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 anything that breaks a kitbot frame is probably breaking most custom frames of similar weight, too. - dtengineering [more] |
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based off of this,
http://www.chiefdelphi.com/forums/showthread.php?threadid=70758
changes i made include,
I used 2x6's for the sides and ends,
I used a sheet of 3/4inch plywood for the bottom,
and i substituted wooden corner brackets for shiny, steel L-brackets (which i picked up at my local ACE)
its quite a bit heavier as you would imagine.....21.2 punds to be exact(still lighter than last years, kit chassis, which is what i was going for)
the only tools i used were,
my cordless drill, my caulk gun, and a 7/16 rachet and wrench, (dident need a saw as Home-Depot does four cuts for free)
I used Liquid Nails, and 3' wood srews, with washers on them, to hold it all together,
any comments or questions?
Discussion
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24-12-2008 14:20
Cory
Re: pic: my version of a wooden chassis
31.2 lbs???
We've never used the kitbot frame, but it just seems entirely implausible that the bare kitbot chassis could weigh more than that. Maybe with gearboxes, chains, motors, and wheels?
24-12-2008 14:26
MrForbes
Re: pic: my version of a wooden chassis
I think that's right Cory, the kitbot chassis with transmissions, wheels, and motors would weigh about 30 lbs.
gorilla, I'm curious why you made it of such thick wood?
24-12-2008 14:27
gorrilla
Re: pic: my version of a wooden chassis
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Originally Posted by squirrel
I think that's right Cory, the kitbot chassis with transmissions, wheels, and motors would weigh about 30 lbs.
gorilla, I'm curious why you made it of such thick wood? |
its supposed to be 21.2
(i did my math wrong)i used the 2x6's because 3/4inch plywood in florida is $32
and I was thinking about using a bearing block as well as a ball bearing in the wood itself for the canitleverd wheels
also i wanted to be able to use screws as well as the liquid nails.......
i figured the extra weight was worth it
and i wanted to be able to just bolt our supershifters to the wood also
24-12-2008 14:34
MrForbes
Re: pic: my version of a wooden chassis
We found precut 1/4 sheets (2 feet x 4 feet) of 3/4" birch (cabinet) plywood at 3 different building supply places for about $14-$18. Sutherlands, Lowes and Home Depot have it in stock.
24-12-2008 14:38
gorrilla
Re: pic: my version of a wooden chassis
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Originally Posted by squirrel
We found precut 1/4 sheets (2 feet x 4 feet) of 3/4" birch (cabinet) plywood at 3 different building supply places for about $14-$18. Sutherlands, Lowes and Home Depot have it in stock.
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thats what i used for the bottom...
i had a discussion about that with my team, and we thought it would be better to have thicker sides if we were going to use cantileverd axles
what i could have done, is just had the 2x6's for the sides, and the plywood for the ends and bottom.....
24-12-2008 14:54
Cory
Re: pic: my version of a wooden chassis
If your frame right there weighs 21.2 lbs, you're going to have a significantly heavier base than if you used the kitbot, not lighter.
24-12-2008 15:04
gorrilla
Re: pic: my version of a wooden chassis
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Originally Posted by Cory
If your frame right there weighs 21.2 lbs, you're going to have a significantly heavier base than if you used the kitbot, not lighter.
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not really, the kitbot after we put the four cims and two supershifters and all the electronics and chains and (IFI)wheels was just about 36 pounds,
with the wooden frame, im planning on using directely driven (AM)wheels and only two chains, the BB transmission should work nicely,
im still deciding weather we should use the supershifters or the banebots(i think this is were the weight could be made up ot lost), its really all a matter of what we want to use if for(probobly just for testing and demos)
i still think it will be lighter(even if its only by a pound ill be happy)
24-12-2008 15:27
Rick TYler
Re: pic: my version of a wooden chassis
That's going to be a seriously strong chassis. Once you get all your components mounted, get yourself a 2" spade bit and whack some speed holes down the center line of those 2x6s. Remember, the stiffness of a beam goes up as the fourth power of its cross-section. 2x6 studs are really, really stiff on edge -- and the breaking point is also very high. You can easily remove material without compromising strength below a danger point. That 3/4 ply is heavy, too. Do you have a piece of 1/2" you can use? You really don't need that 3/4.
On the other hand, a cheap, strong chassis. Have fun!
24-12-2008 15:35
gorrilla
Re: pic: my version of a wooden chassis
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Originally Posted by Rick TYler
That's going to be a seriously strong chassis. Once you get all your components mounted, get yourself a 2" spade bit and whack some speed holes down the center line of those 2x6s. Remember, the stiffness of a beam goes up as the fourth power of its cross-section. 2x6 studs are really, really stiff on edge -- and the breaking point is also very high. You can easily remove material without compromising strength below a danger point. That 3/4 ply is heavy, too. Do you have a piece of 1/2" you can use? You really don't need that 3/4.
On the other hand, a cheap, strong chassis. Have fun! |
Home-depot was out of 1/2 inch 1/4 sheets.......(would probobly save a pound or two without compromising strength)
thats really what i was going for with the wood,
its going to be 6wd if we have enough of the AM wheels left
it is really strong, i dropped it, kicked it, jumped on it , stood on it, and hit it with a hammer repetedly(and im not a small person) the only thing im concerned about is taking an hit on the side, and cracking the 2x6(but there will be bupers so it shouldent be that big of a problem)......
oh and interestingly, i think the bottom panel added a lot of stiffness, before i had it on, it would kinda flex out a litle bit
24-12-2008 15:42
Vikesrock
Re: pic: my version of a wooden chassis
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Originally Posted by gorrilla
not really, the kitbot after we put the four cims and two supershifters and all the electronics and chains and (IFI)wheels was just about 36 pounds,
with the wooden frame, im planning on using directely driven (AM)wheels and only two chains, the BB transmission should work nicely, im still deciding weather we should use the supershifters or the banebots(i think this is were the weight could be made up ot lost), its really all a matter of what we want to use if for(probobly just for testing and demos) i still think it will be lighter(even if its only by a pound ill be happy) |
21.2 lbs chassis
+ 9.2 lbs Supershifters (as is, without any lightening)
+11.0 lbs CIMs
+ 4.0 lbs 6 AM Plaction wheels
= 45.4 lbs
That is with no electronics, and no chains. You'd have to remove a ton of material for that to come in anywhere near 36 lbs.
24-12-2008 15:50
gorrilla
Re: pic: my version of a wooden chassis
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Originally Posted by Vikesrock
If electronics are included in that 36 lbs than this base should be significantly heavier than your base from last year.
21.2 lbs chassis + 9.2 lbs Supershifters (as is, without any lightening) +11.0 lbs CIMs + 4.0 lbs 6 AM Plaction wheels = 45.4 lbs That is with no electronics, and no chains. You'd have to remove a ton of material for that to come in anywhere near 36 lbs. |
I meant the AM kit wheels, and I might use BB transmissions, and we only have two cims extra currently so it might be just 4wd for now....
the electronics shouldent be more than 8 pounds for it
24-12-2008 15:54
Cory
Re: pic: my version of a wooden chassis
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Originally Posted by gorrilla
I meant the AM kit wheels, and I might use BB transmissions, and we only have two cims extra currently so it might be just 4wd for now....
the electronics shouldent be more than 8 pounds for it |
24-12-2008 16:16
Vikesrock
Re: pic: my version of a wooden chassis
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Originally Posted by gorrilla
I meant the AM kit wheels, and I might use BB transmissions, and we only have two cims extra currently so it might be just 4wd for now....
the electronics shouldent be more than 8 pounds for it |
I can't imagine the kit wheels are a whole lot lighter than the Plaction wheels, they are probably heavier.
Of course the base will be lighter if you start removing functionality. comparing this base as a 4WD with 2 CIMS to your base last year is not an apples to apples comparison.
24-12-2008 17:34
gorrilla
Re: pic: my version of a wooden chassis
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Originally Posted by Vikesrock
A Banebots 12:1 2 CIM gearbox is 3.75 lbs so that's still 7.5 lbs.
I can't imagine the kit wheels are a whole lot lighter than the Plaction wheels, they are probably heavier. Of course the base will be lighter if you start removing functionality. comparing this base as a 4WD with 2 CIMS to your base last year is not an apples to apples comparison. |
our base last year was 2wd with 4 cims
if im only using two victors, and the main block, and the power distribution panel, it should be around 8 or 9 pounds. weight isent really a concern for this, i just wanted to make it strong enough and still be lighter than the kit chassis with everything on it, just wanted to prove a concept to myself and my team
24-12-2008 17:52
MrForbes
Re: pic: my version of a wooden chassis
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Originally Posted by gorrilla
oh and interestingly, i think the bottom panel added a lot of stiffness, before i had it on, it would kinda flex out a litle bit
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If you can get some 1/4" and 3/4" plywood, I strongly suggest you build one similar to ours and see how you like it...you might be surprised how strong and light it is.
24-12-2008 18:54
gorrilla
Re: pic: my version of a wooden chassis
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Originally Posted by squirrel
When we made ours, we did not attach the ends to the sides at all. We glued/stapled the sides to the bottom, then glued/stapled the corner gussets on the top. With 3/4" sides, and 7/32" (slightly thinner than 1/4") bottom and gussets, it is very stiff and strong, and only weighs 13 lbs. The 7/32" bottom can flex a bit in the middle, but should have no problem supporting the electronics, as well as heavier stuff near the edges.
If you can get some 1/4" and 3/4" plywood, I strongly suggest you build one similar to ours and see how you like it...you might be surprised how strong and light it is. |
why dident you?
ill see what I can get....
im not very good with small objects and I tend to break things easily(which is why they call me gorrilla)
i was thinking about the dead axles when i made the decision to use 2x6's that way they could be supported better without putting to much stress on the wood
i think i could combine the two designs, like keep the 2x6's for the sides, but have the plwood for the ends and bottom, I like those steel L-brackets, they added lots of lateral stiffness
24-12-2008 19:10
MrForbes
Re: pic: my version of a wooden chassis
There is no need at all for the steel corner brackets if you use the triangle gusset plates on the top. All they do is add weight.
The 2x6 sides are way overkill, if you think you need some more strength at the axle attachment points, you could double the plywood at that area, but it really isn't needed. The cantilevered axles are short, and if they are made of 1/2" bolts then they are very strong, and the nuts and washers used to attach them spread the load out over a large area of wood. Also birch plywood is harder and stronger (because it's laminated from plies that go different directions) than a fir 2x6.
There is a lot of engineering thought behind the design we came up with....
24-12-2008 19:19
gorrilla
Re: pic: my version of a wooden chassis
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Originally Posted by squirrel
There is no need at all for the steel corner brackets if you use the triangle gusset plates on the top. All they do is add weight.
The 2x6 sides are way overkill, if you think you need some more strength at the axle attachment points, you could double the plywood at that area, but it really isn't needed. The cantilevered axles are short, and if they are made of 1/2" bolts then they are very strong, and the nuts and washers used to attach them spread the load out over a large area of wood. Also birch plywood is harder and stronger (because it's laminated from plies that go different directions) than a fir 2x6. There is a lot of engineering thought behind the design we came up with.... |
If we were gonig to use it for competition I would use your design but intstead of dead axles, i would use directly driven wheels so there ould be as little pressure on the shaft as possible,
i also think that its way overkill for just a demo-bot, but if we had to use wood next year, i know that it would be a very long decision on which way to do it,(probobly would end up a mixture of both)
could you list what you think are the pros and cons of both?
24-12-2008 19:27
MrForbes
Re: pic: my version of a wooden chassis
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Originally Posted by gorrilla
If we were gonig to use it for competition I would use your design but intstead of dead axles, i would use directly driven wheels so there ould be as little pressure on the shaft as possible,
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| could you list what you think are the pros and cons of both? |
24-12-2008 19:35
gorrilla
Re: pic: my version of a wooden chassis
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Originally Posted by squirrel
There is no need to have as little pressure on the shaft as possible, if you make the axle shaft strong and well supported. If the shaft is short and large diameter and well supported, it can take a lot of load!
The neat thing about the wood chassis concept, is that you can build a couple of them, using different designs, for not much money. Then you can see how they work. |
but wouldent having the wheels directly driven do both jobs at the same time and be stronger and lighter?
ill see if i can get back to home depot and get some more wood,
ill try building your design and see what happens
24-12-2008 19:40
MrForbes
Re: pic: my version of a wooden chassis
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Originally Posted by gorrilla
but wouldent having the wheels directly driven do both jobs at the same time and be stronger and lighter?
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We used a cantilevered dead axle design last year, and it was very strong and light. It's hard to compare two designs without having some drawings or pictures of them, though.
24-12-2008 19:42
gorrilla
Re: pic: my version of a wooden chassis
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Originally Posted by squirrel
Yes, it could be stronger and lighter...but you might not be able to make it have all 3 wheels on each side driven by two motors, which is something we think is kind of important.
We used a cantilevered dead axle design last year, and it was very strong and light. It's hard to compare two designs without having some drawings or pictures of them, though. |
ill see what happens in the next week or two I have off
ill put some dead axles on my current frame to see how they would work out
24-12-2008 19:44
Rick TYler
Re: pic: my version of a wooden chassis
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Originally Posted by gorrilla
the only thing im concerned about is taking an hit on the side, and cracking the 2x6(but there will be bupers so it shouldent be that big of a problem)..
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- Rick
24-12-2008 20:20
gorrilla
Re: pic: my version of a wooden chassis
is the bearing really needed fo the dead axle? couldent you just drill a half inch hole and put the bolt through it? would a simple bronze bushing work?
25-12-2008 00:37
MrForbes
Re: pic: my version of a wooden chassis
A dead axle does not use a bearing, the bearings are in the wheels. The axle can be bolted to the chassis.
25-12-2008 01:31
MrForbes
Re: pic: my version of a wooden chassis
Gary is working on the Inventor model of the chassis, adding the axles so you can see how we are planning on making them. Hopefully we'll get to our fab shop this Saturday and put on the axles and some wheels. Meanwhile here's a video of the bare chassis showing how strong it is.
http://www.youtube.com/watch?v=VhNhnrPTRMw
25-12-2008 07:57
gorrilla
Re: pic: my version of a wooden chassis
wow, it dident even flex at all
I just dident think with it being thin plywood, you could get a strong enough connection to the other pieces
like there wasent enough for the pieces to hold onto.....
Im thinking 1x6' s for the next one
25-12-2008 16:56
Rick TYler
Re: pic: my version of a wooden chassis
Most robotics kids underestimate the strength and flexibility of wood and wood composites. Here's a link to a Wikipedia article on the de Havilland Mosquito, a WWII British fighter-bomber made largely of plywood: http://en.wikipedia.org/wiki/De_Havilland_Mosquito. It could carry 1,000 pounds of bombs nearly 1,500 miles, and fly almost 400 miles an hour.
Or how about a plywood/composite boat that can go 50mph and has a hull that only weights 875 pounds?: http://www.bateau.com/studyplans/MG2....htm?prod=MG20
Nothing we do with robots is as tough as these engineering problems.
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