Design Dilemma

[Eventorizon]

I am currently stuck between 2 designs... 1 I have been working on for about 8 months but I have discovered has quite a major flaw and another design which is much better but would need another 6 months or so of development before I could even build it...

Design 1 has gone through about 20 iterations to reach it current stage. It has a 1.8Kg disc, 4 wheel drive and a Shrimech/lifter, however, after a CAD materials mix up, I have hit the weight limit in CAD and still have the welding, ESC's and wiring to take into account. The armour is already thin at 8mm HDPE and the Chassis is looking flimsy with the uprights in 5mm Alu 6061 and the base & struts in 3mm Alu 6061.

The second design is initiative. The disc is mounted in a pivoting frame so if the robot is flipped the disc mount moves to let the wheels touch the ground and the disc is still driven. However, as with ever design, there are going to be a huge number of problems to solve before it can be built and given it took me over 6 months to bring the other design to a stage I was happy and confident to build it might take the same again for this one.

From my position I see I have 3 options€¦

1: Continue with the current design until it all fits in under the weight limit by thinning the armour, chassis, messing around with the internal cut outs and lightening the disc.
2: Remove the shrimech from the design and go back to a previous version and redevelop the design. This would allow for thicker armour and a stronger chassis but leave the robot with a fundamental flaw, no self righter.
3:Move to the second design and develop it until I am confident It will work as planned.

My hope had been to enter one of the competitions after I finish my 2nd year at university, sometime in June. Options 1 & 2 would allow me to do so but with, in my opinion, an inferior design. 3 would mean that I would have to wait until September/October but would mean I would have a better design.

There is an upside... all the design share the same electronic parts (apart from 1 ESC in option 3) so its only the chassis design changing here!

Any and all ideas, suggestions, comments and solutions are welcome!!!

[Anttazz]

To save weight, would it be possible to run it from 4WD by using 2 motors and running belts between the other 2 wheels?
Then using something like an XL which hardly weighs anything and save yourself the weight of another ESC too. Also, if you're not using LiPo's you could change over to them and save yourself a load of weight.

[Max]

You could stick with your first design and add hoops (like on the first drumroll) to make it self right. This would be much lighter than your self righter and cheaper! You could also just use 2 wheel drive rather than 4 wheel drive. I also think I remember reading that you are using 2 speed 900s for the weapon you could reduce this to just one or use a brushless setup.

[PJ-27]

I think I speak for a lot of people when I say this but...

GET OFF CAD AND START BUILDING!

Seriously, you will learn so much more and actually experiencing the problems and working with them, fighting with your robot and meeting others cannot be simulated.

There are so many little things you'll run into when building that you just can foresee that'll mess up even the best laid plans.

It's good to have an idea of when you want to make, and a plan to get it in weight, but the knowledge to get that right in theory takes years to accumulate so pick a design and get building.

If you know for a fact that your first design will be over weight then make some tweaks like what Tony suggests.

I like the articulating disk idea though. I suggest you have a maximum of 2 teeth of the disk though, otherwise it'll end up 'grinding' against other bots and never get a good bite. You'll also probably want some more weight in it, although Inertia XL's disk is 2kgs (I believe) and that's very effective.

[Laser]

As Pj said get to an event and look around.

my first robot was useless and I learnt sooo much by going to an event.

as for weight try only 2wd, use just HDPE/ nylon 6, Lipo's

[graeme]

There are prob only 2 full combat events for feathers this year in the uk and they are going to be in april so i would build it for then and then improve it for 2013.

[Anttazz]

You could stick with your first design and add hoops (like on the first drumroll) to make it self right.

I wouldn't, they didn't work and have probably shortened Jamie's life considerably with stress. I remember at RL Edinburgh last year he was having flashbacks when there was a Design your own Hoola-hoop desk

[psycho_fling]

tbf cad is a great tool and if you want to go down the route of machining etc it makes sense, working out the problems etc will be harder but will make things cheaper by using cad

[Eventorizon]

To save weight, would it be possible to run it from 4WD by using 2 motors and running belts between the other 2 wheels?

I have tried belts in the design and I just can€™t seem to make it light enough, but I know it works so I am probably doing something fundamentally wrong.

It's good to have an idea of when you want to make, and a plan to get it in weight, but the knowledge to get that right in theory takes years to accumulate so pick a design and get building.

And its not all CAD I have made 4 prototypes, 2 from card and 2 from laser cut wood, the final one is a functioning robot. The reason it got redesigned, again, was that the motors I chose just were not up to battle. Check this link for a video

Also, if you're not using LiPo's you could change over to them and save yourself a load of weight.

I have steered away from LiPols because of the cost and the possibility of explosions, and the fact I cant have them in my rented flat or in uni (stupid health and safety)

When are the 2 full combat events this year? I cant find them on the site€¦ only the heavyweight ones.

[Gabe01]

Simple, to make your Robot lighter you need to make it smaller, two motors are sufficient, and then you can almost half the width of your Bot. I am designing my feather at the moment and playing around with the bits. I have built three heavies and you must think compact and small. I remember Ian Lewis shoving his arm and hand into our first Robot, a good lesson learnt