V7 SLR Posted April 4, 2002 Share Posted April 4, 2002 The standard K front pulley is a heavy ol' piece of kit. Seems that if you're intent on reducing your rotational ineretia, that you should also look to this pully. Now, whilst I've heafted it about I have no idea about its rotational inertia but it must be more than an ali equivalent. Can you get one anywhere and if so, at what cost? Link to comment Share on other sites More sharing options...
Johnty Lyons Posted April 4, 2002 Share Posted April 4, 2002 Nig i tend to agree but I'm waiting to see what way Pace are planning to handel their Dry sump drive as I believe there might be a light weight solution there Any how are you having a late lunch or just pretending to work Did Mick get you? jj Link to comment Share on other sites More sharing options...
R2D2 Posted April 4, 2002 Share Posted April 4, 2002 Be careful about Aluminium bottom pulleys, they clearly rotate at engine speed and bursting forces are quite high. Crossflows and BDA s use steel pulleys to replace the standard cast iron as they have been known to break. Alloy cam pulleys are much less stressed as the rotate at half engine speed. If you do fit an alloy you want to be sure it is a good quality 7000 Series heat treated to T6 condition. This will probably be 75% of the strength of an EN8 steel pulley. Link to comment Share on other sites More sharing options...
sjwb Posted April 4, 2002 Share Posted April 4, 2002 Nearly right. The front pulley is tuned to the crankshaft assembly and is in fact a torsional damper. If longevity is to be preserved then change the material at your own risk. As for aluminium bursting in this application due to rotational forces, not a chance. Steve B Link to comment Share on other sites More sharing options...
Mike Bees Posted April 4, 2002 Share Posted April 4, 2002 Both Caterham and QED sell a damperless front pulley which is smaller in diameter (gears down the alternator). It's still steel and pretty hefty, but is a lot prettier than the stock one (I've only seen Caterham's offering) and must therefore be better. Mike Link to comment Share on other sites More sharing options...
Rob Walker Posted April 4, 2002 Share Posted April 4, 2002 I have the Caterham on fitted cost £45 IIRC. The standard pulley will overload your alternator if you venture above 7800 as its drives the alternator 3 times per rev of the crank. The sting in the tail is the shorter belt costs a bomb and is difficult to source other than Caterham. Edited by - Rob walker on 4 Apr 2002 20:14:14 Link to comment Share on other sites More sharing options...
Mike Bees Posted April 4, 2002 Share Posted April 4, 2002 I paid 11ukp (which I thought was pretty steep) for a 700mm belt from Lucas, it's off a diesel Escort van. Don't know if it's the same the Caterham one - I have a larger than standard ali pulley on the alternator so mine's running doubly slow. Mike Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted April 4, 2002 Share Posted April 4, 2002 ................. yet from your other posting Mike it can still produce 16.3 volts!!! Link to comment Share on other sites More sharing options...
AMMO Posted April 5, 2002 Share Posted April 5, 2002 I changed the pulley on my alternator for a larger one. Went to my motor factors and sourced a Gates 6 groove poly-vee belt to suit. The catalogue lists them in around 10/15mm length increments. Cost was around £10/11.00. Am having a smaller ali crank pulley made(1800 Zetec)so will have to source a shorter belt soon. This topic was discussed under the heading "Harmonic dampers" a while ago. AMMO Link to comment Share on other sites More sharing options...
V7 SLR Posted April 5, 2002 Author Share Posted April 5, 2002 Johnty, email off-line. I've now seen a smaller crank pulley and a larger alternator pulley. Presumably this is to offset the belt size, although both pulleys were wider. How many grooves in the standard one? I totally agree that the other "driver" for this is to reduce the revs that the alternator runs at... I better go have a look at that other thread then. Link to comment Share on other sites More sharing options...
Rob Walker Posted April 5, 2002 Share Posted April 5, 2002 Nig, No the larger alternator pulley is not just to be able to fit the larger belt, its to provided a larger reduction in the alternators revs. The point to bear in mind is that if you reduce the alternator gearing too much it won`t charge at tick or when moving in traffic. The Caterham R500 is about right as the alternator will still charge at 1100 plus crank rpm`s Link to comment Share on other sites More sharing options...
Roger King Posted April 5, 2002 Share Posted April 5, 2002 Why not do what a bloke wrote into CCC about. He was going to drive his alternator electrically to gain a few horses from the engine. I kid you not, but it was about 20 years ago. Link to comment Share on other sites More sharing options...
sjwb Posted April 5, 2002 Share Posted April 5, 2002 Nothing wrong with him thenwink.gif Steve B Link to comment Share on other sites More sharing options...
R2D2 Posted April 5, 2002 Share Posted April 5, 2002 April Edition of CCC ? Link to comment Share on other sites More sharing options...
V7 SLR Posted April 5, 2002 Author Share Posted April 5, 2002 I've had a look at the other thread. Seems there are considerations I'd not even imagined (nothing unusual there) particularly regarding the damping effect. My initial concern was to reduce rotational inertia (imagining that this is cheaper than a new flywheel for this year's budget), but I appear to have stumbled rather unwittingly onto a greater problem of over-revving the alternator too, which in turn may liberate a horse or 2 at max revs. So, I think it's a good idea and am willing to "push to the back of my mind" concerns over damping. I'm not alone either accrding to the other thread. Now I need some details of where to buy either a) a crank pulley and different-size belt, or b) a crank and alternator pulley (assuming the belt remains the same length). I know Caterham do a steel crank pulley, but if it's worth doing.... ali it has to be. It has to drive my dry sump pump belt too. Peter C seems to have a nice one if you take a look at DVA's web site. Where was that from and how much? Apologies for misspelling pulley in the title. Irritating isn't it? Link to comment Share on other sites More sharing options...
Peter Carmichael Posted April 5, 2002 Share Posted April 5, 2002 A solid pulley without a steel crank is a bad idea. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted April 5, 2002 Share Posted April 5, 2002 My titchy alternator doesn't charge until ~3000rpm which is a pain in the bum.gif as the car cannot survive indefinitely (note the spelling while we are having spelling practice - "definIte" - think about it being related to "finite" and there won't be a problem because "finAte" doesn't exist - bloody annoying that so many threads are contaminated with "definate this" and "definately" - if you're so certain learn to express it properly. Not a dig at Nig; there are lots of perpetrators. There might be children watching and then they will think you're a prawn for being unable to spell or pick up your bad habits. Let's stop the rot.) in traffic and discharges the battery at a phenomenal rate if the lights are on. The discharged battery makes the car more likely to stall and then it won't start again. Apparently my alternator shouldn't be driven above 12,000rpm and I have geared for this. Above 12,000rpm the brush wear is accelerated (not "accelArated"). smile.gif Edited by - Peter Carmichael on 5 Apr 2002 13:04:16 Link to comment Share on other sites More sharing options...
V7 SLR Posted April 5, 2002 Author Share Posted April 5, 2002 Forgive the ignorance but what is a "solid" pulley? I guessed that the reason my standard pulley was a "damper" was simply because of its weight/inertia? Are you saying that there is some in-build damping absorbing material (rubber? Don't laugh)? Doesn't look like there is. Looks like an iron wheel. The cam belt pulley, now that the alternator pulley is removed, wobbles around a lot. I haven't a clue why this is, and couldn't even guess at whether this has some damping material behind it, but I wasn't intending to replace that. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted April 5, 2002 Share Posted April 5, 2002 Your big pulley is made in two cast iron parts and they are joined by a high hysteresis rubber anulus. This allows relative movement and dissipates energy as heat. The dry sump pulley is on the part attached directly to the crank. The alternator pulley is the bit mounted on the rubber anulus. Link to comment Share on other sites More sharing options...
Paul Ranson Posted April 5, 2002 Share Posted April 5, 2002 He said 'anulus'. Heh heh heh heh. Paul Link to comment Share on other sites More sharing options...
DohNut Posted April 5, 2002 Share Posted April 5, 2002 So let me get this right Peter C is irritated by bad spelling, and yet he frequents a site where a significant number of contributors appear to be Dyslexic. Keep taking the vallium Peter it is not going to get any better. Nick Link to comment Share on other sites More sharing options...
Stijn LUYCK 1 Posted April 5, 2002 Share Posted April 5, 2002 Good one Paul ... smile.gif Link to comment Share on other sites More sharing options...
Peter Carmichael Posted April 5, 2002 Share Posted April 5, 2002 I said it once. I said it twice. Link to comment Share on other sites More sharing options...
Mike Bees Posted April 5, 2002 Share Posted April 5, 2002 Nig - the cambelt pulley is held in place by the crank pulley. The location of the crank pulley is a nasty piece of work on the K-series, if you've ever balanced a K crank assembly (using appropriate machiniry (tee hee) I hasten to add) then you'll have noticed that you get a different unbalance result just by removing and then re-affixing the crank pulley. Anulus - snik snik. I say 'rubber ring'. Mike Link to comment Share on other sites More sharing options...
V7 SLR Posted April 5, 2002 Author Share Posted April 5, 2002 Oh bollards. sad.gif I'm not going to rebalance my crank assy now, just because I've removed the alternator/crank pulley. It's a PITA to learnt this Mike, but better now than just after I've changed it (thanks). I thought that having a locating lug on the cam belt cog and a corresponding one on the alt/crank pulley would mean it all falls back together again in perfect harmony. In practice, is this imbalance large enough to cause a problem or is it simply marginal imbalance when detected on a hyper-sensitive bit of apparatus? I take your point Peter about the alternator not charging. Rob said the same on the previous page. I hadn't realised it was so marginal. I wonder by how much I could reduce my pulley's circ/diameter (whatever) and still achieve charging at idle. I don't rev as high as you (8000 and a shade, max) so I've no need to gear mine down that far. To be honest, my prime motivation was to reduce inertia, but if my current wheel is made the way you say it is (rubber sandwich) then I'd be as well to leave alone. Boo. I so wanted a nice shiny ali wheel exposed at the front of the engine. Link to comment Share on other sites More sharing options...
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