Author Topic: Quick fix, circuit breaker, save your brick from burning.  (Read 1517 times)

Offline rbm

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Re: Quick fix, circuit breaker, save your bike from burning.
« Reply #25 on: May 19, 2019, 03:55:22 PM »
TMG, I think the idea is sound, but it's going to have to require some experimentation.

There are a number of constant voltage unfused circuits in the motorcycle:
  • FI relay feed
  • injectors
  • temp sensor
  • LSR
  • Ignition sw

If ever there was a fault that caused a short circuit current draw from the battery on any part of the wiring upstream of the fuse box, then that wiring would burn up.  Daveson has chosen to install a protective device in a subset of of the above listed circuits to protect the wiring.
 He stated his objective was to add such a device because the ageing insulation in the bike could increase the risk of such a short happening.

You're right, this device needs to bear the typical current that would flow through this part of the circuit without tripping.  And it has to trip when current through it exceeds that which can be carried by the wiring before the wire heats up and burns the insulation.  The BMW engineers would have designed the system to only draw sufficient current to not exceed the safe operating envelope of the upstream wiring.  For example, once the engineers knew all the system current requirements under typical operating conditions, then they would select a wire size that could safely handle that current after being suitably derated.  Therefore selecting a protective device like a circuit breaker that is rated for the maximum current bearing capability of the diameter of wire means that it can also safely handle the typical system load under normal conditions without tripping.  It's only when a fault occurs in the wiring upstream of fuse box that causes a short circuit that the breaker trips.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline daveson

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Re: Quick fix, circuit breaker, save your bike from burning.
« Reply #26 on: May 26, 2019, 04:42:40 AM »
Hi

I did some more tests and replaced the circuit breaker.

First I repeated the short test on the first circuit breaker , but this time measured the current as well. It was about 100 Amps,  again it didn't trip,  so I think it's crap, because it was supposed to trip at about 47 Amps.

Next I tested three ETA circuit  breakers, 10 Amps,  15 Amps and 20 Amps. (28V DC) They all tripped with the trip test. Then I did the load test with the 10 Amp,  it didn't trip, and didn't get warm, so I assumed the others wouldn't. This time I remembered to include the horn. It's also good to think that all components will never be powered at the same time while riding anyway.

I haven't done the test ride as the weather is lousy, but I'm confident it's less than the load test.

Since it passed the load test and  short test (test ride to come) I think I can now consider this as job done,  unless there is something else I'm not aware of. I'm sure this can be improved but I have to stop somewhere.

I'm planing to leave it as is for a few weeks and if there are no unwanted trips,  I'm thinking of replacing it with a 10 Amp Narva circuit breaker, if there are I'll go 15. Either, one like the first, or I see another one on the net, like a normal fuse.

I will post a photo later.

Would the fuse type one be good enough, as the connections are bolted originally?

Was I right in assuming this method covers all the unprotected wires except those to the starter relay and alternator/battery?
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline daveson

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Re: Quick fix, circuit breaker, save your bike from burning.
« Reply #27 on: May 26, 2019, 06:35:48 AM »
Circuit breaker photo.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline daveson

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Re: Quick fix, circuit breaker, save your bike from burning.
« Reply #28 on: May 29, 2019, 04:30:55 AM »
So it has passed the last test,  a couple of test rides. I don't know if this is a B curve circuit breaker, but the insulation seemed undamaged by the short test. I'm thinking I'll leave this one till summer and maybe try the circuit breakers that look like a normal fuse,  where it would be well protected with the other fuses.

I spose I'll leave it at that.

Thanks everyone, not just for the steep learning curve, but I just found this one really interesting. And thanks again Rob for fixing this modification.

I'm bloody rapt.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline daveson

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Re: Quick fix, circuit breaker, save your bike from burning.
« Reply #29 on: June 08, 2019, 05:48:23 AM »
Update: Removed the 10 Amp circuit breaker and replaced with the 15 Amp one, in the photo above.

After about ten rides of one hour,  and say another ten at fifteen minutes, the last two rides of fifteen minutes resulted in a total of two unwanted trips. The low beam headlight was on for all rides,  but while the indicators and brake lights were also on, the circuit breaker tripped.

So from today on I will be riding with the 15 Amp relay, and see how it goes.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline Laitch

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Re: Quick fix, circuit breaker, save your bike from burning.
« Reply #30 on: June 08, 2019, 06:26:05 AM »
. . . while the indicators and brake lights were also on, the circuit breaker tripped.
During the next testing phase, also beep the horn. Just don't inadvertently launch anybody into road rage. :giggles
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline daveson

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Re: Quick fix, circuit breaker, save your bike from burning.
« Reply #31 on: June 08, 2019, 07:47:19 AM »
Yep, good idea, I'll try that on an empty road. I spose in an emergency you could have just about everything on at the same time.

All three passed the load test, with all lights on for one minute, but I only pressed the horn for about one second,  didn't want to draw attention. I guess it failed the test ride because the engine was at operating temperature. The first of the two trips was after three sweeping left hand turns,  so lights on longer than usual,  plus I spose 10 amps is just too low.

Hopefully the 15 Amp will last a year with no trips, if not,  I'll go 20.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline daveson

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Re: Quick fix, circuit breaker, save your bike from burning.
« Reply #32 on: June 17, 2019, 05:37:48 AM »
OK so this quick fix wasn't as quick as I thought,  but I'm thinking this latest test will be the last,  since it past this combined load test and test ride.

At normal operating temperature, on a long straight empty road I had the horn and all lights on for one minute, that is hazards, brake, low beam plus horn and high beam flasher buttons pressed at the same time.  It's hard to appreciate how long one minute is until you ride with all lights and horn on for one full minute. It's a really,  really loooonng OCD amount of time. I've probably had a dozen rides of various types with the 15 Amp circuit breaker, no trips. There's a good chance I'll just leave this one in permanently.

Plus I'm going to push a proper battery isolator further up the "To Do" queue, as so many here have already done.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline Laitch

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Re: Quick fix, circuit breaker, save your bike from burning.
« Reply #33 on: June 17, 2019, 08:53:28 AM »
It's hard to appreciate how long one minute is until you ride with all lights and horn on for one full minute.
It's easier to appreciate if you've stood in front of a stranger who was pointing a loaded firearm at you.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline daveson

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Re: Quick fix, circuit breaker, save your bike from burning.
« Reply #34 on: June 17, 2019, 09:29:11 AM »
Wow that minute would be  hours longer than the minute I was thinking of.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

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