Colin Anderson Posted August 13, 2018 Author Share Posted August 13, 2018 Well just engines "might" be able to help, but it would require me to send the throttle assembly to them - with our wonderful postal service? Er no. 9 times out of 10, it'll be fine, but that one time..... Contacted Ripmax to see if the pro 21 throttle stop screw assembly might fit the bill - they didn't know and haven't had them in stock since 2013! Still on their web site though! Okay, off to Apex fastners (Slough) to see if they might have M4 fine bolts of any kind - Nope. Now I'm back to square one. I know for sure that the thread is definitely M4 fine, but finding some in this country is proving difficult. I did find one place, but come on, £6.70 for one! Quote Link to comment Share on other sites More sharing options...
Colin Anderson Posted August 13, 2018 Author Share Posted August 13, 2018 Sorry Dave, managed to miss your comment! I'll check that lead out. Thanks. Quote Link to comment Share on other sites More sharing options...
Colin Anderson Posted August 13, 2018 Author Share Posted August 13, 2018 Couldn't find one, Dave. Do you have a link? Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted August 14, 2018 Share Posted August 14, 2018 This chart makes me think that we are not looking for an M4 Chris **LINK** Am going flying, but later will find you a bolt and send it PM me an address Quote Link to comment Share on other sites More sharing options...
Colin Anderson Posted August 14, 2018 Author Share Posted August 14, 2018 Many thanks, Dave. I followed the link and sent them a message. Quote Link to comment Share on other sites More sharing options...
Colin Anderson Posted August 14, 2018 Author Share Posted August 14, 2018 I meant to say, many thanks Denis. 👍 Quote Link to comment Share on other sites More sharing options...
Colin Anderson Posted August 21, 2018 Author Share Posted August 21, 2018 The thread of the throttle stop screw turned out to be M4 fine, the same as the needle valve. M4 fine bolts seem to be incredibly hard to find or get hold of in this country, but, thanks to a fellow modeller (Barry Lewis - thanks mate) some suitable bolts were sourced from Pro Bolts; at 12 mm length these were shorter than I would have liked and had domed heads, rather than cap heads, but they would do the job. Once I got the bolts I took them up to a machine shop I know in Maidenhead (8 miles from me) and got them to reduce the ends of two of the bolts to make locating pegs to engage in the throttle barrel - £8 for the bolts, £5 to have the ends reduced. I got them back today and fitted one into the throttle assembly, complete with a spring from a defunct pen. The throttle barrel is now secure and functions as it should. All that remains to do now is to fit the assembly to the engine and test it. Thank you to every one who contributed and especially Denis Watkins who sent me some bolts to try out if the kindness of his heart. Quote Link to comment Share on other sites More sharing options...
Dave Hess Posted August 21, 2018 Share Posted August 21, 2018 Is this it? **LINK** Quote Link to comment Share on other sites More sharing options...
Colin Anderson Posted August 21, 2018 Author Share Posted August 21, 2018 Hi there Dave, When I first started searching I thought it might be, but looking at the images, the peg that engages the throttle barrel looks way to long. I did contact them both by email and by phone and they really couldn't give me any information on the speciation soft this part and whether or not it would fit my engine - mine is a 21, but it's not a Pro. However, although these items are on their web site, they don't actually have them and have not requested any stock since 2013 and therefore believe them to be unavailable. This is why I aquired some M4 fine bolts and got an engineering firm to modify them for me. This solution should work fine; it locates the throttle barrel correctly and allows it to move properly throughout its range. I've now got to test the engine. Before fitting this engine to a plane, I'm going to have to reposition that throttle arm. I'm not exactly clear on how this is achieved on this throttle. The screw in the middle (first image) is to adjust the low speed mixture; around this is a brass collar with 3 notches in it and, on throttle barrel itself, what appears to be a grub screw with an Allen key head (second image). Which one of these actually allows the arm to be adjusted? Edited By Colin Anderson on 21/08/2018 23:13:14 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted August 21, 2018 Share Posted August 21, 2018 The Grub screw on the outer edge will allow the throttle lever to be re-positioned. Quote Link to comment Share on other sites More sharing options...
Colin Anderson Posted August 22, 2018 Author Share Posted August 22, 2018 I had a hunch that I this was the case, but wanted to be sure. Many thanks for that. 👍😊 Quote Link to comment Share on other sites More sharing options...
Colin Anderson Posted August 22, 2018 Author Share Posted August 22, 2018 Well, that was easy! Quote Link to comment Share on other sites More sharing options...
Colin Anderson Posted September 7, 2018 Author Share Posted September 7, 2018 Happy to report that I fired up both Thunder Tigers (20 & 21) successfully this morning. They start easily and run fine. I noticed today that the 20 is also missing a screw (there's only one holding the throttle body in place, instead of the two that this engine should have); it doesn't appear to effect the running in anyway. Both engines ran a little slow to my ears, but that might have something to do with the 11 X 6 propeller (the only one I had to hand for testing) that I had fitted. What did surprise me was that the 21, without a silencer, wasn't any louder than the 20 with one! just need to figure out what the correct propeller size ought to be. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted September 7, 2018 Share Posted September 7, 2018 Ground clearance usually helps the choice Colin, and the model My 3 foot wing span edge runs fine on a 9 x 5, but if you are stuck for clearance, then try the 8 x 6 Quote Link to comment Share on other sites More sharing options...
Colin Anderson Posted September 7, 2018 Author Share Posted September 7, 2018 It's going into a 48" Tiger Moth, Denis. A don't believe that they'll be much of a problem with ground clearance, although I've not checked this yet. As I'd bought both these engines secondhand I needed to make sure they both ran okay; thankfully, they do. I only had an 11 X 6 to test them , but I feel this was a little big for these engines (3.5 cc), so yes, they'll probably be happier on a 9 or an 8. I'd thought to use the 21 in the Moth, but as it's a car spec version (over large head and a pulley at the front end) I don't think it'll be practical - it'll be a tight fit within the cowl, the pulley doesn't allow sufficient thread for a prop nut to hold the propeller on and I haven't found a silencer for it yet. I think it'll be better and more practical to fit the 20 (it's only fractionally under 3.5 cc), as its smaller and lighter than the 21 and does have a silencer. Now I've cleaned it up it looks much better than when I aquired it. Quote Link to comment Share on other sites More sharing options...
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