seanychen

My Feedback: (4)

While browsing the web, I stumbled across the page that shows the new Thunder Tiger F-75s 4-stroke that's under development. Looks interesting, however a little late in the game, in my opinion.

http://www.acehobby.com/ace/TTR9802.htm

NM2K

My Feedback: (14)

Hmmm, it looks like a TT copy of an OS FL-70.

Sport_Pilot

Looks like it, but it is like the TT .91 it won't be a copy.

Kmot

My Feedback: (24)

I took notice of this engine at the iHobby Expo. If you will look at it, you will notice it has much shorter pushrod tubes than the existing TT four strokes. Short stroke, high rpm is my thinking. I asked one of the Ace reps there but he was not informed of anything to discuss.

Sport_Pilot

I think the push rods tubes just look short because they end at the lower part of the head instead of the rocker box. Though it could well be a short stroke engine.

seanychen

My Feedback: (4)

Wow, there is actually hardware. I thought it was only in CAD format, like the OS 120 AX for a long time. Well, with YS 63 and Saito 82 out there, this Thunder Tiger is going to have to do very well to compete. The picture sure looks nice though.

seanychen

My Feedback: (4)

On second thought, it does strike me a bit as a "bored out" 54. If it has the light weight of their 54, then the 75 will indeed be a potent candidate.

MrMotor

Here are some specs. Bore 28.3 MM, Stroke 19.6MM, Weight 16.5 oz. Rated power of 1.3 at 11K and practical RPM of 2K through 12K. It looks like the production engine no longer will have a black head. It uses a 2 needle carb. There is no pricing available yet and if they price it like the 91 two stroke there may not be many buyers for the engine.

w8ye

My Feedback: (16)

The OS and magnum 52's are 23 X 20.6

The 70's are 25.8 X 22 for the OS and 25.9 X 22 for the Magnum 70

So the Thunder Tiger is very short stroke. It looks like they used the crank of the 54 and the piston of the 91?

The TT 54 is 24 X 19.6 Street price... $169.95
The TT 91 is 28.3 X 23.8 Street price... $189.95

So I guess the Street price of the 75 will be $179.95?

You look on the Ace site and they want $400 for a 91.

Enjoy,

Jim

seanychen

My Feedback: (4)

I think this is not unlike the Saito 82, which has the same bore of Saito 100. I guess over-bore design is the trend of light-weight 4-stroke nowadays.

NM2K

My Feedback: (14)

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I don't know how they are now, but years ago it was difficult to get a hobbyshop to open an account with Ace. They were a PITA to deal with.

Sport_Pilot

Since TT bought them out they have improved, but are still spotty. Apparently they still have some deadwood to get rid of.

William Robison

My Feedback: (3)

Paul:

Quote:

ORIGINAL: MrMotor

...It uses a 2 needle carb...

The web page (link in first post) says "Precision air bleed carb..." It also says "Ringed piston" so it won't be an "FL" type POS.

Bill.

MrMotor

Bill
I think it was just a concept engine back then which you can see if you enlarge the picture. I am looking at their new product information book showing an actual engine with the needle inside the carb arm. Their part number is TTR 9802 for the F-75S but no prices are listed yet. The writer, I don't think knew what he was writing about as he also mentioned a swept back needle for safety on a rear carb engine.

William Robison

My Feedback: (3)

[b]Paul:

I wondered about that "Improved carbutetor, swept back for safety...." Wasn't just the needle. But the picture looked like normal carb mounting.

Bill.
[b]

seanychen

My Feedback: (4)

Bill,

The description on Ace's web page on this engine was referring to TT's 2-stroke. Looks like they need a different description for 4-strokes.

hngzy

I ran tt f54s(with two needle) today .I fond the power more then OS f52,Use apc 11X7 prop ,
It can up to 11500rpm.So I think tt f75 must be powerful then os fs70.

Ed_Moorman

My Feedback: (1)

Now don't get me wrong. I believe that Thunder Tiger engines are a high quality product except for the valve train problem with the .91FS. A guy at my field had that happen and he sent it to Ace who fixed it. Power has never been a question as their 4-strokes, especially, have been tops in power except for YS.

TT engines have always taken a long, long time the break in and they are heavy. The .91FS weighs nearly a half pound more than a Saito .91. I have a Magnum .91 that runs great and the TT weighs 4 ounces more than it. This may be OK if you fly scale and need some weight up front or if you are a sport flier that doesn't care, but with a light weight engine, I can run it very easy and have the same performance.

But it seems to me they are a day late and a dollar short, if I can use an old cliche. Why bring out a .75 when Saito has an .82 that only weighs an ounce more than a .46? If your company is strapped for cash and you need a mid-size filler engine that you intend to price low for sport fliers who hate OS and don't want to fork over the extra $ for a Saito, I guess it's OK. From what I read in the other forums, the Saito .82 is selling like hot cakes with the fun fly guys. Looks to me like TT needs an .85, then bump the .91 to a 1.10 or something. Why go smaller if you aren't going to be super light?

Another thing is parts and service. Ever try to find Thunder Tiger parts? I can tell you about Hobby Services (OS & GMS) and Global Services (Magnum). I had 2 GMS .32s on a TwinStar. One was not turning like the other and quit frequently. I mailed it back to Hobby Services. The next week I got it back with a new piston, cylinder and rear bearing. No charge. My buddy and I dunked a twin flying boat in the lake with 2 Magnum .52FSs on it. A couple of months later, we had it on another twin and the engines sounded really bad, grinding and clanking. We sent both in to Global. A couple of weeks and new bearings and 1 new ring. No charge. We even asked for an estimate. You beat those 2 for service and then we'll talk buying your engines.

Sport_Pilot

I think the Magnum weighs the same as an OS .91. My TT .91 weighs just over two ounces more than my OS .91. But has a lot more power. Used in planes that needed some nose wight, such as a Fokker Dr 1. TT publish's their wight with muffler, OS and possibly Magnum without, I think that is where the extra two ounces comes from, the muffler.

There is no valve train problem that a little lock tite cannot solve.

IMO the TT .75 should be more powerfull as the Saito .82 if their power to displacement ratio is the same as the .91. A .82 is only .07 cubic inches larger, not hard to make that up with a short stroke large valved higer reving four stroke. But some will probably not be comfortable with letting a four stroke rev past ten grand.

Ed_Moorman

My Feedback: (1)

The TT .91FS is a powerful engine and you have is in a scale plane, even one with a very short nose so you are using the weight correctly. If I have a plane that builds tail heavy, I always go to a larger or heavier engine for power. I have a scratch built Nieuport 27 and my Magnum .91 is in it instead of the lighter Saito .91, but...

You want to talk weights. Maybe the OS is heavier than the Magnum, but I have both a Magnum .91 and 2 Saito .91s and I know what my digital scale says. All I can say for Thunder Tiger is what their web site says, and they list it without muffler. All my engine weights are with muffler, exhaust pipe, prop nuts, washer, etc.

TT site .91 wt without muffler: 25.7 oz.
My Magnum .91 w/muffler 22.5 oz

Difference 3.2 oz. I figure with muffler, it'll be over 4 ounces difference.

My Saito .91 (either regular or Black Knight) 19.7 oz

Difference: 6.0 oz. I figure that's close to a half pound with the TT muffler.

My Saito .72 came in at 18.1 oz and the .82 is actually lighter by a fraction.

Sport_Pilot

Ed,
I think they have stated their weight incorrectly, as I recall my TT .91 weighed just under 26 ounces with muffler. The OS weighed just under 24 ounces with muffler. I thin bothe were one or two tenth's over the manufactures listed weight. Pretty sure the instruction manual listed it at 25.7 with muffler. For some reason all of the two stroke engines have their weights listed with muffler and four strokes without.

From Towerhobbies

OS .91 FS Surpass

Weight-With Muffler: 24.2oz (686g)
Weight-Without Muffler: 22.6oz (641g)

So the muffler weighs slightly less than two ounces. The TT mufler is slightly bigger.

This also makes the OS slightly heavier than the Magnum.