Dual Power Heads, Spur sprockets required?

[Eduardo K]

I'm looking to run two 660 clones on one bar and in the process of working out what I'd need. I was on the Granberg site checking out their FAQ and saw the bit in bold below.
Are spur sprockets really required? I'd love to hear opinions, experience, etc. I'm interested in keeping things simple, but not at the cost of safety or added frustration.
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From the Granberg FAQ - https://www.granberg.com/frequently-asked-questions/

-I want to use dual power heads, what do I need to know?
There are two things you need to know. First, the power heads need to be equivalent in size to within 10cc (Two 90 cc saws are good, a 90cc and an 80cc is OK, a 90cc and a 70cc together will not work). Second, you must use spur sprockets rather than rim sprockets. Rim sprockets in a dual power head set up may throw the chain off. Aftermarket spur sprockets are available through your chain saw dealer.
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Thanks!

 

[Wonkydonkey]

I'm by no way experienced using two power heads,, I had heard before you needed similar power heads, which after some time seem to be disproved, for what ever reasons
As one power head (the main)is pulling the chain to do the cutting, then the other powerhead is pulling (taking up the slack so to speak) or that extra pulling power behind.

So my thought is bigger power head does the main work and the 2nd is really just the helper to give a bit more grunt
As for throwing chains. That comes like when back bar cutting and the chain drops out of the rail because it’s hot and goes slack. Ie stumping off…& not so much just cross cutting.
And I’ve thrown chains back baring while stumping with a spur

I'd be interested to hear other’s thoughts & Experiences

Edited to add bits…

 

[Funky sawman]

I'm by no way experienced using two power heads,, I had heard before you needed similar power heads, which after some time seem to be disproved, for what ever reasons
As one power head (the main)is pulling the chain to do the cutting, then the other powerhead is pulling (taking up the slack so to speak) or that extra pulling power behind.

So my thought is bigger power head does the main work and the 2nd is really just the helper to give a bit more grunt
As for throwing chains. That comes like when back bar cutting and the chain drops out of the rail because it’s hot and goes slack. Ie stumping off…& not so much just cross cutting.
And I’ve thrown chains back baring while stumping with a spur

I'd be interested to hear other’s thoughts & Experiences

Edited to add bits…

Obviously you wouldn't want to have say an 066 running 13,000 paired with a 3120 that's limited to 10,500. I think matching rpm is more important than matching size and or model of the saws

 

[huskihl]

I watched and helped dual 661’s for several hours with rim sprockets. Saw no problems at all

 

[Nutball]

Rims float, so they can align themselves where needed.

 

[Eduardo K]

I watched and helped dual 661’s for several hours with rim sprockets. Saw no problems at all

Thanks for chiming in. I'm not sure what could possibly be their reason for specifying spur sprockets, but I don't know a lot of things. I'll plan on giving it a shot with the rim sprockets first and go from there...

 

[Pincher]

My guess would be the spur has a load bearing surface for the tie straps to ride on. The second powered is adding power by pulling on the slack side of the chain.

 

[Nutball]

Don't rims have more load bearing surface area for the tie straps?

 

[Pincher]

Don't rims have more load bearing surface area for the tie straps?

Your right! I got that bass asswords.