robot

[Laser]

Re: robot

Thats a good idea and thanks jamie. So I just get a motor and attatch it to a sisscor jack?

[Laser]

Re: robot

Another question how long does take to fully unwind?

[joey_picus]

Re: robot

It's dependent on the motor - if you hook it up to a scramjet it'll take less than a tenth of a second, whilst tests with rats in geared hamster wheels are ongoing.

(looking at videos of Kaizer or Psycho Fling should give you an idea)

[RogueTwoRobots]

Re: robot

So I just get a motor and attatch it to a sisscor jack?

Sort of. Rather than using the whole scissor jack, I just used the threaded rod that goes through the middle of it, and a small nut from one end. The rest of the jack was just discarded. You could just attach a motor to the scissor jack and use the whole mechanism but it would be quite bulky for a featherweight and the shape and size of it would probably dictate your robot's design to you.

Another question how long does take to fully unwind?

Depends on the speed of the motor, whether it's overvolted, what your leverage ratio is etc etc. But for Kaizer, full travel from up to down takes 1.5 seconds max at full speed. I use a speed controller with it though, so can make it go up and down at whatever speed is best for the situation. The nut only travels about 2-3 inches along the threaded rod for full lift so it's possible to get the mechanism quite small.

If you were using the whole scissor jack mechanism then you could be looking at around 10 seconds (just a guesstimate) for full travel.

[daliad100]

Re: robot

How is the threaded rod held in there?

Do you use the reverse thread on the drill, make larger normal thread in three hole, a pin/screw through both bits or something completely different?

[RogueTwoRobots]

Re: robot

The shaft of the drill motor is from the very first drill motor I ever took apart (circa 2004). I didn't have a decent set of screwdrivers so ended up chewing up the reverse threaded screw and couldn't get the chuck off. So I took a hacksaw to the shaft which got the chuck off but took the threaded portion of the drill shaft with it. So I drilled into that, tapped it and fitted a short piece of M8 bolt to use as a shaft.

When it came to making the lifter, I just drilled an 8mm hole in the end of the threaded rod from the car jack, slipped it over the piece of M8 bolt and held it in place with an M4 grub screw. This didn't hold it very well though as the grub screw would occasionally come loose, or if I moved the lifter blade below horizontal (to lift up the front of the robot if stuck) it would pull the threaded rod off the drill shaft.

So I cut a bit off the threaded rod until flat-ended again and drilled a 6.5mm hole into the end of it this time. I tapped it with an M8 thread and then screwed it on to the piece of bolt/drill shaft. Secured again with a grub screw which held up fine, but this time the piece of bolt was unscrewing from the drill shaft, so I re-cut the thread to freshen it up, applied some Loctite to it and fitted a 4mm grub screw on that section of it too. So now there is a grub screw holding the one end of the M8 bolt onto the drill shaft, and another holding the car jack threaded rod to the other end.

A bit convoluted I know, but since I've done that (and secured the two grub screws with Loctite too) I have had absolutely no problems with the connection at that point and it has lifted robots without any hassle

[ady]

Re: robot

if your finding it difficult to do, wouldnt it be possible to leave the drill chuck on the motor and attached the threaded shaft that way?

[RogueTwoRobots]

Re: robot

Yeah, that is another way to do it actually. Once the rod is in the chuck, you could even drill a hold through both the chuck and the rod and fit a bolt or pin of some sort to stop the rod from slipping or coming loose.

If I remember rightly, the reason I didn't do this was because the diameter of the rod was too big for the chuck. Most cheap cordless drill chucks have a capacity of 10mm diameter and my piece of threaded rod was 12mm diameter. Not a problem if you have a lathe and can turn a section of it down to fit, but I didn't and I found that my home brew method of decreasing the diameter by trimming with an angle grinder wasn't accurate enough (off-centre cutting led to rod wobble when it was spinning)

There are probably some smaller jacks out there that will have a smaller diameter threaded rod though, which should work fine if the chuck method is your favoured form of attachment.

[Laser]

Re: robot

Thanks guys, but where do you get the threaded rod from the middle of the sissor jack?

[Laser]

Re: robot

I'm not going off the actuator idea but would a good battery pack be 8xAA rechargables put together and then have a heatshrink around them?

[Metal Demons]

Re: robot

I'm not going off the actuator idea but would a good battery pack be 8xAA rechargables put together and then have a heatshrink around them?

Nope, those don't have terribly high capacity and have dismal discharge rates.

You want significantly better cells than those.

[Laser]

Re: robot

what kind of batteries do you recommend then?

[Laser]

Re: robot

are overlander batteries good

[psycho_fling]

Re: robot

i would buy from this store on ebay, good prices and good products never had any touble form the cells and the guys there are great for advice

http://stores.ebay.co.uk/componentshop

[Laser]

Re: robot

What about these batteries http://cgi.ebay.co.uk/5-PCS-A123-NEW-18 ... _Batteries or are lead asid better