lasko220v

My local club is planning to use a thunder tiger pro 46 as the standard racing engine and wants to require a 9-6 prop and rev the engine to 17000 rpm. Is this recomended for this sport type engine if broke in properly? The matching plane is a sig four star. Thought these engines were designed to run slower and more powerful at a lower rpm. Any thoughts would be appreciated.

SitNFly

My Feedback: (54)

Mine was happy on an 11x5 at just under 12000 RPM. Don't know how they'd act at 17K; horsepower peak might be in that vicinity. One way to find out, yank it and bank it .

jeffy

I think you would be bery happy with a 9-7

I myself am a happy camper with this setup

daven

My Feedback: (1)

They run Thunder Tiger 40's on 9x6 apc props here around 17k and the motors seem to hold up fine.

With the bigger 4 star I would think a 9x7 or even 10x6 might be more appropiate.

What %nitro will you be using?

XJet

I've heard some say that the stock bearings are not too good at RPMs of 17K+.

Just keep an eye on them -- they have a metal retainer and when that lets go it can make a very nasty mess of your motor. If I were running my TT46Pros at those RPMs I'd replace the bearings with some that have a polymer cage as insurance against this.

$7 for new bearings versus $80 for a new motor -- it's cheap insurance!

Jezmo

It won't have any problems at all. It's a pretty draggy airframe so running a 9" prop will help keep the speeds down. Don't worry about the engine though, it will be just fine. We run TT 40Pro's on World Models LA Racers for our entry level pylon racers. We call them Club 40.

The current AMA 424 rules limit 424 class planes to a TT40Pro with an unmodified 9X6 APC on it. They turn about 17,000 as well and I have had NO problems so far. I have a TT46Pro that I have run on my LA Racer at 17,000 with NO trouble. I have also run my Magnum 46XLS at the same rpm's with NO trouble on it either. I put a Jett-Stream pipe on the Magnum with an 8.8X8.75 APC Pylon Prop and with a few other mods had it turning over 18,000 also with no trouble. Good luck with your racing and hope you enjoy it.

I also change the bearings like XJet said. The stock bearings don't hold up well even if you aren't turning them up. Get the poly cage bearings as they hold up better for high rpm.

vicman

My Feedback: (10)

I have experienced bearing failure with a 9X6. [:@]
9X7 or even 9X8 is no prob for the .46.
Other than the bearing issue a 6-32 threaded rod and jam nuts mod to the muffler it's an excellent engine. I put on even par with the .46FX.[sm=thumbup.gif]

XJet

I'd put the TT ahead of the OS. At least the TT won't spit its liner-plating out the exhaust port :-) (stands back and waits for the liner-peeling argument to resurface :-)

What's your issue with the muffler bolts? I've had *zero* problems with any of my TT46Pros -- although the first thing I do is swap the stock muffer out and use a Tower/GMS 3-piece one instead -- that gives them a real wake-up and puts them well ahead of a stock OS 46.

Cyclic Hardover

My Feedback: (3)

Been running a 46pro and 9/7 apc on a Shrike 40 for years along with a Performance Specialites Ultrathrust Muffler

Razor-RCU

My Feedback: (50)

I agree a 9x7 apc would make more sense. The perfect prop in general and keeping the RRR's down a little. I would have everyone run a 10x6 on the 4* 40. A 9" is kinda small on that draggy thing---

speedster 1919

My Feedback: (3)

Sounds like your club has standardized the 4star and a TT46. It will be an even playing field for everyone if you standardize the prop choice of size and brand. Why not go for the 10x6 for everybody and get your rpm's down at little bit so your engines last longer. The trouble is someone always wants to cheat. You can control that a little if your club provides all props and fuel to everybody at the start of your race. The props can all be pre balanced and picked out of a box or pile at the start of the race. The fuel can be supplied to each racer at the start of the race. this way nobody has a chance to doctor fuel or shave prop at home. A fund can be started to pay for props and fuel.

Jezmo

The club 40 racers are doing the "everybody uses from one fuel jug deal". We aren't doing the prop thing though. They are slow and draggy enough that there just isn't enough to be gained by shaving props. You can more than make up any advantage that would give by simply flying a "Tight course".

vicman,
Were your bearing failures on stock bearings or good quality poly caged bearings? In my experience the stock metal caged bearings are pretty much junk but I haven't had any problems with the poly caged ones even at over 20,000 rpm's. I change them every season or even sooner if I see anything going on that don't look right. (Pitting, spalling, washboarding, etc.) If it isn't silky smooth it's outa there. I get my bearings from Paul at RC-Bearings.

Edited to add: I agree with everyone that a slightly larger prop makes more sense for a beginner class. 10X5, 9X7 makes more sense than a 9X6 and it's going to increase the life of the engine. (Especially for those who don't put in the good bearings) No one would have any advantage as long as everyone is running the exact same prop which is what is all about to start with.

vicman

My Feedback: (10)

It would seem you answered your own question. The bolt stretches and breaks after a few dozen flights. In C-40 we are required to use the stock muffler. The .46 & .40 are exactly the same.

My bearing failure was with the stock metal sheilded unit. No problems out of the aftermarket jobs. I get mine from Nelson.

buzzingb

My Feedback: (2)

If you keep the fuel mixture right you won't have any trouble. The rear bearing may wear more quickly at these rpms but can be replaced with better one if it does.

vicman

My Feedback: (10)

The bearing didn't wear out. The shield comes off and gets ingested into the rest of the engine...would you like a pic? For under 20 bucks to change the bearing and fix the muffler you get an excellent performer.

ChrisAttebery

My Feedback: (15)

We race the WM T-34 with a stock OS 46AX on a two pole 650' course out here. By far the two best props are the APC 10x5 and 9.5x6. I would imagine the 4* with a tt46 would be very similar.

Chris

XJet

We race with 12x4 props on the TT46. You would be surprised at how fast a Skyraider will go with a good 46 up front and a 12x4 APC -- plus you get ballistic vertical :-)

Cyclic Hardover

My Feedback: (3)

I guess when that happens, doesn't sound like no Jett eh? I had the idle bar fall off one time in a 61pro. We all thought it was bearings until we opened it up right their. Piston looked like it was polished by a food processor!

I recall since it was a Tower plug and a new engine, I sent it all back and they gave me a new one

Jezmo

Thanks vicman,
That's kinda what I was a thinkin. I've never had any of the good ones fail. Take care and happy racin.

MJD

My Feedback: (1)

If your club is planning to require a specific prop, engine, and airframe why not avoid any potential issues with the engine (as noted by others already) and run a 9-7 or 10-6? Obviously the goal is to keep things simple and level the field, so the prop choice is not critical - therefore why not use a choice that is kinder to the engine and more suited to the aircraft? The 9-6 seems a bit counter-intuitive.

MJD

jeffie8696

Why would the club choose to run the engines "on the ragged edge" so to speak?

XJet

In a word.... "FUN"

And isn''t that what the hobby is all about?

vicman

My Feedback: (10)

The club doesn''t make the decision. It''s the guy twisting the needle.

jeffie8696

If the decision to standardize was based on keeping the cost down in order to make it more affordable to more flyers then I would have to say using the larger prop to keep the revs down might help with the engine life. But if everybody can afford a new engine every week then what the heck, go for it. You could standardize the fuel to be something like Sig 20% all castor(or more), to mimimize engine damage . I like the stuff personally, I just went there today and picked up a case.

MJD

My Feedback: (1)

So, it''s less fun with a differnt prop? I don''t understand. Esp. if it potentially would perform better with more disc area.