30C Diesel Starter Motor

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cobbadog
Posts: 684
Joined: Tue Oct 11, 2011 6:18 am
Location: beautiful Coopernook NSW. near Taree. NSW. Australia

30C Diesel Starter Motor

Post by cobbadog » Tue Dec 03, 2019 4:54 am

This is how it was described to me when I bought a few spare parts last weekend. This is an old style starter motor with the solenoid attached to the top of the starter motor itself and that cover is made of brass and held on with 2 nuts. This thing weighs a ton, I have never picked up a starter motor this heavy before.
Anyway, I hooked up a portable jump starter battery and connected the cables to the + & - posts then bridged the + to the centre brass pole for the ignition wire to attach and away it went.

Questions are;
How fast do these rotate at?
Is anyone interested in it?

Obviously if someone is interested in it, a pick up would be the best way of getting your hands on it as postage would be way over the top.

ALANJ
Posts: 59
Joined: Wed Oct 11, 2017 9:13 pm
Location: Co. Durham

Re: 30C Diesel Starter Motor

Post by ALANJ » Tue Dec 03, 2019 12:36 pm

This starter motor, or cranking motor as Lucas/Cav preferred to call them , is probably the early CAV unit ,fitted to 25/30 D,s amongst others in the early 50,s.We had two such tractors on our farm and these starters were totally reliable although they had a fearsome reputation with the repair shops .Apparently they were difficult to work on and parts were ,evidently , very expensive compared to the Lucas which replaced them.
They are worth a mint in the UK if in good working order. AJK.

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cobbadog
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Location: beautiful Coopernook NSW. near Taree. NSW. Australia

Re: 30C Diesel Starter Motor

Post by cobbadog » Wed Dec 04, 2019 5:17 am

Thank you Alanj,
Yes it is a CAV unit identified by the CAV embossed in the 4 brushes at the back end of the motor. IT surely is a very heavy unit. Yesterday I removed the brushes, cleaned the communtator and the gaps between the segments, lubrictaed the rear bush and the main part that slides nicely forward to engage the driven gear. The clutch in the drive gear works perfectly and I have my jump start battery all charged up nicely ready to do a test on what speed it runs at using my mechanical engine tacho that can be held against the shaft and will read the RPM.
Next trip into town I will pick up a new "O" ring seal for the brass cover and then see if anyone is after a strong old starter motor. So as it sits out the back now, it does work but I need to know at what RPM so it may help out any interested buyers decide if they want it or not. I am not after a lot of money for it but would like to re-coupe part of my outlay.

ALANJ
Posts: 59
Joined: Wed Oct 11, 2017 9:13 pm
Location: Co. Durham

Re: 30C Diesel Starter Motor

Post by ALANJ » Wed Dec 04, 2019 7:45 am

To obtain an approximate figure do the following. 1- count the teeth on the flywheel and starter bendix gear. 2- divide the flywheel number by the bendix number. This is the gearing ratio. 3- most old Diesel engines require a cranking speed of approx 250/300 RPM Therefore multiply the 250/ 300 by the gearing ratio and you are in the approximate ballpark. Hope this helps.
AJK.

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GeoffDEAL
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Joined: Tue Jan 27, 2009 8:25 am
Location: New Zealand

Re: 30C Diesel Starter Motor

Post by GeoffDEAL » Wed Dec 04, 2019 9:12 am

Hi cobbadog have never seen one of those starters with a brass cover most were pressed steel sheet, my understanding of them is not so much speed as the torque they had to turn over a diesel, the petrol starters probably run faster on free load, as ALANJ says its all about gearing.

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cobbadog
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Joined: Tue Oct 11, 2011 6:18 am
Location: beautiful Coopernook NSW. near Taree. NSW. Australia

Re: 30C Diesel Starter Motor

Post by cobbadog » Wed Dec 04, 2019 10:54 am

Thanks for the suggestions. I have no engine to count the teeth on the flywheel so establishing the ratio would be tricky but I will take some pics of it tomorrow as I ahve aday off to play with the toys. I still have the cover off so will take a pic of that end and will try to show how what I call the bendix can move forward to engage the pinion gear to the flywheel. Although it moves freely both back and forth and can easily be rotated it is still a strong spring that holds it back. When you grab the pinion gear you can rotate the armature by turning the gear in one direction but rotating it in the opposite direction nothing moves because of the clutch which comes into play when the engine starts and rotates faster than the pinion gear.

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rid54
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Joined: Mon Oct 13, 2014 8:20 am
Location: Vallentuna, Sweden

Re: 30C Diesel Starter Motor

Post by rid54 » Wed Dec 04, 2019 9:32 pm

The "bendix" is the starter motor gear, and it is normally moved into position by the solenoid pulling the gear fork against a return spring. There is also (normally) a "freewheel" or one-way clutch, that allows the starter motor gear to move freely, when the engine starts, as to unload it, and allow the return spring to pull the starter gear out of the flywheel ring gear as you let go of the start switch (or equiv.). Starter motors (generally!) are partly or fully serial motors and they have a very pronounced torque-vs-speed characteristic, that is, they give more torque as they are slowed down, to beat the heavy cranking of any cold engine. Diesel starters are generally more powerful than starters for electric ignition engines, as diesels rely on cranking speed to fire up.

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cobbadog
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Joined: Tue Oct 11, 2011 6:18 am
Location: beautiful Coopernook NSW. near Taree. NSW. Australia

Re: 30C Diesel Starter Motor

Post by cobbadog » Thu Dec 05, 2019 3:42 am

With a fully charged jump starter battery I connected the cables and got the Tacho ready to measure the RPM. It came in at between 2350 - 2400 RPM and this thing really does have some torque, it takes a lot to hold it steady when it kicks into action. So hopefully tomorrow I will pick up an "O" ring to seal the end cap and it is ready for a new home if anyone wants it.
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