Thunder Tiger F-75s
 

Since everyone spoke highly about Thunder Tiger, I figured I ought to buy the 75 and give it a try. I also have a Saito .72, OS .70 & Magnum .70.

I haven't mounted the 75 on my test bench yet bacause I have a JBA .56 to break in. It'll be next.

I plan to use it on a Neptune seaplane.

The first thing I usually do is to weigh the engine with everything on it: muffler, glow plug, prop washer & nuts and needle valve.

Thunder Tiger F-75s: 18.2 ounces or 518 grams on my digital scale.

It is a good looking engine. It comes with a glow plug, 2 wrenches, a large one that fits the muffler and prop nuts and a small one for valve adjustments. It also comes with 2 feeler gauges for setting the valves. The carb is a two needle carb, not an air bleed as stated in the advertisement. The oil drain nipple is in the center of the backplate.

I'll report back when I have rpm data.

RE: Thunder Tiger F-75s
 

Isn't that exactly what the AX .55 weighs? It is a very nice looking engine.

David

RE: Thunder Tiger F-75s
 

....Sweet !! That's a cool looking muffler, show a pic of it, please. :D

FBD.

RE: Thunder Tiger F-75s
 

That's a nice engine Ed. As usual I look forward to your report.

RE: Thunder Tiger F-75s
 

Here are a few more pictures of the TT F-75s.

Take a look at the side and rear views. There are 2 tangs that project from the rear cover. Each has a hole in it. What the heack are these???

RE: Thunder Tiger F-75s
 

I would turn that carb around before you burn your hand trying to adjust the HSN! [X(]

RE: Thunder Tiger F-75s
 

Nice looking engine

RE: Thunder Tiger F-75s
 

....I'm thinking the lugs have something to with the intake, perhaps some type
of an aircleaner for cars and trucks ???

RE: Thunder Tiger F-75s
 

Choke lever pivot

RE: Thunder Tiger F-75s
 

Correct, the 91FS has this too and it's functional on that engine. Looks as if they decided the 75 didn't need a choke (which it probably doesn't, other 4-strokes get by without them).

RE: Thunder Tiger F-75s
 

Those lugs with holes is for threading the engine on a string and wear it around your neck. It's very bling ya' know..
Love that black muffler... It looks killer

RE: Thunder Tiger F-75s
 

Mine looks absolutely beautiful, the machining is on par with any other engine I've seen. The first few tanks were 15% with an APC 12-8. Interestingly their break in procedure is very similar to Saito's. After two tanks I was getting 9500 and 2300 idle. I got roughly the same RPM's with an APC 13-6. Mounted in my Revolver and flew it. After about the fifth flight the engine suddenly came alive. Am now up to 10,000 and 2100 idle. I am hoping the RPM's will rise and fall a little bit with the next few tanks. I love the lower profile which is why I used it instead of my Saito 72. The 72 would have required major hacking of the cowl, the TT did not, although I'm not afraid to use the Dremel to ensure adequate cooling.

RE: Thunder Tiger F-75s
 

I'm scratching my head about this one.

Is it the very latest version of the motor?

I have a local magazine from the middle of last year with a review of the TT .75 and the reviewer goes in depth about the new lubrication system in the motor which reads like the new OS Alpha series. He describes it as a sealed system with no crankcase vent.

RE: Thunder Tiger F-75s
 

Mine is new, from the US distributor for TT. The crankcase vent is on the backplate, it's not a sealed system. Unless TT has an even newer engine in the works I don't know what he is talking about. Mine looks like Ed Moorman's pics.

RE: Thunder Tiger F-75s
 

What a beauty!
While it may not appear so, I'm thinking this engine is based on the 54 design. My reasoning is that the stroke is exactly the same between the two. Same crank?
Since this is a 'short stroker' I would guess that it should be able to swing a pretty big blade with authority but at a slightly reduced RPM. I am correct in thinking that a short stroke engine will produce a greater amount of power at lower Rs than the same bore with a longer stroke... right? Greater low end power.(?)

I really like the nice engineering changes that were done to this one! I wonder if all of their 4 bangers got or will get a re-vamp..?

I wish I had more money and time!

RE: Thunder Tiger F-75s
 

Jazzy, usually we think of long stroke engines as torquers and low end engines. The big bore, "over square" engines are normally thought of as high rpm engines.

The TT F-75s appears to have the bore of the .91 and the stroke of the .54. This is very over square.

RE: Thunder Tiger F-75s
 

Thunder Tiger showed this engine in 2005 at the iHobby Expo. It has taken a long time to go into production. They gussied it up a bit with the black muffler and machined fins.

RE: Thunder Tiger F-75s
 

Thanks Ed, I guess I had it backwards. I can see how the shorter stroke will allow for high Rs.

Wow! upon closer examination it does look like they put the 91's piston on the 54's crank and rod!

Can anyone compare the three engines side-by side or at lest one of the other two? It would be interesting to see how it's profile height compares to the others.

Very interesting...

RE: Thunder Tiger F-75s
 

I just measured all of mine. Two were mounted, but I took the distance, which I thought significant, from the bottom of the mounting lug to the top of the valve cover. This is how high it will stick up when mounted in a plane. The TT, which has a short stroke, may be shorter on the bottom, making you think it might clear a cowl, when it wouldn't.

Thunder Tiger F-75S 3 3/8"
OS .70 Surpass II 3 3/4"
Saito .72 3 5/8"

The TT is 1/4" shorter than the Saito and 3/8" shorter than the OS. The OS is definitely a bigger and heavier engine. It does run very well, as all my other OSs do.

RE: Thunder Tiger F-75s
 

I got a chance to put a few more bench runs on the F-75S. My tank is an old tank from an ARF or somewhere. I think it is 6 or 7 ounces. I ran 2 tanks before using an 11-8, as specified in the TT instructions. This afternoon, I ran one more on the 11-8 and switched to an APC 13-6, which is what I usually run on a .70 size 4-stroke. I ran 2 more tanks on the 13-6, making a total of 5 tanks through the engine. The highest rpm I saw was 10,100. This is with an OS F plug and 10% Omega castor blend fuel.

It should gain some more rpm. I know that Saitos may take a couple of gallons to really come in and I understand that Thunder Tigers do, too.

RE: Thunder Tiger F-75s
 

I was going to run it some more on the bench, but Flaps is putting together a Neptune seaplane for me and called up and wanted the engine. I had to take it off the bench, clean it up and get it over to him. I'll have to try other props on the plane. I did want to try an APC 14-4W and I have one in the package, ready to mount.

RE: Thunder Tiger F-75s
 

Handsome engine, Ed. I was pleased to read that it comes with some tools too.

jess

RE: Thunder Tiger F-75s
 

Here are a couple more photos, one on my test stand and one with the wrenches. The large wrench is for the muffler & prop nuts. The smaller on is for the valves. It also comes with 3 hex wrenches. It's a very nice package of tools.

RE: Thunder Tiger F-75s
 

That is one handsome engine.

It is nice to see a reasonably priced alternative to O.S. and Saito, if you want something a little more finished than a Magnum ..

RPM figures please!

RE: Thunder Tiger F-75s
 

These are the figures that a local reviewer achieved.

All props are APC using 10% Nitro, 20% Morgans Coolpower Oil.

12x6 11,100
12x7 10,600
12x8 10,000
12x9 9,600
12x12 7,800
13x6 10,400
13x7 9,900
14x6 8,500
14x7 7,500