Liftoff (FW) build diary

Ah recognised the Sabertooth :wink: I got the 2x60 in there, I know its not highly recommended but we've used it with no issues last November... fingers crossed!!
Yes that L shaped piece is there because I got a piece of titanium in a roughly similar shape and thought I'd use it but triangular shape would be a better bet - will re design!

Drive is still a question mark, I had tracks on it and maneuverability was top notch, the down side was the added weight and less grip. I might go the 4WD way like you said or tracks again - both are possible in the available space.
Yes the wedge shape really looks like a stealth something - keeping it as low as possible - the highest point is just 160mm!

Thanks for the encouragement hope to make it to an event in the Uk next year

Hammerhead II used that decoupled setup with reasonable succes, and I based the Gravity 2-3 setup on it.

Good to hear that Mario - I'll try to look up Hammerhead II to see how it's set up.
I tend to get a bit discouraged when I start complicating things...got to find some local waterjet cutting shop to do these little bits and pieces as most will be done from titanium and that's a nightmare to cut without proper tooling - I'll post a few close ups of the lever system - if there's anything wrong please point it out, thanks

Couldn't find any close up views of Hammerhead II internals... anyway here's my setup:

My concern here is that the links come almost in a straight position, and not sure if it will be too much of a mechanical disadvantage to overcome.

http://i8.photobucket.com/albums/a49...ps3663d520.jpg

Flipper up

http://i8.photobucket.com/albums/a49...psfa374aef.jpg

Why not using bigger wheels or a Hard drivetrain and not needing a selfrighter?

In theory I can see that it works but in reality... I wonder about the strength of the parts and the leverage you get.

Do you have accsess to something like MD Solids. You can used that to optimise the geometry of the mechanism my messing with the lengths of all the shaft and that kind of thing.

I am not sure what an alternative method might be but I don't think this will work reliably. Sorry...

You could run a cable or two to pull it up and possibly down

It looks like you have plenty of space to put in some friction driven wheels on top of the drive wheels, much like Crushtacean, seen at around 1:15 - http://www.youtube.com/watch?v=gEmRBaHRx7M - (I believe they worked like that, if not it serves to explain this)

Just trying to think sideways. This is a really nice robot!

fantastic work, loving the cad drawings too,

Thanks for the replies guys... For drawings I'm using Sketch up, got used to it now but some times its a real pita :evil: don't have MS solids Alex, will see if its downloadable and have a try there.
Material for the levers will be 4mm thick Gr5 Titanium - I think that will be suitable for the job, the problem is geting it into shape. There's no way I can form the levers in titanium using normal hand tools, the only solution is having them waterjet cut - I'm currently looking for some local shop which could do it for me without costing an eye :|
For sure I'll make a mock-up of the system using wood or acrylic just to see if the system works at all...hate surprises!!
Wheels on top might work to retain mobility upside down but I'd need to get the thing back in upright position to be able to fight!

http://i8.photobucket.com/albums/a49...psc13f3fb5.jpg

Been thinking about cables Jordan, its possible to do it that way - got to refresh my memory on cables and pulleys (its been a while since I last worked on a 737!) Off to the drawing board!!
Thanks for the ideas!

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.

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 :(

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

Quote:

---

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

---

:lol: I'll try!

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

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! :roll:

http://i8.photobucket.com/albums/a49...ps409e254d.jpg

http://i8.photobucket.com/albums/a49...ps3a237928.jpg

looks good :D

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! :D 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.

http://i8.photobucket.com/albums/a49...psbcdffcda.jpg

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

http://i8.photobucket.com/albums/a49...ps4c030100.jpg

http://i8.photobucket.com/albums/a49...ps0d789291.jpg

http://i8.photobucket.com/albums/a49...psd6b5bb73.jpg

http://i8.photobucket.com/albums/a49...psa49eda9d.jpg

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.

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 :roll: 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!! :lol:

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

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! :D
Will post a couple of drawings tomorrow...

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 :crazy:
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

http://i8.photobucket.com/albums/a49...psb7b566d6.jpg



Drive wheel and attachment to GR02 motor - exploded view

http://i8.photobucket.com/albums/a49...ps501c1a8f.jpg



Drive wheel and GR02 assembly

http://i8.photobucket.com/albums/a49...pscdae55b9.jpg

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 :proud: And again, great CAD! An exploded drawing in Sketch-up!

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 :roll:

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!

I've already done the GR-01s, and I'm working on other components. Search for them in the workshop.

Maybe we should open a new topic and make a sticky....then all post and link their components there...
I've uploaded the sabertooth esc... don't think I need to upload the GR02 now :roll:

I put a GR02 up there and have loads of other components that could go.

So I've dismembered Liftoff and got it to a shell again in preparation for the rebuild - one thing is bothering me tho. When I first put it all together I used normal chipboard wood screws to join the HDPE parts together - now I'm not convinced they'll re tighten as much as they used to do.

I had read somewhere on the forum that you could use wood inserts for better results. Now I've had a look on ebay and found what I need, just want to know what size you recommend, I'm using 10mm HDPE so the insert must fit within the thickness...

These are what I was looking at these two, both fit within the thickness, but the screw size is different

http://www.ebay.co.uk/itm/M3x12mm-Slott ... 3f0c4473b0

or

http://www.ebay.co.uk/itm/M4-x-10mm-Unh ... 4169c14f67

I've used the m4 1s before and they seem pretty good at holding the first bot together dropped it a few time and it stayed in 1 piece

I'll go for them then, I'm just using them for the removable access panels - plan to weld all the rest...

Those are for wood! They won't work in plastic!!!

These are designed for plastic...

http://www.ebay.co.uk/itm/M5-BRASS-I...item4d01fc65a2

You can get ones with flanges or without. You just press them in. I drilled my holes fractionally smaller and then heated them to give them more bite but the principal is the same.

Good you mentioned that Alex, otherwise I would have bought the wrong ones :?

didn't cross my mind there were ones specific for use on plastic!.... thanks for that :wink:

I imagine that the inserts for wood would work fine in hdpe as normal woodscrews work fine and it tends to work in a similar way to wood with chisels and saws etc.
I would also imagine that the wood inserts would stay in better when they had the force of a bolt pulling on them or an armour plate is getting ripped off.
just my opinion, I imagine both types would work.

No, cos I got the wrong ones. The wood ones in HDPE either don't go in at all or over stress the threads so much that they pull out with a bit of a tug.
The ones designed for plastic, I haven't been able to pull out, even when I have wanted to. Yeah, don't put them in until you have to and you are sure!

Quote:

---

Originally Posted by Eventorizon

No, cos I got the wrong ones. The wood ones in HDPE either don't go in at all or over stress the threads so much that they pull out with a bit of a tug.
The ones designed for plastic, I haven't been able to pull out, even when I have wanted to. Yeah, don't put them in until you have to and you are sure!

---

oh, my bad! just ignore me. :uhoh:

there are a few kinds that you can get for wood if as ive got the wrong version before you need to get 1s with what looks like an screw thread on the outside

the 1s in you links should work fine as there similar to what ive used before

Ok thanks to everyone for your input, much appreciated.

I have also found this : http://www.tappex.co.uk/ which gives a good explanation of which to use where.

Been abroad for some weeks so I had to abandon the build for a while... Now that I'm back home I can go about putting the pneumatics together and hopefully give it a test some time soon.
​ I'm replacing most components from the previous set up which had an empty weight of 3.7kg. The new set up weighs in at 2.6kg, that's a weight saving of 1.1kg, not bad eh! :D

Flow should improve as well - I'm using a different type of QEV which I had to modify to fit in limited space available (basically I had to plug the inlet and drill/tap a 1/8bsp inlet at the side) The smallest restriction from buffer to the ram will be 11mm as compared to 8mm of the previous setup - that should in theory help as well...

Some photos of old vs new QEV, old weighs 310gr, new weighs 120gr

Attachment 3676

And connections from buffer tank to ram

Attachment 3677

Did some testing this evening, and I'm happy with the results. Pressurised the system to 5 bar (need to buy myself a proper compessor for higher pressures :uhoh:). Was a bit concerned whether the 5/2 way valve would work properly, its miniscule compared to the rest of the system was worrying me! but I confirmed that it does not affect in anyway the flow through the system.
I can now turn my attention to the rest of the build.
Video in action
http://www.youtube.com/watch?v=BqQqzTKcLCg