BullardRM

My Feedback: (39)

I have a 3W 75 rear intake mounted in a H9 330. We started it up this weedend and could only get 6200 RPM using a 22X10 prop. I called Cactus today and they said that was normal and it was a "low end high torque" engine. Does anyone else have any experience with this engine? I was very disappointed in the initial perfromance. My buddy that flys DA 100's was expecting to tack 9K. Did I get a dog here?

BKH

My Feedback: (4)

I think you should try a 26-10 and it may turn the same RPM. Sometimes I think Good Buddy has a tendency to under-prop a motor sometimes.
Brian

MikeEast

My Feedback: (3)

i do, you should get about 6800 with a 26x10. I use a Mezjlik. The 3W 75 is a real brute and a smooth reliable engine. Mine starts very easily and has fantastic transition. All I do it rock it back and forth 15 times with the ignition off at full throttle. Three of 4 flips with the ignition off to get it wet. . Then a couple of flips a couple of clicks above idle with the ignition on and it fires. Off with the choke and it usually fires on the 1st or 2nd flip. Runs like a scalded dog. I can perform Knife edge loops with my 21# Edge with ease.

RickP

My Feedback: (2)

I've got 4 gallons through my 75I-us TOC. So far it is AWSOME. I had a problem with my Ingition switch that drove me crazy causing a high speed miss, that took me two weeks to find, but it's no fault of the motor. I'll try to get some RPM numbers this W/E.
RickP

Dan767

My Feedback: (19)

I have one with a 24X10 prop on my Lanier Edge. Flies quite well. Starts easy, great transition. I think you're under propped also.

3dd

My Feedback: (6)

yes way under proped.i run a 24x10 on my 3w 60 at 6500 rpm and 27 pounds of thrust

IanB

My Feedback: (1)

did you really mean 22x10 that looks like a misprint to me...........what kind of prop.........there is no point in quoting prop sizes as two props of the same length and pitch can have a totally different load.
However ANY 22x10 should turn WAY more rpm than that and its is not right your distrubutor palmed you off with such a banal excuse as "low end high torque"

vatechguy3

My Feedback: (11)

i'm running a 24x10 3w prop, and it runs about 6800-6900. if you're only getting 6200 with a 22x10, then you may want to adjust your needle settings!!

tony

m.gramling

My Feedback: (8)

I am run a 3W 24x10 on 3W 75USi-side carb, and on 50:1 it was taching 6500-6600 at the end of flight. I will swap over to a 26x10 this year. Pulls my 21lb carden cap with ease.

tito1

My Feedback: (24)

hi guys ;
i have a NX 26x10 on mine i have it on my G202

FormerCA.

My Feedback: (8)

I see you are in Fla. which is humid just like here in La., those engines are set to run rich in dry, Arizona air, and that means that it will be slobbering rich in humid air. You are also VERY underpropped. Don't try to chase the needles on breakin, but you can certainly improve on the above numbers. 32:1 lawn-boy for 4 or 5 gallons, then over to a good synthetic of your choice. 24X10 for breakin then 26X8 or 26X10 after-you'll love it.

ShawnM

My Feedback: (6)

Yup, get that little prop off of there and see what you got before trying to tune the engine. I'm only on my fourth flight with mine with a 24X10 3W prop and it pulls my 23# Giles like a freight train. I haven't even tached it and I don't care what the numbers are cause it runs great. I can't imagine what it's gonna do after I get to the 26X10. I have'nt even touched my needles and it runs smooth and strong from idle throughout the RPM range.

I could be wrong, but I believe what he ment by "low end high torque" is that the 3W motors will swing very large props at respectible RPM numbers. When I bought my engine from Aircraft Int. I was told that the 75 would swing a 27X10 with authority after fully broken in. Now that's some serous power coming from a 75cc engine[>:]

Some more proof of that would be the oil testing that was told about on here with a 3W-42 swinging a 24X10 prop right at 6000 RPM. Now that's torque, I'd bet alot of 50's wouldn't do any better including the DA....and I have one.

Stick2000

My 3W75IUS,

The 22 X 10 prop is recommended for 1 hr. run_in
before flight per the manual. I used a 24 X 10 for the
next 2 to 6 gallons of gas. Tach at this point 7200 rpm.

I change to a Mejzlik 26 X 10 and after 15 to 20 gallons
it tach at 6800-6900. It pulls my 23 1/2 # 33% Edge
with out of site vertical performance.

This engine is gaining more power (small amount) after
approximate 35 gallons of gas. It really is a power house,
with easy starts and handling characteristics.

Give it time to break_in properly and you'll have a engine
that gives great performance.

Stick2K

IanB

My Feedback: (1)

You know i just find it hard to believe as In my opinion the main mechanical property that may result in "low end high torque" would primarily be a long stroke. As an example the DA 100 has a longer stroke than the 3w106............and yet I often hear of this mythical beast of "low end high torque". Can anyone explain to me in a basic mechanical way.........how this "low end high torque" is achieved?????

famousdave

My Feedback: (61)

I set up all 3W-75i engines the same way:

24x10 MenzS to break in with 3--4 gallons of Lawn Boy Ashless or Bel Ray S2

After break in : I switch to a Bolly or Mezjlik 26x10 The bolly is heavier and makes for great down line braking and idle !
It won't spool up as fast though so its not as good as the Mezjlik for 3D

This engine is a powerhouse that rips the 26x10 once broken in. I have measured 40 pounds of static thrust with that prop. Who cares about the RPM - its power that counts.

I have this setup on my Columbo Anderson 31% at under 20 pounds it hovers right around 1/4 throttle.

Flawless midrange and absolutely superb idle.

BTW - 22x10 is what you break in a DA50 with.

DP

TD1

ShawnM

Don't believe everything that you are told, I have a 3w 42 and it want swing a 24x10 on its wildest dreams, the biggest prop that it can take is a 22x8 3w @ 6300 rpm. this is from my own experience not form what I have heard or told by a friend as some people will tell you.

famousdave

My Feedback: (61)

TD1 - What does a 3W-42 have to do with a 3W-75?
I don't see the connection.. were you trying to make a point??

DP

rc bugman

My Feedback: (30)

DP

TD1 is doubting that the 3w-42, I used in the 60 hrs of oil testing would turn a 24 x 10 at 6000 rpms. It actually varied from 5600 to 6150 depending on the oil mix. Shawn was quoting that data as an indication of 3W torque.

TD1: You need to try it on the 3w-42. You may be surprised. My engine turned that rpm range for the entire 60 hr oil test discussed earlier in the engine forum.

Elson

ShawnM

My Feedback: (6)

Thanks for bailing me out there rc_bugman, thanks for the oil test!!

I am looking at my manual for my 3W-75 and can't find anywhere that it recommends a 22X10 prop. My manual says (word for word) "for breaking in a smaller propeller is recommended: 24X10"

Why we have two different manuals I don't know, I don't doubt yours says a 22X10 if you say so, but a 22X10 prop is a 50cc size. Heck, most 50's are recommended to be broken in with a 22X8. Maby one of ours is a misprint, maby not, it could be one of ours is a revised manual, but a 22incher seems awfully small to me. I'm using a 24 and it is doing fine, it pulled hard and ran smooth from tank #1.

I wish I could explain the torque thing, but I just don't know. Maby somebody will explain it??

Shawn

TD1

Desertpig

I was just making a comment on the statement that ShawnM made in relation to the 3w 42

TD1

rc bugman

What oil ratio were you using and what prop was it? the engine didn't get to hot?


ShawnM

I apologize for doubting

rc bugman

My Feedback: (30)

TD1

A 24 x 10 is too large a prop for a 3w-42. I used it to raise the engine temperature into the 200 degrees f range to test the oils. Outside temperatures were 25-40 degrees F. I was also surprised at the ability of that engine to turn that large of prop. I tested oil mixes from 20:1 to 100:1. The results are listed under the engine forum. They were posted by big bird. I could not get the pictures to load.

Elson

eraser

I have the 75i and am breaking it in on a 24x10 like Cactus aviation recommends. On my very first run it tached at 6400 rpm slightly rich. Now I have 10 flights on my CA extra 31% and it will hover at about 1/3 throttle (the plane is 21lb. and the field elevation is 5300 ft.) The engine is now taching at 6800 rpm and getting stronger all the time, awesome. How soon can I go to a 26x8 or 10?

ShawnM

My Feedback: (6)

TD1, I too was in disblief to see the #'s he was getting, but I sure do believe him. If I'm wrong about anything I don't mind being called on it so no problem

Out of three of us that fly together here there are four 3W motors, one BME, a DA, and a couple of Brisons and all of the 3W's have loads of power and have been smooth running from the get go. They are our favorite.

Eraser, most everbody always says 5 gallons of fuel, but my manual says 2-3 hours which will probably be close to the same amount. Since we are breaking in 3 engines and are all using out of the same jug here I'll just go by the run time and then slap on that 26X10 3W prop I've got here and see what happens.......,but I'd really like to put it on now

Shawn

Stick2000

Hey guys,

After this discussion about a 22X10 prop for break_in
I pulled out my manual and reread that section.

Quote " We recommend to run the engine with a smaller
propeller (22X10) for approximately one hour. This can
be done in the model or on a test bed. " Unquote.

I took this to mean that the smaller prop would help
with initial running-in for a brief time and then the use
of a 24X10 prop to complete the break_in.

I switch to the Mejzlik 26X10 when the engine began
rippin the 24X10 prop.

3W recommends prop sizes from 22X12 to 26X12 for
this engine.

In any case, I think like others here that this is one
fine engine !

Stick2K