RunRyder - 4 stroke 91

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Audacity Models Pantera 50 - Tiger 50 > 4 stroke 91

Machinehead01
Senior Heliman
Location: USA

What would it take to run a 4 stroke 91 in a Pantera? There are lots of those available and I'm curious what mods would have to be done?

Thomas

I didn't say it was your fault, I said I was going to blame you!

08-23-2008 05:22 AM

MaxAdventure
Senior Heliman
Location: Boulder, Colorado

there are three things against you from the start:
heat, RPM, Power/weight

have you found an engine that can handle those? I've been wanting a 4 stroke since the beginning, read everything I could. Not much success due to those three.

If you have an engine that can handle that, then you'd have to see where the head ends up. If the case matches a reg .91 lower width and can use a .90 BBC mount, you just have height to contend with, assuming your crank isn't too long or can be cut. I've carved up the cooling shroud for electric conversions, and I imagine you could easily clearance for a four stroke, but would you get air flow across the top as well? The number one problem I've read is the heat, even running high nitro.

If you do it, I'd love to read a build thread!!!

-da (Max)
AMA 198798
issues? I have subscriptions...

08-23-2008 05:34 AM

JKMRS
Heliman
Location: Czech Republic

OS has a 52 size 4 stroke heli engine

http://www.osengines.com/engines/osmg1952.html

The engine looks pretty much like a std plank one. No oversized cooling fins, or anything that would hint that heat will be an issue.

There's not much details on the site, any idea what makes this a "heli" engine, i.e. what mod a std 91 size should go through to be fitted in a heli?

J.

08-23-2008 09:22 AM

Mr.HillBilly
Senior Heliman
Location: Salesville, OH - USA

I thought that the 4 strokes could take the extra heat. I know they do not like to be over revved they do a instant stop from full speed.

I figure the biggest prob. is you would need to find a 12 tooth pinion and a matching main gear to get the head speed up fast enough to be usable. At 11K it would only be cranking out head speed of 1400 with the current BBC.

It would sound cool tho.

08-23-2008 01:27 PM

jbeech
Ex rrAdvertiser
Location: Sanford, FL (Orlando area)

Major issue is gearing. The 4S engine runs really well at 9500-10,000 RPM and as a consequence, you simply work backwards fomr desired head speed to select a gear ratio, which puts the engine in the sweet spot. it's my opinion all the 4S models have used too high a gear ratio with the idea of running the 4S engine in the 11-12k RPM region. Hence, simple math revels 10,000 RPM / 2000 RPM means a 5:1 gear ratio is about what it takes. As for the cooling, I suspect our stock Pantera cooling fan is indeed up to the task. Go for it!

My 2¢

John Beech - GM (and janitor)
Audacity Models

08-23-2008 04:20 PM

MaxAdventure
Senior Heliman
Location: Boulder, Colorado

I mentioned heat as number one, because it was the most common issue I read about when I was thinking about it. I did some more searching today, found a few interesting links but not quite as concise as I'd hoped to share, so you don't have to trust my poor memory. I did find this link that summarizes a lot of other experiances I've read about:
http://www.daverc.co.uk/heli.htm

What John said, the Pantera cooling fan is superior, may relieve that cooling issue. (and no, I have no idea why it's an issues in helis, I'd agree my plane 4 strokes totally run cooler than my 2 strokes) going .91 should cover the power issue.

All you would have to overcome is shoe-horn it in with the right gearing! I think we're all eager to see you succeed!

-da (Max)
AMA 198798
issues? I have subscriptions...

08-24-2008 06:53 AM

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Audacity Models Pantera 50 - Tiger 50 > 4 stroke 91

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