrobots.com/robotforum/index.php?topic=2368.0

I am in the process of making a robot kit as cheaply as possible for engineering students.

The idea is out of the box readiness. Using nothing but what's in the box you can create a robot, albeit simple. From those same parts, you can then spend your own time and money expanding it to create some cool and functional robots.

The chassis I am leading toward is one I've recently used and was decently impressed with:
http://www.trossenrobotics.com/store/p/3172-Robby-RP5-Chassis-Only.aspx
This has two 9 volt motors and comes with a battery holder (6 AAs).

This one has caught my eye though, but may be a bit too cheap on quality:
http://www.superdroidrobots.com/shop/item.asp?itemid=484&catid=68


I have been debating whether or not to merely provide pieces to a chassis and build one from scratch, but I want it to be simple as possible. Any help or suggestions would be great help!


i have the cheap one, but i baught the tamiya dual motor gearbox and assembled it in the c configuration, i swapped the base plate out for a piece of pvc and made a plexiglass top frame,  and i have a nice robot frame, now if only i could get the electronics part down  :-\

Offline Half ShellTopic starter

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Re: Cheapest prebuilt chassis
« Reply #13 on: November 23, 2007, 10:50:01 PM »
Maverick, could I get some pictures and perhaps a bit more details?

Offline maverick monk

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Re: Cheapest prebuilt chassis
« Reply #14 on: November 24, 2007, 09:26:31 AM »
i used this gearbox
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHA15&P=7
in the setup that allows for independent steer

i baught this track kit
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXBFP9&P=7

and this base
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHA16&P=7

i replaced the botom part with a piece of pvc sheet and got this



edit: shown with 4.8v on simple switch for chassis testing

edit edit:
[youtube=425,350]qLNDhQ24bTw[/youtube]
very very tough, but very slow
« Last Edit: November 24, 2007, 12:26:01 PM by maverick monk »

Offline Half ShellTopic starter

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Re: Cheapest prebuilt chassis
« Reply #15 on: November 24, 2007, 01:10:57 PM »
Excellent! Thank you for all the information. Wow, if that was merely directly powering the motors it seems that you have a significant curve over a given difference. Was that because of the gearbox?

I like the fact that this has to be built from scratch unlike the RP5 which comes complete. Since this a kit I feel that gives more of a feel of ownership to the kit purchasers.

All told that comes to about 25 dollars sans plexiglass, so 5 dollars cheaper than the previous chassis. Was the bottom being replaced by plexiglass absolutely necessary or did you feel like the bottom included would have been fine?

Also, is it similar/the same/completely different from this? : http://www.superdroidrobots.com/shop/item.asp?itemid=484&catid=68 Because if that is merely a combination of what you got but much cheaper, I can easily buy the plexiglass for a new top and work from there.

EDIT: I now notice that it IS the same thing. Sorry bout that.

Thanks so far!
« Last Edit: November 24, 2007, 01:12:49 PM by Half Shell »

Offline maverick monk

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Re: Cheapest prebuilt chassis
« Reply #16 on: November 24, 2007, 01:34:39 PM »
that vehical doesnt have the independent tr4ans, it can only go strate, you could use the supplied plate, but it has holes in it, and i didnt want dirt getting in. btw, i used pvc, not plexiglass, the seccond shelf is plexi (not shown, it holds electronics)

Offline blueroomelectronics

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Re: Cheapest prebuilt chassis
« Reply #17 on: November 27, 2007, 12:15:03 AM »
Not a fan of the Tamiya treads, they are too stiff and tend to come off unless the chassis is dead straight.
The Tamiya Gearboxes and wheels are excellent though.
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Offline Half ShellTopic starter

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Re: Cheapest prebuilt chassis
« Reply #18 on: November 27, 2007, 08:37:58 AM »
So what is that in the picture? Which microcontroller plugging into the Tamiya gearbox with wheels?

Offline Steve Joblin

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Re: Cheapest prebuilt chassis
« Reply #19 on: November 27, 2007, 10:26:48 AM »
The Junebug (left) PICkit 2 compatible programmer / debugger shown with the Mongoose Robot Chassis (right)... check out blueroomelectronics.com for details


Offline Half ShellTopic starter

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Re: Cheapest prebuilt chassis
« Reply #20 on: November 27, 2007, 12:05:09 PM »
Apparently Mongooses are only available at Creatron parts but they don't actually list the chassis. Do you know the price or where they actually list that chassis?

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Re: Cheapest prebuilt chassis
« Reply #21 on: November 27, 2007, 07:43:53 PM »
Pre built chassis?  For engineering students?  You're taking away from the engineering aspect, IMO!

I would give them some sheets of 1/16" polystyrene, some glue safe for it, and an Xacto knife and say "engineer your own chassis!"  It can be done in less than an hour, and makes each project unique, as well as offers some chance to execute some engineernig skills

Offline blueroomelectronics

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Re: Cheapest prebuilt chassis
« Reply #22 on: November 28, 2007, 02:34:36 PM »
IMHO the chassis does look a little better than cardboard or a block of wood. It's a Tamiya double gearbox, Tamiya 58mm Wheels and a Tamiya Ball caster. It's also a precisely manufactured little black anodized aluminum frame. The electronics use a PIC18F2525 and a SN754410 quad half-bridge but what sets it apart from a bog standard frame is a pair of rotation sensors with 108 transitions per wheel rotation. It was built as a basic platform for your own experiments, just so happens it can take a standard LCD for diagnostics. The schematic is on my site. It's about the same price as a Parallax BOEBOT $149, the programmer (Junebug) is $45

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