Dynastarter

[onenyala]

I have 2 Volvo MD1B engines - one in the boat another spare each with dynastarters.
There is a significant difference in the circumferences of the sheaves on the two dynastarters which of course results in a significant difference in the rate of rotation of the amatures which are driven off the flywheel.
The circumference of the flywheel is 119 cms
The circumference of the smaller dynastarter sheave is 16cms and the larger 24cms.
At the working rpm of the engine - 2400 the rotation of the dynastarter armatures is 18,200 for the smaller sheave and 12100 rpm for the larger.
Both dynastarters are identical.
Can an electrically knowledgeable person tell me the pros & cons of the difference in rotation speeds and perhaps the correct sized sheave.
Both dynastarters seem to work OK both on starting and charging even though one rotates at 50% more rpm than the other.


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[johnsomerhausen]

You could e-mail to "pentavolvo.se" and put the question to them. They are a bit slow in replying but you'd get the answer "straight from the horse's mouth"....
john

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[johns]

sorry i canthelp you but you might be able to help me when my md1b is running the coolingwater sometimes gets very hot and then cools down this hapens about every 10to15 minutes is my engine overheating how do you tel without a tempature gage

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[onenyala]

I'm no expert but the obvious seems to be the thermostat. It sounds as though it is opening and closing at too high a temperature.

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[onenyala]

It sounds as though the thermostat is opening and closing at too high a temperature. A temperarure gauge will only tell you what you already know!

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[Mirelle]

Thermostat

You will find a thread on this, started by me, about 6 months ago. I replaced the thermostat on my MD2 and it did just this for a few weeks, then it settled down, but it is certainly running at a higher temperature than the old thermostat did. I used to be able to just keep my hand on the rocker covers and now I just cannot!

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[William_H]

Just by way of background the smaller pulley on the dyna starter will enable in start mode the starter to spin faster hence draw less current from the battery a desirable attribute giving better starting especially on a tired battery. The down side is that in generator mode it spins very fast. The problem is a physical one that the armature can fly apart due to centrifugal forces.. Electrically the speed doesn't make so much difference because the charge rate is controlled by the field current and this will easily adjust to very high speed or a slower speed. It would be interesting to see if the dynastarter with the smaller pulley has the same diameter armature and if it appears to be potted with resin to hold the wires together. A larger diameter armature will give more torque but is more succeptible to centrifugal force It may not be safe to swap the pulleys over if they are different. This whole compromise is why we don't see many dyna starters.

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