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Posted by Michael Betts.

Engineer on team #177, Bobcat Robotics, from South Windsor High School and International Fuel Cells.

Posted on 7/15/2000 11:39 AM MST


In Reply to: Connections posted by Dodd Stacy on 7/14/2000 4:55 PM MST:



: Another dumb gearhead question. Is it really better, safer (lower resistance) to make crimp fitting connections on very heavy gauge wire - like 6 Gauge - than to make proper solder (or silver soldered) joints?

A 'proper' crimp is better than solder. PbSn solder cannot hold up to the physical stress and strain to which a large gauge wire is normally subjected to and silver solder has it's own set of problems, such as acid flux, making it unsuitable. In a 'proper' crimp connection, the wires actually cold flow within the crimp. Production, high reliability crimps are actually made with an pneumatic or hydraulic tool or press. Such a tool can exert pressures of over 15 tons on the crimp. At the high school, a manual crimp tool is often used.

The problem is that each connector has it's own crimp tool, unique to the manufacturer and model, which are expensive and long lead items.

To crimp 6 AWG wire, we use an old, manual, T&B crimp tool (2 to 8 AWG) which was 'donated' by IFC to the school. This old crimp tool we use has 20' handles and we add sheet metal shims (outside of the crimp lug) until it is 'almost' impossible for one person to crimp. In fact, when crimps are being made by some of my younger and/or female team members (I'm not being sexist here... it is a matter of upper body strength), I will slide a couple of 30' sched 40 pipes over the handles to improve the mechanical advantage.

Look up Team 177 at one of our future events and I'll have the kids demonstrate how we do it. We plan to be at Rumble, Riverrage, Bash and the Expo in the next few months.

A proper crimp is one of the strongest 'links' in your electrical chain and will NOT fail or loosen. You will rip the electrical terminal off of the lead acid battery long before the crimp fails (voice of experience here...).

Talk to an electrician in your facilities dept (school or company) and they can probably let you borrow (or have) an old tool.

Having said all that, the only crimp connection which I have the students routinely replace with solder is at the connections on the FP motors. These are meant for toys and, obviously, do not enjoy the quality inspections or standards that the automotive components in our kit do.

Remember to strain relief whenever a solder connection is used!


Good luck.

Mike