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Cam drive noise reduction
- Thread starter ivymike
- Start date
I have some experience with this. My original idea that actually led to some (but very little) success was to machine a flywheel that had a diameter in the center that would run the cam and an outer diameter that grabbed the starter. (It made the flywheel look similar to a v-belt pulley except the 'v-groove' had teeth to grip a timing belt.)
Anyhow I recall the biggest problem being that since I was using a 350 Chevy as a test motor the camshaft end had to be far from the block to align with the flywheel so there was a lot of torsional stress and a lot of flex through the camshaft. Granted I was using modified parts and not parts made specifically for the purpose so that aided in the dilemma. I truly think it is a reasonable concept, which is why I started. Given a few months I believe someone could have something designed that would run very well.
If I continued to use a 350 SBC I would obviously make custom cranks and camshafts but also add a neck to the block to move the cam bearing closer to the drive gear on the cam. This goes along with obvious modifications like belhousing clearances and so forth.
But in the end I toyed with the nodal drive concept a while back but ended up doing some rotary valve design instead so I never did make too much progress. Let me know if you get anything out of it because it has always interested me.
-Justin
Anyhow I recall the biggest problem being that since I was using a 350 Chevy as a test motor the camshaft end had to be far from the block to align with the flywheel so there was a lot of torsional stress and a lot of flex through the camshaft. Granted I was using modified parts and not parts made specifically for the purpose so that aided in the dilemma. I truly think it is a reasonable concept, which is why I started. Given a few months I believe someone could have something designed that would run very well.
If I continued to use a 350 SBC I would obviously make custom cranks and camshafts but also add a neck to the block to move the cam bearing closer to the drive gear on the cam. This goes along with obvious modifications like belhousing clearances and so forth.
But in the end I toyed with the nodal drive concept a while back but ended up doing some rotary valve design instead so I never did make too much progress. Let me know if you get anything out of it because it has always interested me.
-Justin
GregLocock
Automotive
Justin, sounds sensible, but do you really need it with a toothed belt, on an SI engine? I would have thought that Ivymike's application, gear drive on a CI, would have a much harsher vibration problem than yours. What problem in particualr were you trying to cure?
Isaac, I read a paper on this, in about 1990. The chances are it was a research engine at Ricardo, ISVR, AVL or (unlikely) Perkins. It will probably be in the IMechE Proceedings.
Cheers
Greg Locock
Isaac, I read a paper on this, in about 1990. The chances are it was a research engine at Ricardo, ISVR, AVL or (unlikely) Perkins. It will probably be in the IMechE Proceedings.
Cheers
Greg Locock
I do not doubt that a gear drive on a CI engine would have some harsh modes but I did not see that Ivymike mentioned anything about CI engines.
The whole project started with a guy and his idea and we ran with it. The purpose of my involvementwas to replace the front cam drive on an engine to see if dual small superchargers can be mounted in its place. I know it sounds a little out there and it sounded a little wild to me too but it actually became quite fascinating. There were many ideas that floated across the design table but they all concluded with two small superchargers a little larger than a coffee can. They could be mounted low and off to one side on an engine and not interfere with modern ammendities like a/c compressors, dual alternators but still drive off the crank. There was also the cold air induction thing and a bunch of other little things that provoked the idea.
I got dragged in when they realized the cam drive was in the way of where they wanted to mount their superchargers. The only thing that actually worked well was the cam drive (pat myself on the back) and I am sure the induction would have been good also had they been given a little more time to tune and test.
-Justin
The whole project started with a guy and his idea and we ran with it. The purpose of my involvementwas to replace the front cam drive on an engine to see if dual small superchargers can be mounted in its place. I know it sounds a little out there and it sounded a little wild to me too but it actually became quite fascinating. There were many ideas that floated across the design table but they all concluded with two small superchargers a little larger than a coffee can. They could be mounted low and off to one side on an engine and not interfere with modern ammendities like a/c compressors, dual alternators but still drive off the crank. There was also the cold air induction thing and a bunch of other little things that provoked the idea.
I got dragged in when they realized the cam drive was in the way of where they wanted to mount their superchargers. The only thing that actually worked well was the cam drive (pat myself on the back) and I am sure the induction would have been good also had they been given a little more time to tune and test.
-Justin
- Thread starter
- #6
I designed a nodal gear drive a few years ago for a large truck engine with OHC. Here are some basic pointers, sorry if this is obvious stuff!
Use helical gears instead of spur
The backlash (movement between teeth) of gears is critical, centre distances must be controlled closely, so use an idler on an adjustable centre where the gear spans the head/block joint on an OHC engine. The idler can be positioned manually or VW have a design on the Toureg V10 engine where the idler sits on a scissor bracket to always ensure correct centre distances
Make sure the gear stub axles are securely bolted to the engine
If you want some examples I suggest you look at some European truck engines of around 12 litres
I don't know of any websites or text books, I'm not sure it is the sort of thing that is published in that way!
Best of luck
Perky
Use helical gears instead of spur
The backlash (movement between teeth) of gears is critical, centre distances must be controlled closely, so use an idler on an adjustable centre where the gear spans the head/block joint on an OHC engine. The idler can be positioned manually or VW have a design on the Toureg V10 engine where the idler sits on a scissor bracket to always ensure correct centre distances
Make sure the gear stub axles are securely bolted to the engine
If you want some examples I suggest you look at some European truck engines of around 12 litres
I don't know of any websites or text books, I'm not sure it is the sort of thing that is published in that way!
Best of luck
Perky
I don’t know what a nodal gear drive is, but the Citroen 2CV had a very simple zero-backlash cam gear drive. One gear was a normal helical gear, while the other was composed of two half-width helical gears on a splined shaft. A spring between the two (a belleville washer would be better) pressed them apart and the helical angle assured that one was firmly in contact with teeth on each flank of the single gear. I don’t know whether the split gear was the driving or the driven gear, and can see advantages to either arrangement. I’m sure that the purpose was longevity, rather than quietness, but the idea is applicable to either objective. If it doesn’t solve your noise problem in itself, maybe it can be applied usefully to another solution, as Perky indicates that backlash is critical for a nodal gear drive.
patprimmer
New member
As I am not a gear designer, I don't know what a nodal gear drive is, but if there is an idler gear that could be easily replaced at say every 50,000 miles, it mightr be feasible to make it from a plastic like Nylon 4.6 or carbon fibre reinforced nylon.
If it will withstand the load, it would certainly reduce noise. Nylon 4.6 is relativly unknown, having only been produced comercially in about the last 15 years, but bit retains good mechanical properties up to nearly 300 deg C. Yes that is 300 Deg C
In automotive timeing chain tensioners, it typically triples the life when substituted for the traditional material which is graphite and molybdenum disulphide filled nylon 6.6
Regards
pat
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If it will withstand the load, it would certainly reduce noise. Nylon 4.6 is relativly unknown, having only been produced comercially in about the last 15 years, but bit retains good mechanical properties up to nearly 300 deg C. Yes that is 300 Deg C
In automotive timeing chain tensioners, it typically triples the life when substituted for the traditional material which is graphite and molybdenum disulphide filled nylon 6.6
Regards
pat
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
- Thread starter
- #10
For your reference, Cummins make large displacement Diesels, their "ISX" family of engines, that have split cam gears available, "scissors" gears as they describe them. They work somewhat like the split gears described earlier on the Citroen 2CV, but with damper springs like a clutch driven disc.
They are very successful in reducing gear noise at certain specific engine speeds corresponding to what I believe are camshaft torsional modes. That is, the cam gear noise is not present at all engine speeds without the anti-backlash gears.
Only the "ISX-3" engines now have these split gears; Cummins seem to have lost their way, NVH-wise, since the abrupt departure of Tom Reinhart.
Regards,
R
They are very successful in reducing gear noise at certain specific engine speeds corresponding to what I believe are camshaft torsional modes. That is, the cam gear noise is not present at all engine speeds without the anti-backlash gears.
Only the "ISX-3" engines now have these split gears; Cummins seem to have lost their way, NVH-wise, since the abrupt departure of Tom Reinhart.
Regards,
R
poepatterson
Materials
AUTOMOTIVE AND TRUCKS, EARTH MOVING EQUIPMENT USE A VISCO MATERIAL SANDWICHED BETWEEN STEEL LAYERS THAT ARE THEN DIE FORMED INTO VALVE COVERS, OIL PANS, ETC. SOLE PURPOSE IS NOISE REDUCTION.
JOHN PATTERSON
JOHN PATTERSON
Guys,
Has anyone ever tried making the idler gear or the intermediate gear with softer material compared to the drive and final driven gears?
Toyota has a balancer shafts system that uses some sort of plastic for the intermediate helical gear. To use plastic for cam drive is questionable but softer metal specifation with certain surface treatment is worth considerations.
Also check for gear with spring and damper integrated to the gear itself. Honda uses a lot of gear drives to drive the cam in their motorcycles. They finally decided to use chain though, nevertheless, the technologies involve in their gear system are very respectable.
Has anyone ever tried making the idler gear or the intermediate gear with softer material compared to the drive and final driven gears?
Toyota has a balancer shafts system that uses some sort of plastic for the intermediate helical gear. To use plastic for cam drive is questionable but softer metal specifation with certain surface treatment is worth considerations.
Also check for gear with spring and damper integrated to the gear itself. Honda uses a lot of gear drives to drive the cam in their motorcycles. They finally decided to use chain though, nevertheless, the technologies involve in their gear system are very respectable.
patprimmer
New member
Nylon 4.6 is a relatively new type of nylon can withstand considerably more temperature than the traditional types.
I have seen it used successfully on timing chain tensioners, typically tripling the life over a nylon 6.6 component. I have also seen it used as a valve spring retainer. Although I would not seriously recommend it for that, it should be worth considering as an idler gear, especially if the metal gears were cut to a profile that suited the plastic part.
If reinforced with carbon fibre, it would be stronger still, if somewhat expensive, but it would be quiet, and could be moulded as a finished or at least semi finished component, which would reduce machining costs to partly offset the material cost.
Reinforced nylon 4.6 retains excellent mechanical properties to 295 deg centigrade. Carbon fibre has much better bearing properties than glass fibre.
Regards
pat pprimmer@acay.com.au
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I have seen it used successfully on timing chain tensioners, typically tripling the life over a nylon 6.6 component. I have also seen it used as a valve spring retainer. Although I would not seriously recommend it for that, it should be worth considering as an idler gear, especially if the metal gears were cut to a profile that suited the plastic part.
If reinforced with carbon fibre, it would be stronger still, if somewhat expensive, but it would be quiet, and could be moulded as a finished or at least semi finished component, which would reduce machining costs to partly offset the material cost.
Reinforced nylon 4.6 retains excellent mechanical properties to 295 deg centigrade. Carbon fibre has much better bearing properties than glass fibre.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
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Pat
We also use that nylon for the cam timing and oil pump chain tensioners. It is surprisingly durable and tough.
As for the Toyota's balancer shafts intermediate gear, the color is brownish. There was a publication in Japanese, few years ago indicating that it is made of some sort of composite material. I was also surprised that Toyota uses it for the balancer shaft gear. Quite high load at high rpm I guess.
Anyhow, if someone manages to apply it as the idler gear for the cam drive, it is possible that we will see Honda obtain license of the technology for its motorcycle. Potentially good business...
We also use that nylon for the cam timing and oil pump chain tensioners. It is surprisingly durable and tough.
As for the Toyota's balancer shafts intermediate gear, the color is brownish. There was a publication in Japanese, few years ago indicating that it is made of some sort of composite material. I was also surprised that Toyota uses it for the balancer shaft gear. Quite high load at high rpm I guess.
Anyhow, if someone manages to apply it as the idler gear for the cam drive, it is possible that we will see Honda obtain license of the technology for its motorcycle. Potentially good business...
spdingtkts
Mechanical
Competition Cams sells a distributor gear made of "Carbon Ultra-Poly Composite".
Honda uses both gear drives and chains on their bikes. They use a spring loaded scissors gear to eliminate backlash.
Several other motorcycle manufacturers have fitted gear drives in place of the original chains on their racebikes in the past. These do not utilize a scissors gear and the noise can be pretty shocking. The first time I heard a Kawasaki Superbike engine with a gear drive installed I thought someone dumped a bucket of bolts in the engine.
Honda uses both gear drives and chains on their bikes. They use a spring loaded scissors gear to eliminate backlash.
Several other motorcycle manufacturers have fitted gear drives in place of the original chains on their racebikes in the past. These do not utilize a scissors gear and the noise can be pretty shocking. The first time I heard a Kawasaki Superbike engine with a gear drive installed I thought someone dumped a bucket of bolts in the engine.
patprimmer
New member
"Carbon Ultra-Poly Composite". Now that is a truly meaningless "marketing" term.
It could mean anything from used candle wax, or sap from a tree after a forest fire, to graphite fibre filled polly ether ether ketone, or graphite fibre filled polyimide or anything in between.
Regards
pat pprimmer@acay.com.au
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It could mean anything from used candle wax, or sap from a tree after a forest fire, to graphite fibre filled polly ether ether ketone, or graphite fibre filled polyimide or anything in between.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
Later model Ford 300cid (4.9l) I6's used a 'composite' timing gear, but I don't know what the exact material is. It is siginificantly quieter than the helical cut metal gears they initially used and seems to wear well. I don't know when the changeover date was (there is probably a range of transition years anyway) but if I were to guess it would be the late 70's. I also don't know if the industrial version of the same engine used the composite gears or metal till it was phased out.
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