Thunder Tiger 21 Question.

[Colin Anderson]

I bought this recently at Wings 'N' Wheels. Unfortunately I didn't notice at the time but the bolt and, presumably the spring that retain the throttle barrel were missing. Does anyone know where I might aquire one or, failing that, what the bolt size and thread are? I'm aware that the end of the bolt would have a reduced diameter to engage in the throttle barrel's slot. I've tried contacting the manufacturer, but they can't help without a part number; I asked RipMax also, as they show something similar on their website. In addition, what would the prop size be? And yes, I realise that this has a car head fitted, but I'm assured it will be fine in a plane. I also have a Thunder Tiger 20 and I presume this would use roughly the same prop range?

[Richard Wills 2]

If it is a car 21 motor, I can't see any pics, they are ported to run at very high rpm, up to 30,000, making it pretty much useless in a plane. The prop would have to be tiny.......

[Colin Anderson]

Thanks, Richard. I aquired both a 20 and a 21. As the the 21 appears to be in much better condition - at least outwardly - I'd planned on using it in a 48" Tiger Moth I'm building. I hadn't realised that it's ported differently; does this mean then that it incapable of running at lower revs? The motor is definitely a 21 and has a larger head - presumably to aid cooling. By any chance would you know the prop range for the 20. Strange that the images don't show.

[Denis Watkins]

A short M3 bolt or cut down M3 will do the job, but some were M2

The model, model weight and fuel count too as to decide a

8 x 5, 9 x 4 -- 9 x 6 prop.

Giving acceleration on the ground, or in the air as required by a vintage style or an aerobat

Start with the 9 x 4 on the Tiger, with a steady tickover as well as full needle being the indicator that the prop is close to the correct selection

 

Edited By Denis Watkins on 11/08/2018 20:18:02

[Colin Anderson]

Thanks Denis. Here are the images of the Thunder a Tiger in question .

[Colin Anderson]

Richard. I've managed to put the images up.

[Mike Etheridge 1]

As my local butcher knew I flew model aircraft he asked me if I could assist him in starting his two IC /RC cars he had bought from new and could not get them to run properly. With a great deal of confidence I accepted the challenge some weeks ago. The cars are still in my garage and have been an absolute nightmare to date. One of the cars has a Thunder Tiger 21 engine with a pull cord start and the other larger car has a Thunder Tiger engine also but with a drill shaft starter arrangement. I have managed to start both cars with great difficulty and neither have run consistently. The Thunder Tiger engine with the pull-cord start has played havoc with my arthritic fingers and last week the cord broke as did the pull cord return spring. I have managed to repair both the cord and the spring but have warned the butcher that the car needs a new pull cord / spring at £17. He paid me for my efforts with two large pork chops which my wife and I had last Friday. Prior to that he gave me half a dozen kebabs ! The drill start motor runs OK until you remove the glow starter. The engine has a metal throttle assembly whereas the smaller 21 engine throttle is made of some form of plastic. I intend to have one more attempt at starting the larger engine and will leave the glow starter connected and hopefully run the engine in.

Your pictures have not come out Colin!----They have now Colin and the throttle does look like the car engine type, and I would contact 'Just Engines' and get them to provide you with a replacement throttle (s)

 

Edited By Mike Etheridge 1 on 11/08/2018 20:25:32

Edited By Mike Etheridge 1 on 11/08/2018 20:28:05

Edited By Mike Etheridge 1 on 11/08/2018 20:29:31

Edited By Mike Etheridge 1 on 11/08/2018 20:31:23

[Denis Watkins]

Easily make that bolt Colin

Run in an M2 carefully just to establish the thread

With a dremel, reduce the end to produce a smooth pin

And get a spring on there from the scrap box

Alternately most carbs carry one of these bolts, so pick up a spares or repair from the auction site

[Colin Anderson]

Many thanks, Richard and Denis. Both answers are of great help. 👍😊

[Richard Wills 2]

Colin,

That motor is early 80's as used in the Thundertiger challenger 83. It was not one of the modern high revving motors, rather an aero engine with a different cooling head. most likely be more than OK in an aero application.

[Colin Anderson]

Thanks Richard. That is indeed encouraging news.

[onetenor]

I would try hotter plugs in them.

[Colin Anderson]

Thanks. Got to get the throttle operational first, then I'll see if and how it runs with whatever it currently has fitted.

[Keith Berriman]

Looking at the shortened shaft I would think as others it's a car engine. Years ago that's what I used to do on my expensive Rossi 21

[onetenor]

Oh yes swap that heavy head for an Aero one

[Keith Berriman]

Comment deleted

Edited By RC Plane Flyer on 12/08/2018 15:23:29

[Colin Anderson]

Yes, it is a car engine, but I'm given to understand that it's fine as an aero engine too. It does have a slightly bigger head - for more efficient cooling in a car, I presume - it also has a pulley on the front. I have both this and a 20; however, the 21 is in as new condition (apart from the missing throttle screw) so I'd prefer to use that, as I believe the capacity is very slightly bigger. Once I've sorted out the screw I'll run them both on the bench to assess them before making a final decision.

[Mike Etheridge 1]

These are the pictures of the car Thunder Tiger engines I have been struggling with. The first picture is of the drill start motor, the last four are of the pull-cord start motor. They are obviously more up to date motors than Colin's and both cars have 2.4 GHZ radio.

Edited By Mike Etheridge 1 on 12/08/2018 19:02:34

[Colin Anderson]

Definitely more modern than mine, Mike and slightly bigger capacity, going by the 28 on the crankcase; but thanks for posting.

[Colin Anderson]

Okay, following suggestions I tried an M3 bolt in the hole - way too small, so an M2 will won't work either. Size appears to be very close to M4, but this will not screw in and I'm not inclined to either force it or tap it out - Sod's law says that I'll find exactly the right part once I've done so!

What is interesting is that, if I unscrew the needle valve and screw that into the hole it screws in perfectly. Examining the threaded shank of the needle it's the same size as an M4, but to my eye has a slightly finer thread. If I can find out what this thread is I'll be a lot closer to making up something that'll work

[Dave from the future]

M4 would normally be 0.7mm pitch, M4 fine would be 0.5mm - could that be it?

Dave.

[Colin Anderson]

That's what I like about this hobby, I'm always learning something! Up until now I thought M4 was just M4! I never realised that there was an M4 fine. There's an easy way for me to find out. There's a little place on the Slough trading estate that seems to have almost any bolt you could think of - it's an Aladdin's cave of bolts and fasteners; at least it is to me. I'll go there tomorrow and see if they've got any; if they have and it fits, you might just have solved this! Cheers Dave. I'll also be checking with just engines, on the of chance that they have the actual part.

[Denis Watkins]

There is M3.5 too Colin, if M4 is too big

[Colin Anderson]

Yeah I noticed that, Denis and that comes in course and fine too. This is an education. If just engines can't help, I'll get onto apex fasteners in Slough.

[Dave Hess]

As far as I can see, that screw is identical to the one in an OS 30LA.