"1/2 A" & "1/8 A" airplanes These are the small ones...more popular now than ever.

Close look at GP .07 Thunder Tiger

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Old 12-21-2007, 11:25 AM
  #51  
GrahamC
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Default RE: Close look at GP .07 Thunder Tiger

It is an apples oranges comparison the Norvel 074 to the TT GP-07. The Norvel has a longer stroke than the TT so by that should be happier with a larger prop. The TT 07 stroke is pretty much the same as the Norvel/AP 061 engines - 10mm. That would indicate to me that it should be happier swinging smaller diameter props which a user report by Randy Randolph also suggested.

There are many 07 size car engines about all to a one being made in the far east. In the very first post of this thread the insides of the TT GP-07 reminded me of some of the bits out of car engines that I have seen. Makes me wonder if TT took the guts from a car 07 and purpose made a crankcase for plane use.

I still think the GP-07 is capable of more than what most have been seeing and would respond to some simple tweaks and fitting. I am still looking for a used one to hack into but haven't had any luck - even on that big auction site. (donations to the "Lets see what we can turn the TT GP-07 into" project are always gratiously welcome.)

cheers, Graham
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Old 12-21-2007, 02:40 PM
  #52  
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Default RE: Close look at GP .07 Thunder Tiger

Right on Graham, see below.

================================================== ================================================== ===========================

GP .07

Specification:
Displacement: 1.13 cc. / 0.069 cu. in.
Bore: 12.0 mm. / 0.472 in.
Stroke: 10.0 mm. / 0.394 in.
Crankshaft: M4x0.7
Practical RPM: 3,500 ~ 24,000
Output: 0.20 BHP / 18,000 RPM
Weight: 95 g. w/muffler / 3.35 oz.

================================================== ================================================== ===========================

Norvel .074

General Specs:
- 1 cylinder
- Displacement: 0.074 cubic inches
- Bore: 11.7 mm
- Stroke: 11 mm
- High RPM: 22000
- 0.380 bhp @ 22000 RPM
- Weight 2.65 oz.

================================================== ================================================== ===========================

I've been able to stuff .09 parts into the MP Jets .06 and have just done the same with a Norvel .06
This makes both of them short strokes compared to the original.

With the GP 07, already a short stroke, we don't have much room to play with.

One fairly certain way to gain 1.5K, from my experience with the Brodak/CS engines, is to install an insert taking a turbo plug. Or, if you can find one, a Norvel .074 glow insert ought to do the same.

I've been told by Great Hobbies that the GP .07 is discontinued and parts will be in short supply down the road. I have a couple of rods on the way to see if they can be adapted to the Norvel .074
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Old 12-21-2007, 09:42 PM
  #53  
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Default RE: Close look at GP .07 Thunder Tiger

I have been thinking about auctioning mine off on the Bay.

Mainly because I went with a used Norvel .061 on my Sig Hummer and don't want to experiment with the GP.

I'm thinking $45.00 plus shipping would be a good deal for someone.
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Old 12-21-2007, 10:18 PM
  #54  
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Default RE: Close look at GP .07 Thunder Tiger

It makes no sense to have over 3 ozs worth of metal that can only turn a 6x3 @16,000. For the same amount of weight invested you could have 2 Cox .049s mounted side by side turning the same prop twice!
If your engine has a wobbly crank, $45 might be asking quite alot for a piece of junk.
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Old 12-21-2007, 10:36 PM
  #55  
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Default RE: Close look at GP .07 Thunder Tiger


ORIGINAL: combatpigg
If your engine has a wobbly crank, $45 might be asking quite alot for a piece of junk.
CP,

For all I know they might all have wobbly cranks? It was that way out of the box.


I really need to send it in to see what TT has to say about the crankshaft clearance.
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Old 12-21-2007, 10:41 PM
  #56  
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Default RE: Close look at GP .07 Thunder Tiger

This isn't the first time I've heard of a low time TT.07 with enough wobble to be noticeable. If TT can help with a better fit engine, that would not only be good for you but also good for their reputation.
These engines remind me of the cheap Testors/McCoy .40s that would run pretty good for awhile, then almost instantly develope the loose crank/dead piston disease.
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Old 12-22-2007, 02:06 AM
  #57  
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Default RE: Close look at GP .07 Thunder Tiger

My guess is this mystery wobble is just a result of the natural resonance of the engine, as soon as the RPM's match this frequency a vibration is produced.
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Old 12-22-2007, 02:13 AM
  #58  
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Default RE: Close look at GP .07 Thunder Tiger

No, if you can take a propped engine in your hand and work it enough to produce a noticeable amount of side play, then there is no mystical stuff going on........the fit is too loose. If you can force air bubbles out the front end during a mild pressure test, then the engine is shot and will never be an efficient air pump.
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Old 12-22-2007, 08:34 AM
  #59  
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Default RE: Close look at GP .07 Thunder Tiger

Hey combatpigg, i used to have an electric plane that used a 4oz speed 480 motor and a 5oz battery pack that would barely turn a 6x3 at 16500 so my TT.07 is looking pretty good compared to that. As for the crank problem i noticed that my propnut was not tapped straight and requested anther one from ACE hobby, i guess if most people didn't check this and ran their engines that there would be lots of extra vibration that could lead to the problems of the side play they are having.
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Old 12-22-2007, 08:47 AM
  #60  
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Default RE: Close look at GP .07 Thunder Tiger

ORIGINAL: 1705493-AndyW

I've been told by Great Hobbies that the GP .07 is discontinued and parts will be in short supply down the road. I have a couple of rods on the way to see if they can be adapted to the Norvel .074

Another one bites the dust.

Kind of sad actually even though this one is not that great. Did they actually have the rods in stock or did they have to order them? If they will be a good or even very close substitute I will have to get a couple. A button for turbo plugs would be dead easy to make.

If the TT GP-07 is discontinued I think I will stay away from it then. I was considering playing around with them only because they were available.

There seem to be few choices in 07 or .95CC size engines for the car crowd. Here is one marketed by Trinity:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXMYK5

And Trinity is not the only one with these size of engines. I have stumbled across at least a half dozen different brands / sources / manufacturers. They all look pretty much the same and all originate from the far east. Many familiar names too, Ofna/Picco, Toki, SC etc. I should have kept the links to the many web sites I stumbled over, I guess I will have to go looking again.

I am still a bit confused when looking at some of these engines however. I though .061 was 1CC not .07 = .95CC - Depends I suppose whether you use the new Metric Math or old Imperial Math

Looks more like a traditional model engine than the GP-07. I couldn't find bore/stroke/weight info but I am sure it is much heavier than the Norvel 074. Twin ball race however. The car guys are a little less concerned about the weight and they also want the power to peak much higher up in RPM.

Now, the Trinity 095 is about the same price as the TT GP-07, and would need more mods to convert to plane use. I wonder how much weight could be removed by removing all of the extraneous mounting points etc. And for that matter, what about replacement parts - rod piston etc Would they be a suitable replacement for aging Norvel 074 engines?

cheers, Graham


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Old 12-22-2007, 12:46 PM
  #61  
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Default RE: Close look at GP .07 Thunder Tiger

Microsprint, I'm not a machinist but have made a few spinner nuts. I don't see how that process can go wrong. What I have seen were props that did not have squared hubs and would force a spinner nut to sit cockeyed when tightened.
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Old 12-22-2007, 01:21 PM
  #62  
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Default RE: Close look at GP .07 Thunder Tiger

When i called ACE hobby they had said they were having problem with the prop nuts on the .07 and mine was way off. I guess they were shaping the cone first and they had some kind of jig to hold it while tapping it. If it were me i would drill and tap it first and then shape the front. I'm going back to my shop on boxing day to give this engine another run and see what i can do to get some more RPM's out of it, i will also weigh the muffler as it seems it's much larger than an AP .061 muffler.
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Old 12-22-2007, 01:52 PM
  #63  
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Default RE: Close look at GP .07 Thunder Tiger


ORIGINAL: GrahamC

ORIGINAL: 1705493-AndyW

I've been told by Great Hobbies that the GP .07 is discontinued and parts will be in short supply down the road. I have a couple of rods on the way to see if they can be adapted to the Norvel .074

Another one bites the dust.

Kind of sad actually even though this one is not that great. Did they actually have the rods in stock or did they have to order them? If they will be a good or even very close substitute I will have to get a couple. A button for turbo plugs would be dead easy to make.

If the TT GP-07 is discontinued I think I will stay away from it then. I was considering playing around with them only because they were available.

There seem to be few choices in 07 or .95CC size engines for the car crowd. Here is one marketed by Trinity:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXMYK5

And Trinity is not the only one with these size of engines. I have stumbled across at least a half dozen different brands / sources / manufacturers. They all look pretty much the same and all originate from the far east. Many familiar names too, Ofna/Picco, Toki, SC etc. I should have kept the links to the many web sites I stumbled over, I guess I will have to go looking again.

I am still a bit confused when looking at some of these engines however. I though .061 was 1CC not .07 = .95CC - Depends I suppose whether you use the new Metric Math or old Imperial Math

Looks more like a traditional model engine than the GP-07. I couldn't find bore/stroke/weight info but I am sure it is much heavier than the Norvel 074. Twin ball race however. The car guys are a little less concerned about the weight and they also want the power to peak much higher up in RPM.

Now, the Trinity 095 is about the same price as the TT GP-07, and would need more mods to convert to plane use. I wonder how much weight could be removed by removing all of the extraneous mounting points etc. And for that matter, what about replacement parts - rod piston etc Would they be a suitable replacement for aging Norvel 074 engines?

cheers, Graham

I, too, am a little interested in the small Trinity, but the info in the Tower ad is really confusing. No bore, no stroke, "bore size" given as a cubic measurement, & contradictory cc-to-cu in info. Other sites on the web list the same generic confusing information. Anybody have any real info as to what size & weight this engine really is? Anybody try to convert to aircraft use? ................. George K.
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Old 12-22-2007, 01:58 PM
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Default RE: Close look at GP .07 Thunder Tiger

That is the most bass-ackwards way to make a part that I've ever heard of! Can you think of a simpler job than making a spinner nut?

I guess hitting the button that looks like a BigMac at the McDonalds cash register is a simpler job, but you know what I meant
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Old 12-22-2007, 05:27 PM
  #65  
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Default RE: Close look at GP .07 Thunder Tiger

That's what happens with cheap labour or maybe it was piecework, i will say that the PRO .46 and PRO .36 that i have are great.
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Old 12-22-2007, 06:01 PM
  #66  
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Default RE: Close look at GP .07 Thunder Tiger

Yep, TT has some pretty great and low price engines that really scream. I wonder what % of the total market share their .46 has? I'll bet it ranks very high in popularity.
I like the idea of their .36 to power some .25 sized warbird kits.
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Old 12-23-2007, 02:17 AM
  #67  
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Default RE: Close look at GP .07 Thunder Tiger

So please tell me what have we been able to learn from this thread ? I myself think the TT .07 is really nice looking and if the power to weight issues could be overcome perhaps it could be useful. Can I ask what is the limiting factor behind it's apparent lack of power and what can be done to it to improve it? Bigger carb? different timing? better ports? How much power would if have to make before it was considered acceptable? Could it be put on a diet? run lower compression and use 30% nitro? Ball bearing crank? Who among us has the capability to work out these limitations? If the engine is being discontinued this is all moot but I think you get the picture. I myself have a 325 hp Mustang but I know how to get more out of it. Who can "fix' the 07? Please. Anybody. JOE [8D]come on you know you want to. I recently have been delving into the inner workings of a lot of different engines lately and I think I can see room for improvement but I do not have the facilities to implement them.
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Old 12-23-2007, 09:22 AM
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Default RE: Close look at GP .07 Thunder Tiger

1st is Great Planes discontinuing the GP 07 or is Thunder Tiger discontinuing their engine?

Just because GP says it's being discontinued doesn't mean TT is getting rid of it.

I just wish TT would make a few minor changes to improve their engine. An example is they could stroke the crank very easy during the machine work. It's also been sugested that raising the cylinder sleeve improves port timing, and that could be done at the factory easily enough.

I am planing on making some cylinder shims to try on mine, plus making sure the case casting is lined up with the ports.

Right now I am concentrated on completing my Sig Hummer.
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Old 12-23-2007, 10:53 AM
  #69  
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Default RE: Close look at GP .07 Thunder Tiger

Scoot on back to October when Cat 1 gave his "tuning" procedure for the TT 07.... that's in 966230 post # 15. He claims 10 minues with the dremel can improve things Greatly.
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Old 12-23-2007, 12:10 PM
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Default RE: Close look at GP .07 Thunder Tiger

Here's an idea...

Having little to no experience in 1/2A, maybe TT timed their little .07s in a similar manner as their larger counterparts. When they ran them and got a reliable runner they said "ship it" - not knowing that the smaller engines really need a much higher HP/weight ratio than their larger cousins. (i.e. with no regard to maximun output) Sounds like a little work with a Dremel would improve breathing greatly.

But isn't this really a moot point? I mean if they're being discontinued...

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Old 12-23-2007, 12:29 PM
  #71  
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Default RE: Close look at GP .07 Thunder Tiger

......HP to displacement ratios of .05 engines compared to .50 engines is about the same in most cases that I've noticed. Thunder Tiger probably uses the .074 as their "training engine" for new employees to practice on?

Even though TT is capable of much more, they are running a business.
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Old 12-23-2007, 01:30 PM
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Default RE: Close look at GP .07 Thunder Tiger


ORIGINAL: combatpigg
......HP to displacement ratios of .05 engines compared to .50 engines is about the same in most cases that I've noticed.
Whaaaat? .380 HP for an .074 ci engine is the same ratio as 1.5 HP for a .45? Someone help me with my math here, but that doesn't sound quite right. Wouldn't that be like 5 HP / ci for the little Norvel and about 3 HP / ci for the average sport .45?


(CP I respect you, your knowledge, and your accomplishments greatly - I only ask for clarification.)

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Old 12-23-2007, 02:04 PM
  #73  
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Default RE: Close look at GP .07 Thunder Tiger

The .074 actually makes less than .38HP. I measured my diesel at 105W at 11,000RPM . And the posts I've seen here indicate that it makes just as much on glow at 17,000. So that's about 1.9HP/ci.

I posted this in another thread. This is something I wrote a while back.

http://www.maxxprod.com/mpi/tips3.html

The Watts/Lb in the engine listing should be Watts /cubic inch. This is based on many engine reviews at useful RPM not peak ratings.

A sport engine is closer to 1.7HP/ci. A good bearing engine is 2.4HP/ci.
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Old 12-23-2007, 02:37 PM
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Default RE: Close look at GP .07 Thunder Tiger

PBJ, I think .38HP from the .074 is a bit optimistic. My overall impression after looking at dozens of run sheets is that a typical .05 TD puts out about .12HP, a .10 about .25HP, a .15 about .4HP and a .45 puts out about 1.2HP, which is pretty proportional. There are extreme examples that invalidate these rule of thumb figures, but they aren't the norm.
I think what you were saying earlier was that TT didn't have high enough power goals for their .074 before going into mass production? If so, I think that is an understatement.
If this engine was worthy, it would have grabbed up the huge vacuum that was left by Norvel and made a real good run with that. This forum would have been filled by now with great threads about TT.074 projects instead of what we actually have, which is for the most part just a huge vacuum.
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Old 12-23-2007, 03:12 PM
  #75  
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Default RE: Close look at GP .07 Thunder Tiger

Car motors?
Every time I look at car engine, I see a giant heat sink that needs some hacksaw attention, and a micro-stub of a front case that wont let a prop clear the carb... because they stick that carb out plenty far over where they expect just a pinion gear/clutch.
.... and what kind of prop are we gonna run on a 35k .074 engine? That sounds sooooo not MAS 6x3.

I just dont get why TT did it.
Norvel made an 074 with the power of a .10
and now we hear that TT made an 074 with the power of an 049
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