Predator Hotsaw?

[bwalker]

Rotax, What does the pred ru for a motor? Has any one adapted a 300hp outboard into a hot saw?

 

[eyolf]

I think Rotax Robert's 215 Buick Aluminum v8 is a good choice; they're light, and have fairly good output when tweaked.

A friend had one in a drag car; actually several of them. Buick 340 cranks will fit if you grind the mains to fit the smaller bearings of the 215 block. Use the 340 rods, and Venolia would make pistons with an extremely short deck height. Sleeve the block out, but leave at least .187 water jacket. Put those old 61-63 Buick specials into low 12's and stay street legal. Tubbed, gutted, big tires and big gears, even faster.

Not very long-lived, though. Little Aluminum block was just too flimsy for that HP level in a drag car. I doubt that RR can apply as much load with the chain saw bar so he'll have lots less trouble holding it together!

6 cylinder inline Merc or V6 OMC engines would be just as heavy, and not have the bark of a detroit V8. I think that's the big draw with a V* hotsaw...the crowd appeal.

Maybe an old Merc inline 6 with 6 tuners?

 

[dbabcock]

Ben,
I talked to KD, Robert and others about this exact thing. The powerhead to one of the Mercury 2.5 Liter V6 EFI outboards makes over 300 crank HP at around 9000 RPM (the so called "Drag" motor). The whole motor with a 15" short shaft and sportmaster gearcase, weighs in at a hair over 350 lbs. I rebuit the powerhead on my '92 2.5 EFI OS some years ago and would estimate that the weight of this to be in the 150 lb. range. Put all the other crap on it and the final saw weight might be less than 300 lbs. (about 200 less that the '63 aluminum blocked, 215 CID Predator saw). Since the cut would be made at full RPM, you wouldn't have to worry about the broader torque curve of the bigger 4 stroke.

Talk about intake flow; the 2.5 uses 7 petal two stage Boyesons on a V block. That's 14 petals per cylinder. When you look into the air intake horn, all you see is reeds.

 

[dbabcock]

I agree about the bark of good old American iron, but an unmuffled 153 CID 2 stroke with radical exhaust porting at 9 grand is a real eye opener (and ear coverer). Better yet, work has been done in fitting 6 expansion chambers to these engines. The sound and power increases are tremendous. Remember that these engines are designed for continuous loading, not a <1 second cut. 400 HP or more is not out of the question for a cutting application. Factory new power head is in the range of $8500.

One final note to close my verbosity: From what I gather, the problem isn't how much power you have, it's how well you can get the power to the wood. In the case of saws like the Predator, the ultimate limitation may be how much pressure you can actually put on a well rakered 3/4" harvester chain. In this case, a heavier saw may in fact "hook-up" better.

 

[bwalker]

A v-8 sounds like crap compared to the ear piercing roar of a v-6 two stroke with open stinger expansion chambers.

How about he ultimate hot saw. Mount the outboard motor on some sort of tracked vehicle that would allow it to pull up to the log. Then add a hydraulic carriage that would force the bar into the cut. Down force could be tuned for optimum cutting speed.

 

[dbabcock]

Yeah, taken to it's ultimate condition, imagine that the guys who run the saws just sit on a log and run the unit from their laptops. They could even wear business suits with chaps and bomber caps. A real crowd pleaser for the nerd audience.

 

[z4lunch]

V6 merc

Doug
Steve here... WOW is that cool!!! I won't beable to sleep for a week. HOW Fast?
Steve

 

[dbabcock]

Here's the writeup:
http://www.screamandfly.com/screamandfly/lentzkow_pipe_project.htm

 

[v6bill]

Predator Hotsaw

Rotax get in here i cant keep my big mouth shut v6Bill

 

[Rotax Robert]

OK V6bill, you asked for it "MY SAW IS FASTER THAN YOURS" maybe you better talk to Doug about getting that piped 6cyl. although it would be a bit light for you. Cool pic though.

Some clown recently told me of the changes he would make to the Predator stating that he could probably knock a second or so off of our times, but when your already under 1 second how does that work? Oh well...I sure am ready for the season to begin though.

 

[dbabcock]

Aw come on, Bill! You're among friends here. You can say anything that you want.

 

[dbabcock]

Not so fast, Robert. The guy might actually be a rocket scientist. We've been over this before: If the Predator cuts through the log in less than zero seconds, then we will all go back in time. Sheesh, can't you remember anything I've taught you?

 

[Rotax Robert]

Yeah I remember now, but I don't think I can pick the darn thing up when I am 8 years old again and if I go to far back then the engine was'nt even made yet and I would have to try and lift a flathead 8 or something.

 

[dbabcock]

Yeah, but if Rasputin Greffard was cutting with you, he could go back in time to where he was 16 years old again and that would make everything socially acceptable.

 

[glens]

Whatever you do, make <i>sure</i> you're using a chain newer than the bar!&nbsp; It would be terrible to have to contend with a chain spinning at those speeds with nothing to contain it.

 

[dbabcock]

Good point, Glen. Consider that since Robert's clothes are newer than he is, that they would disappear early on. Then he'd be Gypo Logger.

 

[Rotax Robert]

Ok I've just about had-it....Darnit I am even starting to sound like Gypo.

Franks Planks

 

[dbabcock]

Rotax is Dennis. I am Gypo and Gypo is Che. Fish is evil.

 

[bwalker]

Doug,I though Gypo was Dennis and you where stinky grommet?

 

[dbabcock]

Oh yeah, I forgot. Thanks for reminding me, Beavergirl!