LYNX Beetleweight

Hi all, i've decided that i'm going to start designing a beetleweight version of Hatchet called LYNX, why LYNX? because in America LYNX deodorant is called AXE and i thought that was a cool coincidence. I'm hoping to build this alongside Hatchet 2 and have it ready for the end of this year/beginning of next year. I'll also be trying a Brushless motor for the axe, i realise that this means i'll have to gear it down quite heavily but hopefully i'll be able to get some advice on the best way to do that.

The specs so far (likely to change but it's a start)

HDPE for the chassis, what thickness do people usually go for?
1 -1.5mm Aluminium baseplate
2 1000rpm Ebay gearmotors
Brushless motor for the axe, geared down heavily
Mini Hatchet style axe ( of course)
3s 11.1v Lipo battery

Just a quick question, i may depending on how difficult it would be build an overhead bar spinner beetleweight like Massacre or Hazard. Are the rules regarding removable links the same as in feathers? i.e a hollow shaft with the link accessible through the top?

I would think so, though the slaughterhouse is known to bend the rules here and there.

Yes Sam.

Shouldn't be too hard to do. I'm more than happy to make you a smaller version of the Massacre shaft. I have a beetleweight Massy designed up somewhere too but I won't build it I don't think. Message me if you are interested.

Right so, Putting the mini hatchet on hold for a while and i'm going to be designing an overhead bar spinner, an extremely stupid overhead spinner i might add. Basically whilst looking through some old bits and bobs i found a whacking great big lawnmower blade that looks perfect, 350mm long, 45mm wide and about 4mm thick weighting roughly 400g. The idea is to have a Hazard/massacre type chassis made from 10mm nylon about 200mm by 180mm and the blade on top sitting about 40-50mm high spinning at roughly 4000rpm. I am under no illusions that this is a good idea and i expect it to send itself flying on more than one occasion but still it should be fun.

That's a long bar! Overall dimensions and weight of the weapon sound perfectly plausible. If you needed to make it a little more stable the lawnmower blade could perhaps be shortened, or it'd be fairly straightforward to make one/organise a custom one. Best of luck!

Cheers Ellis hopefully i can get it working properly, my biggest worry is the motor not being able to spin up the very long blade quick enough but only time will tell. The blade in question http://i921.photobucket.com/albums/a...psb30fc958.jpg

Great stuff. I approve lol. That bar is perfect.

Does look perfect! Great find!

I made a BW with a lawn mower blade a while back, exactly the same as that. Struggled with weight and a good fixing on the blade. though.
New one uses a smaller SS bar.

You might want to rotate the bar. The way your holding it now will generate lift :D

Cheers guys, it was an awesome find and it does at least look the part, PJ is that Spinza that you were referring too? i'll be going the same route as harry went for Massacre for the mounting the bar i.e a hollow shaft with the link out the top and the blade mounted to a pulley with a bearing in. The only problem i can see at the moment is the motor, i don't see the point of trying to fit a right angle gearbox in a robot of this size/weight so i'll have to try and find a motor that 1) is lower than 50mm and 2) is powerful enough to spin the blade up quickly. This looks ideal but not sure about how good they actually are http://www.hobbyking.com/hobbyking/s...arehouse_.html

Erm......it's out of stock
Unless you go for another one like that
Is it an inrunner

I won't be buying it any time soon just looking atm, and no it's an outrunner it just has a very narrow can

I've decided on the weapon motor after a very long and tedious search http://www.hobbyking.com/hobbyking/s...dproduct=14736 new stock is currently "in transit" to the hobbyking uk warehouse so hopefully it will be in stock when i come to buy it. The shaft will be cut down from 24mm to 18mm which will make the motor 45mm high. Just going by the specs it seems like a hefty little motor, i'll be running the bar on a 2.5:1 reduction at 3s which will give it an overall theoretical speed of 5772rpm but with losses more like 5000 although i doubt i'll run it at full speed very often.

Might get one of those motors myself.

That should do the job well. 420w at 3s from an 88g motor is quite the figure. Am also interested. :D

What model battery are you looking at using?

Unsure on the battery at the moment, having never used lipos i can't go from experience. I was thinking about getting a Turnigy Nano tech as they're none too expensive and some have quite a good C rating.

They do look good on paper but I have heard from several that the nanotech series' ratings are wildly over the truth. I think Gary used them last year in his feather and was disappointed. I have used the regular Turnigy packs (second hand!) but having never had them in a high power bot can't really comment on their performance. I can say confidently that they are batteries. :)

The packs from Component-shop seem to be quite good, and although pricey Optipower are the real deal. You can get a roboteer's discount to soften the blow with them.

Yeah i read Gary's report on the ones he used for his Boner (sorry) it may be that i buy ones with a larger C rating than woulod normally be required so even if it is bull it might still be enough. There's one i found with a 65 - 130c rating so i'll give it a go and see from there. This bot probably will be quite power hungry as i'll be running the blade and 4 gearmotors on the drive. If all else fails like you said the Optipower ones are the real deal and i should consider them an investment discount or not.

I've used Nanotechs in my RC cars and plane. After they nearly all got stolen from my van I started using Gens-ACE and Zippy lipos and the feel a lot better to me in terms of performance.

Okay awesome, i hadn't heard too many good things about Zippy lipos but if you're saying they've got the edge on performance over the Turnigy ones i'll give them a look. They're actually the cheaper option so it's a win win if they work.

Yes, that was Spinza.

The trick is to not underdimension your batteries. If your system pulls 150A don't get batteries that only pull 150A in burst. For that 25-50 grams extra get that piece of mind.

I've been looking at drive motor options and just a quick question, obviously many people use the 1000rpm gearmotors from ebay and they're definitely an option but i seem to recall seeing a beetle fbs using four of these type of motors that i presume are usually used for antweights? http://www.ebay.co.uk/itm/2-Pin-Term...item2c725c215c just wondering how others feel about using them.

I'd be interested to see how well the high power versions of those gearmotors from Pololu worked in a beetleweight, as they have far more power than an ant can actually put down. They're about 12W each peak, so I'd think 4 of them would happily power a beetle.

Those ones on ebay are unlikely to be the high power version though, probably more likely the 4W version, which wouldn't be much use in a beetle I'd have thought.

So Hatchet went to it's new owners today and i'm now left with just an empty cradle in my room where it used to sit. This has spurred me on to get something built so as of next month i will be buying parts to get the overhead done. I already have a shopping list so here's a quick run down, feel free to comment.

2mm stainless steel baseplate roughly 180mm x 200mm

10mm Hdpe chassis and structure

This motor here to drive the blade http://www.hobbyking.com/hobbyking/s...tor_420w_.html

4 of these for the drive http://www.ebay.co.uk/itm/12V-1000RP...item4d02e1d617

2 Botbitz 10 amp escs's

70 amp red brick esc to control the blade http://www.hobbyking.com/hobbyking/s...k_70A_ESC.html

Possibly this Lipo http://www.hobbyking.com/hobbyking/s...dProduct=32243

Buying this setup from Harry that he originally made for a beetle massacre.
http://i.imgur.com/Q6Ec4TD.jpg

Let me know what you think, feel free to make any comments on areas you think could be improved.

Not really an update but whilst on ebay last night I stumbled across a cheap link for the 1000 rpm motors, 2 for 6 pound is an absolute bargain http://m.ebay.co.uk/itm/390840968185?nav=SEARCH

That's a total steal if they perform like the others. I might get myself some of those, good spot!

I've ordered a couple of these to try out. Worth a try at that price!

Just a little update, changed the design slightly after plonking the weapon set up on top of the feathers disc. Will get a round base plate cut probably out of 3mm Ali but for now here's a picture, Tornado Mer style! http://i921.photobucket.com/albums/a...psaa09bd96.jpg

"Blows away cobwebs" Made the decision to put Wraith on the back burner for now and start on Lynx. I realised that I can't use Wraith until next year so I'll finish the bits I have the parts to finish and then come back to it later.

Ordered the weapon motor and esc for Lynx today and a few other little bits, I'll get started finishing the weapon set up tomorrow and should hopefully have it spinning in the next couple of weeks depending on how long Hobbyking takes to get it arse in gear.

If you ordered from the UK warehouse it should be quite quick, a matter of days.

Pretendobot pics! Nothing special but I can now at least start Lynx, got the baseplate material yesterday which is a piece of 1.5mm stainless (200 x 200mm) and I'll get to attaching the weapon set up today, more parts are on the way including the weapon motor and esc and some hdpe for the body, should have a weapon spin up early next week. http://i921.photobucket.com/albums/a...psdc8f1ec2.jpg http://i921.photobucket.com/albums/a...psbaf85403.jpg

Little update, no pictures just words unfortunately. I've decided that whilst i love the overhead design i don't think i'd ever be able to get the blade low enough to hit the really low robots, so that idea's getting put on the pile and Lynx will now be.....DUN DUN DUNNNNNN a mahooosive undercutter! think relic from the states only more Beetle, same massive blade but hopefully a more effective design to use it in, i WILL be making some progress soon, i promise.

Got bored of waiting for Hobbyking to get the motor i ordered in stock so i cancelled it and bought one of these instead http://www.hobbyking.com/hobbyking/s...arehouse_.html possibly a TAD overkill seeing as the blade will now be theoretically doing around the 8000rpm mark, anybody worried?

Well considering I'm running a 200w motor at 1.4:1 I should think that will make the bar spin quite nicely. :P

Yeah i don't think this motors going to have much trouble at all :) Just a quick question, if i run the bar at 3s it'll be going around 8000rpm and have theoretically 1198.2 joules of energy, if i go 4s it'll be around 10,000rpm and will have theoretically 1872.2 joules of energy. How does that compare to some of the other spinners?

Well RPM can produce a theoretical max KE of 215 joules when going 13,000rpm :P