Cam chains w/o tensioners ?

[motorhogman]

Out of being bored I was surfing some youtube vids and came across this guy. At 6.22 min in he says he has friends that run Their TC88 cam chains without tensioners.. ?

First time i ever heard of this being done..  Wouldn't that mess up cam and valve timing ?  I'm not going to try it but just wondering what you guys think of this or ever seen it done ?

Here

[Pirsch Fire Wagon]

I've seen that before.

IMO without the Tensioners the chain loses it's leading edge on the Pitch Surface which increases the amount of chain on the prior to the Top Land and prevents wear. Eventually it would wear to the Bottom Land. Jumping several Teeth and Grenading the Motor???

I ain't smart.... but I ain't doing it.

[motorhogman]

I've seen that before.

IMO without the Tensioners the chain loses it's leading edge on the Pitch Surface which increases the amount of chain on the prior to the Top Land and prevents wear. Eventually it would wear to the Bottom Land. Jumping several Teeth and Grenading the Motor???

I ain't smart.... but I ain't doing it.

I'm with you.. On both counts.. The chain is so loose without the tensioner on it I'd be inclined to think Big Problems

[03rg]

Interesting. Kevin Baxter just did a video on the subject. I guess it's "trending"   
https://www.youtube.com/watch?v=dAco6a4-2nk

[CndUltra88]

That guy is relatively new to you tube.
I have watched a couple and would suggest the members here are better informed.
His latest vloggers is about the death wobble.
Just my .02 worth.
Thanks to all who share their knowledge here at HTT with little or no expectations of anything other than a thumbs up for sharing information.
Rob

[Hossamania]

If it worked without tensioners, you can be sure the Moco would do it. Why wouldn't they? Think of the money saved if no tensioners were needed.

[Scooterfish]

Looking back at the early twin cam days 20 years ago.

Harley announces a recall on all twin cams to solve the tensioner ware,

Bring your bike the the dealer to have tensioners removed 

[cheech]

If it worked without tensioners, you can be sure the Moco would do it. Why wouldn't they? Think of the money saved if no tensioners were needed.

You bet.
That original video also, he compares no tensioners to Older Chevy and Ford V8's.
Which isn't accurate because in those applications the chain is designed to have no slack (exact fit so to speak) for the cam to crank center distance in each.
And like Baxter said both shafts are supported close to the cam drive.
If there is slack, something's worn.
Whereas the Harley wasn't designed as such.

[motorhogman]

Interesting. Kevin Baxter just did a video on the subject. I guess it's "trending"   
https://www.youtube.com/watch?v=dAco6a4-2nk

Thanks for posting this.. Kevin did a good job explaining why this is a really bad idea. 

[thumper 823]

Porsche with their 911 / 930 series flat-six which is inherently balanced uses hyd tensioners.
Uses more valves,  and is a LOT more steady dynamics!
Always look to real engineering.
A Harley?
LOL

The  Harley, I can just imagine at low RPM how nasty that cam is going over center first
forwards and then bumping backward some of allowed.
YIKES!

[CarlosGGodfrog]

It would seem that a sharp engineer could come up with a spring or hydraulic loaded idler gear mounted to the cam plate.
Automotive engines used to have them in the aftermarket.

[Sycho01]

Surprised that a aftermarket company hasn't developed a new chain to used without the tensioners.

[motorhogman]

Surprised that a aftermarket company hasn't developed a new chain to used without the tensioners.

I thought that myself.. Then when i watched Kevin Baxter talk about the bearing support being a distance from the gear on a TC engine vs the bearing support being right there on the automotive design I understand why.... I think....lol

[thumper 823]

Its the over-center action from the valve springs
The cam drives the valves,, but the springs fight it .
Once the cam nose goes over there is a horrendous force from them on push back.
It would take a chain with so much tension to make this work  (for very long).

[Hossamania]

It would seem that a sharp engineer could come up with a spring or hydraulic loaded idler gear mounted to the cam plate.
Automotive engines used to have them in the aftermarket.

It would have to be pretty small with an even smaller bearing to disintegrate and cause big problems.

[motorhogman]

Its the over-center action from the valve springs
The cam drives the valves,, but the springs fight it .
Once the cam nose goes over there is a horrendous force from them on push back.
It would take a chain with so much tension to make this work  (for very long).

I guess that why the spring tensioner design is strong enough to take a finger off ya.. 

[thumper 823]

Plus there is no harm in having a tensioner unless it is done wrong as Harley has with the primary chain.
Porsche spins their stuff twice as fast as a V twin with a tensioner.
They had problems in the early years, but as soon as they went to the hydraulic tensioner, the problem was over.
  From an engineering point of view if the swing back of the chain can be less than 180 deg. it takes a lot less parasitic drag out of it.
In other words, it should go around the drive sprocket to the   (cam gear(s)  then to another sprocket at about 45 deg then back to the crank.
Even big caterpillars and army tanks do this on with their tracks.
It is not because they want extra track length.

[92flhtcu]

Thumper-made a lot of money back in my Porsche days upgrading to the Hydraulic Tensioner set up.....

[thumper 823]

yes, the standard ones broke.
I put the Hyd ones in my 911S too.
I wish I had not ever sold that car.
But now i see myself looking at the caymans...
A mid-engine is the way to go....
GT40 would be better, but out of my league !