Liftoff (FW) build diary

[PJ-27]

Re: Liftoff (FW) build diary

Maybe I missed something, but why not just design it so that the flipping arm is also the self righter?

I thought about using friction drive for a second set of wheels but quickly decided against it since I figured as t he tyres ware they will no longer touch each other and any debris will jam between them.

[Liftoff]

Re: Liftoff (FW) build diary

The first version of Liftoff had no problems with self-righting because as you said PJ, the design of lifting arm acted also as a self righter...but there were also disadvantages to that design.
The hinge point was at the very edge of the machine and the ram was vertical, the recoil caused the robot to flip upside down when it missed the target. And to be able to self right properly I had to decrease the usable pressure to around 7bar or less as otherwise it would somersault and end up upside down again!

So I redesigned the system placing the hinge mid-way on the machine, and with the ram in horizontal position hoping to eliminate the tendency of the machine to flip upside down when it misses the target.

I could try to redesign the the flipper hinge so that it would travel further up and act as a self righter - but I fear it would be in a too much of a mechanical disadvantage

[PJ-27]

Re: Liftoff (FW) build diary

Most of the flippers throw themselves over when they miss a target. Wouldn't an easier option be to not miss?.....

[Liftoff]

Re: Liftoff (FW) build diary

Wouldn't an easier option be to not miss?.....

I'll try!

Received more parts today, miniature 2/5way valve and Qev

[Liftoff]

Re: Liftoff (FW) build diary

I finally got most of the parts I will be needing for the upgrade - the design is still not final, but I've got some new parts with which I should be able to make all things work... just need some time to get going with it now!

[firefly1]

Re: Liftoff (FW) build diary

looks good

[Liftoff]

Re: Liftoff (FW) build diary

Final changes to the design ready... Changed the flipper hinges to a simpler piano hinge type, I'm assuming it will be up to the job! It shall be a medium duty 4mm pin hinge.

The self-righter mechanism was the biggest headache - but I think I have a simpler more effective system now...took some advice from posts on this build and came up with a Linkage/Slide/Cable system... from its description, it does not sound simple at all! But since I have almost all the parts required already - then it's very doable..

In theory it should work...now I just hope that in the end it does its job! :wink:



These are the parts, two links and the slider. The slider is pulled by a cable connected the the flipper arm and slides down the guide, then returns back by means of two flat power springs.



Slider parts: Slide and cable, power springs, guide.

[Eventorizon]

Re: Liftoff (FW) build diary

Thats awesome! I can see that working wonders, though you will have to check the cable after every fight. Your Sketch Up work is superb to, you aught to move over to Solidworks or Autodesk; even blender might do it. It would make your life so much easier.

[Liftoff]

Re: Liftoff (FW) build diary

Yeah, I'm a bit concerned about the cable snapping at the end swage, but I guess I'll only get to know after testing it but I think there's space for modifying/beefing up things if it fails.

Been using sketch up for quite some time so I got used to it - though have to admit that it makes me swear sometimes! Mainly use it as its free!!

[Mega Masher]

Re: Liftoff (FW) build diary

Hi, your robot looks epic. By the way, what size wheels are you planning to use?

[Liftoff]

Re: Liftoff (FW) build diary

Thanks :wink: The wheels I planned to use are twin 73x20mm banebots to give me a with of 40mm.
Like this:
http://www.technobotsonline.com/banebot ... re-30.html

But the drive system will be different from what's in the drawings... I'm still obsessed with having it track driven!
I know it was a real pain to set it up and it was not the most efficient drive system at all - but I designed a new set up which hopefully should work...the steady bearing on the gimson motors will come in handy for this!
Will post a couple of drawings tomorrow...

[Liftoff]

Re: Liftoff (FW) build diary

As promised - the tracked drive system design. Running track drives for these last 4 years on different machines always gave us trouble - but I have to admit the early ones were quite rudimentary systems
Main problems were : excessive side load on the motors as they were not supported at the far end, causing the motor to heat up and draw a lot of current. Another issue was track alignment, without proper precision engineering the track would try to slide off the wheels and rub against the sides.

In this new design the drive wheel is supported at both ends, that should take load off the motors. Alignment of the track is achieved by adjusting the forward idle roller. The fwd roller is mounted on shock absorbers which can be adjusted to move fwd or aft. This should hopefully keep everything aligned and tensioned . Both wheels are flanged to help prevent the track coming off...

The pics: :wink:


Tracked drive system V.04





Drive wheel and attachment to GR02 motor - exploded view





Drive wheel and GR02 assembly

[Eventorizon]

Re: Liftoff (FW) build diary

That looks awesome! I have been wanting to fit tracks to one of my machines for a while, I might just have to nick that idea And again, great CAD! An exploded drawing in Sketch-up!

[Liftoff]

Re: Liftoff (FW) build diary

Good! I'd only be too happy to know my work was useful to someone else! I really learnt a lot from this place.


I've always run our machines on tracks and I like it to stay that way - but having said that, it does not mean its superior to other types of drive. I actually think its got more disadvantages than advantages...mainly being: increased weight, complicated (more things to go wrong) and believe it or not , less traction! The main advantage is its ability to move over uneven surfaces, that is - it difficult to get stuck.

Thanks for the compliments on the drawings...but as I said, once you get used to it, its quite simple...will try to upload some of the components just in case someone would like to use them

[PJ-27]

Re: Liftoff (FW) build diary

I said a few times in the past we should have a cache on here of everyone's SketchUp components. Saves everyone making the GR02!