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Old 10-15-2009, 08:01 PM   #31
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Quote:
Originally Posted by MadRussian View Post
Heres one for ya,
What about rotary!!
OS makes a Wankle Rotory Engine.
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Old 10-15-2009, 10:14 PM   #32
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Rotory would have worse fuel economy than what we have right now.But would be cool.
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Old 10-15-2009, 10:21 PM   #33
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setting the gearmesh with a rotary can be rough as well unless it is geared really tall, center shaft and all
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Old 10-15-2009, 10:27 PM   #34
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Old 10-15-2009, 10:40 PM   #35
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I ran my GT4 this whole season and love it. The powerband is very smooth on the 4 stroke. It is an O.S. FS-26. I get about 13-14 minutes of runtime per tank. The conversion kit is made by Thump R/C out of Spokane, Washington. The engine turns much less RPMs, so it's geared a lot taller than std. with a nitro TC3 second gear pinion. The clutch was a bit different, too with the less revs. It has surprisingly good top end! It can pull the big gear and still have great bottom end power. But of course, with the bigger engine, it does weigh a bit more than the standard 2 stroke .12 size engine, and I had to go thicker dampening just a touch. Also had to add 1/2 ounce of lead weight up front to control wheelies from the Thump power!!

I think Damon has started working on fitting an 8th scale with a four stroke.......
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Old 10-15-2009, 11:08 PM   #36
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Very very cool.Ive seen what you guys are doing in another thread.And have seen video as well.All I can say is wow.
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Old 10-15-2009, 11:13 PM   #37
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Ive seen you guys talking about this in the nitro engine forum.Im ready to try something new.I think 4stroke 1/8 scale would be sick.
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Old 10-15-2009, 11:33 PM   #38
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I love the sound the engine makes. It's louder than the .12 trucks, not by much. They smoke a lot more running 30% nitro heli fuel with at least 20% oil.

There are a handful of us GT"4" racers here in the Northwest who race these in our Regional Series, the Northwest Championship Tour. The engine is legal for our series, but of course would not comply with ROAR rules, so I couldn't run this at a ROAR sanctioned event. But the fun factor is definetly there!

So can they compete with the 2 strokes?
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Old 10-15-2009, 11:36 PM   #39
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TQ and 1st at NCT race #5 NCT Finals in Pasco, WA
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Old 10-15-2009, 11:39 PM   #40
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Man i would love to see you guys race.That setup looks factory.Too bad GT class has died down like it has.
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Old 10-15-2009, 11:47 PM   #41
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Still some GT racing here and there, but yes it's too bad it's losing turnout...

Have to wait and see if Damon can figure out something for an 8th scale buggy now.
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Old 10-16-2009, 01:43 AM   #42
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I posted these in another thread, but here's the 4-stroke truck that I made for RC Nitro Magazine about 8 to 10 years ago.
Attached Thumbnails
What About 4Stroke!-gt4st_1.jpg   What About 4Stroke!-gt4st_2.jpg   What About 4Stroke!-gt4st_3.jpg   What About 4Stroke!-gt4st_4.jpg  
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Old 10-16-2009, 01:45 AM   #43
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Ihad that issue sweet.
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Old 10-16-2009, 11:59 AM   #44
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Some or many of the issues with current 2-stroke engines have the potential to be designed out with the 4-stroke since it'd have to be a ground up engine design. #1, Pistons and sleeves don't "cost" $130, it's just what we pay for them currently because we've proven we would. There is no justification under the sun why a ABC sleeve of any level of prescision costs what it does for a car engine. Also notice that airplane engines are 1/2 to 1/3rd the cost of .21 Nitro engines partially because they don't have to be built to NHRA standards since they spin @ 1/2 the speed which brings me to...

#2. A 4-stroke of double the displacement would spin @ 1/2 the speed lowering wear on most of the critical parts immensely. Useable power would come across a broader range of RPM with taller final gears. More tractable=easier to drive.

#3 Cooling- who's to say this wouldn't be a fan/shrouded engine like that on a weed whacker or lawnmower? With forced air cooling the engine could be placed a number of different ways that didn't require a huge cooling head sticking out of the car.

#4 Engine configuration. There's no good reason that this would have to be a pushrod/rocker valve train (come to think of it, why are plane engines this way?). It could be tubular rotary valves or something along those lines.

#5 technology. Aren't the bigger plane guys using fuel injection? Imagine never having to look at your car after 30 minutes of trying to find a tune with the needles.

There's been a few blurbs about motocross 4-stroke progress here too, the very first competitive 4-stroke was Yamaha's, it was every bit as fast as the 250's from day one. Now 450cc motocross bikes have WAY more power than any 250 2-stroke offroad bike ever has. They are within 2-5 hp of the old 500cc 2-strokes, which were almost completely unridable by anyone of less than pro level. A current 250cc 4 stroke would eat a 2 stroke 250 on the track, not with peak hp, with drievability (though I imagine at this point they're pretty close in HP). 4-strokes were first driven into motocross by the manufacturer's marketing desires (Ricky Carmichael was the last to campaign a 2-stroke to a championship) but now a 2-stroke wouldn't be competitive. Jeremy McGrath also broke out a lone 2-stroke at the beginning of his "comeback" to supercross. He abandoned it because he couldn't get good starts and struggled to clear the jumps that the 250cc 4-strokes were able to do. The conversion from 2-strokes to 4-strokes in Moto GP roadracing was even more remarkable.

All that stuff about re-build costs of 2 and 4 stroke moto bikes is unfortunately true. Moto friends of mine refer to modern 4-stroke moto engines at 1-cylinder Formula 1 engines. It's not really applicable to R/C since the 2-stroke moto's are ringed pistons (refer to #1 in previous post section).
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Old 10-16-2009, 01:14 PM   #45
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Hey beefhead. I have a buddy here in town with an old GS Storm he wants to sell cheap. I've been thinking about getting it and putting an O.S. 48 I've got in it. It's an old engine I've used in my planes for a long time but it just keeps going. I really don't think a good 4-stroke will wear out any sooner than a good 2-stroke. As far as price goes, O.S. has their FL70 priced under $200 now and it's a good engine. If they can do that they can make a smaller one for the same money or less. I think making a plane engine work for cars will be mostly a matter of linkages. I still have clutch parts I used with my O.S. 21 from the early 90's that had a threaded crank so I don't think that should be an issue. It's something I've wanted to try for a long time anyway and now that I'm starting the new hobby shop here in Wichita I'll probably work on it between customers and get input of theirs on the project.
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