Rango - Build diary

[overkill]

I would be very wary about using titanium for pins - I tried saving weight with some very expensive Ti bolts and every one of them sheared, where the steel bolts never did. Those steel disks look fantastic, keen to see how they rip into the opposition!

[Max]

The drum looks awesome! Out of interst is this going to be invertible? I assume so but can't imagine how without it running with the drum on the ground!

Also are you using timing pulleys with the timing belts for the wheels or just plain pulleys?

[Ellis]

Hey Nick, that's a bit worrying! I'd want a refund, haha. Will bear it in mind.

Max, it isn't very invertable, if that makes sense. The back wheels run on the ground when inverted (and the drum just slides) but there is so little weight over them I doubt it'll do anything. If I have any weight left I'll stick some magnets in the top panel back there in the hope it might give enough grip to prevent being counted out.

All of the belts/pulleys on the drive are toothed.

[mrsam]

Looking good that drum reminds me so much of k2

[overkill]

With all those M8 bolts around the drum, I can't see you having any problems with the disks shifting much. BTW: if you are having weight issues, why not bore out the drum a bit more? The weight near the centre of rotation will be adding very little to the KE of the weapon. That might give you back enough weight to add the hold-down magnets.

[daveimi]

I like the single tooth drum, that must have taken some balancing.

[Ellis]

@Nick: That is an option, yeah. I had the bore left at 25mm because in the event of the drum getting a massive, bearing disintegrating hit, I can pop some 25mm OD 20mm ID bronze bushings in there (I'll make some spacers to fill the bearing pockets) and get a form of weapon for a fight or two. I doubt the alu shaft will enjoy that much but if it's the difference between a win and a loss the shaft can get remade!

There are so many variables weight-wise that I could be half a kilo under or over. #planning

edit: thanks David, I don't yet know what the balance is like (this is all still with Jeroen), but it should be close to negligible as-is, if not I can take some material out of the drum and get it bang on.

[overkill]

Those roller bearings should take major punishment but its always good to have a plan B. Looking at the photos again, what's stopping axial movement along the shaft? That's the weak spot for the roller bearings; are you using thrust bearings between the ends of the drum and the frame?

[Ellis]

There will be spacers/shims around the shaft between the bulkheads and the bearings, putting a bit of preload on the rollers and spacing them between the bulkheads. Very similar to Dave's 720, as that seems to work well. He knows imitation is the purest form of flattery.

[Mouldy]

This year i'm covering 720 up between fights and getting an armed guard...everyone seems to be stealing my ideas lol

looks good though- how come you didn't use the bulkheads to pre-load the bearings like on 720 and take it as an opportunity to fit a wider drum? To heavy? What is the total weight of your drum btw?

[overkill]

@ Dave: Too late; look out your window - is that a drone circling your place RIGHT NOW?

[Mouldy]

Hope not, i'm at work lol

[Ellis]

Lol. Inb4 titanium drum for Rango in 2015.

I'm not sure how I could get preload on the bearings differently when they sit behind the discs as they do. Could have used thrust bearings or something between the bulkheads and the faces of the discs, but it's more fuss than it's worth I think, for a slightly wider drum. The clearance is 2mm from the boltheads to the bulkheads as it is, I'd have to use weaker headed bolts to make it wider.

Also the spinning mass will be about 2kg, maybe a tad over, at around 8000rpm. Never intended for the weapon to be the main aspect of the robot, I think Harry described Rango once as a jumped up rambot and that sounds accurate to me. :P

[harry hills]

You made a rambot with where the weapon is more reliable than the drive. You're special.

[Ellis]

Jeroen has done more work on the drum, and it's now nearly ready to send. He has put loads of time into this, and has supplied nothing but quality and knowledge with a speedy turnaround. Couldn't be happier.





Meanwhile in the mudshack I call a workshop () I have modded the wheel pulleys. 3 bolt holes each and a large bore to accept the biggest bushing I could make that still had a small flange, so there's less heavy steel and more air-light oilon. Drilling the-


-half-holes sucked!



Also now organised is the watercutting for the 3.2mm hardox wedge, through Mario, who will also be welding it up.

It will all hopefully be in my hands a week or so before we leave. What even is planning?