Dump the gear and go timing chain?

[Mike E]

I started questioning what I put up afterwards. I was ignoring too much about what forces the torque creates in the gear tooth. I dug out an old text book and this is how it says to analyze forces in gears.

The gears have these forces F and the Reactions R. The angle F is at depends on the pressure angle of the gears.

That makes our gear drive look like this.

Breaking out the idler gear.

It looks like the two reactions R would add together to a vector pointing to the right and up. But that amount depends a lot on the pressure angle. If you had enough pressure angle, the two forces and reactions could completely cancel each other out.

 

[Mike E]

I don't quite agree with the direction of some of your forces.

Well, the directions I had originally were right, but the magnitude was so much smaller than the force driving the tooth that the whole theory was meaningless.

I think the 2 forces cancel each other in the gear drive so the net force is zero becausse the direction of rotation is reversed , or am I a failing student ?

Yes, your mostly right. But there is a small component of the force trying to suck the idler in between the cam and crank gears.

 

[Alky V6]

This is how I picture it.
The yellow lines are the vector forces.
Mike, I agree. After all considered, I think there is a small force trying to suck the idler into the gears. But, is that force large enough to worry about, as far as the idler bearing and shaft are concerned?

 

[Mike E]

This is how I picture it.
The yellow lines are the vector forces.
Mike, I agree. After all considered, I think there is a small force trying to suck the idler into the gears. But, is that force large enough to worry about, as far as the idler bearing and shaft are concerned?

It depends a lot on the pressure angle of the gears and the layout of the gears.
I could do the math pretty easily if I had the right dimensions, pressure angle of the gears and torque required to rotate the cam. My geardrive is at the machine shop, so I can't measure it.

 

[Alky V6]

It depends a lot on the pressure angle of the gears and the layout of the gears.
I could do the math pretty easily if I had the right dimensions, pressure angle of the gears and torque required to rotate the cam. My geardrive is at the machine shop, so I can't measure it.

That may change in a dynamic situation, with changing cylinder pressures, but it would be interesting to see what you come up with.

 

[J-B Racing]

I am thinking of going Gear Drive. My Springs are #320 closed @ 2.00`` and just at 1.750`` it is at #500 and this engine ran with a Chain. Has anyone used the Milodon #13800 Drive, and does it fit under the stock Cover?

 

[Mike E]

Like I said in my email, you could put the motor together and run it with the chain at first. Inspect it regularly and if it seems to be stretching the chain quicker than normal, you can swap it over to a gear drive.

I'm pretty sure that milodon part number is discontinued, but I could be wrong.
A gear drive can fit under the stock cover with some work. Here is one I did not long ago.

 

[Nick Micale]

Guys, here is some good information from my buddy who has a pretty fast stage II, stage II headed car. Middle of last season he broke the timing chain and he went and replaced it with a new known good brand timing chain. He has the motor at the machine shop to look things over/freshen it up. Well, the machinist found that the timing chain is loose already with only seven passes. This was a brand new timing chain!
I guess I am sticking with Gear Drive for sure!
Prasad

After breaking a few chains over the years, I installed a new chain that is used on current Rollmaster sets.

When this chain reached 40 9 sec. passes, I removed it even though it had the same tension and slack as when installed. The chain was send to Cloyes who agreed to test it for me. Their results showed the chain had only stretched 0.001".

Also when this chain was installed, I lowered my valve spring pressures considerably. This was a result of my discussions with Ken Dutweiller concerning this problem. His comment was too much valve spring pressure which is not needed.

On a Buick V-6 engine approaching 1900 HP built by him, the spring pressure is under 300#'s on the seat. His 2000+ HP SBC runs with 350#'s on the seat with 750#'s open pressure.

I plan to stick with my chain and figure out the cam profile and spring pressure to make it reliable.

 

[Alky V6]

I am thinking of going Gear Drive. My Springs are #320 closed @ 2.00`` and just at 1.750`` it is at #500 and this engine ran with a Chain. Has anyone used the Milodon #13800 Drive, and does it fit under the stock Cover?

I believe that is the part no. of my geardrive. That is the ball bearing idler with large shaft. The stock cover will need some mod. Instructions were included with the gearset on how to mod the cover. Confirm the part no. though. The installation instructions came with a different part no. on it, and when I called Milodon at one point in time to get a replacement idler bearing I was changing out during an engine O/H, they told me that my set was actually a 13800 due to the idler design. I'm only going by what they told me.

 

[Alky V6]

Mike could be right about that part number being discontinued. When I purchased my set long ago, they were telling me that my set was one of the few left. They were planning to discontinue production of that part. I would think that if enough people were to ask for the part, maybe they might bring the design out of moth balls and produce some more.

 

[Alky V6]

I plan to stick with my chain and figure out the cam profile and spring pressure to make it reliable.

Nick, I have to think that after all these years, someone, including yourself, would have figured out a reliable chain driven system for the more aggressive cams. Why has it taken so long?

 

[J-B Racing]

Thanks Mike for the pics. Thanks Don, Thanks Nick as well. Always good answers from you guys..
I will keep using the Chain and I will inspect regularly.

Joe

 

[norbs]

Thanks Mike for the pics. Thanks Don, Thanks Nick as well. Always good answers from you guys..
I will keep using the Chain and I will inspect regularly.

Joe

Joe if you ever break the chain, you could cause $1000's of dollars damage, why would you take the risk?

 

[Alky V6]

I have not been able to come to a conclusion as to what part number my gear drive is. 13800 or 13805.
The instructions that came with the gearset state it is 13805. The instructions do mention the large single bolt that mounts the idler gear.
One gearset uses a flat needle roller radial bearing with the idler gear, and the other, like my set, uses a ball bearing with the idler gear.
I'm going to assume the flat needle roller radial bearing idler gear is the 13800 gear drive set.

 

[Alky V6]

I've contacted Milodon to get clarification on the different Buick V6 gear drive part numbers and idler bearing styles. Ken at Milodon confirmed that they no longer make the gear drive for the Buick V6. Demand fell off too much.
He is going to check a picture I sent him against blueprints, and get back to me on the exact part number of the set I have.
Ken said that he recalled that one gear drive set was known as the Stage I set, and the other was a Stage II Competition gear drive set.

 

[Alky V6]

Thanks Mike for the pics. Thanks Don, Thanks Nick as well. Always good answers from you guys..
I will keep using the Chain and I will inspect regularly.

Joe

I'm with Norbs on this one. With the spring pressures you listed,... I don't know?

 

[Alky V6]

Next time I have the engine down, I'll be blueprinting the gear drive assembly, in case I need to make replacement parts for it.

 

[Alky V6]

Here's the scoop from Ken S. at Milodon.
The 13800 was Milodon's first generation gear drive that was made available for the Buick V6. It used a flat needle radial bearing to locate the idler gear. They refer to that bearing style as a conventional cheater style bearing. The 13800 gear drive did not fit Stage II blocks. It may have not fit Stage I blocks also, but I didn't get clarification on that. It was probably made for production blocks before the Stage blocks came about.
The 13805 gear drive set is a second generation set, considered the Stage II Competition gear drive for the Buick V6. It uses a high speed ball bearing to locate the idler gear, with a large idler shaft that fits through the middle of the ball bearing and screws directly to the mounting plate. It was designed to fit all Buick V6 blocks. Production and Stage blocks. Obviously, it also fits the TA block. The idler design was changed in this gear set due to durability concerns from customers that were using the 13800 style idler gear bearing.
The updated 13805 design level is the much more preferred design level to use, according to Ken.

Complete kits are no longer available through Milodon. Although, some individual parts still are.
The cam gear is the same as their SBC cam gear.
The idler gear and shaft are the same as their SBC idler gear.
The crank gear is specific to the 13800, 13805 gear kits. There isn't a crossover part number to another application.
Ken eluded that mounting plates may still be available. An easy part to reproduce.
The cam gear hub, I didn't ask if there was a cross application part, and I didn't ask Ken if they were still individually available. Although, the cam hub would be relatively simple to reproduce.

Contacts that Ken suggested for available kits that may still be out there are;
Kenny Duttweiler
Ohio George Montgomery in the Michigan area. George's Speed Shop.
They bought up a lot of kits and may still have some new ones available. Or, maybe individual parts.

 

[J-B Racing]

I'm with Norbs on this one. With the spring pressures you listed,... I don't know?

Because you have answered my question that they are no longer available. I am not going to sit around for a Gear Drive to show up at my door to close up the Motor!! The search will continue, but in the mean time the Chain will go back.

Joe

 

[norbs]

I'm sure Mean Mike might have a spare?