This may seam like a silly question but i dont know so...When buying a engine, and you want your plane to be as powerfull as possable do you go with the engine with more, RPM range or, BHP?
Thanks 3D profile lover!!! Brian
The numbers that manufaturers give are BUNK. I ask around the forums (here and RCU mainly) and find if anyone has the plane/engine combo I'm looking at. Then I ask for prop size, top rpm, trasition speed, and overall impressions.
There aren't many engines that simply none of the Bros have tried, so ask anytime...
Now that I look back, I didn't do a good job answering your question. Given only the two figures to work with, I'd say rpm, as long as they also give the prop used. For example, some will say, "Our 46 will turn 18,000 rpm." They do not say that this test was done at 10 degrees Farenheit, with 30% nitro, and a 8x8 El Cheapo prop. To me, that number is BUNK.
With real information like, "Our 46 turns a 10x6 prop at 16,000 rpm on 10% nitro..." I can work with that and make a guess that an 11x5 will also run near te 16,000 mark and a 12,25x3.75 or 12x4 will also run somehwere in the 14,000 to 15,000 rpm range with similar fuel and atmosphere.
Companies are trying to sell engines, so they try to make it look as good as possible. A 46 size engine can range in BHP easily from 1 to 2.25 horses. That number is derived in near perfect situations with undersize props to let the engine scream to achieve a high number. Small prop BHP is meaningless when you look at 3D planes or even good aerobatic planes. The number we need, is the number they won't tell us. We need to look at the torque of the engine. That is what will hepl determine if the engine will, for sure, crank the oversize props that we use. If it runs a 10x6 at 16,000rpm, will it turn the 12x4 at 14,000... Only the torque (or experience) will tell.
Like I said, however, it's best to come up with a plan, and just ask around. It's also good to ask about weight (incl a muffler), as some manufacturers don't seem to know that all of the time either.
Ya thanks alot i just learned alot!!! So in that case ive got the power-line eagle profile 3D .46 size plane and i was thinking about geting the towerhobbies .46 bb abc engine would be a good choice (i looks like it has the best specs. for the best price, but like you said that dosent mean much)? Which is why im asking what engines do you guys have w/ weight, prop size, ...
What engine should i get? I want to hover and the best performance as possable (just like every one else)!!!
Thanks alot for your time, Brian
If that plane comes at 5 pounds or less, the TH (built by GMS, I think) 46 will pull it fine. There are two in my club on Sig Somethin' Extras (easily 5 pounders) and they do great, even on only an 11x3 prop. They will easily turn the 12x4 and 12.25x3.75 APC props, adding even more thrust. The real trick to that motor is the tuned exhaust it comes with. It is a real screamer.
Neither of the two TH 46s I've seen had any problems with reliability either. Both seem reallt good.
Another low cost powerhouse looks like the Magnum 52. It looks ptretty good for the money. I think it's about $80.
Good luck, and let us know how it works out for you.
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