V7 SLR Posted February 4, 2003 Share Posted February 4, 2003 AMMO, I had the good fortune of reviewing some alternative K series pulleys last night. This is what I found... Caterham supply an alternative steel pulley where both the d/s pulley and the alt pulley are the same size. Both are the size of the current d/s pulley. I don't know where to measure a pulley's diameter from but measuring across the outer diameter (including the flange) and subtracting a "bit" to try to account for the flange makes the pulley "about" 90mm. If I understood you correctly, you think that by reducing the alt pulley to 110mm still means the alt is over-revving, why not take Caterham's idea and make both pulleys the same size (that being the size of the d/s pulley)? Using my dubious method of measuring alt pulley I can say that across the flanges it is 55mm as PC said which I averaged out to be 50mm (but I have no idea where you are supposed to measure). I would be interested in your calculations as to what idle speed would need to be maintained for this pulley size in order to continue to benefit from charging. Holding a (Caterham) steel pulley in one hand and an alloy pulley in the other and "twisting" them in front of me I can say that there is an enormous (and surprising) difference between their rotational inertia's (forgive the terminology). The standard pulley will only exaggerate this difference. Although the K crank is cast, as stated above, I have spoken with someone who has run a highly tuned K for 3 years with an alloy pulley with no detriment. This was almost entirely sprinting though. The concern is whether at cruising (road) speeds the harmonics will cause any damage. I was not able to confirm whether the alternator and d/s pump could act like a damper although my suspicion is that is does. Whatever, the harmonic damper in the standard pulley is certainly designed for a specific combination of components as fitted to Rover cars. The Caterham flywheel and (in my case) forged pistons undoubtably alter that component count. How much is uncertain. We are going to investigate modelling the vibrations further with respect to the standard damper and the belt driven ancilliaries. Suffice to say I am still interested and am saving furiously to be able to afford such (and a steel pump rotor). Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
V7 SLR Posted February 4, 2003 Share Posted February 4, 2003 Some corrections/further observations (having re-read the entire thread again): 1. Mike Bees has the steel pulley and a larger alt pulley and still charges OK at 1000rpm. I therefore propose the alt drive is made the same as the d/s pulley drive. 2. PC said 50mm, not 55 as I thought. This is in line with my meaurements (including the "averaging" factor). 3. I assume that even though I averaged the d/s pulley out at ~90mm and others have stated ~80mm that you will endevour to make it accurate next to an original. I think this is probably more important than the alt drive speed. And another thought ... I might be interested if anyone makes a d/s pump pulley with deeper flanges so as to help prevent a belt being thrown... and on this same score maybe the flanges on the crank pulley might benefit from deeper flanges too? I understand they cannot be too deep or changing a belt will prove troublesome, but there must be enough scope for a little extra depth..?? Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Peter Carmichael Posted February 4, 2003 Share Posted February 4, 2003 If the ali pulley is the same size as the caterham steel pulley, then you can remove the lower timing belt cover with the pulley in situ. This is a very useful feature. A deep flange is probably unnecessary and more of a hindrance than you might think. If belt alignment is a problem, the belt tends to climb out of its grooves. It will still attempt to do this even with a deep flange and will probably shred as a result. If you want the belt to stay on, don't use a poly-vee. A vee belt usually requires lots of tension to transmit as much power as a poly-vee. A poly vee can have trouble with high revs, being centrifugally thrown away from the pulley. If you compensate by upping the tension, you throw away the benefits of a poly-vee belt and might as well be running a vee. FWIW, I don't think the poly-vee or flange represents a problem. Both of my incidents with belts failing have been caused by problems of alignment and integrity of the belt run to a non-standard alternator, mounted on a non-standard bracket. A non-standard pulley on a standard alternator should be easy to make reliable and problem free. Link to comment Share on other sites More sharing options...
AMMO Posted February 4, 2003 Share Posted February 4, 2003 So guys what would you like, 110 mm or smaller? If smaller I can telephone tomorrow to get an alternative quote. Question: How much thread is engaged when the bolt is screwed into the crank? I want to increase the section where the bolt goes through the pulley. How deep is the shoulder between the cam belt pulley and the end of the crank? Thanks. AMMO Link to comment Share on other sites More sharing options...
Dave York Posted February 5, 2003 Share Posted February 5, 2003 HI Ammo, Still room for one more on the order? If so please add me to the list. David York Whoever said ... If it aint broke, Don't fix it... Just doesn't get the point! Link to comment Share on other sites More sharing options...
Peter Carmichael Posted February 5, 2003 Share Posted February 5, 2003 I would be happiest with a small diameter (80mm or so - the same as the dry sump pulley and Caterham steel pulley). Link to comment Share on other sites More sharing options...
V7 SLR Posted February 5, 2003 Share Posted February 5, 2003 Me too. Same diameter alt pulley as d/s pump please. Makes a lot of sense to do do this. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
AMMO Posted February 5, 2003 Share Posted February 5, 2003 I have just had the original order ammended to 80mm front and rear. I'm having the section where the bolt goes through increased from 8 mm to 10 mm. 12 mm would be better still but I'm worried about the engaged thread of the pulley bolt. I would like 1.5 times the thread diameter of the bolt engaged if possible. Can anyone help with the engaged length of the bolt? Thread and pitch of bolt would be nice as well. I only have the original pulley as pattern. I can predict that the five off quote is going to be out of the window so will probably have ten made to get the price. So Dave consider yourself in. AMMO Link to comment Share on other sites More sharing options...
Lawrence_Z Posted February 5, 2003 Share Posted February 5, 2003 I can't remember the engaged length, but its certainly quite a lot on my engine. Also there is a large spreader washer in there that you may wish to utilise, or perhaps fashion a special to replace it, complete with rebate for the screw head thus not shortening the engaged length. Lawrence Link to comment Share on other sites More sharing options...
Luke Beaumont Posted February 5, 2003 Share Posted February 5, 2003 Ammo, if it'll wait till the weekend I'll bring my front bolt & cambelt pulley for you to inspect. Link to comment Share on other sites More sharing options...
AMMO Posted February 8, 2003 Share Posted February 8, 2003 Lawrence Thanks for that info. Luke I need the dimension from the end of the crank nose to the cam belt pulley (or length of crank nose to shoulder and cam pulley width). Also length of thread of pulley bolt. Pop parts around if you like. AMMO Link to comment Share on other sites More sharing options...
AMMO Posted February 12, 2003 Share Posted February 12, 2003 Got the quote yesterday. As suspected five off is not worth it. I am going ahead with a batch of ten. These are more expensive to make than the Zetec ones that retail at £79.00 + VAT. I will however stick to the £80.00 + VAT originally mentioned and absorb the cost myself. I will also keep four on the shelf for any late comers. As we are agreed on 80 mm diameter front to rear the ali pulleys will be interchangeable with the steel pulleys fitted to some dry sump engines. Delivery 3 - 4 weeks. AMMO Link to comment Share on other sites More sharing options...
V7 SLR Posted February 12, 2003 Share Posted February 12, 2003 Great. When/where should we send money? I'm in the Midlands, but if it would help with postage (which I'd pay for obviously) I might be able to arrange someone to pick it up. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Hiu Flaughn Daughn Posted February 12, 2003 Share Posted February 12, 2003 er... here's something else to consider: if the front end of your crank is dancing a Mr Whippy jig, and the rear end of your crank isn't, then the ignition timing on the front cylinders is going to be different to the rear. This would mean you're ignition mapping will be limited by the most advanced cylinder (could be front or rear, depending on the torsional mode and torsional displacement wrt. the flywheel/encoder. Anyway, the TV damper on the end is designed to do the Mr Whippy jig in lieu of the crankshaft. Cheers, Hiu Link to comment Share on other sites More sharing options...
New Barbie Posted February 12, 2003 Share Posted February 12, 2003 I'd like to come in on this as well now, what's the score with sending the money ?? Link to comment Share on other sites More sharing options...
AMMO Posted February 12, 2003 Share Posted February 12, 2003 Count, I have added you to the list. Send no money now. I'll be in touch closer to delivery time. AMMO Link to comment Share on other sites More sharing options...
Peter Carmichael Posted February 12, 2003 Share Posted February 12, 2003 Hiu, And your cam timing is determined at the front pulley end, so you have to look at those same vibrational modes to work out where your greatest propensity for valve piston contact might occur. This means that heavily counterbalanced crankshafts (which will store the same amount of energy at reduced torsional strains) are better! Once you have allowed for the stretchy belt and stretchy conrods and everything else it might just be as well to leave a considerable gap. 😬 Link to comment Share on other sites More sharing options...
AMMO Posted March 29, 2003 Share Posted March 29, 2003 Pulleys will be in on Monday. Could you please get in touch to arrange paymet and delivery. Thanks AMMO Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now