Chassis support for Picaxe based bot... help please?

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No0bert

Member
I have just resumed my project and still dont have a valid chassis idea, here are some pictures, please dont hesitate with any and all suggestions.

But some might not be considered because of the fact that I dont have a welder, CNC, lots of scrap metal.
I have not drilled on the caster wheel, because I think I might upgrade after realizing all of the bot's weight will be on the caster.



You can see that it bends a bit... hence the reason for a different strategy.






I am desperate for any and all ideas... please help!
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Jeremy Leach

Senior Member
It would help if we knew a bit more about the whole BOT you're trying to create ;) Will it have 4 wheels, 3 wheels - or is it a Segway transporter?! What's it going to do? What are the metal rods? If it's just the flexing you are worried about then why not just strengthen the design? It looks quite a heafty thing you're making!
 
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slurp

Senior Member
Think about levers and forces, if the motors where "in-board" there would be a lower bending force at the mounting.

That's aside from Jeremy's comment on strength etc...

regards,
colin
 
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papaof2

Senior Member
If you plan to continue with a wood chassis, the interior angle brackets need to be two or three times as long as the existing ones and they should be attached using through bolts and nuts - with lock washers at eash end and a large fender washer between the screw head or nut (whichever is in contact with the wood). The larger brackets are thicker and provide more support; the bolt and nut provide a much more secure connection than wood screws.

A metal chassis (aluminum with appropriate reinforcing) may actually be lighter than your wood chassis and can often be worked with the same tools as wood.

Look for some *old* electronic devices with dimensions close to what you want and see if you can adapt the chassis (many newer electronic are mostly plastic).

If you can find a plastic child's ride-on toy, you might have a useable chassis if you add some reinforcing (probably metal) where the motors mount.

John
 
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boriz

Senior Member
Bah. You can use matchsticks if you like. Just remember Triangles, Triangles, Triangles.
 
slimplynth

slimplynth

Senior Member
Best purchase this year has to be a 7 quid, cordless glue gun from Aldi. Nothing that it can't fix.. well except fingers, doesn't help them work better at all.
 
hippy

hippy

Ex-Staff (retired)
You've basically built a U and that is not intrinsically sturdy, with the tie-bars, you've built a parallelogram and that's not much better.

One simple solution is to put ends on to create a box, or use diagonal wooden ties which stops the sides of the box moving about their pivot point where they are currently joined.
 
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No0bert

Member
Jeremy Leach said:
It would help if we knew a bit more about the whole BOT you're trying to create ;) Will it have 4 wheels, 3 wheels - or is it a Segway transporter?! What's it going to do? What are the metal rods? If it's just the flexing you are worried about then why not just strengthen the design? It looks quite a heafty thing you're making!
Click to expand...
Two Wheels and a caster in the middle, roam around, for sturdiness.
 
slimplynth

slimplynth

Senior Member
boriz said:
"7 quid, cordless glue gun from Aldi"

Yep, got one. You too?. LOL.
Click to expand...
;) also got the Aldi generic dremmel tool (10 quid), it worked ok(ish) on my first project box because it lacked enough power to cause any immediate damage (variable speed control too) but can't see it being much use elsewhere.. the power lead annoyingly falls out... hold on.. i'll get the glue gun :D

I could easily spend my weekly wage in aldi and quite happily starve

... back on topic though, this seems to be about the same size... goto 1min46 to see it working
 
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No0bert

Member
papaof2 said:
If you plan to continue with a wood chassis, the interior angle brackets need to be two or three times as long as the existing ones and they should be attached using through bolts and nuts - with lock washers at eash end and a large fender washer between the screw head or nut (whichever is in contact with the wood). The larger brackets are thicker and provide more support; the bolt and nut provide a much more secure connection than wood screws.

A metal chassis (aluminum with appropriate reinforcing) may actually be lighter than your wood chassis and can often be worked with the same tools as wood.

Look for some *old* electronic devices with dimensions close to what you want and see if you can adapt the chassis (many newer electronic are mostly plastic).

If you can find a plastic child's ride-on toy, you might have a useable chassis if you add some reinforcing (probably metal) where the motors mount.

John
Click to expand...
Good idea, however being as I am not very creative could you point me in the right direction regarding the plastic chassis or metal chassis. IE suggest computer chassis or something?
 
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papaof2

Senior Member
When looking for a chassis, you need to think outside the box - literally: what box makes a good chassis?

Look at these possibilities:

10"x6"x4" aluminum box $27
http://www.mpja.com/prodinfo.asp?number=16295+BX
lightweight, but the wall thickness isn't specified - load carrying ability unknown

12"x7"x6" steel ammunition box $6
https://www.surpluscenter.com/item.asp?UID=2009050310545831&item=1-1099&catname=
11"x6"x10" steel ammo box $8
https://www.surpluscenter.com/item.asp?UID=2009050310545831&item=1-2259&catname=
Check for other sizes at local gun shops or gun shows - there were at least 5 sizes at the last gun show I attended - plus you won't pay shipping. (And you probably thought only people interested in guns attended those shows ;-)

A latched ammo box is very sturdy - a 200lb (14 stone, 91kg) person can stand on it without damage. A larger box (some are 18" - 24" in the longest dimension) may be more stable for a wheels + caster chassis and would provide space for batteries inside (to keep the center of gravity low).

John
 
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No0bert

Member
papaof2 said:
When looking for a chassis, you need to think outside the box - literally: what box makes a good chassis?

Look at these possibilities:

10"x6"x4" aluminum box $27
http://www.mpja.com/prodinfo.asp?number=16295+BX
lightweight, but the wall thickness isn't specified - load carrying ability unknown

12"x7"x6" steel ammunition box $6
https://www.surpluscenter.com/item.asp?UID=2009050310545831&item=1-1099&catname=
11"x6"x10" steel ammo box $8
https://www.surpluscenter.com/item.asp?UID=2009050310545831&item=1-2259&catname=
Check for other sizes at local gun shops or gun shows - there were at least 5 sizes at the last gun show I attended - plus you won't pay shipping. (And you probably thought only people interested in guns attended those shows ;-)

A latched ammo box is very sturdy - a 200lb (14 stone, 91kg) person can stand on it without damage. A larger box (some are 18" - 24" in the longest dimension) may be more stable for a wheels + caster chassis and would provide space for batteries inside (to keep the center of gravity low).

John
Click to expand...
While I like the fact that you were the only one to actually give me links, I don think that that is very sturdy, further suggestions?
 
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papaof2

Senior Member
No0bert said:
While I like the fact that you were the only one to actually give me links, I don think that that is very sturdy, further suggestions?
Click to expand...
You've obviously never used an ammo box as a surrogate step stool ;-)

I would suggest finding a local gun shop or gun show and examining the ammo cases firsthand.

Here's one place to find schedules of gun shows in the US:
http://www.rkshows.com/

Properly braced wood can be very sturdy - people have also been making wagons and buggies for a long time. Check your local library for books on making furniture and farm equpment.

John
 
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No0bert

Member
I really want to make the motor mountable horizontally, however it is extremely confusing, I might just add these to the spare parts bin, and search for motors mountable via horizontally... I think it would be sturdier and overall better in the long run.

If you want to make more suggestions on how to make this alteration, please do! What you mentioned did not make much sense to me though.
 
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No0bert

Member
I want something similar to this:



where I can mount these underneath the wood (flat-horizontal) and put the metal rods through this. Would this provide enough support?
 
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No0bert

Member
hmmm, I dont think so, I just searched it up.

More similar to these guys:







Except, able to support over 250 lbs, and I can put metal rods through
 
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chipset

Senior Member
two words CARBON KEVLAR lol. Technically all you need is some mixing cups, a few paint brushes and a pair of good scissors. If you want some extra strength add in some honeycomb. If you splurge on a drill and some really nice Ti drill bits you could build a spaceship haha.

Really all joking aside might wanna look into composites. If you get creative you can have a damn sturdy and brick house strong chassis shaped anyway you want. Your wood design is about as flimsy as it gets. Look at race cars if you want ideas for strength with light weight and the least amount of parts.

an aluminum monoocoque riveted together would be easy to make with a pair of tin snips and a drill and worked on even formula1 till the mid 80s
 
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Andrew Cowan

Senior Member
Depending on the diameter of axle.

Using a 16mm or above diameter axle should give you plenty of strenght. Those blocks can easily take the weight of a person (spread over two or three blocks).

I have used them, although not on my robot.
 
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No0bert

Member
Andrew Cowan said:
Depending on the diameter of axle.

Using a 16mm or above diameter axle should give you plenty of strenght. Those blocks can easily take the weight of a person (spread over two or three blocks).

I have used them, although not on my robot.
Click to expand...
Are their holes on both sides? Because what I was planning to do was put two in the middle of the rods, on each end, upside not horizontally. I would slide the rods through and hopefully everything be ok.

Would this work?
 
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No0bert

Member
Andrew Cowan said:
Ah. Do you have access to a milling machine and lots of aluminium?

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Click to expand...
In my first post I mentioned I do not have access to spare metals, or high power machinery.

But what did you have in mind?

And since you realized that its not spinning on an axle, are the pillow blocks still reliable?
 
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No0bert

Member
I dont understand, if I were to use pillow blocks underneath the chassis, horizontally upside down, that design would be useless... And quite frankly i dont think I am able to make somethin like that, so I just need someone to verify these pillow blocks things.
 
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Dippy

Moderator
Those 2 metal rods simply hold the 2 motor assemblies together, is that right?

So you simply want to connect your wooden box firmly on top of those rods, yes/no?

If so, can't you get some blocks that look like anti-roll bar bushes as used in cars?
The bottom 'half' screws to chassis and the top bolts on and squeezes a tough rubber bush onto the bar. They may need a little mod as you don't want any sliding. A drilled hole and pin would sort that.
Looks a bit like those conduit/pipe mounting brackets except much stronger.

If not, then sorry for the above as I have no idea what is needed :(
 
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