y' know broke you got me thinking - you've got a point about the inner cv / trans flange bolts, their not very big, high quality yes but not much metal there, if the flywheel bolts shear then so should they.......if the clutch is engaged.....if not, and the engine is travelling very quick and the power is cut suddenly, maybe the momentum of the flywheel can shear them.....if their not fitted (torqued) right......dunno there's got to be a point where if you are tuning an engine, the original fasteners cannot clamp up hard enough to stop slippage - dowelling the crank has long been a practise done on high revving engines - with these bolts with a proper fitting shank on them, its like having dowels but without the machining hassle
zetec cambelt pullies - no keyway on them, just bolted on - scarey as if they slip, adios engine - but seen to work.....hmm....
high revving engines and flywheel departure. coincidence? some vibration harmonics going on here maybe?
A quick Google of How a Bolt Works resulted in finding a page covering bolted joints. A portion of it is as follows... The other type of joint is loaded by shear force (Fs). In a joint loaded in shear, the friction between the parts keep them from moving when subject to a shear force. The friction between the parts carries the load, not the fastener. An example of this type of joint would be a shock absorber mount or the driveshaft flange on an airhead. The greater the preload force, the greater the clamping force, the greater the friction, and the stronger the joint. With a properly designed and tightened joint, the bolt will not experience a direct shear load. It was from a BMW bike site, which explains the mention of airheads. I've added the bold and underline to highlight the points I was making about the flywheel bolts on your VR. The orignal page is here http://home.jtan.com/~joe/KIAT/kiat_1.htm Broke
the issue is that on high revving engines, the bolt, when torqued to std specs, cannot exert enough clamping force to keep the flywheel on the end of the crank - after all, the contact area is actually very small - hence some dowels to try and help it out - the arp bolts are torqued to std specs but because they fit the holes so well, axtually act as dowels as well as fasteners - well thats my theory anyhow
Some good thoughts on this thread. Just a few more to add: Some output shafts have an outer ridge to allow the inner CV to locate into the output shaft face - how does this influence the various forces at play? The ridge clearly locates the inner CV ?reducing? the potential shear forces at play, and restricting them to 2 directions only? Ditto wheels with hub centres to sit on. On a Group 4 Escort, they used to use large shank wheel studs, with the corresponding 'Group 4' inserts in the Minilites. From a conversation had at Gartrac, the design beefed up the location of the wheel, since AFAIK the rear hubs don't have hub centres for the wheel to locate on. This seems to suggest shear forces being acknowleged as an issue which they're engineering around.
The lip around the CV flanges wouldn't change rotational shear forces at all, the shear forces would be when the CV didn't spin and the flange was trying to spin....the bolts (if loose or under spec or whatever) would shear and the CV would no longer be connected. The lip on the flange wouldn't reduce the shear forces seen by the CV bolts at all. Same with the hub for a hubcentric wheel...the hub just centers the wheel, but won't affect the rotational shear forces. It might help in lessening the shear forces seen by the bolts from something like loading the vehicle with a lot of weight....the shear forces of the vehicle weight pushing down on the wheel bolts or the forces seen when the car was launched off a hill or something, but the rotational forces wouldn't be changed....a high power drag launch would still shear them the same with or without a hub. Broke
How about the front brake disc, merely located with a small counter head screw, the bolt holes in the disc are not a tight fit round the wheel bolts, yet this small screw does not shear. . . . The only time i can see shear forces becoming an issue is when parts are not properly tight and there is movement
A very thought provoking point about the hub centres supporting the weight of the vehicle and keeping the stress off the wheel bolts. Imagine how that weight increases under braking... If we acknowledge shear forces exist on CVs and road wheels (albeit controlled by hub centres and output shaft ridges) going back to the flywheel then, there must be some shear forces at play?
Theres on'y gonna be shear forces at play if he stiction isn't sufficient to keep the 2 parts in situ... A correctly torqued up bolt should keep the 2 surfaces together, and they shouldn't move. The bottom suspension to hub bolts do the same job, again they're much larger bolts, but the camber doesn't constantly change through them moving.
The threaded bolt is replaced with a sleeved one because a threaded bolt will carry the load accross the threaded area only. With a sleeved one the load is distributed more evenly.
Neither should be taking any shear loading, as mentioned before, the clamping force of the bolt holds the parts tight together, the friction between the 2 parts is what keeps them from moving, not the bolt. The bolt is just a clamp to increase the friciton between the parts. The only shear load the flywheel would see is rotational forces, as there is no weight being exerted in any other direction on it, like the CV. The wheel has forces coming from directions other than rotational, so the hub center would help support some of those (but not rotational at all), while the CV flange lip wouldn't do much as there is nothing but rotational shear being put through the CV bolts. *edit* - interesting thing I was told... About 90% of the torque applied in tightening a bolt is used to overcome friction - 50% of the torque is consumed by friction of the bearing face of the nut or bolt, whichever surface is rotated; about 40% is consumed by the contact flanks of the threads. The remaining 10% is useful in producing bolt tension. Broke
Good `thread` guys. Thought I`d feedback some experiences (hillclimbs & sprints) Mk1 1800 8v with 140bhp / 117lbft @ flywheel using a lightened flywheel and standard bolts revving to 7200. 160 standing starts @ 4 - 6000 ..... no problems Mk2 2000 9A with 200bhp / 160lbft @ flywheel using a lightened flywheel and standard bolts revving to 7800 - road use plus 10 standing starts @ 4 - 6000 and bolts found to be fatigued / weak so replaced with standard - these have only lasted ~ 2,000 miles so ARP`s next time.
yes it does... did so several times on the disk taking up the slack in its clearance holes to the studs I ran, and sheared off the M6 screw easy as. 4 x M12 studs however... was somewhat immovable thankfully. (Brembo's when I ran them)
sorry to bump this rather than start a new thread, would you say the ARP wheel bolts help solve a issue with high reving engines, or high torque engines? I've just order a clutch thats spec'ed for 400lbs, but my motor redlines at 4500 rpm, limits at 4800'ish so it's not a high revver, but just a bucket of torque if it's advised to upgrade while clutch if off, where can i get them in the uk? cheers crispy
ARP Studs fitted to my project c/w Helix 4 puk ceramic paddle and Sachs HD Pressure plate together. They cost me arround 45 from Integrated Engineering in the US.]
http://www.arp-bolts.com/Images/ARP_EU_Distributors.pdf http://www.intengineering.com/ARP-Heavy-Duty-VW-Audi-p5006925-1-2.html
