Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys?

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Thu 2 Sep 2021 03:45
Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys? - edlithgow

One of those "never noticed/thought about that before" things.

Recently replaced the alternator with a used one. Had a squeal after replacement, which has worsened, and the belt, driving off the crankshaft pulley to alternator and water pump, now looks badly worn, with missing teeth.

It seems possible the new-to-me alternator has a bad bearing, which has stressed the belt, or it could be it was just due for a coincidental failure. The car seems to drive OK (briefly, since no water pump drive) without the belt so clutch release bearings etc dont seem to be part of the problem.

I can't remember if the drive belts on my previous smooth V-pulley setups had teeth. though I'm pretty sure early ones didn't. and I wonder if the wrong belt might have been fitted.

Teeth (or rather the gaps between them) could allow greater flex of the belt, reducing internal frictional losses. OTOH the Internyet seems to make a simple distinction between V belts (which are smooth) and synchronous belts like timing belts (which have teeth or cogs, because slip is not tolerable).

https://www.linearmotiontips.com/synchronous-belt-v-belt-motion-design/

Do your V-belts have teeth (if you still have V-belts)?

Edited by edlithgow on 02/09/2021 at 03:47

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Thu 2 Sep 2021 05:51
Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys? - edlithgow

Searching for Charade G11 (probably the same) alternator belt images seems to show both toothed and smooth examples, so, assuming a majority of these images are genuine, (as opposed to a random generic belt picture) perhaps it doesn't matter.

Doesn't give confidence that they are mostly described as "fan belts" though, since there is no fan involved.

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Thu 2 Sep 2021 08:08
Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys? - Bolt

They are alternator belts, as most cars have electric fans and as you know the belt toothed or not only drives the alternator and possibly water pump, though can depend on design, ie how cheaply they can get away with driving as much as possible on one belt...

the toothed belt was iirc designed to reduce heat which caused faster belt wear not that I have noticed any difference though cuts down on rubber use....

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Thu 2 Sep 2021 09:16
Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys? - Oli rag

Some of the industrial machines I have worked on use toothed V belts with some pulleys. From what I remember the toothed or notched belts were introduced to give a higher torque capability on certain applications. Fairly sure that they are interchangeable with the normal belts using the same smooth pulleys.

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Thu 2 Sep 2021 10:17
Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys? - Bolt

They are alternator belts, as most cars have electric fans and as you know the belt toothed or not only drives the alternator and possibly water pump, though can depend on design, ie how cheaply they can get away with driving as much as possible on one belt...

the toothed belt was iirc designed to reduce heat which caused faster belt wear not that I have noticed any difference though cuts down on rubber use....

Sorry, meant to say Auxillary belt, does the same job anyway...

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Mon 6 Sep 2021 16:37
Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys? - edlithgow

Got a Mitsubishi one that is about the right size and seems to be working OK. The tooth profile is different but since they don't engage with anything that shouldn't matter.

Just the occasional chirp from it now. Perhaps it needs tightened up a little.

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Mon 6 Sep 2021 17:50
Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys? - Andrew-T

The toothed belt was IIRC designed to reduce heat which caused faster belt wear not that I have noticed any difference though cuts down on rubber use....

No doubt toothing the belt will help a bit there, but I would have thought that as the main strength of the belt is in the textile backing, adding teeth improves flexibility while going round the pulleys ? And dissipating the hysteresis in flexing, of course.

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Tue 7 Sep 2021 21:39
Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys? - focussed

It sounds like the belts you all are describing are cogged vee-belts. Used to increase flexibility of the belt, reduce heat and improve power transmission efficiency and the life of the belt.

On industrial machines a downside can be that they "buzz" on high speed drives.

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Thu 9 Sep 2021 12:47
Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys? - percy

Just a thought.

Is the belt running on the bottom of the (secondhand/worn?) pulley "vee" rather than on the sides?

If this is the case the "grip" would be poor and lead to slippage/noise.

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Thu 9 Sep 2021 15:38
Daihatsu Skywing (like Charade Mk2) - Toothed belt on smooth V-pulleys? - edlithgow

Dunno. Not sure how I'd tell, but I suppose its possible.

I could maybe take an impression of the pulley profile by pushing something into it (plasticene? chewing gum? RTV silicone? Aluminium foil?) and compare it with the belt profile.

It seems a bit unlikely though since the pulleys are steel, and I'd think would have to wear quite a lot to bottom-out a new belt.

Edited by edlithgow on 09/09/2021 at 15:41

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