Volvo MD2B belt starter ideas?

[Akestor]

Probably there is no easy solution to this but ....
I am installing the engine in the boat tomorrow (Westerly 31 Longbow Ketch) , old bosch dynastarter is completly rusted, and the Sev alternator looks better and if it works i ll have to buy a regulator for sure. As i dont want to spend the summer handstarting i am already looking for starter solution.

A new dynastart is around 200 euros +relay price +VAT and I ll have to start her with the levers up every time.
Is there a posibility that i could replace the gear of a clockwise rotation starter with a 2 belt pulley and start the engine with the levers down? Or.. do belt driven starters already exist? (didnt see such thing online)
A fly wheel ring gear is quite expensive and i want to avoid removing that flywheel anyway!

Thanks for any feedback/ideas

 

[pyrojames]

I bought an old MD2C with a ring gear and starter and swapped them over. I still have the 55mm crankshaft nut socket!

 

[Topcat47]

Starting with the levers up is always easier on these old engines as they have heavy flywheels that need a good run to get up to speed.

 

[William_H]

OP may have given up too soon on the old dynastarter. The parts that rust will be the laminations of the field coils (inside the body) and possibly of the armature. (the rotating part.) The surface rust will not affect operation. The critical parts are the copper windings and the commutator plus of course brushes. The number of segments of the commutator is number of coils of the armature the more coils giving more rotational torque on start. The relative sizes of the pulleys of course give the gear ratio of the dynastart to the engine which must be low ratio ie large difference of pulley diameters to give power to overcome difficulty to turn the engine over. However smaller pulleys on the dynastart will limit the friction of the belt drive and may also cause the dynastart to rotate too fast at max engine RPM. Resulting in armature disintegrating.
The large flywheel pulley is dictated by room for the flywheel. So can't be much bigger.
Now if we look at an ordinary starter motor the gear ratio is large (number of teeth on ring gear versus number of teeth on the pinion) and gets a lot of power to rotate the engine. However that ratio would destroy the starter motor if it remained engaged so we get the engagement system. To use a starter motor might work if you could arrange the engagement system to be retained however the flywheel diameter restricts the gear ratio because you would need a largish pulley on the starter to get the belt grip but large means poor gear ratio. So poor starting torque. Such that I suspect direct drive of the starter motor to the pulley ie no disconnect might be OK because drive ratio will mean starter does not spin too fast at full engine RPM.
So I am going around in circles here. Obviously best bet is to fit a ring gear and bell housing to take an ordinary starter.
Next option is to refurbish the dynastart or get another high powered 12v (or 24v electric motor to drive by pulley.
Some modern starters (google light weight starter for aero engine) use a higher speed motor and gear box before the pinion) Nice idea but still not suitable for continuous rotation at max engine speed.
So it a bit of a miracle that dynastarts ever worked and they do need decompression of the engine.
Lastly you might look at spring powered emergency starters, inertia starters or even pyrotechnic starters. Whatever you do you are in to inventors territory so prone to failure. olewill

 

[[448]]

Well, as I said when you first posted on this, I have the flywheel and starter, and pyrojames above has the essential socket for the nut.

If you can't get the dynastart to work, swapping over to a proper starter is the simplist way to go.

Where are you?

 

[Tam Lin]

I bought a new dynastart a few years ago from a company on the Thames I think. Then I put in a new engine!

 

[Akestor]

Well, as I said when you first posted on this, I have the flywheel and starter, and pyrojames above has the essential socket for the nut.

If you can't get the dynastart to work, swapping over to a proper starter is the simplist way to go.

Where are you?

I am in Athens Greece. That sounds interesting! Have you thought a price?

 

[Akestor]

I bought an old MD2C with a ring gear and starter and swapped them over. I still have the 55mm crankshaft nut socket!

Hi! You bought the engine for parts you mean? Did you use a monster torque wrench or tightened the nut by feel?

 

[Akestor]

OP may have given up too soon on the old dynastarter. The parts that rust will be the laminations of the field coils (inside the body) and possibly of the armature. (the rotating part.) The surface rust will not affect operation. The critical parts are the copper windings and the commutator plus of course brushes. The number of segments of the commutator is number of coils of the armature the more coils giving more rotational torque on start. The relative sizes of the pulleys of course give the gear ratio of the dynastart to the engine which must be low ratio ie large difference of pulley diameters to give power to overcome difficulty to turn the engine over. However smaller pulleys on the dynastart will limit the friction of the belt drive and may also cause the dynastart to rotate too fast at max engine RPM. Resulting in armature disintegrating.
The large flywheel pulley is dictated by room for the flywheel. So can't be much bigger.
Now if we look at an ordinary starter motor the gear ratio is large (number of teeth on ring gear versus number of teeth on the pinion) and gets a lot of power to rotate the engine. However that ratio would destroy the starter motor if it remained engaged so we get the engagement system. To use a starter motor might work if you could arrange the engagement system to be retained however the flywheel diameter restricts the gear ratio because you would need a largish pulley on the starter to get the belt grip but large means poor gear ratio. So poor starting torque. Such that I suspect direct drive of the starter motor to the pulley ie no disconnect might be OK because drive ratio will mean starter does not spin too fast at full engine RPM.
So I am going around in circles here. Obviously best bet is to fit a ring gear and bell housing to take an ordinary starter.
Next option is to refurbish the dynastart or get another high powered 12v (or 24v electric motor to drive by pulley.
Some modern starters (google light weight starter for aero engine) use a higher speed motor and gear box before the pinion) Nice idea but still not suitable for continuous rotation at max engine speed.
So it a bit of a miracle that dynastarts ever worked and they do need decompression of the engine.
Lastly you might look at spring powered emergency starters, inertia starters or even pyrotechnic starters. Whatever you do you are in to inventors territory so prone to failure. olewill

Thank you for your detailed feedback! Many new things i didnt know. I will look for the options you mention.