Prove it to me....Camshaft Gear Drive is a HP Killer

[Tom68]

386159317_169155396237838_5118093754094154449_n.jpg

[PackardV8]

Whazzit ??

[Alaskaracer]

Lots of misinformation out there on gear drives. They are my preferred choice of drive for a cam in any application. Years ago Hot Rod magazine did a back to back to back test of a Mildon gear drive, Jesel belt, and timing chain. Gear drive made the most power out of all of them.....I ran a three gear style in my old pickup....had well over 200k on it.....other than normal wear, bearings looked new....Oh, and ran a fluidamper as well....If I listened to all the BS out there on those, that engine should have blown up and broken stuff just after startup......and don't for a minute think it had an easy life. I drag raced that truck, towed with it, street raced with it, off roaded, you name it.

[Jeff Lee]

Indy lite series (don’t remember the years) ran Buick V6’s exclusively and all had Milodon gear drives. Over 1,000,000 miles and not one failure attributed to gear drive “issues”

[hoffman900]

27 year old paper, but puts some data to all this and much better than anecdotal information:

Camshaft Timing Drive Analysis for a Winston Cup Race Engine

One of the major objectives in automotive engine design is to efficiently and reliably transfer power throughout the engine. This study's objective is to evaluate the reliable means of transferring radial position, as efficiently as possible, between the cam and the crankshaft on a NASCAR Winston Cup race engine.
There are three accepted methods by which the radial position can be transferred between the cam and the crankshaft. These methods are timing chains, belts, and gears. This study encompassed all three of these methods. As the study progressed, the main focus shifted to three styles of timing chains: a conventional roller chain, a silent chain, and a newly developed inverted tooth power transmission chain. The cam drives were evaluated through both analytical and experimental data using the following criteria: harmonic frequency amplitudes, tensile and fatigue strength, chain efficiency, motored torque, dynamometer durability, and race performance.

https://www.sae.org/publications/techni ... nt/962513/

[Tom68]

27 year old paper, but puts some data to all this and much better than anecdotal information:

Camshaft Timing Drive Analysis for a Winston Cup Race Engine

One of the major objectives in automotive engine design is to efficiently and reliably transfer power throughout the engine. This study's objective is to evaluate the reliable means of transferring radial position, as efficiently as possible, between the cam and the crankshaft on a NASCAR Winston Cup race engine.
There are three accepted methods by which the radial position can be transferred between the cam and the crankshaft. These methods are timing chains, belts, and gears. This study encompassed all three of these methods. As the study progressed, the main focus shifted to three styles of timing chains: a conventional roller chain, a silent chain, and a newly developed inverted tooth power transmission chain. The cam drives were evaluated through both analytical and experimental data using the following criteria: harmonic frequency amplitudes, tensile and fatigue strength, chain efficiency, motored torque, dynamometer durability, and race performance.

https://www.sae.org/publications/techni ... nt/962513/

Roush test I think, didn't test belts, discounted for strength, imagine the ignition latency retard plus the belt stretch at speed retard.

I ran an Aussie Cup car in the late 90s with a belt, don't recall seeing retard setting the timing, I didn't do the dizzy though.

[Tom68]

Whazzit ??

12HP 18,000 rpm 125.

https://www.visordown.com/features/gene ... ft-benelli

[hoffman900]

27 year old paper, but puts some data to all this and much better than anecdotal information:

Camshaft Timing Drive Analysis for a Winston Cup Race Engine

One of the major objectives in automotive engine design is to efficiently and reliably transfer power throughout the engine. This study's objective is to evaluate the reliable means of transferring radial position, as efficiently as possible, between the cam and the crankshaft on a NASCAR Winston Cup race engine.
There are three accepted methods by which the radial position can be transferred between the cam and the crankshaft. These methods are timing chains, belts, and gears. This study encompassed all three of these methods. As the study progressed, the main focus shifted to three styles of timing chains: a conventional roller chain, a silent chain, and a newly developed inverted tooth power transmission chain. The cam drives were evaluated through both analytical and experimental data using the following criteria: harmonic frequency amplitudes, tensile and fatigue strength, chain efficiency, motored torque, dynamometer durability, and race performance.

https://www.sae.org/publications/techni ... nt/962513/

Roush test I think, didn't test belts, discounted for strength, imagine the ignition latency retard plus the belt stretch at speed retard.

I ran an Aussie Cup car in the late 90s with a belt, don't recall seeing retard setting the timing, I didn't do the dizzy though.

A lot has changed in 30 years.

I do find it funny how pushrod builders discount camshaft angular velocity changes while Ilmor, Cosworth, Honda, and all the OHC racing designers put so much effort in minimizing it. The V8’s, with data Billy Godbold has shared, do suffer from it. He also shared how the lobes used on WoO and other Sprint Cars would barely survive a lap if it weren’t for the pump drives acting as dampers to control it. Seems like a no brainer to me and it’s all 80yo technology to control it.

[ClassAct]

27 year old paper, but puts some data to all this and much better than anecdotal information:

Camshaft Timing Drive Analysis for a Winston Cup Race Engine

One of the major objectives in automotive engine design is to efficiently and reliably transfer power throughout the engine. This study's objective is to evaluate the reliable means of transferring radial position, as efficiently as possible, between the cam and the crankshaft on a NASCAR Winston Cup race engine.
There are three accepted methods by which the radial position can be transferred between the cam and the crankshaft. These methods are timing chains, belts, and gears. This study encompassed all three of these methods. As the study progressed, the main focus shifted to three styles of timing chains: a conventional roller chain, a silent chain, and a newly developed inverted tooth power transmission chain. The cam drives were evaluated through both analytical and experimental data using the following criteria: harmonic frequency amplitudes, tensile and fatigue strength, chain efficiency, motored torque, dynamometer durability, and race performance.

https://www.sae.org/publications/techni ... nt/962513/

Roush test I think, didn't test belts, discounted for strength, imagine the ignition latency retard plus the belt stretch at speed retard.

I ran an Aussie Cup car in the late 90s with a belt, don't recall seeing retard setting the timing, I didn't do the dizzy though.

If it is the Roush test, they used a floating idler gear drive and not a fixed idler gear drive.

Other than that Roush test I’ve never seen a SHRED of actual testing that showed the GD transferred more harmonics, cost horsepower or anything else.

[hoffman900]

27 year old paper, but puts some data to all this and much better than anecdotal information:

Camshaft Timing Drive Analysis for a Winston Cup Race Engine



https://www.sae.org/publications/techni ... nt/962513/

Roush test I think, didn't test belts, discounted for strength, imagine the ignition latency retard plus the belt stretch at speed retard.

I ran an Aussie Cup car in the late 90s with a belt, don't recall seeing retard setting the timing, I didn't do the dizzy though.

If it is the Roush test, they used a floating idler gear drive and not a fixed idler gear drive.

Other than that Roush test I’ve never seen a SHRED of actual testing that showed the GD transferred more harmonics, cost horsepower or anything else.

In general. They all do it, either input from the crankshaft end or the camshaft going into resonance on its own + the acting of the loads on either side of the lobe. The less ratcheting the camshaft sees, the more aggressive lobe you can get away with for a given rpm / service interval.

[Joe-71]

Comes down to NVH in automobiles that are mass produced. Cost vs dependability vs NVH. Joe-71

[hoffman900]

Comes down to NVH in automobiles that are mass produced. Cost vs dependability vs NVH. Joe-71

Not at all, it’s a cost thing on production cars. I’m talking racing set ups

I’m talking racing engines. A hollow camshaft with a quill drive through the timing gear grabbing the cam down its length would help.

[Jeff Lee]

I was at the speed shop yesterday. Milodon 3-gear drive: $560
ProForm 4-gear BBC $135. And what does one expect for 1/4 of the cost?

[Rick!]

27 year old paper, but puts some data to all this and much better than anecdotal information:

Camshaft Timing Drive Analysis for a Winston Cup Race Engine

One of the major objectives in automotive engine design is to efficiently and reliably transfer power throughout the engine. This study's objective is to evaluate the reliable means of transferring radial position, as efficiently as possible, between the cam and the crankshaft on a NASCAR Winston Cup race engine.
There are three accepted methods by which the radial position can be transferred between the cam and the crankshaft. These methods are timing chains, belts, and gears. This study encompassed all three of these methods. As the study progressed, the main focus shifted to three styles of timing chains: a conventional roller chain, a silent chain, and a newly developed inverted tooth power transmission chain. The cam drives were evaluated through both analytical and experimental data using the following criteria: harmonic frequency amplitudes, tensile and fatigue strength, chain efficiency, motored torque, dynamometer durability, and race performance.

https://www.sae.org/publications/techni ... nt/962513/

I'm not $35 smarter after reading that paper. My experience with Hy-Vo chains are that they are stronger but heat up lubrication fluid significantly more than silent chains. This was in a snowmobile chaincase where the ratios were close to 2 (or 1/2 depending on how you look at it). We had to use synthetic gear lube (Mobil 1) in production to lower chaincase temps as regular gear oil would break down and give that wonderful burnt smell. So, the efficiency data produced by Roush and Borg Warner is suspect until the test setups are properly described - how was the lubrication performed would be one question. How is it that a chain that is 22% heavier than the double roller is "measurably" more efficient than a lighter chain? The minimal information and results about harmonics leave a lot to be desired in the report also. One poor resolution waterfall plot doesn't tell me much. Were the orders all of crankshaft speed, or drive tooth orders or what? Blowing up the graph and assuming linear scales on the ordinate and abscissa, it looks like 8th order camshaft speed creates the largest amplitude accelerations. This would indicate that either the intake or exhaust valve inputs into the cam cause the torsional mode at 8700rpm (crank). My spidey sense tells me that it the intake valves may be more suspect since they have the highest mass/inertial resistance to acceleration. (Have a cup of coffee and mull that over a bit - the magical "harmonics" could fundamentally just be excited by the bumps on the cam and how much oomph is needed to open heavy valves on increased spring rate springs?) So, did Roush fix the root problem or just install a stronger chain to band aid the symptom?

Mr. Lee may not like the efficiency results of the gear drive but that deserves a BS flag thrown also. 20hp extra to turn a dual idler system at 7000rpm? Why would F1 engines even think of using such power robbing mechanisms? (sarcasm)
Gear to gear efficiencies are in the neighborhood of 97%-98%.
Chain drives are around 93%-95%, maybe a tad higher, some say up to 98%. Cross-Morse touts "up to 99.7% transmission efficiency". That would be ratio and power input dependent - the smallest sprocket in a chain system (and belt system) is where the friction and heat are generated due to fewer teeth in contact with the chain/belt.
Somebody measuring a 20hp difference in motoring torque for the gear drive at 7000rpm should be questioned as to how that might be possible. Using the graph and a rusty calculator, I get about a 10hp difference over the belt and chain drives using their data. A poorly designed gear train would be the first item to analyze. One would assume this testing was performed on an engine on an AC motoring dyno (Henkel, AVL, etc) so the measuring equipment should be reliable.

The Milodon 3 gear system is proper with the crank and "idler" gear being the same diameter. Here's an article with input from the company owner. It's even got a picture of an AMC engine with the system!

Sorry for the rambling, I'm open to other interpretations of the SAE paper.

[Jeff Lee]

Yes, great article. Al are all of these “tech” articles, basically a sales pitch. But if you read it and put some common sense into your interpretations, then you should be able to discern the issues and benefits of a gear drive and 3-gear quality unit over a 4-gear that has obvious mechanical design flaws.
https://www.enginelabs.com/engine-tech/ ... e-systems/