Not happy!

I just can't catch a break with designing vertical spinners - they all come out WAY too heavy! I modelled the frame in Rhino and calculated a rough weight, 14Kg or over 50% of the total. Adding in the rest of the major parts has the weight headed well over 30Kg .

I can definitely hack out some weight from the frame but its not going to be enough without a serious design change. Replacing internal bisalloy parts with aluminium or titanium is an option, as is using thin-wall tubing. The biggest change might be to ditch the bisalloy completely and go with a welded titanium frame.

The weapon can always be lightened, which would be disappointing. the brushless weapon motor could also be downsized, its just something I had in stock and is probably over powered.

The drive train can be lightened by using thinner wheels and that has a flow-on effect of making the frame 50mm narrower and saving steel. It might be possible to replace the DeWalt motors with brushless out-runners; I'm not sure if that will really save much weight.

Back the the drawing board...

Where's the bulk of the weight coming from? The top down drawing looks like there's a lot of dead space inside. Hard to say without a 3d plan
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

The frame is the heaviest part, then the disk, then the drivetrain. I did cut out some space at the front and now there is much less wasted space at the front. drive motors can be moved in a little and the wheels can be thinner to reduce the frame width, but that was a feature to reduce gyro forces - I guess that will have to go.

The heaviest part of the frame is definitely the wedge. the base plate extends out to the front of the wedge and there is some extra bracing under it as well. I can definitely lose some weight there. The base plate was going to be lightened with some cut-outs and now I'm thinking about removing most the steel under the motors and batteries and using a Ti insert.

Nick,

Just to let you know these were the drivetrain configurations that we used on Touro Light (5" wheels):

RG2007 - 42mm Banebots + RS-775 Mabushi/Leshi @ 24V > We won the turnament, but it sucked, I replaced every motor after each fight.

RG2008 - 42mm Banebots + Dewalt New Style @24V > The motors improved, but the gearbox couldn't handle the increased power. Several gearbox locked up which let to burnt motors and Victors.

RG2009 - Moded Dewalt Powerdrive @33V - The mod was a new front including double bearings to be able to use an overhanging shaft. Big mistake to use the Dewalts New Style on 33V, mechanically it was good, but some motors cooked. At the end of 2009 I left RioBotz to live in the UK.

RG2010 / 2011 / 2012 - The original idea before I moved was to machine a custom 25:1 gearbox (T-Box style) and use the Dewalt Hammerdrill 36V motor @ 33V. But the remaining team decided to use Astro 90 motors and TWA-69 gearbox, which worked ok, but are to expensive IMO. I don't recall which was the voltage. They had a major failure in 2010 that resulted in a fire, but I don't know the reason.

At the end of the day, I think that 36V hammerdrills are a really good choice for lightweights. Brushless might to good as well (I am working on it as I write you...)

Regards,
Eduardo

Thanks Eduardo! I have to agree, the 36V DeWalt motors are hard to beat at the moment. Finding a small, high voltage ESC to drive them is difficult; I have been waiting for the Robot Power Vypre ESC for about 3 years now, perhaps a Bot Bitz hacked ESC would be better...

36V is what 10S... If you could get away with 8S which is 32 ish at full charge I have a 200Aer sitting here.

Otherwise maybe this bad boy. http://hobbyking.com/hobbyking/store/__10332__Turnigy_Monster_2000_200A_4_12S_Brushless_ESC.html

Steve
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Steven Martin
Twisted Constructions
http://www.botbitz.com

I'd look at a RageBridge. it will do 10S and has current limiting which will help you out.
They are $180ea and they also come with a "No questions Asked", $85 repair / replacement warranty.

LOL @ Robot Power Vyper. If it takes 3 years to bring a controller to market, you've got problems.
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https://www.halfdonethings.com/

I don't think the RageBridge has the current capacity - it does up to 40A, while the Dewalt motor has a 300A stall current. It would be current limiting as soon as the bot had to do any pushing. There are other controllers that would work, but they are all quite large and will increase the weight even further

The RageBridges are driving new style 18V Dewalts without explosions, so they might not be too bad. 40A is also the continous day in day out rating for the ESC, not just a 1-3minute rating like on ESC's like the Victors. You might find that even if it's hitting current limiting, your still going to have plenty of power. 36v @ 40A is still a potential ~1400w of power. Since your design is a spinner, I don't think you'll run into much issues even if your on a 40 or 50A current limit (you can up it to 90A). Look at Demon, runs around on drill motors with just 25A of current limit from the Scorpion XXL, doesn't seem to worry him
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https://www.halfdonethings.com/

Hmm, good points, so I guess I will just have to try a few options. Chris Baron says the Vypres are progressing slowly but steadily, so they may be out before I need them. I can always test at a lower voltage using Victor 885 controllers

I drew in the new IFI gearboxes in place of the larger and MUCH heavier P80 boxes and they make a gigantic difference! They have a 42mm face like the old Banebots gearboxes used in Touro light, but have larger steel gears and better construction, so its likely they will handle the output of the 36V Dewalt motors - I will be running them at lower voltage anyway.

Using the smaller box allows smaller 3.5" Colson wheels to be used and reduces the width of the bot, giving much needed weight reduction Now I just have to find smaller batteries to fit the smaller frame...

Do have a link to the IFI gearbox
Been searching around without success - found Innovation First International but no product catalog

Sure, here you go: http://www.vexrobotics.com/vexpro/gearboxes/versaplanetary.html

Make sure to download and read the manuals at the bottom of the page before ordering - its confusing without the diagrams!

Thanks, looks like they have a few broken links on their site at present as I get page not found.
I will keep watching, hopefully they will fix soon

Works fine for me.
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Steven Martin
Twisted Constructions
http://www.botbitz.com

Same here, I got everything on those pages to work just before I posted the link. I'd be checking that your browser and DNS settings haven't been hacked!