Engines - general questions.

[Tom Major]

Once again thank you Doctor for very valuable advice.

I have received ordered screws for .10FP today so I thought it might be good idea to try them. All screws are perfect fit, so since I had engine out, I gave it a little clean with polishing paste.





Sadly I was unable to remove all blemishes, but it already looks much better. Now all components are drying out and once they did, I can reasemble most of the engine - set of gaskets still didn't arrive, neither did prop, so I'm guessing I will manage more during weekend. Now I only have backplate to clean/polish, but don't want to touch it in case ordered gaskets don't match.

[onetenor]

Isn't it more usual to measure threads to the inch?

Tom Solvol do an aluminium polish now.

[Martin Harris - Moderator]

Posted by onetenor on 30/11/2017 22:40:05:

Isn't it more usual to measure threads to the inch?

It's the convention...for imperial sizes.

Metric threads are specified by pitch.

[Tom Major]

Speaking of threads... does anyone know what is thread size on the crankshaft? Disaster happened as it turned out I don't have prop nut for .10FP...

Now little engine is back in one piece. I managed to salvage backplate gasket, but still need to wait for head gasket, hope new set arrives tomorrow.

All moving parts are oiled and engine turns over smooth like never before. Despite bolts being only tightened by hand and lack of head gasket, I can hear very nice popping sound, of course followed by air leak. This one should run sweet once I finish it, in the meantine I can get back to .40FS and also got 3 Cox engines to test

Edited By Tom Major on 01/12/2017 01:03:04

[Peter Miller]

Not sure what size of prop thread, I think it is 5 mm but I do have an OS 10 FSR which I could let you have the prop nut off if you want It is a bit low on compression but does run.

PM me if you need it

Edited By Peter Miller on 01/12/2017 08:39:09

[Denis Watkins]

You are right

It is M5 guys

[Tom Major]

I just finished looking for any matching nut, found one of same diameter, but no joy with pitch . I'll message you shortly Peter.

Gaskets arrived today, new head gasket is so much thicker than old one - that is like tinfoil.

[Steve Hargreaves - Moderator]

M5 is quite a common size Tom.....a local engineering supplies company will sort you out....even a trip to Halfords might elicit an M5 nut or two...

[Tom Major]

I know it is quite common Steve, I was surprised I don't have even one fitting... There is not many specialist shops in my huge city, but I will try to visit Wilko if I finish work early enough - they should have various sizes in stock.

[TartanMac]

Looks like a nice project you have here and that is a nice 10FP. I used a pen style magnet to get the collets out my four stroke engines I just pushed down on the retainer to expose the collets then use the magnet. I got it off ebay around £1.20 that includes delivery. If you don't already know you should be careful pulling the valves out. Over time the top of the valve gets wider with the rocker arm hitting it. What I do is get some wet and dry push the valve with your finger into its seat so it does not rotate in the head once you have the spring and collets and retainer off. Go round the top edge above the collet gap with your wet and dry be careful not to put a curve on the edge where the collet top edge sits. Then clean the debris off with a paper towel and put some oils on it then clean it again make sure no metal is still on the stem then gently push the top of the valve stem down to the guide and see if there is resistance. If so sand a little more then repeat. you don't want any resistance really and be careful cleaning and make sure everything is off the valve and the top of the guide.

I did this with my Laser V twin build and after rebuild there was no oil coming up between the guide and valve. My Enya has worn guides from just years of use and it kills the engine I am getting oil over flowing the rocker area and a big power loss. I replaced the ring new ceramic bearings recut the valves cutting through small pitting on the edge of them and they seal great. But when you push down when the springs are on they have a notch feeling. They move side ways and don't seat straight away so at high rpm the valve is not really sitting on the seat. it only makes 1.1hp with a 16x6 and 1.4 with a top flite 14x8 all because of the guides. Just something to watch out for.

[Tom Major]

Some really amazing advice coming in, thank you.

Didn't touch FS as I got back from work not long ago, but spent few minutes with Testors McCoy .049 that only came in post today - cylinder was pinching the piston a bit, on closer inspection I have noticed tiny chip/dent, most likely caused by careless cylinder removal. I have used thin file to get rid of it and surprisingly piston moves up and down freely, fair compression still present, looks like it might be a runner 😀. It's a shame that not many of these little engines remain complete, I have another one with cracked crankcase and both are missing starter spring. I am hoping I will be able to get at least one running, just need to order 1/2a prop to test it.

Also finished .10FP, there wasn't much to do, just put new head gasket in and tightened the bolts. Here is a shot of two gaskets for comparison. What difference £1.29 can make...

I checked once again few nuts that I could use on the crankshaft and am not sure if it really is common M5 - none fit...

 

 

 

 

 

Edited By Tom Major on 02/12/2017 23:20:17

[TartanMac]

I bought a domed nut for my 15LA it was M5. If you check the Just engines website under spares for O.S 10LA it has the nut under M5 and the spinner nut. fits 10fp la and 15LA. Should be the same. You could phone them check the thread.

[Martin Harris - Moderator]

OS list the thread size of the 10 FP as M5 in my handbook. The 15 FP has an unusual 7/32-32 UNF thread (@ 5.5mm) - could they have beefed up later 10 FP crankshafts?

Dig out that iffy vernier and measure the shaft diameter behind the thread, measure the distance covered by 10 threads and if the results aren't 5.0 mm (+- very little) and 8mm then you don't have a standard M5 coarse thread. Let us know the results if they don't confirm the expected 5mm thread dimensions and we can help identify the thread.

Edited By Martin Harris on 03/12/2017 00:15:26

[Tom Major]

Measurement was bang on 5mm on the shaft and about 7.6mm over 10 threads. Went to Wilko and just grabbed pack of M5 bolts with nuts and washers. What an amazing fit !. Of course they are madde of cheese, but for the time being will do just fine . Now to finish test rig and .10FP can have its final run before another cleaning and storage.

In other news, package with Cox props that I ordered over a week ago most likely went missing in post. Can't have everything I guess...

Thank you all for advice.

[onetenor]

If nuts really are soft use two as locknuts..Actually I have always found Wilco's fastenings to be good quality. What makes you suggest that they may be otherwise ?

[Tom Major]

Work related experience. I used to maintain hotel for 1.5 years and believe it or not, we had most stuff from Wilko or BnQ. Tools, fastenings, you name it. I've seen my fair share of rounded off nuts, stripped threads etc .

[Engine Doctor]

Hello Tom the crank thread is a 5mm x 0.8 pitch . Any decent fixing shop should be able to supply a quality steel nut.

If you google Model engine Crankshaft threads various list come up. Good job it wasn't OS 15 max as they had a odd ball thread 7/32 x 32 , an old ME model engineer thread rarely used and difficult to source replacements .

[onetenor]

The nuts maybe hard to get but taps are fairly easy to find. To find nuts try Model Fixings and Wheelspin models. and EKP supplies for nuts and taps and all your model fixings No I don't have shares before you ask.

[Tom Major]

I wouldn't think you do have any shares with them mate .

Thanks again for pointers, notes taken.

Today was not a good day... All props that I ordered last week still didn't turn up. Props for Cox most likely went missing in post, prop for .10FP was sold out before I ordered it and got message from shop followed by cancellation.

Oh well, finished work late anyway, might as well get back to .40FS and get them valves out and finally start putting it back together. I have a prop for this one :D

[Tom Major]

Hi .

I have some questions again. My .40FS is still in pieces and I didn't take valves out yet. I can't find my feeler gauges so didn't want to start another job I can't finish. Anyway, I've seen OS FS toolt kit containing said feeler gauges, but is it correct that this one kit is good for all OS four strokes? I don't know why, but I'd expect valve clearances to be slightly different on different engines...

In other news, .10FP is almost good to be installed in the model . Had another test run today and managed to burn whole tank of fuel in one go, throttle response is ok, just airbleed screw needs some tweaks and I'll get going with little ship. Here are few final seconds before tank dried out.



Another thing, would you store brand new and unrun engine in oil or just wrapped in plastic bag? I finally received another Cox I bought few days ago and most likely won't run it anytime soon...



Cheers
Tom

[TartanMac]

Sound like it is in good condition Tom pretty snappy response nice one

[Denis Watkins]

Lightly oil and turnover, then into a plastic bag Tom

Airbleed, just screw halfway across a clear hole,

And I use the OS feeler gauge on all my 4 strokes, but I may be corrected

[TartanMac]

This is a link to the O.S 40FS manual you can get a lot of manuals online these days Great planes do the same.

http://manuals.hobbico.com/osm/fs30s-40s-manual.pdf

[Tom Major]

I checked few OS four strokes and it looks like it will be the correct tool kit. Handy to know, ordering it now.

Thanks for the link TartanMac

[dave windymiller]

Going back to the earlier posts be aware that there are some odd size metric screws used on many engines

For example, my OS fp20 uses m2.6 screws on its backplate. m2.5 screws appear to "fit" but are loose and will most probably damage the thread if tightened

You can often get these odd sizes off ebay and they might have to come from abroad but are not expensive (10 of 2.6mm X8mm cap head for £2.60 inc post from china!)

Dont assume its 2.5, 3.0 or 3.5mm