HERE INFOS ABOUT OS 75 AX
 

http://www.rcgroups.com/forums/showthread.php?t=711025

VERY GOOD RUNNING BUT WEAK FOR THISE SIZE overprop by os it cant turn 14x6 apc more then 9500 rpm

RE: HERE INFOS ABOUT OS 75 AX
 

....in my opinion, this over square engine should be running a 12-7 prop. ;)

FBD. :D

RE: HERE INFOS ABOUT OS 75 AX
 

That's actually very good rpm for a .75, that's right where my Fox .74 turns a 14x6 and about 100 rpm less than my Irvine Q .72. These numbers are using Fox 5% fuel with 20% castor.

RE: HERE INFOS ABOUT OS 75 AX
 

http://www.osengines.com/engines/osmg0575.html



SPECS: Displacement: 0.75 cu in (12.3cc)
Bore: 1.02" (25.8mm)
Stroke: 0.93" (23.5mm)
Practical RPM: 2,000-16,000 RPM
Power Output: 2.4ps/15,000 RPM
Weight: 20.39 onuces (578g) w/o muffler
26.46 ounces (750g) w/ muffler
Recommended Props: 14x6, 14x8, 15x7

RE: HERE INFOS ABOUT OS 75 AX
 

Oh my god! The smallest prop OS recommend is 14-6 and up to 15-7:eek::eek: Woooow that are some serious sizes for a puny 75.
9500 rpm on 14-6 huh? then my guess will be around 8200 rpm on a 15-7 and that can`t make the engine happy at all

RE: HERE INFOS ABOUT OS 75 AX
 

A 14 x 6 seems like way too much prop for a .75.

Having said that, a little while ago I saw a GMS.76 pull an APC 13 x 8 (about the same load as an APC 14 x 6) at 10,300 rpm so perhaps it is a bit low.

RE: HERE INFOS ABOUT OS 75 AX
 

This would be a real POS where I'm at. Still better off getting a G90. The OS 75ax IMHO is just one of the latest "sucker buys."

RE: HERE INFOS ABOUT OS 75 AX
 

Just received my monthly subscription to Fly RC. Once again I am disappointed that the evaluation of an engine, this time the 75AX, tells me very little towards the true worth of such an investment. In my opinion the .75AX is an "odd-sized" heavy weight that hopefully has more going for it than just the "glowing evaluation" found in this month's Fly RC. Jim

RE: HERE INFOS ABOUT OS 75 AX
 

I will try today with another props on my showtime 50 and let you know how it run

RE: HERE INFOS ABOUT OS 75 AX
 

You should try a 14-4of some sort, preferably a wide one. I expect that to be a great prop for it

RE: HERE INFOS ABOUT OS 75 AX
 

I am NOT renewing my subscription to Fly R/C because it shows MORE interest in electrics..
If I wished that I would be taking "Quiet Flyer"

RE: HERE INFOS ABOUT OS 75 AX
 

JIm,
Why not try and email me with your comments and suggestions if you are so unhappy with my engine reviews? My email is right at the top of the page in each issue.

I am always interested in knowing just why some guys see my reviews as "dissapointing" as I think I do the most thorough, fair and well rounded review in any magazine published today.

I gave the OS 75AX a glowing review because the engine performed just great - with the exception (if you guys bother to actually read my reviews you will always see the negatives or slight faults) of the fact it will hang a bit coming down quickly from a high throttle setting to a low one. A minor point for me but some may need to know.

Honestly, I dont know what else one can do with an engine than:

- break it in as per the manufacturer's directions
- run the snot out of it with many sized props and plugs and various fuels
- mount and test fly the engine
- give data such as temps and rps for said various fuels and props
- discuss the internals and externals, the quality and value

SO what the heck am I missing??

THanks,
Andrew Coholic
[email protected] <-- if you prefer to not go through the Fly RC channels...

RE: HERE INFOS ABOUT OS 75 AX
 

Then I suggest emailing the editors and asking for more glow and gas articles and submissions. The ONLY way to let the guys at the mag know what you want to read is to let them know. There are many emails listed for contacting the editors and they are more than willing to listen.

WHy complain to a group fo modelers on a chat site? Talk to the magazine editors, thats who will listen and make changes. Unfortunately electric stuff is very popular right now and thats what most of the new products are related to. But if you want more of anything you have to let yourself be heard.

AJC

RE: HERE INFOS ABOUT OS 75 AX
 

Good points, Andy.

RE: HERE INFOS ABOUT OS 75 AX
 

I had try today my 75 w many props and the engine feel nice with 13x6 APC 11.400 rpm but not strong to run correcly the APC 14x4 wide
i will try witn others props in few days

RE: HERE INFOS ABOUT OS 75 AX
 

I'm one of the suckers who just purchased the .75AX. Plan to bench run it Sunday. Will use T-F power point 13x8 cut down to 10x8 for the break in prop and Omega w/ 15% nitro.
Based on a little experience and what I've been reading, you all are expecting this 2 stroker to swing to much prop, OS included.
This is just a punched out 61fx, a little more bore and stroke in the same weight package, which is what I want. I think 14x6 is going to be the high end of the prop range.
I'll let you know how things work out.
SE

RE: HERE INFOS ABOUT OS 75 AX
 

....I would think running the engine above 12,000 would be desirable. Anything below that
would be lugging the engine in my opinion. ;)

FBD. :D

RE: HERE INFOS ABOUT OS 75 AX
 

Sucker. [sm=greedy.gif][sm=greedy.gif][sm=greedy.gif]

All kidding aside, I'll bet it works out fine for you. Probably won't have to drill anything, swap carbs, try 4 different pumps, and launch an internet poll to learn how to get it to run well either.

OS DOES love to specify large props don't they? Has anyone considered for a moment where these motors are made? Japan you say? Yeah. Japan is a real small, and densely populated island. Noise is a major issue, and large props are quieter in operation than small ones. An overly large prop may not show the engine at it's peak, but it will be quieter than a smaller prop turning a much higher rpm. Since everyone here is clearly better informed than OS on matters relating to glow engines, it is a simple matter of installing the prop which you find to work best for you. Problem solved hey?

Have fun with that "odd sized" .75.

RE: HERE INFOS ABOUT OS 75 AX
 

....quite frankly, 'Race....if it wouldn't turn 13.5 with a MAS 11-7 1/2 prop....

....I'd can it. [X(]

RE: HERE INFOS ABOUT OS 75 AX
 

I don't own one (yet), but I don't think this engine was designed to rev. Rather, I think it is more in the line of a trials motorcycle engine. Low speed tricks and lots of grunt. Much like my Jett .76L; a two stroke that thinks it's a four stroke. Some folks seem to suffer from monomania: rev, rev, rev. :)
Putting a high revving pipey engine in a 3-D or sport plane makes as much sense to me as using a motocross engine in a trials bike.

RE: HERE INFOS ABOUT OS 75 AX
 

Dave, I don't own a 75AX. What would I put it in? I'm about to be buried by .40 sized profiles here...all of which have their own engines.

I suppose if "Max RPM" with a smallish prop were the only consideration....the doors would be wide open for a whole lot of engines to jump in, and eat the AXs lunch. I don't believe the 75 was ever intended to be a speed champ through the radar traps.

(I do own a 55AX, and it may be no speed demon either, but it is the CAT'S ***** where 3D work is concerned!)

The AX series as a whole however, has been rather successful. What these engines bring to the table is a very broad range of USABLE power settings. Not just ON & OFF. They require no modifications...no special considerations. Just fuel, set the needles semi-close, and you're going to have a good day. That's a big deal in a market full of one trick pony engines.

Why should the .75AX be anything but a continuation of that success?

Take from it what you will.

RE: HERE INFOS ABOUT OS 75 AX
 

I thinking in same way apc 14x6 is the max prop

compare the propellers 13 inches of apc and the 14 inches, the shape is different,14'' thicker and has my more difficult to turn. I ordered several propellers for new tests bolly 13.5x5 zinger Wood 14x4 14x5 to reach more thrust and less speed

RE: HERE INFOS ABOUT OS 75 AX
 

No personal shots intended. I have many OS engines and like them all but bought them early on in my RC days in the last 10 years. very good , reliable engines (except the 91fx but lets not go their). I also own many Super Tigers and Jetts.

My only issue with the 75 is not performance as I'm sure it will run as well as the rest. I just feel OS has lost its mind on pricing and we have engines equal if not better at a better cost and to me that is a Super Tiger. Even ST has a 75 and to me this size of an engine is pointless when a 60 and a 90 are readily available.

With OS, your not buying a better engine here, your buying a name. I have BGX 3500. My plans in the next year will be with another 3250. (had one before). I know Some St's have carb issues and I have gone through this and feel I can tune my way out of it.

However my next project, I am not taking any chances and will install a different carb but even with this, cost wise i still come out way ahead than a new BGX with near equal performance.

RE: HERE INFOS ABOUT OS 75 AX
 

I was thinking about getting this engine for a 40 size profile but after reading these posts it seems my saito 82 will turn a 14x6 apc faster and it weighs 7 or eight ounces less. I know my saito will turn an apc 14x6 a little over 10k. Am i right about this engine or did i miss some posts?

RE: HERE INFOS ABOUT OS 75 AX
 

Definately stay with your Saito 82 as it will be ALOT better suited and much lighter in your 40 size profile