Lotus Elan

pre engaged starter motor

PostPost by: a d price » Wed Jan 07, 2015 9:20 pm

Could somebody tell me what a pre engaged starter is and where can I get one. I have seen them described under sensible improvements and do they make a big difference
a d price
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PostPost by: ericbushby » Thu Jan 08, 2015 11:11 am

Good morning A.D.
I will try to answer this.
As the traditional Lucas stater motor accellerates, the inertia of the deliberately heavy pinion causes it to move inwards along the spiral cut in the shaft until it engages in the starter ring.
When the pinion reaches the end of the spiral the motor is already up to speed and jerks the flywheel into rotation. The pinion teeth and ring teeth are chamfered to improve the chances of a clean engagement.
A pre-engaged motor works differently.
First, the shaft is extended to engage the pinion into the starter ring. Only when fully engaged does the motor start.
Notice that the engagement now occurs on the other side of the starter ring so it will be useful to check that the ring teeth are chamfered on both sides. They usually are.
I understand that the pinion needs to have nine teeth to be like the Lucas one. I bought the Powerlite one as recommended by Olly ,' the local Lotus specialist.

One improvement is that if the engine just fires once the starter is not thrown out and will continue cranking until you let go the switch.
Now for the technical bit.
Mine used to go -- Wow--err--err-- Wow--err--err -- Wow.
It now goes --Wow-Wow -Wow with a reduction in current from 190 amps to 160 amps
I hope this helps,
Eric in Burnley
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PostPost by: bob_rich » Sat Jan 17, 2015 8:06 pm


I used a Wosp LMS113 on my +2S130 and it seems to work fine but only after a problem partly of my own making. The Wosp unit comes with a 9 tooth pinion and requires a 110 tooth flywheel starter ring. My flywheel had a 132 tooth ringear on the flywheel due to a mix up and after a few cranks damaged the flywheel ring gear. so engine had to come out. Wosp checked over and replaced the pinion free of charge (although the pinion was not really damaged). So make sure you get a pinion to match the ring gear that you have whichever option you go for. There is quite a bit on the subject of pinions and ring gears on other posts

best of luck

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PostPost by: patrics » Sat Jan 17, 2015 9:05 pm

I have a wosp starter motor on my race engine, no hint of a problem starting cold or hot - we have a pit stop half way through race so have to turn engine off but never had to worry about it.
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PostPost by: TroonSprint » Sat Jan 17, 2015 10:03 pm

All cars now have pre-engaged starters. The old inertia starters work perfectly well but cause wear on the flywheel ring gear because, as has already been said, they hit the gear already spinning. Also the inertia starters are old technology and are less powerful than a modern unit. I have a Wosp pre-engaged unit on my ?lan.

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PostPost by: Chancer » Sat Jan 17, 2015 11:47 pm

The pinion isnt really spinning but the shaft is so there is an inertial shock when they engage, I think that most of the flywheel wear occurs when the engine starts and the pinion throws out, the inertia working once again but this time the engine starting spins the pinion faster than the shaft can accelerate so it throws out instead of in.

The bendix mechanism of an inertia starter motor was a really clever invention in its time.

Great description of the "Wow--err--err-- Wow--err--err -- Wow" :)

The people around where I live here in France are somewhat simple, they cannot string a sentence together without lots of "euuhhs" never more than 3 seconds of speech without one, often just a few incoherent words strung together with "euuhhs" so you have to try and guess what they are trying to say. When a group meet together for the mandatory shaking of hands, kissy-kissy and chit chat before a club session or whatever it always reminds me of a convention of lucas inertia starter motors :lol:
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