Why does the solenoid have two connections to the starter motor. What does this second connection do, from the workshop manual it appears to connect to part of the winding.
JCB 3CII starter solenoid connection
-
- Moderator
- Posts: 8677
- Joined: Sun Aug 05, 2007 8:36 pm
- Real name: Jeremy Rowland
- Has thanked: 1873 times
- Been thanked: 1692 times
Re: JCB 3CII starter solenoid connection
Hi Dave; I'm certainly no electrical expert but my best guess would be a connection to the motor field coil windings?
Jeremy
Jeremy
-
- Posts: 309
- Joined: Thu Jul 04, 2019 11:44 am
- Real name: ian
- Has thanked: 126 times
- Been thanked: 114 times
- Flag:
Re: JCB 3CII starter solenoid connection
A couple of possibilities come to mind regarding the four terminal solenoid.
1. it allows you to use two batteries that would normally be isolated.
2. it's an easy way to double the current rating of the contacts
3. the 'Aux' terminal isn't connected to anything internally and is only provided as a distribution point
In the first pic, what I assume it the brushes connection may be for convenience as it would allow the brush assemble to be easily removed for maintenance.
I've had a look at the 3c Mk2 manual in the files section and the starter motors shown are quite conventional.
Which circuit do you think most closely matches your machine?
1. it allows you to use two batteries that would normally be isolated.
2. it's an easy way to double the current rating of the contacts
3. the 'Aux' terminal isn't connected to anything internally and is only provided as a distribution point
In the first pic, what I assume it the brushes connection may be for convenience as it would allow the brush assemble to be easily removed for maintenance.
I've had a look at the 3c Mk2 manual in the files section and the starter motors shown are quite conventional.
Which circuit do you think most closely matches your machine?
-
Topic author - Posts: 37
- Joined: Sun May 15, 2016 8:24 pm
- Real name: David
- Has thanked: 1 time
- Been thanked: 3 times
- Flag:
Re: JCB 3CII starter solenoid connection
It is connection 5 lug in the picture, the solenoid connects opposite terminals and because of the link all get connected to the battery +. if link was removed you could connect another battery.
-
- Posts: 309
- Joined: Thu Jul 04, 2019 11:44 am
- Real name: ian
- Has thanked: 126 times
- Been thanked: 114 times
- Flag:
Re: JCB 3CII starter solenoid connection
Seems that part is still available. It's listed as fitting a Lucas M50 and a GEU436, but I can't find anything with the twin field connections.
I can't find an exploded diagram of the solenoid, but based on your description, I'm pretty confident the four terminals are to provide two sets of contacts and hence double the current rating.
https://www.charnleys.com/part/leyland_heavy/bau1779/lucas-starter-motor
I can't find an exploded diagram of the solenoid, but based on your description, I'm pretty confident the four terminals are to provide two sets of contacts and hence double the current rating.
https://www.charnleys.com/part/leyland_heavy/bau1779/lucas-starter-motor
-
- Posts: 64
- Joined: Wed Jul 07, 2010 10:37 pm
- Real name: Kári Össurarson
- Has thanked: 1 time
- Been thanked: 15 times
- Flag:
- Contact:
Re: JCB 3CII starter solenoid connection
A bit of googling turned up this. It's a part of the service manual for Ford 2720 industrial engines, but it includes a detailed description of the Lucas M50 starter.
The takeaway is:
1. Yes, the motor actually does have two positive terminals (the bolt on the side of the body and the pigtail coming out of the end).
2. Yes, the solenoid has two corresponding contacts. Not merely for power doubling though. Apparently, one contact will always "make" when the coil is energized, but the other only once the starter pinion has fully engaged. Thus, should the teeth of the starter pinion butt against the teeth of the ring gear, only low power will be applied to the starter to move the pinion and allow it to engage, and only then is full power applied.
Ingenious, but the first time I've come across such an arrangement. Ah well, you always learn something new.
--
Regards, Kári.
The takeaway is:
1. Yes, the motor actually does have two positive terminals (the bolt on the side of the body and the pigtail coming out of the end).
2. Yes, the solenoid has two corresponding contacts. Not merely for power doubling though. Apparently, one contact will always "make" when the coil is energized, but the other only once the starter pinion has fully engaged. Thus, should the teeth of the starter pinion butt against the teeth of the ring gear, only low power will be applied to the starter to move the pinion and allow it to engage, and only then is full power applied.
Ingenious, but the first time I've come across such an arrangement. Ah well, you always learn something new.
--
Regards, Kári.
-
- Posts: 309
- Joined: Thu Jul 04, 2019 11:44 am
- Real name: ian
- Has thanked: 126 times
- Been thanked: 114 times
- Flag:
Re: JCB 3CII starter solenoid connection
I tip my hat to you.
It hadn't occurred to me to chase exotic M50's as I have two machines with them and they are quite conventional.
Technically it is a "better" system, but has obviously been found to be not worth the added complexity.
I suspect a bevel or lead-in on both the pinion and ring gear teeth has been found to be just as effective.
Thank you to both of you for a surprisingly interesting question and the correct answer!
It hadn't occurred to me to chase exotic M50's as I have two machines with them and they are quite conventional.
Technically it is a "better" system, but has obviously been found to be not worth the added complexity.
I suspect a bevel or lead-in on both the pinion and ring gear teeth has been found to be just as effective.
Thank you to both of you for a surprisingly interesting question and the correct answer!
-
Topic author - Posts: 37
- Joined: Sun May 15, 2016 8:24 pm
- Real name: David
- Has thanked: 1 time
- Been thanked: 3 times
- Flag:
Re: JCB 3CII starter solenoid connection
Many thanks, that answers the Question. Have just replaced faulty solenoid, Tractorspares in UK, supply this as the correct one for a Leyland4/98NT engine with Lucas M50 starter. Was trying to understand how it worked when all diagrams on the internet only showed one connection to starter motor.
Thanks David
Thanks David
Who is online
Users browsing this forum: No registered users and 47 guests