Chain and Sprocket Helm Issues

[Australiandad]

Originally Posted by jimbunyard

Also, measure the chain; that, the number of teeth and the shaft configuration tells you the correct sprocket. 'B' in this case is the hub configuration; the through-drilling of that hub, is likely custom to the pedestal manufacturer, and would probably best be done by the machinist who finish-bores the sprocket for you.

Hey Jim thanks heaps for your efforts they are kindly appreciated. Sometimes it is hard to see the wood for the trees and commonsense falls by the wayside. At this stage I think I will re use the original sprocket, however at the first sign of any issue (as suggested) I will be replacing the chain and sprocket with new ss ones that are readily available. Thanks again for the effort, I hope I will be able to return the favour..

[Australiandad]

Hey Dan thanks for the reply, unfortunately a sprocket I have found out is not a kinda thing someone just makes up these days, so I have been told. It’s a kind of CBC machine type job. 1 x costing around $400 AUD but if it’s any consolation a 2 nd one would only cost around $50 AUD. It’s the set up and engineering calcs that cost. Boy do I wish it was just a make it up as you go type thing.

[Australiandad]

After repairs, just hope it’s ok I’ll know tomorrow.

[ggray]

Be sure to replace the chain.

As the chain wears, the pitch increases, and it won't fit the sprocket anymore, putting the load unequally on the teeth in contact.

Old maintenance men told me that "sprockets and chain wore together" and still matched each other but that is impossible.
New chain makes sprockets last longer.

[Australiandad]

Originally Posted by ggray

Be sure to replace the chain.



As the chain wears, the pitch increases, and it won't fit the sprocket anymore, putting the load unequally on the teeth in contact.



Old maintenance men told me that "sprockets and chain wore together" and still matched each other but that is impossible.

New chain makes sprockets last longer.

It’s the same sprocket and chain, just 2 freshly capped teeth.

[jimbunyard]

Replace the chain if necessary, it will be obvious if it is worn. The sprocket shows little actual wear, if it is standard steel roller chain, I'd bet there isn't much wear on the chain.

I'd be more concerned with the chain's tension; if there is a provision to adjust it, make sure that the tension is correct.

in the first picture below, the red arrows highlight what seems tp be wear near the tips of the teeth, which may be from too loose a chain.

The green arrow shows wear near the root of the tooth where ideally it should be.

The gold arrow indicates what appears to be the unworn original finish of the sprocket, in the high pressure section of the sprocket, suggesting the low wear of the sprocket...

The orange arrow points out what looks to me like the most worn section of the sprocket; the raised metal around the hole suggests some wallowing out that might be of some concern. It seems likely that the sprocket is held on with a roll pin. If this is the case, and there is room, a tight fitting bolt and nut might hold the sprocket more securely. If clearance is tight, room could be made by using a thin-headed-section bolt and nut and/or filing/grinding some flats on the hub. Also, it may be possible to rotate the sprocket 180 from its' original position to put the unworn section of the sprocket into play, as indicated by the green arrows in the second picture...

Obviously making some assumptions from halfway around the world, so please take them with a big grain of salt...

[Australiandad]

Thanks Jim I’ll have a bit of a look, however the picture I haven’t shown was the cable thimble and wire grips being drawn into the sprocket, almost over it! As the previous owner did a dodgy cable replacement without centering the chain on the sprocket. Things were so out of whack inside that helm I don’t think I’m going to get a clear picture of the wear caused by the chain for at least 40 - 50 hrs at sea. If need be I’ll find a stainless chain and sprocket and have the hub and key way machined to suit the helm.

[beneteau-500]

Forget bearing service or consolidated bearings. Go to BJ bearings they are in dandenong they do specialise in transmission parts ie chain and sprockets

[Australiandad]

Originally Posted by beneteau-500

Forget bearing service or consolidated bearings. Go to BJ bearings they are in dandenong they do specialise in transmission parts ie chain and sprockets

Thanks for that will do if the repair fails

[RaymondR]

Was the chain actually jumping teeth when in use or are you primarily concerned with the wear you observed on the sprocket?

[Australiandad]

Originally Posted by RaymondR

Was the chain actually jumping teeth when in use or are you primarily concerned with the wear you observed on the sprocket?

The chain wasn’t jumping it was trying to pull the cable thimble and cable clamps over the cog (unbeknown to me) and in the process damaged the cog. So I have rectified the chain alignment and attempted a repair on the sprocket. Just want to make the helm good with out blowing the bank.

[jimbunyard]

Originally Posted by Australiandad

Thanks Jim I’ll have a bit of a look, however the picture I haven’t shown was the cable thimble and wire grips being drawn into the sprocket, almost over it! As the previous owner did a dodgy cable replacement without centering the chain on the sprocket. Things were so out of whack inside that helm I don’t think I’m going to get a clear picture of the wear caused by the chain for at least 40 - 50 hrs at sea. If need be I’ll find a stainless chain and sprocket and have the hub and key way machined to suit the helm.

To clarify a bit.

I saw from the statement in your first post that the cables were wearing across the tips of the teeth, and it was obvious in the pictures that something other than the chain was causing the odd 'notching wear'.

What I didn't say clearly was that two types of wear are shown on the sprocket; off-center notching and tip polishing along the shaft axis.
While they may have the same ultimate cause, misaligned or mis-routed and/or loose cables, they probably have two different solutions.

You're obviously addressing the misalignment/routing, my post showing the different areas of wear was intended to stress that normal wear for a sprocket in most cases would (should?) be concentrated at the root of the tooth, and that the tip wear (other than the notching), and lack of tooth root wear evident in the pictures seemed to indicate inadequate chain tension.

Since I'm not familiar with your system, the only assumption I could make where tip wear would be 'normal' would be if the system were set up so the chain was a rack, and the sprocket was a pinion, which in my opinion (haha) who be a singularly bad engineering design; for power transmission, the chain should engage with as much of the sprocket as possible, I would consider a third a minimum...

Don't really like making off-the-wall suggestions, but if there is no provision for tensioning the chain, I would try and add one, probably with either a spring or an idler of some sort...

[Australiandad]

Originally Posted by jimbunyard

To clarify a bit.

I saw from the statement in your first post that the cables were wearing across the tips of the teeth, and it was obvious in the pictures that something other than the chain was causing the odd 'notching wear'.

What I didn't say clearly was that two types of wear are shown on the sprocket; off-center notching and tip polishing along the shaft axis.
While they may have the same ultimate cause, misaligned or mis-routed and/or loose cables, they probably have two different solutions.

You're obviously addressing the misalignment/routing, my post showing the different areas of wear was intended to stress that normal wear for a sprocket in most cases would (should?) be concentrated at the root of the tooth, and that the tip wear (other than the notching), and lack of tooth root wear evident in the pictures seemed to indicate inadequate chain tension.

Since I'm not familiar with your system, the only assumption I could make where tip wear would be 'normal' would be if the system were set up so the chain was a rack, and the sprocket was a pinion, which in my opinion (haha) who be a singularly bad engineering design; for power transmission, the chain should engage with as much of the sprocket as possible, I would consider a third a minimum...

Don't really like making off-the-wall suggestions, but if there is no provision for tensioning the chain, I would try and add one, probably with either a spring or an idler of some sort...

You are right there is no chain tensioner. I can add tension by simply tightening he cables however I to much tension and I risk damaging the cable conduits. In my case the cable runs through conduit to get to the quadrant I don’t have a single pulley in my steering system. The tighter the cable the more friction it has to overcome, get the adjustment right is important. In the past the cable may well have been to loose.

[RaymondR]

If it was not jumping the sprocket I would just reinstall the old sprocket and not worry about it.

[gulfstar37]

Originally Posted by Australiandad

Attachment 162686Attachment 162687

After repairs, just hope it’s ok I’ll know tomorrow.

Looks like you've done a wonderful job repairing the missing teeth. How was it done?

Originally Posted by Australiandad

Thanks for that I think there’s a Bearing Services in Frankston I’ll get onto it tomorrow, I just wasn’t sure about the fact that it has been cast in brass. Thanks again.

Originally Posted by beneteau-500

Forget bearing service or consolidated bearings. Go to BJ bearings they are in dandenong they do specialise in transmission parts ie chain and sprockets