Lotus Elan

Sprocket wear

PostPost by: Quart Meg Miles » Mon Jun 27, 2022 9:14 pm

I'm rebuilding my old engine for the last time, I hope, and am wondering about wear on the three sprockets. Although this engine has survived 290,000 miles of service the crankshaft is still within limits, just, due to my careful warming up but will the original cam and layshaft sprockets have worn sufficiently to affect the engines timing stability?

All three look the same and many people will say "just replace them" but if they ain't broke why fix them. Is there a criteria or gauge for assessing them?

I'm going to look at some Ford sites to see what is on offer anyway, no point buying racing items for an original road car. Thanks guys (and dolls).
Meg

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PostPost by: rgh0 » Tue Jun 28, 2022 12:37 am

Look at the tooth profile on the jackshaft sprocket as that will be the least worn and be near new still, if you dont have a new sprocket to compare with. Compare that to the profile on the cam sprockets and the crank sprocket.

With a high mileage engine you will probably see a little more wear on the cam sprockets (whats acceptable in terms of a "little more wear" is debatable) and a lot more wear on the crank sprocket. ( in general you should replace it if it has a "lot more wear")

I have a collection of old sprockets with various amounts of wear and when I get a chance I will try to quantify these vague little versus a lot statements a bit better in terms of actual measurements

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PostPost by: StressCraxx » Tue Jun 28, 2022 2:02 am

Much of my professional career has been in industrial machinery reliability engineering. As Rohan advises, there's a point where enough is enough. We used the method described in the link provided below.

https://www.renold.com/company/latest-n ... sprockets/

I don't like to replace parts that don't need to be replaced, but don't like to wait too long either. If it's close to "wear out" it's time to replace. Chain and sprocket wear will retard both cams over time.
Last edited by StressCraxx on Tue Jun 28, 2022 2:49 am, edited 1 time in total.
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PostPost by: rgh0 » Tue Jun 28, 2022 2:13 am

My background is similar in industrial machinery reliability. With modern technology the adding of continuous vibration monitoring and analysis to a machine costs very little compared to 20 years ago.

It's really time modern cars had vibration analysis on their major components as adding it to the current electronic systems would cost very little. Currently you can analyse for everything that is electrically related on a modern car through the cars own systems but we still rely on human sensing of noise and vibration to detect mechanical problems.

You can get small battery powered wifi transmitting sensors that can be magnetically clamped onto equipment that we use here where I work, maybe I will borrow a few and test them out on the Engine, Gear Box and Diff of my Elan :)

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PostPost by: reb53 » Tue Jun 28, 2022 7:08 am

"You can get small battery powered wifi transmitting sensors that can be magnetically clamped onto equipment that we use here where I work, maybe I will borrow a few and test them out on the Engine, Gear Box and Diff of my Elan :)"

I wouldn't do that Rohan.
If you do you'll be horrified.
And if you give us the results so will we...... :)

Ralph.
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PostPost by: Quart Meg Miles » Tue Jun 28, 2022 9:12 pm

Thank you, guys. There doesn't seem to be any difference between my big sprockets, and the crank sprocket, which I had forgotten about, is a rather different profile anyway and looks nothing like the others. I can buy "remanufactured" cam sprockets at £26 (GBP) inc tax, which isn't too bad, but I didn't notice if they made the crank one.

I hope to visit St Wilkins tomorrow to change the water pump and I'll see what he thinks of the sprockets and perhaps he has a crank one for comparison.
Meg

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PostPost by: types26/36 » Wed Jun 29, 2022 12:46 pm

Don’t forget to check the tensioner sprocket as they also wear …….hope you can see the wear on these pics.
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