Author Topic: B25 Electronics shelf  (Read 299 times)

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Oliver Pi

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B25 Electronics shelf
« on: 30 May, 2022, 22:53:45 »
Hello All,
I'm coming down the home stretch with revival work on a 1970 Starfire.  I didn't enjoy contact breaker points back when that was all that was available so the bike has a Boyer Brandsden unit.  The rectifier and zener diode likewise were dispatched in favor of a tympanium regulator/rectifier.  All that to preface a question regarding the attached photograph.  I built a tray from aluminum sheet that holds the Boyer unit as well as the tympanium.  The tray is under the seat adjacent to the oil tank.  I assume (danger!) there will be enough air flow to keep these components cool.  I have no experience with these particular electronic devices and wonder if anyone out there vouch for or forewarn me of the arrangement shown in the photo.  I don't want to cook my electronics if it can be avoided.

Farewell for now,
Oliver

spaceman

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Re: B25 Electronics shelf
« Reply #1 on: 31 May, 2022, 07:52:38 »
Modern rectifier/regulators (RR) work by shunting excess current from the alternator to ground when the voltage rises above about 14.5V - the excess power is dissipated as heat within the RR. This particular RR appears to be designed to be bolted to the bike frame in order to provide a path to dissipate the heat generated rather than being finned to allow air cooling.

The present arrangement is probably not ideal but I doubt if it will cause any problems. One of the bikes I ride has an RR in a similar place (mounted on top of a plastic air box) and, although finned, has almost no air flow over it. It also probably dissipates twice the amount of power as the B25 and has worked happily for at least 5 years in my possession without any problems.

DAVE BRADY

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Re: B25 Electronics shelf
« Reply #2 on: 31 May, 2022, 08:10:56 »
Hi,

I can't wait to see the completed bike in that stunning yellow.  In the meantime I would think that the aluminium tray has more than enough surface area to act as a heat sink, especially if the RR is flat on the underside and therefore in full contact.
I have an RR behind the battery on one A65, sitting in place of one of the coils behind the side cover on another and the one on my wife's bike is under the seat.  They are finned ones but not in any particular airflow.
How hot do they get?  I must remember to touch then after a run.
I suppose that running with lights on will help to keep them cooler as there is less or no surplus to get rid of.

Dave.

Oliver Pi

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Re: B25 Electronics shelf
« Reply #3 on: 31 May, 2022, 12:14:11 »
Thanks to you all for your experience and observations on this component arrangement.  As the project continues I am keeping my eyes open for other mounting locations if the need arises. 
Yes indeed the yellow color is bright!  The original blue color, aside from a great name (Flamboyant Aircraft Blue), didn't ring my chimes - so yellow it is!

Farewell for now,
Oliver

Chile_bike

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Re: B25 Electronics shelf
« Reply #4 on: 16 June, 2022, 13:10:15 »
Hello,
I put a Kubota alternator on the B31, as the magdyno was sent to join the Prince of Darkness. I looked at commercial RR's, and the power dumping is horrible. I've only got 11 ponies to start with. My RR only conducts when the load requires it, and open circuits the alternator otherwise. The OC voltage is only 45v at 6k revs ( Rated speed, not the B31), and heat is not a thing. If you are up for a bit of electronics, I'll have a spare board somewhere. I did put load dumping on the board, but never bothered with it.  The Kubota part is just a giant bike dynamo, but the 3phase requirement is catered for.

Oliver Pi

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Re: B25 Electronics shelf
« Reply #5 on: 02 July, 2022, 15:41:13 »
A cool and innovative solution!  I will pass on the Kubota fix at this time, but my hat is off to your initiative and vision to see and complete the job. 
Oliver

Ian C

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Re: B25 Electronics shelf
« Reply #6 on: 02 July, 2022, 16:03:03 »
I made a similar frame with plate for my B44 which picks up on the oil tank and upper toolbox mountings.

Trebor

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Re: B25 Electronics shelf
« Reply #7 on: 03 July, 2022, 14:06:45 »
Hi

I have both my boyer electronic ignition and the combined rectifier/regulator unit in a similar configuration under my B25 seat and not had any problems.

Regards

Rob