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Author Topic: First Robot Build Advice  (Read 715 times)

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Offline Jackson21Topic starter

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First Robot Build Advice
« on: October 22, 2013, 12:08:19 AM »
Pretty new to the world of robotics, and was hoping to get advice for the components of my robot. I'll give you a run down on what I want it to do first. There's a link at the bottom of my design using Sketchup 8.

V1 - Basically just a tracked chassis. Unsure if RC or computer operation(wireless) would be better. I'm thinking RC transmitter as it is more portable but computer would be easier to control I think. Maybe even an Xbox 360 controller, any advice? Also, don't think I'll be adding a micro at this stage as there isn't really a need for it(unless I go console controller).

V2 - Adding a live feed camera that can be viewed via Ipad if possible(wifi?). I was also thinking maybe a small spotlight of some description. Probably need a micro for this too. Advice on cheaper easy installs?

V3 - Now here's the tricky one, a robotic arm capable of lifting 2-3kg AND live feed sensors so it's 'self aware'(IE - If i ran a pre-programmed command, the arm would align itself correctly before it began the command). I want the arm to be able to spin and bend at the base, bend in the middle, 180* axis for the claw to spin on and open and close claws. This is the part I really need help with the actual build, but also still advice on which components/brands/sites/etc. to use.

Here's the basic build with a few ideas of what's already going into it - http://sketchup.google.com/3dwarehouse/details?mid=6d49d24d5b6d2ca07b6cbfce0b28bdcb&prevstart=0

Cheers,
Jacko :D
« Last Edit: October 22, 2013, 08:32:15 PM by Jackson21 »
Malory: It's okay! They're just blanks.
Lana: Well, see, you say that ..
Malory: But they were blanksóweren't they?
Sterling: Only if the back of his skull picked that exact moment to explode outward.

Offline gerard

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Re: First Robot Build Advice
« Reply #1 on: October 22, 2013, 08:25:04 AM »
well for V1 you need to get your measurements down
i can tell you from personal experience that making a tracked platform from scratch is not easy...
you need to find some pre-made tracks and wheels first, then build your robot around that
budget is also a pretty large factor, how many $ are you planning to spend on this?

Offline Jackson21Topic starter

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Re: First Robot Build Advice
« Reply #2 on: October 22, 2013, 05:41:16 PM »
Everything on the plan is on a 1:1 scale. There will be some minor tweaking like size of servos, reciever, etc. until I can get the specs for the parts I'm using but I've allowed for flexibility here. Was hoping to find a pre-made track and adjust wheel size and number of links to get a good fit. As for money, well I want cheap as possible obviously but don't want really shitty components. So, lets just say $500 in total. But that is flexible if it has to be  :P
Malory: It's okay! They're just blanks.
Lana: Well, see, you say that ..
Malory: But they were blanksóweren't they?
Sterling: Only if the back of his skull picked that exact moment to explode outward.

Offline Jackson21Topic starter

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Re: First Robot Build Advice
« Reply #3 on: October 23, 2013, 11:26:37 PM »
Really friggin struggling to find tracks :'(. This is the best I've found so far -

http://www.ebay.com.au/itm/100-Lego-TREAD-LINKS-16-GEARS-Kit-technic-nxt-robot-mindstorms-tank-crane-/291000510870?pt=Building_Toys_US&hash=item43c0fb6996

Anyone had any experience with Lego before? Or know where to get rubber track? Needs to be 788.5mm long but we will just round that up to 800mm. I would prefer too have plastic/metal links with rubber pads.



Malory: It's okay! They're just blanks.
Lana: Well, see, you say that ..
Malory: But they were blanksóweren't they?
Sterling: Only if the back of his skull picked that exact moment to explode outward.

Offline bdeuell

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Re: First Robot Build Advice
« Reply #4 on: October 24, 2013, 02:28:54 AM »
You could look at any of these tracks:

http://www.lynxmotion.com/c-94-tracks.aspx

http://www.superdroidrobots.com/shop/category.aspx/treads-and-tracks/55/

http://www.ebay.com/itm/HONDA-HS828-HS-828-HS828-K1-SNOWBLOWER-SNOW-BLOWER-TRACK-42755-768-013-NEW-/390619701650?pt=LH_DefaultDomain_0&hash=item5af2bfa192

I haven't used any of them or the lego so I cant say how well they work.


I have built a custom set of rubber tracks from incline belting material ... but they took a fair amount of time to develop and construct. If this is a route you seriously want to pursue I can elaborate on the design I developed and what I might do differently next time.

Offline gerard

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Re: First Robot Build Advice
« Reply #5 on: October 24, 2013, 08:17:21 AM »
You could look at any of these tracks:

http://www.lynxmotion.com/c-94-tracks.aspx

http://www.superdroidrobots.com/shop/category.aspx/treads-and-tracks/55/

http://www.ebay.com/itm/HONDA-HS828-HS-828-HS828-K1-SNOWBLOWER-SNOW-BLOWER-TRACK-42755-768-013-NEW-/390619701650?pt=LH_DefaultDomain_0&hash=item5af2bfa192

I haven't used any of them or the lego so I cant say how well they work.


I have built a custom set of rubber tracks from incline belting material ... but they took a fair amount of time to develop and construct. If this is a route you seriously want to pursue I can elaborate on the design I developed and what I might do differently next time.


i made a set of custom tracks for my large tracked platform
i used v-belts and pulley wheels
then i screwed bike wheel tread on to the belts
it works perfectly, and you can easily make the tracks any length

beats throwing $1 grand at uperdroid tracks lol :P

Offline Jackson21Topic starter

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Re: First Robot Build Advice
« Reply #6 on: October 24, 2013, 07:23:31 PM »
Hmm, was really hoping not to spend more than $50-60 on these, certainly not $500. I've found plastic chain links that can be used with Lego sprockets. Figured I'd just pull the middle wheel out and retro fit the sprocket onto some large wheels and make it AWD. But I would still like to hear more about both your idea's before I start because I really would prefer tracked.

Cheers,
Jacko :D
Malory: It's okay! They're just blanks.
Lana: Well, see, you say that ..
Malory: But they were blanksóweren't they?
Sterling: Only if the back of his skull picked that exact moment to explode outward.

Offline bdeuell

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Re: First Robot Build Advice
« Reply #7 on: October 25, 2013, 05:00:46 PM »
If this is your first robot I would caution against building your own tracks unless you have a lot of mechanical experience. There are a lot of moving parts associated with tracks which usually translates to a lot of potential failure points. My design also required quite a bit of manufacturing the v-belt design mentioned sounds much easier in that regard.

I have attached a picture of the tracks I designed.

The design I developed used this incline belting material http://www.mcmaster.com/#5987k124/=p3etsb. This material needs to be spliced together to form continuous belts. There is alligator splicing that you can buy and install yourself but it will create an uneven spot in the belt that wouldn't have worked well with my pulleys, for this reason I chose to have the belt spliced professionally. When they splice the belt professionally they are able to create a smooth seam that is bonded with a vulcanized rubber. Creating this type of bonded connection is challenging to do yourself ... I tried ... the belt must be cut in a tapered manner so that large areas can overlap and bond without adding to the thickness, the appropriate adhesive is also critical. I had my belts spliced by a local belting company http://www.pooleyinc.com/index.html they did a very nice job, even did it for free as this was a school project.

Once these continuous belts are constructed some sort of feature to engage with the pulleys must be added, this could be a series of holes in the belt or blocks attached to the belt or a combination of both. THese features are used to keep the belt on the pulleys as well as aid in providing drive torque. For my design I chose to create round holes on each side of the pelt for pins to engage in. keep in mind that the belt will deform around the pulleys and sufficient clearance on theses features must be accounted for. I would rethink this design if I built tracks again, I think a single row of holes or blocks in the middle might work better.

Then you will need to make some custom pulleys to run this belt on. I machined mine from PVC plastic then pressed pins into a series of holes around the diameter to engage in the belt. I also created hubs from aluminum and installed them with heat so they were bonded to the plastic pulley. The diameter of the pulley must be determined so that the engagement features will line up as the pelt curves around the belt. Note the spacing of theses features on the diameter of the pulley will be less than the spacing of the features on the belt lying flat; I determined correct pulley diameter with a scrap wheel by machining smaller until it looked like it would fit well with a belt around it.

Other things to keep in mind is that many track designs have tensioner mechanisms. There will be forces acting on the treads in many directions especially when turning and the design will need to prevent the tracks from walking off the pulleys.

Offline gerard

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Re: First Robot Build Advice
« Reply #8 on: October 25, 2013, 09:57:02 PM »
screw splicing, i used STAPLES :D
it works great, because the actual tension is on the v-belt, not the tire...
and the friction between the belt and the pulley wheels is more than enough for traction
i will post some pictures today in a separate thread

Offline Jackson21Topic starter

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Re: First Robot Build Advice
« Reply #9 on: October 27, 2013, 07:51:38 PM »
Thanks for the advice bdeuell, I'm an electronics technician by trade, so Ive had a fair amount of mechanical and electrical engineering experience, however, for the sake of price and simplicity, think I might try this v-belt idea. And I found your post Gerald, thanks for the help!

Cheers,
Jacko  :D
Malory: It's okay! They're just blanks.
Lana: Well, see, you say that ..
Malory: But they were blanksóweren't they?
Sterling: Only if the back of his skull picked that exact moment to explode outward.

Offline gerard

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Re: First Robot Build Advice
« Reply #10 on: October 27, 2013, 09:59:17 PM »
No problem! :D
Just a warning, the V belt system will require some high torque motors...
Have at least 1Nm of torque for every Kg the robot weighs, and you should be ok

Offline Jackson21Topic starter

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Re: First Robot Build Advice
« Reply #11 on: October 28, 2013, 04:58:44 AM »
Oh $***, really?!
I've just bought 13kg-cm (1.25Nm) servos.
Hopefully it weighs less than 2.5kg then. Just out of curiosity, are you from the US or elsewhere? Because I noticed that you used washer motors in your tracked build, but when I searched them, they were all from the US and P+H was ridiculous to Aus!

Cheers,
Jacko :D 
Malory: It's okay! They're just blanks.
Lana: Well, see, you say that ..
Malory: But they were blanksóweren't they?
Sterling: Only if the back of his skull picked that exact moment to explode outward.

Offline gerard

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Re: First Robot Build Advice
« Reply #12 on: October 28, 2013, 08:35:31 AM »
Oh $***, really?!
I've just bought 13kg-cm (1.25Nm) servos.
Hopefully it weighs less than 2.5kg then. Just out of curiosity, are you from the US or elsewhere? Because I noticed that you used washer motors in your tracked build, but when I searched them, they were all from the US and P+H was ridiculous to Aus!

Cheers,
Jacko :D

I live in Canada :D
I get my stuff shipped from the US. It's not cheap, but you cant get stuff like this in Canada easily.
I order all my stuff from The Robot Marketplace, they have great customer support and everything you could ever need for a robot!
Your servos should be enough to move your robot, but I do not recommend using the V-belt track system because of its small size. The V-belts work best with large-diameter pulley wheels, and that would make your robot much heavier than 3Kg. My robot weighs about 20-30Kg, and it is all aluminum!!!
Tell me the length you want your robot to be and I will find you some affordable tracks for its size :)

Offline bdeuell

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Re: First Robot Build Advice
« Reply #13 on: October 28, 2013, 05:12:28 PM »
If you want to build your own tracks (building off of the v-belt design) perhaps you could develop a design that uses timing belts instead of v belts. Timing belts do not require a high tension to transmit torque so they might be better suited for a smaller design. You would still need to provide a traction surface on the back of the belt; you could attach tread or something similar as was done in the v-belt design or look into double sided timing belts. The flange height on the pulley is a concern tho as it is typically larger than the belts web thickness and you would want to prevent them from hitting the ground.

I think an off the shelf solution is your best bet if you can find something that meets your needs.

Offline Jackson21Topic starter

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Re: First Robot Build Advice
« Reply #14 on: October 28, 2013, 05:23:23 PM »
Hmm, if a v-belt will be to big perhaps a drive belt from a R/C heli? I've changed the design slightly (in my head) and haven't figured out the exact specs, but i estimate it will be roughly 1000mm per track. My wheel specs; diameter - 66mm, width - 27mm.

I was thinking what i could do would be to get a v-belt (or something similar) and copy your design only on a smaller scale and slightly modified. Ill use pushbike racing tires and screw/glue belt to inside, then screw aluminum tabs to the ends and overlap the tabs. Ill pop rivet them in place, fill the gaps with pieces of tire/belt. This should ensure strength and make it relatively easy to get the length right.

Finally I'll glue small rubber tabs (probably cut up pieces of the tires) onto the wheels to ensure no slip.

EDIT: Just found these, but there's no stock at the moment and I'm afraid to look at shipping costs. Plus I think the sprockets will be to small, think a custom jobby is going to be cheapest and easiest to fit.

http://www.robotmarketplace.com/products/VEX-276-2168.html

Cheers,
Jacko :D
« Last Edit: October 28, 2013, 06:47:37 PM by Jackson21 »
Malory: It's okay! They're just blanks.
Lana: Well, see, you say that ..
Malory: But they were blanksóweren't they?
Sterling: Only if the back of his skull picked that exact moment to explode outward.

 


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