ghostlymoron
Well-Known Member
Anyone know the output from one of these? I understand they are a dynamo rather than alternator.
Dynostart
- Thread starter ghostlymoron
- Start date
cliff
Well-Known Member
From the Bukh Manual:
This applies for engines up to and including No. 89156 for DV10 and No. 93637 for DV20. For engines after these numbers the
gear rim starter is used (page P 7. ) .
Dynastarter
The dynastarter has the following specifications:
Type LA/EJ 90/12/2900+1.0 R
Generator section:
Voltage 14 volt
Max. delivery " 11 Amp
Starter section:
Nominal voltage 12 volt
Output 1 HP
Short circuit values:
Torque 2.1 kpm
Power consumption 300 A
Rotation direction seen from flywheel end .. clockwise
Weight 9.3 kg
This applies for engines up to and including No. 89156 for DV10 and No. 93637 for DV20. For engines after these numbers the
gear rim starter is used (page P 7. ) .
Dynastarter
The dynastarter has the following specifications:
Type LA/EJ 90/12/2900+1.0 R
Generator section:
Voltage 14 volt
Max. delivery " 11 Amp
Starter section:
Nominal voltage 12 volt
Output 1 HP
Short circuit values:
Torque 2.1 kpm
Power consumption 300 A
Rotation direction seen from flywheel end .. clockwise
Weight 9.3 kg
ghostlymoron
Well-Known Member
As I thought, output not very much compared with a small alternator.
William_H
Well-Known Member
Certainly if you want real 12v charging and supply power a Dynastart will not do very well. Dynastart is a dynamo or generator ie the field coil is on the outside and the rotating armature windings are connected to commutator segments so that "rectification" of the AC generated by the coils is done by switching of brushes on the commutator segments. This means that all output current must be conducted through the brushes. So maintenance of the brushes and commutator is important. They frequently have different brushes commutator and windings for the starter function.
One of the difficultes of design of a dynamo is that the rotating armature is complex and subject to destruction by centrifugal forces. So there is a real limit to the speed you can spin it at. By contrast with an alternator only the field coil rotates. This is laid out so that the wire coil is around the axis of rotation and relatively small diameter. The end poles are cunningly designed to give N and S alternating at the circumference. Hence an alternator can be run at high RPM without harm.
So a dynamon or alternator runs at a speed (belt) ratio to the engine RPM but limited by max engine RPM. So a dynamo will have to run slow at idle while an alternator can run much faster at idle. Hence generally an alternator will give a useful charge at idle/low engine speed while a dynamo will not.
With a dynastart you have more design problems. You need a large gear reduction via the belt to get enough torque to crank the engine while when you go to dynamo mode this same belt ratio may give too high dynamo speed. So while it seemed like a cheap option for small engines to share the components of the starter and dynamo in one case and to have it continuously coupled to the engine it has definite limitations. Hence we seldom saw dynastart on cars but rather a separate dynamo and starter.
Certainly the modern alternator can give vastly better charging and by going to an alternator the starter can be optimised for its job of cranking the engine. ie high ratio to get lots of torque then disconnected via pinion drive. For an older engine this is the way to go, ie give up the dynastart. good luck olewill
One of the difficultes of design of a dynamo is that the rotating armature is complex and subject to destruction by centrifugal forces. So there is a real limit to the speed you can spin it at. By contrast with an alternator only the field coil rotates. This is laid out so that the wire coil is around the axis of rotation and relatively small diameter. The end poles are cunningly designed to give N and S alternating at the circumference. Hence an alternator can be run at high RPM without harm.
So a dynamon or alternator runs at a speed (belt) ratio to the engine RPM but limited by max engine RPM. So a dynamo will have to run slow at idle while an alternator can run much faster at idle. Hence generally an alternator will give a useful charge at idle/low engine speed while a dynamo will not.
With a dynastart you have more design problems. You need a large gear reduction via the belt to get enough torque to crank the engine while when you go to dynamo mode this same belt ratio may give too high dynamo speed. So while it seemed like a cheap option for small engines to share the components of the starter and dynamo in one case and to have it continuously coupled to the engine it has definite limitations. Hence we seldom saw dynastart on cars but rather a separate dynamo and starter.
Certainly the modern alternator can give vastly better charging and by going to an alternator the starter can be optimised for its job of cranking the engine. ie high ratio to get lots of torque then disconnected via pinion drive. For an older engine this is the way to go, ie give up the dynastart. good luck olewill
VicS
Well-Known Member
What I believe is sometimes possible is to add an alternator to charge the house battery retaining the Dynastart as the starter motor and also to charge just the starter battery
