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**maddox** · 6 February 2005, 17:05

New link design

Its a link like any other kind of links I have seen. So if it does what the rules ask, you can use it.According to me.

But do you need to pull the 2 links to shut down completely?

**grafix** · 6 February 2005, 19:13

New link design

Hi Jim.

2 things. First, it looks a bugger to arm. I dont fancy putting that lot together, lidding it up and then fighting it. It doesnt look simple nor easy to arm.

Second, not sure about having to have 2 links in a machine before it will disarm and be deemed to be safe.

Other than that, nice work.

Mike.

**m2xt** · 6 February 2005, 19:48

New link design

Only one pointer to make and that is contact resistance. You will find a temperature rise at the wiping connections which will be transferred into the Hawkers which will complain! I remember using a solid copper link between two Hawkers once which very slightly worked loose - the M5 bolts still were too tight to undo with your fingers. This contact resistance caused the copper to heat up, the Hawker case to melt and one cell to fail.

So unless you can guarantee a very low contact resistance (remembering greasy fingers on the key causing tarnishing etc.) that does not worsen in service, I would look for another solution.

Paul

**blazerbotics** · 6 February 2005, 20:40

New link design

Cant you put a 175A connector flat, and have the access from the side/back? How do you access the link if the robot is inverted?

**mute** · 6 February 2005, 21:13

New link design

How about using a 50A connector? These are much smaller than a 175A one.

We use 1 with no problems, although it did burn out the contacts after a years worth of use (caused by initial charging of the capacitors rather than current loading). We run upto a peak current of 300A and its never been a problem.

**jim** · 6 February 2005, 23:50

New link design

Thanks for your responses, all good points...

Mike: The links just push in, like a normal link. The bolts you can see in the picture are static, you dont need to tighten them or anything when arming.

Paul - a good point which I will need to think about. I use a PCB cleaning block to shine up the link before using it, which may be enough, I havent noticed it getting warm yet. However, dangers of heating up batteries notwithstanding, performance and damage to components are secondary to safety.

Alan and Mario have perhaps the most important points. It does require both links to be pulled to make the robot safe, and I think this is where most disagreement will occur. The reason there are two links is because its very nearly a clusterbot . The front and the back are just bolted together at the moment, theres no or mechanical or electrical connection between them and both can run independently. Once I sort out a mechanism to disconnect them, it will be a true clusterbot, but I would still like to run it as a joined up unit if possible. Id really like to keep the two sides independent and that means not running cables between them.

RE inversion - yes, its going to be difficult to remove the links if it gets flipped over, but I think this is true of quite a few robots.

**maddox** · 7 February 2005, 01:25

New link design

Jim.

We have an example in history. Stinger.

In theory you must be able to disarm the whole machine with 1 link.On the other side, I believe that the rules are not put into cast iron.
Not that I will accept a multiple parallel link in machines that could be builded with 1.
Multiple series mounted links for added safety is no problem.

Also, we have run Tough As Nails with the Anderson minipowerpoles. Normaly accepted to 45A, but more than capable to survive 5 minute uses over a 100.
So, if this alternative link doesnt satisfy, the miniandersons are an option.

**bugs** · 7 February 2005, 08:10

New link design

Weve replaced those with normal 50A andersons ages ago, suspecting them of problems. Weve never used minipowerpoles as a link.

**big_nipper** · 7 February 2005, 08:52

New link design

We also use the small Anderson connectors but now use 2 in parallel, but bolted together. Dont forget the the current rating is for the connect/disconnect rating only and will handle far more. Think of them like Relays where they have 2 current ratings, Swithcing current and max on current.

**m2xt** · 7 February 2005, 19:23

New link design

Mark, not so sure thats correct. The rating is also based on the temperature rise. They have a max operating temp of 105 deg C. For example, a 50A connector can officially handle 100A for 16 seconds if you use 10mm2 cable (the bigger the cable the better as it acts as a heatsink) whereas the 175A connector can handle 400A for the same period.

**big_nipper** · 7 February 2005, 19:52

New link design

Looking at thier datasheet:

http://www.andersonpower.com/products/pdf/DS-SB50REV01.pdfhttp://www.andersonpower.com/product...-SB50REV01.pdf

It does state that there max continous current is 50Amp for a 20C Temperature rise with 6AWG (13mm sq) wire, but their figures dont seem to add up.

At the full 50A it states a voltage drop of 10mV, hence 0.5W of power lost in heat. For this to be true then the connector + wire must act like a heatsink of 40C/W and that seems too high with such thick wire.

**jim** · 8 February 2005, 11:35

New link design

I did a bit of work in the garage last night and managed to cut down one of the 175A connectors so that it would fit in. This still leaves the issue of multiple links, however.

**big_nipper** · 8 February 2005, 12:39

New link design

Jim, as I understood it, if you have 2 seperate electrical circuits then 2 seperate links are OK (with 2 seperate power lights) but weather they have to be together (or just near to each other) is a little unclear, and I suspect that if the robot design does not allow them to be together then it should be accepted by the event Organiser anyway. After all to make a Co2 robot safe you have to both pull the link and turn off the Gas and they are not always together so I dont see much difference.

**team_ireland** · 8 February 2005, 12:52

New link design

My feather has 3links. One for drive, one for weapon and another for the rx. All 3 are near each other. So i would not expect a problem.

Regards
Ian

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