JL636

My Feedback: (79)

Without buying a engine, I could use one of the following. A YS 61, OS 70 FS, Super Tigre 75 or 91, or a Magnum 120 four stroke. Any suggestions?
Thanks Joe

krayzc-RCU

My Feedback: (31)

u are going to be in the 5-6 lbs range put the engine on there that will let u have fun with that weight. Only if u r hovering will much throttle be needed for your bird. I have a 4S OS-91 on mind with a 15 x 4. It will t-roll with that around 6500-7000 RPM.

ChrisAttebery

My Feedback: (15)

Out of what you have I'd go with the ST 75 or 90. It's closest to the weight needed to balance the plane and should have decent pullout power. The YS and OS will be underpowered. The Magnum will be overweight.

aussiesteve

100% exactly what Chrisattebery said.

the only addition I would make is - make sure you know how to make the supertigre sing - you will have so much fun with this plane - you will be DOD bofore you know it.

XJet

The only downside with the SuperTigre is that they don't really have a carby that lends itself to 3D.

Getting an ST to hold a steady mid-range and transition without hesitating is a sometimes impossible task.

Still, if that's all you've got it's better than sitting on the ground and watching others fly I guess :-)

aussiesteve

Yep - that is what I meant with my addition

Of course - maybe you could swap a few of the engines listed and get a Saito 100 - perfect match

Deathbunny_SG

My Feedback: (6)

Mojo 60 = Saito 100 all the way! If you have to stick with what you have the st 91 would prolly be the best fit. If you havent started the mojo yet you could always drop down the the 40 size and put the ys on it and you would be rockin

Rcpilot

My Feedback: (78)

I'm building a Mojo 60 with removable wings right now. I'm going to use an SK .90 engine. They are $100 and it should swing a 14-6 or 15-4 prop easily. It's not too heavy.

I was going to use a TH .75, but I know from experience it wouldn't have enough power.

I'm not sure how many guys actually weigh their planes. I have mine completely framed up. I put the entire fuse on the scale and recorded the weight. Then I weighed the wings and the aluminum tube. Then I weighed the servos, battery, switch and RX. Then I weighed the gear and lightweight foam wheels. Weighed the CF tailwheel. Weighed the engine with muffler. Weighed the 10oz fuel tank.

Without covering it weighs right at 6lbs. That doesn't include hinge glue for any of the control surfaces and it doesn't include the servo extensions or the motor mounting bolts. Doesn't include the foam under the RX or the tank.

This thing will weigh an honest 6lbs 4oz when it's done. I'd bet money on it. And just to head anybody off ......... NO! I'm not a newbie builder and I don't build heavy. [>:] Anyone who has one with removable wings will tell you that modification adds 4oz-6oz of weight.

Given the projected weight of 6lbs 4oz, I KNOW the TH .75 won't work at this altitude. I'm QUITE familiar with these engines and pulling weight vertical at 5973' above sea level. The TH .75 would do the job, but it would be sluggish and I ain't building a Mojo just to have it sluggish when punching from a hover. I want POWER! Lots of it!!

If I was you, I'd skip the ST75. I think XJet is right about the carbs. I hate ST carbs. They are like a light switch. You can dial it in to idle. You can dial it in for wide open. But trying to get consistent mid range performance out of a ST carb is just stupid. It's a waste of time.

The YS 61 and the OS 70 will both be very disappointing in this plane. The 120 will be too heavy.

If you have lots of cash, get the Saito 100 or the Saito 115. If you're on a budget, consider the SK90 or a Magnum 91 4-stroke.

fritzdecat

Man I wish there was a gasoline alternative to the the Saito 100... I am effin [:@]sick to death of glow but would love to have one of these beaters to fly before dinner on the back forty.

Rcpilot

My Feedback: (78)

So, build BIGGER profiles and power them with $200 gassers. 1/2 the price of a Saito and runs for pennies per flight. Reliable. Bigger always flies better.

http://www.zrcgf.com/store/Details.c...=27&category=0

fritzdecat

Good point there ...you must be psychic

I was on the phone with the RCGF guy this morning trying to buy a 45

He said they will be in by next week

My right foot is tappin

Deathbunny_SG

My Feedback: (6)

Here yah go, just add your fav 50cc and go nuts [X(]

http://www.ohiomodelplanes.com/92edgehybrid/

fritzdecat

True... Thank you

Yep I have seen all the big profile gassers including the American Eagle version

Still I want a wee gasser with the balls of a draft mule to fly a Mojo 60

The only way it will happen now is with the Saito 100 and I ain't payin no $30 a gal for RC air time

No WAY No HOW

Might buy the RCGF 26 though and scratch build my own...Hmmmm it might happen

Winter is coming and it passes faster if you got a plane to build

Deathbunny_SG

My Feedback: (6)

You could put a 26cc gasser on the 80" omp profiles. The thing is you need to use a rail mount engine or come up with some other way of mounting the engine since its a profile. There is thread about a os 1.6 gas conversion on here that would prolly work great on 80"ers.

fritzdecat

Do you think the RCGF 26 would have the power to yank around that 80" profile you speak of ? Would be great if it did .

Hmmm interesting. Mounting is not hard

Just not sure that is enuf motor. I want overkill times ten


Just this afternoon at teatime I was dreaming about putting a RCGF 45 inside a Sig Four Star 120

Rcpilot

My Feedback: (78)

You can find Craftsman/Poulan chainsaws with a 35cc engine. They convert easily. I haven't run one of them yet. I got a sneaky suspicion they run like a scalded cat. Porting looks good and compression is pretty high. That would probably yank 12-13 pounds around like a rag doll.

fritzdecat

Yeah thats a thought but I looked into that it is more work than it is worth

but if you want to try it heres a site with the answers

http://www.rcfaq.com/ANSWERS/ENGINES...6/POULAN46.HTM


The Four Star 120 Custom build with the RCGF might be the ticket

The pilot in that plane is going to be a hand carved replica of on of Big Daddy Roth's
Freaky Bug Eyed monsters

aussiesteve

I have been toying with the idea of mounting an RCGF 20cc on my mojo 60 because I have a need for a demo plane for the engine. The plane currently has a Saito 100 in it but it has had a range of engines before - including a saito 1.25 (ballistic is the word for that combo)

All I need to do is to sort out the engine mounting - anybody got any ideas or drawings to show me that might work?

Deathbunny_SG

My Feedback: (6)

Not really and thats the problem with gas in that size range, maybe something like the old brillelli SSR on a pipe would fly it good. I think some use the evolution 35 on it. If you dont want to sacrifice power or weight and run gas you need to go to 50cc range and up.

JL636

My Feedback: (79)

Lots and lots of choices! As far as the ST 90 goes and the finicky carb I have replaced that with a carb from OS engine. Slipped right in and fit like a glove. Should take care of the problem. I would still like a Saito 100 but I'll see how the finances go. Joe

T3beatz

My Feedback: (4)

Here ya go steve... its not a thin profile like the mojo but you can get the idea... we were talking about doing this earlier in the RCGF thread. Scroll down to the bottom of the manual. If you are good with wood and/or aluminum you could do this pretty easy with any profile..

http://www.goldeneagleaircraft.com/f1-p-manual2.pdf

T.J.

aussiesteve

Thanks for that T3 - I feel real stupid now - that is about as simple as it gets.

I think I am gonna try it when I get back to Oz next.

JL636

My Feedback: (79)

Has anyone ever replaced ST's carb with a large OS like I did? Joe

Dave McDonald

My Feedback: (19)

I once tried an OS 7D carb on a ST 90 to see if it would clean up the rich and ragged mid-range. The result was little....if any improvement.

I was suprised at the results since others on here have claimed that replacing the stock ST carb with an OS carb made their ST 90s run perfectly. But that wasn't my experience.

I now suspect that the porting and timing of the ST 90 may have more to do with the mid-range problems than the stock ST carb.

XJet

Actually I think it's both.

I've observed that many grossly over-bored engines (and the ST90 fits into this class) have quite shallow transfer ports and that causes a marked intolerance to anything but a perfect air/fuel ratio.

Some engines (like the OS55AX) get away with this because their carbs are very, very good at maintaining an accurate air/fuel ratio at all throttle settings.

However, the ST carb, combined with the narrow transfer ports means that the ST90 is very difficult (and in some cases impossible) to tune to get a crisp mid-range transition.

Some folks get close by carefully selecting props, plugs and fuel (all of which can go some way towards mitigating the design problems) but the limitations still apply.

Others have found that other carbs are "just" good enough to provide a better (more constant) A/F ratio at intermediate throttle settings than the ST one does.

So, a different carb can go a long way towards solving the problems but won't necessarily cure it.