newb question

Old 07-31-2014, 02:27 AM
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sorry, I hate to do this, but im having a hard time finding reason behind the question im about to ask.

Why, as off road racers/bashers, do we not use ringed nitro engines like planes and choppers have? I believe the gasser engines in the 5B-5T are ringed 2 stroke gas engines right? I mean a set of rings is a hell of a lot less expensive than a sleeve every 5-6 gallons no?

Is there something im missing?
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Old 07-31-2014, 02:55 AM
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The high rpm and with that the high forces.
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Old 07-31-2014, 07:52 AM
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The ringed motors rev pretty high. The spec sheets of most ive seen rev up into the mid 20k area. Cant we offset the slightly lower revs with gears? Would the added force of jumps and crashes also lower life expectancy of a ringed motor?
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Old 07-31-2014, 09:07 AM
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Originally Posted by bksrt View Post
The ringed motors rev pretty high. The spec sheets of most ive seen rev up into the mid 20k area. Cant we offset the slightly lower revs with gears? Would the added force of jumps and crashes also lower life expectancy of a ringed motor?
That's not slightly lower that's half. If you couple that with taller gearing for more top end the car has no bottom end snap. If you lower the gearing for bottom there is no top speed. Besides, manufacturers don't really care about saving you money.
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Old 07-31-2014, 10:34 AM
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High rpm is needed to produce hp.
Rings can't handle the high rpm so going with a ringed engine means less hp.

If less hp is OK then sure a ringed engine will work fine.
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Old 07-31-2014, 10:35 AM
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Our engines almost produce 1 hp/cc, that is huge. Compared with largere engines ours just need a ring not larger than 1mm of diameter, it can not withstand the 100kg G-force a piston can create at high revs.
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Old 07-31-2014, 12:10 PM
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The lapped fit piston, with anywhere from 1-3 oil grooves seals better than a single 1mm ring with an end gap ever would. Full size 2 strokes lose performance as a result of ring wear. The first maintenance item on a sled engine is rings around 3000miles because leak down will have already started to effect perfoance. I would rather just run my piston/sleeve to 8-14 gallons then rebuld it, rather than having to tear it down to change a ring.
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Old 07-31-2014, 04:31 PM
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bkrst. Take a look at Losi and Hot Bodies they have the same idea as you. The HB uses a 3 speed Trans. Losi LST XXL 2 1/8 gasoline. This engine will end up in a race buggy soon as Losi releases the engine by itself.
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Old 07-31-2014, 06:11 PM
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Hmm interesting. I still like the idea of gas better. $3-4 a gallon as opposed to $30-40. Id like to see a gas motor buggy, although id rather not see it attatched to a 3 speed trans. My Cen Genesis had a 3 speed and it was a nightmare to set-up. If someone could build one a little more reliable and easier to set-up it might not be so bad.

I wonder if adding an RB s/c would help a 2 stroke gas motor get the power to keep up with a nitro?
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Old 08-01-2014, 01:53 AM
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Originally Posted by Tug Driver View Post
The lapped fit piston, with anywhere from 1-3 oil grooves seals better than a single 1mm ring with an end gap ever would.
I had some talk with a real racecar engineer and he was even jalous that we drive with a ringless piston. The ring is creating resistance taking away some performance. A perfect fitting piston without rings only slides over the oil film.
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