Powerlite starter motors

[ill_will]

In case it is useful to anyone, a couple of bits of info related to powerlite starters, specifically the RAC800 and RAC472.

RAC800 is a pre-engaged type with epicyclic gearbox and includes a solenoid. It is coaxial in design and a bit smaller than the original lucas starter. The one I have weighs approx 3.05kg. According to Powerlite it has some plastic gears and they consider it less durable than the 472 type, but recommend it for racing or if trying to save weight.

The RAC472 type similarly is the pre-engaged type and includes a solenoid, but is an offset design apparently with all steel reduction gears. The example I had weighed 4.04kg.

Both are available in an option where you can reposition the mounting flange relative to the motor body, to adjust clearance (although the product codes might be slightly different.)

The original Lucas unit I have is approx 4.5kg.

Both can be used with or without the onboard solenoid.

[ill_will]

A further update on this.

I ended up getting a RAC800 unit via Kelvedon (their part number is RACESM8) but have had some issues with it and thought the information might be useful for others looking to replace/upgrade their starter motors.

Some dimensions for the RAC800 co-axial starter:

- Pinion throw of approx 8.2mm (confirmed by powering from battery, but you can also rotate the pinion by hand to extend it)
- Distance starter mounting face to ring gear approx 32.4mm (this will vary engine to engine and corresponds to distance block to ring gear)
- Distance starter mounting face to pinion face nearest ring gear (disengaged) 27.7mm
- Clearance ring gear to pinion (disengaged) = 32.4 - 27.7mm = 4.7mm
- Overlap pinion (engaged) = approx 3.5mm (c.f. ring gear width of approx 8.5mm)

The picture below shows a mock-up with the disengaged clearance.

Some people have reported pre-engaged starters chewing up ring gears (NB I do not think this model specifically, but others that are available.) With this amount of engagement the pinion is still meshing in the portion with chamfered reliefs, i.e. not the full gear profile. I wanted to aim for a minimum of 7mm engagement and didn't try running it under power as-was.

After an email exchange with Powerlite, they have confirmed they do a RAC814 which is identical other than having an extra ~5mm throw, which should resolve this issue nicely. I'm exchanging the motor for this type and will update my findings here, but provisionally this sounds like the one to go for.

[shynsy]

Great info.
One word of general warning to anyone checking the mesh of starter motors with ring gears. Always remove all electrical connections to the starter. What I didn't realise that even with the fly lead off when you pull the pinion out it energises the motor. My mistake, but an irreversible consequence. See photo. First real injury after 30 years of tinkering.
Tim

[M100]

It’s staggering that really basic engineering is lacking in something being sold as ‘an upgrade’

[shynsy]

It’s staggering that really basic engineering is lacking in something being sold as ‘an upgrade’

It is also not a new problem. I fitted one of these to my previous elan a decade ago.. the lack of mesh meant it chipped a pinion tooth leaving me stranded. Luckily it was at the top of a multistorey car park so jump started it on the way down.
Tim

[h20hamelan]

modern time
"meant to fit"
wait for comments/complaints
change adverb

sorry about that digit

[alanr]

I am very happy with my Powerlite RAC472MS ( Multi hole) starter. It really powers the engine over!
You do need to get the MS version though.
It took a bit of sorting at the time because Powerlite insisted that the ordinary RAC472 ( not multihole)was suitable for my +2 which when fitted it wasn't and it fitted too close to the sump.

I now wouldn't want to go back to an old type inertia starter!

Alan

[shynsy]

I am very happy with my Powerlite RAC472MS ( Multi hole) starter. It really powers the engine over!
You do need to get the MS version though.
It took a bit of sorting at the time because Powerlite insisted that the ordinary RAC472 ( not multihole)was suitable for my +2 which when fitted it wasn't and it fitted too close to the sump.

I now wouldn't want to go back to an old type inertia starter!

Alan

Despite my issues a decade ago I have fitted powerlite to a number of my other classics and they are much better than the inertia starters.
Tim

[ill_will]

Tim,

Sorry to hear you hurt yourself. The root cause is not one I'd have anticipated so hopefully your post will prevent it happening to anyone else!

To be fair to Powerlite they have been very helpful resolving this, and do not claim that the RAC800 should fit an Elan (which they do for the RAC814.) I have one of their starters in another car and have been very pleased with it so far.

Regards,

Will

[alan.barker]

Still with original Starter on my Sprint no problem.
Alan

[shynsy]

Tim,

Sorry to hear you hurt yourself. The root cause is not one I'd have anticipated so hopefully your post will prevent it happening to anyone else!

To be fair to Powerlite they have been very helpful resolving this, and do not claim that the RAC800 should fit an Elan (which they do for the RAC814.) I have one of their starters in another car and have been very pleased with it so far.

Regards,

Will

Thanks. The incident was my fault entirely and the result of me not thinking things through. Was an interesting experience getting it sorted out and not 100% negative.
Tim

[ElanDNA]

Some dimensions for the RAC800 co-axial starter:

- Pinion throw of approx 8.2mm (confirmed by powering from battery, but you can also rotate the pinion by hand to extend it)
- Distance starter mounting face to ring gear approx 32.4mm (this will vary engine to engine and corresponds to distance block to ring gear)
- Distance starter mounting face to pinion face nearest ring gear (disengaged) 27.7mm
- Clearance ring gear to pinion (disengaged) = 32.4 - 27.7mm = 4.7mm
- Overlap pinion (engaged) = approx 3.5mm (c.f. ring gear width of approx 8.5mm)

Hello Will, I have noticed the same thing and have made myself a new flange.

After an email exchange with Powerlite, they have confirmed they do a RAC814 which is identical other than having an extra ~5mm throw, which should resolve this issue nicely. I'm exchanging the motor for this type and will update my findings here, but provisionally this sounds like the one to go for.

5mm is too much for me, with 4mm I have Pinion disengaged, only 0.5mm play to the ring gear.
I took a few photos and made a sketch during the manufacturing process. See PDF
Then I had another problem to solve with my aluminum clutch housing!
Have fun looking through the PDF in the next Post

[ElanDNA]

Have fun looking through the PDF

Starter Projekt RAC802.pdf

(1.99 MiB) Downloaded 109 times

[ill_will]

Looks like a good solution ElanDNA. I contemplated doing something similar but have quite a few "things to make" at the moment for the EFI conversion, so if the revised unit does fit without modification that will be one job less...

Do you know what the distance from motor mounting face to ring gear was in your case?

[ElanDNA]

Looks like a good solution ElanDNA. I contemplated doing something similar but have quite a few "things to make" at the moment for the EFI conversion, so if the revised unit does fit without modification that will be one job less...

Do you know what the distance from motor mounting face to ring gear was in your case?

Yes I know:

I got my EFI conversion in 1992/93.

Everything has been running since then. I have improved a few little things since then.
It's been a lot of work and as I'm sure you know, you can always do things better the second time round.
Good luck