Its time I started a new topic for my lifter bot Boost, even though I probably won't start building it for another month.

The lifter mechanism is a four bar linkage lik Biohazard's except mine is driven with a windscreen wiper motor acting on the rear link. If my maths is wrong and the wiper motor proves to be too weak for the job, I will try using and EV coupled to a worm drive gearbox. The lifter arm gets almost vertical and should allow self righting. Under no load, the arm should fully extend in just .25 of a second.

The chassis is still undecided it will be about 360 wide by 500mm long (my biggest bot by far!) and will either be made from 40mm tube that I already have, or U section channel. The extra length is due to the lifter arm, which needs to be fairly long in order to get enough hight to flip large bots like Robort.

So far, the only thing I have made for Boost is this 14.4 battery pack:

http://www.robowars.org/forum/album_pic.php?pic_id=528

http://www.robowars.org/forum/album_pic.php?pic_id=529

Since the current demand will be relatively low, I decided not to bother with heat saver rings and to glue the pack together more firmly. I used 8 gauge wire & giant braid in keeping with the Overkill policy. Foam and 2 layers of heatshrink finish the job.
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

... If my maths is wrong well it was WAY wrong! I re-did the torque calculations and a wiper motor only generates 1/4 the required force to get the job done. Better to find that out now rather than later, I suppose.

It looks like the lifter will need a motor like an EV warrior running into about a 50:1 worm drive reduction to get the job done. The other possibility is using a winch motor, which might be lighter but also slower. Finding a small gearbox that will take up to 20NM on the input side is proving difficult - its out there somewhere...
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

not really knowing what you are planning too well but
i think your output torque is going to want to be something like 100NM at 240RPM to come close to just lifting a 13.6kg bot. in 1/4 of a second with a half meter lever.
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Mechanical engineers build weapons, civil engineers build targets

I calculated that the torque at the output of the gearbox had to be 58 point something NM to completely lift a bot (as opposed to just lifting one side. That takes into account the length of the drive arm and the gearing ratio of the 4 bar linkage. I always like to add an over-design factor, so 100 NM is about right.

The drive arm and therefore the gearbox output only needs to do about 1/3 of a revolution to get the full lifter hight so the RPM doesn't need to be all that high - just as long as the other bot can't drive off while the lifter is operating. I would be happy with anything 1 sec and under...

It seems the EV (a good reference point) has about 3NM, while a short Mag motor does 13+NM and obviously a bigger the motor needs less reduction and will produce a faster flip.

If an EV can produce 3NM and spins at around 2200 @14.4V then to get 100NM at the gearbox output (allowing for some losses), I would need 35:1 reduction and would get about 60RPM. That gives a .33 second lift. An EV would be operating at it's maximum with these figures and a 50:1 reduction is more realistic.

Does that sound right, or am I blathering on like a madman?
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

sounds closeish
hoever stall torque and 2200 RPM torque are very *very* different generally
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Mechanical engineers build weapons, civil engineers build targets

that and i pitty your gearbox lol
100NM is probly about the torque output of your van so take a look at your diff and drive shafts then add a robot builders margin ;->
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Mechanical engineers build weapons, civil engineers build targets

Hmm, I'm sure I wouldn't need a 1.8L ICE to get the job done.

Working the problem backwards (& rounding numbers up so I can to the math in my head): Bot =13.6Kg, which is about 133 Newtons anywhere I am likely to have a match. The linkage has a 2.2:1 gear UP, which means 292N on the input side. The ratio on the linkage isn't constant but 2.2 is about the worst it gets.

Perhaps this is where I am way off: the input arm where the gearbox attaches is 0.2m so I get the torque in NM by 292N * .2 = 58.4NM. That's the constant I have to work with - I just need to pick a motor and work out it's torque at a given speed. The gearbox reduction is then 58.4 / the motor's torque * an over design factor.

I only need to produce that at a low RPM so hopefully a car engine isn't required...

(Thanks for the feedback BTW)
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

the other thing to think about is that if you need 58Nm to support the weight of a bot on the lifter arm you will also need to add another 58Nm for every G of acceleration you want to give it

58Nm might hold it in the air, but it won't throw it - because of the bot's inertia.
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The Engine Whisperer - fixer of things

note i was talking about torque not power.

your gear theeth and the like will need to be sized simmilarly in order not to snap off etc.
you have a large force acting on a small area.

perhaps winch gears may do?
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Mechanical engineers build weapons, civil engineers build targets

yeah true it's power, not torque, that accelerates things, but as there's no power being made at stall, you need to have more torque available than you need to hold a bot in the air if you want to launch it.
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The Engine Whisperer - fixer of things

A winch motor will do it easy Nick. I was lifting car tyres with my setup lifter with a 1:5 over drive ratio in the lifting arm and crank. the only problem I had was the winch motor wasn't mounted to anything and tended to lift the supports around it at time

The Winch motors we use do about 53RPM on 12v but have enough torque that you can gear up through your lifting mech to gain speed with out losing much lift.
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https://www.halfdonethings.com/

I was thinking a winch was at the top of my options. Even at 50 RPM, I would be getting the full lift motion in less than .5sec. That would be very roughly 1/10 of a G.

The 58NM is the 'worst case' lifting the entire bot and from watching Elbravo and many other lifters, Its likely that I would only be lifting 1/2 to 2/3 of the total weight as the far side of the bot will still be on the floor. Aiming for 100NM is almost starting to sound like overkill, but I have found several reasonably small gearboxes that will do the job - only problem is that they are mostly cast iron! Its off to Superchaep Auto methinks
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

I just had an idle thought - perhaps this design would be better off as a lightweight. I have a Bosch GPA wound for 12V that could be used and overvolting to 24V would give it heaps of power. Overheating problems would be reduced due to the intermittent weapon use and the gearbox is more likely to fit into the weight limit.
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion