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HomeAircraftHelicopterHIROBOHirobo SDX › OS55 AND SDX MAIN GEAR QUESTION
03-08-2010 09:51 AM  8 years agoPost 1
RussJ

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lockport, new york usa

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I am thinking about upgrading my SDX to an OS 55 engine. My question is, Do I need to upgrade the main gear to p/n 0412-169 (87T) or should I use p/n 0412-291 (89t) main gear?. I would just like to get a few inputs and some opinions from people first to see what is working best before I order the new main gear set. Also, what would be a good choice for the main blades?. 610mm. or 620mm.
Thanks, Russ

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03-08-2010 01:23 PM  8 years agoPost 2
Fernando

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Madrid

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I have two, one with a NR 57 and another one with OS55, both are stock, plain stock, hundreds of flights both. Sorry just 12,9 screws, better than Hirobo hardened ones.

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03-08-2010 11:00 PM  8 years agoPost 3
RussJ

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lockport, new york usa

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Glad to hear the stock gears are working out on the sdx for you with the bigger engines. I was just curius to see if anyone was upgrading the main gear or going to the 89t gear to keep the head speed under control. Greg from MRC-HIROBO made a post a while back reccomending to upgrade the gears and listed the part numbers as well. You mentioned 12.9 grade bolts you are using. Are you referring to the drag bolts or the feathering spindle bolts?.

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03-09-2010 05:37 PM  8 years agoPost 4
Fernando

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Madrid

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blade holders screws, this is a must. Stock ones bend.

I would not recommend going below 8.7, consider that Trexs are flying with 8.5. To me ratios below 8.7 makes the heli a bit ‘soft’. It all depends of how you like it but I would not worry about over reving….

regards.

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03-09-2010 09:37 PM  8 years agoPost 5
RussJ

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lockport, new york usa

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Sounds great. Im ganna leave everything the way it is then, (stock) I prefer to have a nice fast head speed when Im flying. It makes the helicopter become a bit more lively. I have talked to a few other people and they didnt change anything either when going to the bigger engine. The only thing I will get then are a set of blade bolts for it. You are right about the bolts bending, I took a close look at mine and they are slightly bent. That is only after about 6 gallons of fuel and with no major crashes. Thanks again

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