Violent Thunder Tiger

[Bucksboy]

Merco,

In my loft there is my TT that suffered crash damage and the carb snapped off in a crash. I'm sure it's the 130 but is possibly the smaller one, it's been up there 3 years which is why I'm vague. It ran perfectly prior to the crash, the cost of repairs equalled buying a new one so I just hoarded the useless broken bits. Except now I can send them to you and you can do what you want with them, compare them, strip them, take bits, whatever you want. It really is no good to me.

You will have to wait a bit though, I'm abroad for another couple of weeks. That is unless it's all solved before I get back. I'll PM you when I'm nearer to home.

[cymaz]

I had the TT 130 for several years. Even out of the box it was a good motor, ( piston skirt excepted). Never threw a strop. I noticed on running it in the pipe from the carb to the head used to get quite cold. On a warm day condensation would form readily.

I did put an extra head shim in.

Edited By cymaz on 05/09/2017 17:07:55

[Merco 61]

Its very nice of all of you to show an interest,I appreciate it very much.These engines were mass-produced probably in considerable numbers on CNC machines so a fundamental design error should not be possible.I repeat,the quality and internal fits are quite amazing and there really seems little scope for errors in final assembly.Its had about two hours running now,albeit,at low to moderate revs and pretty rich.Dont think it would have managed this if something was too far out mechanically.It appears to be a short stroke,perhaps even over-square but I lack the skill to prove this.Initially the compression/resistance was excessive but this has improved ,as has the addition of an extra shim.Thanks Cymaz.I have been cutting some more rings this evening.Wanted more accuracy than compass cut,so did it this way:Cut a piece if 1/16 birch ply,then Evostik two similar sized pieces of litho plate to make a three layer sandwich.Centrepop with small sharp tool and mark out with scriber in metal compasses.You then get a really fine guideline.Then used my finest (000) piercing saw to cut out ring. Finish edges with wet and dry,immerse in a saucer of acetone which will quickly float the wood and litho apart.No ragged edges or buckling and annealing not necessary.I,ve done similar in the past on my little lathe using copper shim,but sawing is almost as accurate and a lot easier to mark out.As far as throwing the prop: this really has to be a backfire/pre-ignition,which in a non-retardable engine has to a weak mixture. doesnt it? I will persist,and with your help,how can we fail?Cheers for now.

Look forward to hearing from you Bucksboy.

[Martin Harris - Moderator]

I can't remember if you've covered this but the glow plug gives a form of automatic timing - are you using an OS F plug or something else?

Did you ever check the cam timing and are you sure it was exactly at TDC?

[cymaz]

 

 

Is it possible ,now, setting the needles from scratch? This is pretty good if you can't remember the original settings.

It is quite easy to get the timing one tooth out. The dot has to line up correctly 

Edited By cymaz on 06/09/2017 05:24:55

[Bob Cotsford]

Maybe just a daft thought, but here goes. As you say it's normally a weak mixture that causes the prop to kick off and you do say you are running it rich. You also say that it has very good compression.

If it's running too rich, would it be possible that a hydraulic lock is forming with unburnt fuel remaining in the cylinder? Have you tried leaning it out yet?

[Jon H]

A trick i used to use on nitro cars with pullstarts was to slacken the glowplug slightly to allow a little gas to escape. This decompresed the engine a smidge and put less load on the pull start which was very high when the engine was brand new. Could be worth a try, just give the thing some space as the plug will fly out like a bullet from a gun if you let it come out all the way with the engine running

[Shaunie]

Bob has got there before me but I was wondering whether an excessively rich mixture is causing en excessively high compression ratio which is causing the pre-ignition. Whilst a lean mixture can cause detonation and excessively rich mixture can cause similar symptoms You may have got yourself stuck in an "It's detonating, need a richer mixture" loop.

Shaunie.

[Merco 61]

Hello,

Some very good advice,all taken on board. Progress so far.Cut two new shims from litho,timing checked again,tappets set,stronger spinner fitted.new heavier clunk filter(sintered) tank level raised ,no pressure to tank.OS 3 plug.Instant start,steady idle about 2000,open up to full and ran the tank out.Plug connected throughout.Repeat but motor slowly slowed and stopped at about mid throttle without power to plug,not overly worried by this,will try a few different 4str plugs.The engine is quite a different animal now,quite benign but still turns the 16x6 at 8300 which is adequate for intended model(s) and is noticeably quieter.Still a tendency for prop to slip a few degrees when the starter is applied but this,I think is due to my leather washers bedding in.I think they afford a little shock absorbing so no bad thing in case of any further detonations so kinder to the con rod. Best of all,the prop stayed put!! Still some fine tuning to do but may yet come to like this engine.If the pictures attach,hopefully will show the shims and two models for the engine.P51 is based on the Galaxy kit but with home made cowl,Stuka is from John Carpenter plan.

Thanks to you all

Cheers for now

[onetenor]

I'm glad things are improving but hate to say it .We told you so

[Engine Doctor]

hello Merco 61. Looking at your pic of cyl head. The glowplug looks like its protruding into thr combustion chamber ! They are generally recessed just below the surface and this could be causing the advanced timing and prop throwing. The other thing I notice is that the prop nut are on the crank the wrong way round ! the smaller nut with the tapered end is the lock nut that should go on second , unless you have just put them on like that for the pic. Re the dying in mid tank , try re connecting the exhaust pressure tube . . Hope you get it sorted .

E.D.

[Jon H]

The A3 plug is quite hot and intended for 2 strokes so that could be contributing to the problem. I would also not recommend glow power being applied beyond getting the engine started as this will overheat the plug and could cause the detonation issues you have been seeing.

If you havent already try the OS F plug and see how you get on

[Jon H]

Well spotted ED, the nuts are back to front

[graeme jones]

The exploded diagram in the Thunder Tiger 4 stroke instruction booklet shows the nut with the slots fitted first and that's the way they come out of the factory.

Graeme

[Denis Watkins]

Please say

Those lock nuts were not holding the prop that way !

[graeme jones]

As I said in my first post on this thread, I had exactly the same problem some years ago with a TT91FS. It doesn't matter which way round you fit the nuts. I tried both and they still come off, with the prop, still locked together as one unit. Fitting an OS nut set stopped the prop parting company with the motor, but the prop still came loose. The idea of the fuel mixture being too rich can't be right either, as a read of the TT running-in procedure should suggest - "Because of the extremely rich needle setting used during break-in, you may be required to keep the glow plug igniter attached".

My belief is that the metal of the prop driver is simply too soft for the job, the serrations squashing flat as soon as the nuts are tightened. Re-cutting them won't help, they will just squash flat again. My LMS did try to get me another driver from Amerang, but they were never in stock. Perhaps the solution is to fit a driver from another manufacturer, if one can be found to fit.

By the way, I have a pair of TT52FS's which do not have this problem. Their drivers seem to made from a much harder alloy, the serrations being as good now as when they were made.

Graeme

[cymaz]

• Go back to the OS F plug
• Re install the pressure feed to the tank
• Re set the carb needles
• Good luck and my best wishes

[Braddock, VC]

Thanks for posting, TT 130Fs engines now worthless, I fancied one but my bargepole is too short.

[Engine Doctor]

Posted by graeme jones on 07/09/2017 09:06:59:

The exploded diagram in the Thunder Tiger 4 stroke instruction booklet shows the nut with the slots fitted first and that's the way they come out of the factory.

Graeme

Then the diagram is wrong. Large countersunk nut on first then the smaller split taper nut fits into the countersunk nut and if the larger but tries to undo it compresses the tapered nut and grips the shaft thread tighter to stop it loosening. This could explain everything ! I agree with you comments on the soft prop driver though 

 

Edited By Engine Doctor on 08/09/2017 09:57:42

[Engine Doctor]

Posted by Braddock, VC on 07/09/2017 17:03:23:

Thanks for posting, TT 130Fs engines now worthless, I fancied one but my bargepole is too short.

They could join the likes of MDS ,Flash ,remember them? And a few others that make excellent fishing weights or door stops

Perhaps a little harsh as I have used some fine running TT and MDS examples(not many) over the years but the Flash (nasty copy of OS 35 FP) were usually clapped by the time you had run the first tank through them .

Edited By Engine Doctor on 08/09/2017 10:01:55

[Martin Harris - Moderator]

I've never owned a TT four stroke but I do recall having starting problems with a pupil's who used a 91 in a large Frontier trainer. This would throw props on a regular basis when starting and the only way to start it reliably was to apply the glow after the engine was spinning on the starter. I suspect that TT run a higher compression ratio than the other OS clones in an attempt to boost power.

I'm not sure that the split flange nut isn't equally effective both ways round as any movement of the combination in either orientation will allow the prop to slip - i.e. the locking relies on compression of the flange onto the thread to prevent any movement - and all pictures/diagrams published by TT that I've come across show it the "wrong" way round. OS and the other clones have flanges on the larger nut for the drive washer so cannot be used in the TT orientation but reversing it was one of the first things we tried with the 91.

I'd be interested to know what plug (if any) is supplied with the engine?

Edited By Martin Harris on 08/09/2017 10:16:32

[Braddock, VC]

I had a perfectly good mds 48, as long as the fuel was 0% nitro and castor based it ran fine, fwiw moki react in much the same way, iron curtain countries couldn't source nitro and their oil technology is/was prehistoric. I actually sold it for almost the same I gave for it. I also had a flash 35 silencer that eventually fitted my enya 35 and it actually quietened the enya down considerably.

FWIW I think the TT 42 GP is the best engine of its type anywhere, I have 3 or 4. The only problem is the carb retention method which is rubbish.

I had a tt 91 4s and that was a goodun too but the thought of incessant prop throwing seems to me like a send it back job as there is clearly something wrong that the massed might of this forum cannot get on top of.

Edited By Braddock, VC on 08/09/2017 10:20:36

[Braddock, VC]

I'd like to qualify that statement about tt 42 gps, I have only ever had one enya and that was pretty good but I have never been in a position where I could compare the 42 gp with one of the enya plain bearing 40 sized engines. I think enya is also king of the air bleed carbs so they are probably up there with the best.

[Ken Lighten]

Graeme's right, just checked my TT four stroke book and it does indeed show the nuts assembled in the wrong order in the exploded view!!

Graeme, if you look at the photo of the engine on the booklet cover it shows the correct assembly order - at least it does on mine!

Ken

[Engine Doctor]

Posted by Braddock, VC on 08/09/2017 10:28:03:

I'd like to qualify that statement about tt 42 gps, I have only ever had one enya and that was pretty good but I have never been in a position where I could compare the 42 gp with one of the enya plain bearing 40 sized engines. I think enya is also king of the air bleed carbs so they are probably up there with the best.

The Enya 40 ss PB engine will run rings around a TT 42 . Only downside with Enya is that their mufflers are a bit barky. The Flash did do something right with their silencer then