Valen, the worst I have ever had with testing of my rams is that the rod alone left the ram. Had this 3 times up to date.

The first mishap was with Hard's first test with the ram in the robot. The bolt and washer ripped right trough the UHMW PE piston, That is when I changed from normal steel washers to large ali washers to holt the rod and piston together.

The second time was the worst. The entrance of Project II Hex'em in the second dutch wars. The first action of the ram in the arena, and the rod ripped itself from the piston.
What happened was a succession of events; We tested the ram in all situations.
But when we got at the selection ProjectII did prove far underweight. 83 kg, with full bottles. So we increased armor, also on the arm. And we added more batteries to the robot itself.
This larger moving mass with the Stainless steel %12 bolt used to mount the piston to the rod was to much. Stainless A2 70 is not as strong as 8.8, so the bolt sheered of its tread. I replaced after the war with M16 10.9 bolt. And that is keeping up, even after all these years.

The third and last time was when I used a weak kind of ali for the rod. A gravity style featherweight size ram fired in a test stand just launched the rod. The feeble left overs of the tread still clinging on the bolt. A new rod and longer bolt did the trick.


But yes, a Gravity style ram cannot be safe in the "classic system" where the ram connects to the moving mass of the arm.

Maddox last post is yet another reason why this robot scares the hell out of me. But it wouldn't be fun if it didn't.

Here are some pics of the new hinge assembly:






The bolt that is in there acting as a pin in the photos is only temporary obviously. It is hard to see but there is a small piece of 3mm steel plate welded onto the inside of each bracket that will take most of the force from the pin, this being that area that failed first on old hinge.

The brackets also don't look very straight in that second photo do they, but I'll blame that on the angle that the photo was taken.
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Get Some!!!

Secretary of the Queensland Robotics Sports Club inc.

quote:

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Originally posted by kkeerroo:
Maddox last post is yet another reason why this robot scares the hell out of me. But it wouldn't be fun if it didn't.

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quote:

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Originally posted by Valen:
F=MA as you say. The problem is hitting an end stop means stopping the whole thing over the length of flexing you have in the end of the ram. so A becomes astronomical.

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I just gave Devastator a test after putting it all back together and the new hinge seems to work well. I am using a scooter wheel axle as a hinge pin as they fit perfectly and I have a couple lying around. The arm still doesn't want to return correctly.
I can get our wheelie bin 1m off the ground .
_________________
Get Some!!!

Secretary of the Queensland Robotics Sports Club inc.

It will be interesting to see what a properly prepared Devastator can do.
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So even the rain that falls isn't actually going to fill our dams and our river systems

To get the arm retract properly, you need to get the retracting force directly down on the rod.

Best way to to that is to retract the rod and the arm on its own. 1 bungee loop for the rod, in a straight line down, and 1 loop for the arm, whatever position is usable, as long the force retracting is bigger than 13.6 kg.

Do you have any pictures of bungee returns that show the best way to return the ram?
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So even the rain that falls isn't actually going to fill our dams and our river systems

quote:

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Originally posted by maddox:
To get the arm retract properly, you need to get the retracting force directly down on the rod.

Best way to to that is to retract the rod and the arm on its own. 1 bungee loop for the rod, in a straight line down, and 1 loop for the arm, whatever position is usable, as long the force retracting is bigger than 13.6 kg.

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Sorry, due a dead hard disk I don't have access to my own pictures.

The grove in the top of the rod is not something i made

Trophy for Devastator from Eleanor, well done!

http://i41.photobucket.com/albums/e275/trentellis/IMG_0060.jpg
http://i41.photobucket.com/albums/e275/trentellis/IMG_0067.jpg
http://i41.photobucket.com/albums/e275/trentellis/IMG_0068.jpg

I vid to go with this post would be nice, any1?


I didn't want you to get me in the 1 v 1(u didn't), but in the Melee was fine. You pulled off some orsome flips today, just excellent.
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Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.
Albert Einstein.

Cracked the polycarb! Sure that's polycarb?
And that bend in that rod, must have been a pretty decent flip! Wern't picking on the new guy were you per chance kerros?
Video indeed would be kewl.
EDIT: Seem's I might have to take that comment back, seems like eleanor is one tough bot!
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YEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH

Andrew can confirm but in the melee and/or for most of the day Devastator didn't have much force on the flipper arm returning it, making it a bit of a one BIG HIT only show. I would want to flip Eleanor too in the melee after earlier going 1v1 with it and not get to use its flipper once(Payback ). VL coped a ripper flip too, into the roof and straight back down on to its spinning disk .
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Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.
Albert Einstein.

I got it all back together and tested it and the new strap works fine but the arm still doesn't return. I works fine with the arm by itself but it cannot move the ram back into place.
So here is a question aimed at maddox, what lubricant can I use on the piston to help free it up a little?
_________________
Get Some!!!

Secretary of the Queensland Robotics Sports Club inc.

About any kind of thin oil is a good one, but not the types like WD-40.

Another thing, you have to assemble the ram with the rod estended so the piston acts like a centering ring.

And, is there enough force on the rod itself to retract it with the force of the arm pushing it forward into the top?