Spurious Duplex gears.

[InimiaD]

Does anyone know who made/ supplied these adjustable Duplex gears and is there anything missing, possibly another cog/ gear.







In anticipation, cheers.

[mini13]

I think they were from swiftune,

they used a funny type of chain.

[Smiffy]

I'd say it was a mismatch, the tooth profile been different on each gear.
Home made attempt at the slark gear driven cam drive, possibly but that would need the idle gear as well.

[medwaybeat]

Is it the "Manx Racing"? one that has 3 gears and no belt? Think it’s shown in one of Vizards books.

[mk1]

Agree with Smiffy,

There is something missing & it looks like a mismatched set anyway.

The best known example of these is the set done by Bryan Slark. These were based on a set used in F3 engines during the 60's originally designed by Downton.



Come to think about it, the one at the top of the thread looks like the midle has been taken from a set of Kent Cams vernier duplex gear.

[tomkidd]

Are these something that was used to lose the chain?

[mk1]

Yup.

[tomkidd]

The advantage being what?

[dutchacme]

rock steady ignition at high rpms (> 8500)

970 racer

[almondgreen]

Come to think about it, the one at the top of the thread looks like the midle has been taken from a set of Kent Cams vernier duplex gear.

I agree, I had one of these sets.
It was sold to me as a set with a better chain, but when I stripped the
engine, I had the longest chain I ever had....

[mk1]

Those gear driven cam gears were indeed designed to eliminate valve chain & ignition timing lash, however, as far as I can gather, the unexpected side effect was that under certain circumstances the distributor drive shaft disintegrates. This seems to have been as a consequence of some sort of harmonic vibration effect that was totally unexpected & to a great extent unexplained. They are also supposed to knock hell out of oil pumps.

I hasten to say the above is not through personal experience, just third party accounts.

[Mike]

Same reason as the front timing gear on the Cosworth Formula 2 FVA engines and FVC Sportscar engines are located by quill shaft, a sort of torsion bar.

Before that apparently, the bosses on the camshafts holing the timing gears used to break off at certain revolutions.

The science of harmonics eh?

[mini13]

looks similar,

http://www.turbominis.co.uk/forums/inde ... t&tid=4769

no pic with the chain but they used a chain like in this link,

http://www.ramseychain.com/?gclid=CLTCj ... 4wodWHSTUQ

check out the 2nd part no down,

http://www.aptfast.com/apt_parts/Bserie ... eTrain.htm

[ivor badger]

Same reason as the front timing gear on the Cosworth Formula 2 FVA engines and FVC Sportscar engines are located by quill shaft, a sort of torsion bar.

Before that apparently, the bosses on the camshafts holing the timing gears used to break off at certain revolutions.

The science of harmonics eh?

Possibly an addition after camshaft drive failures in the DFVs first race at the Dutch GP in 67. They were then fitted with some sort of torsion damper in the cam drive.

[dutchacme]

Personal experience with a three gear wheel cam shaft drive:
59 mm bullet crankshaft, lightened,
1275 block height,
Longer titanium con rods,
JE pistons with lightened piston pens,
Manx fly wheel,
Lightened vibration damper,
Thin downed distributor drive,
Electronic ignition,
Spider drive
Vernier adjustable main gear wheel
Designed and engineered a post which is press fitted into the front face of the block for the idler. Took the better part of the morning to set up on the milling machine.
Modified 649 camshaft.
Castrol R40
First check after 40 hours of running time did not show any problems with the oil pump (lobe scoring), oil pump drive or gear teeth.

970 racer

[Mike]

Quite probably although the FVA pre-dated the DFV which was "Double Four Valve", using two FVA type configuration heads.

[ivor badger]

Quite probably although the FVA pre-dated the DFV which was "Double Four Valve", using two FVA type configuration heads.

Yes, but the drive didn't fail until the DFVs first race and that less than 6 months after the FVAs first race. So I suspect that since they both used similar heads and bits, that the torsional damper would be retro fitted

[chris-pilling]

cam gears, that old tractor technology.. i imagine they make quite a racket?

[mk1]

dutchacme,

That sounds like quite a setup! What sort of power are you making?

[dutchacme]

Mark,

it is difficult to give an hp reading for the 999. It was dynoed on a Superflow inertia dyno. It required a substantial adaptor piece between the crank and the dyno (extra unknown inertia) and this made that all the hp and torque readings were substantial lower than the previous readings of my 970 engines which were dynode on a water brake.

My previous 970s were all one or two hp over the 100 mark. However a reasonable torque curve is far more important than just out right hp at some silly rpm. Will do some digging to find the torque numbers.

In the end what counts is that I am a tad faster on the track. All my engines are on 1.5 SU’s.

970 racer