P.A.W. 1.49 plain bearing - can't adjust compression

[Mike Etheridge 1]

I would also agree it is not a good idea to use an electric starter on a diesel motor as you need to 'feel the compression' of the engine. I have seen it done though.

I forgot to mention about needle valve adjustment which for starting should be 2 to 3 turns of the needle, too little and the engine will not run so it is best to start with a rich setting. Once the engine is running satisfactorily on a rich setting then the needle can be screwed in and the engine will speed up to a maximum and then it is advisable to turn back he needle to a slightly richer setting otherwise the engine will cut out.

Other than removing some back plates I have never found diesels difficult to dismantle. It is something I had to do quite often with my ED Racer when I used it on a control line Peacemaker. The crankshaft would get knocked back if the plane nosed in. It was then a simple task to remove the 4 back-plate screws and remove the back plate and tap back the crankshaft through the twin ball races.

 

Edited By Mike Etheridge 1 on 12/12/2017 20:00:36

[brokenenglish]

OK, here's a video showing the freeing up of a gummed up PAW 149, including knocking the contra-piston back using the technique that I described. I didn't post it before because this engine has a muffler and an RC carb. but the basic freeing up and getting the thing running are the same.

Tom, who asked the question at the beginning, may get some inspiration from this. It does show the knocking back of the contra-piston in a gummed up engine.

I'm amazed that someone mentioned an electric starter. An electric starter is totally out of context, it doesn't offer any advantage whatsoever to free a gummed up engine!

Anyway, here's a link to my PAW 149. Sorry, I don't know how to show the video here.

http://youtu.be/S4c9JqfufUE

 

 

Edited By brokenenglish on 12/12/2017 20:23:51

Edited By brokenenglish on 12/12/2017 20:24:44

[Denis Watkins]

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[Tom Major]

I didn't expect that seemingly so simple question would turn into such an interesting debate, thank you all who contributed.

After the liner was taken out of fuel, I wiped it off a little and gave it few gentle taps with hammer, thick plastic pen, on wooden stairs (she didn't see me do that :D ). Then I dropped tiny amount of after run oil both over and under contrapiston and tapped it again.

Contrapiston slid wonderfully out of the liner, I found some gunk where it once was, but it was so little I couldn't believe it could have had that serious effect. Then when I tried to insert contrapiston in again I realised how tight fit it really is. Amazing little thing.





I wil have a closer look at both parts, maybe I'll manage to find and remove some more dirt and get it running finally . Putting it back together won't take long, but since it's dark, I'm not gonna attempt to start it now .

Once again thanks you all.

[Mike Stevens]

I would never use electric starter on a diesel.

[brokenenglish]

Posted by Denis Watkins on 12/12/2017 20:31:54:

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Thanks Denis, I'll note that!

[Tom Major]

Interesting channel you have there Brian, a lot to see and learn from your videos

[John Robertson 3]

And THIS is an interesting thread! I have 3 old diesels sitting in my shed. I have absolutely no use for them, but it would be fun to see if they can be revived. Model fuels and a motorhome don't mix well, hence my total conversion to electrics, but still . . .

[Martin Harris - Moderator]

Where do you keep your gas bottles? Is there room for a half gallon of glow fuel?

[Piers Bowlan]

It is not where you keep your fuel but where you keep your model as the stench of diesel is all pervading and seems to hang around forever. I have some old diesels too but if you get some fuel on your cloths you can never get rid of the smell. 'Eau de Ether' is not popular with 'her indoors'!

[Jon H]

It does pong a little but recently when using my Laser Diesel it didnt seem to hang around as much. The model was nicely scented, but the car seemed to get through without issue

[Martin Harris - Moderator]

"Stench"? Philistines! The heady aroma of diesel fuel is on of my favourite childhood memories and every time I catch a whiff of a diesel running I'm transported back in time. Funnily enough, while I watched the video above, I was sure I caught a whiff of ether, the memory is so powerful!

[brokenenglish]

Martin, I (more than) agree entirely!

To enjoy engines, you have to love playing with them and "getting it right".

Those who look upon engines as being "smelly" or "dirty/oily" and a chore to operate, obviously have a right to their opinions, but they'd really be better off with knitting, or goldfish, or electric flight, or some similar pastime...

[Bob Cotsford]

Posted by brokenenglish on 12/12/2017 21:02:50:

Posted by Denis Watkins on 12/12/2017 20:31:54:

Copy your http title

Click on the globe on the middle second row

And paste it into the http line

Walla

**LINK**

Thanks Denis, I'll note that!

and please click on the 'Target' tab and select 'New Window' before clicking ok! This stops links moving away from the current page on opening.

and back on subject - I always found it was the smell of paraffin/kerosine that lingered, not the ether.

[Mike Stevens]

Diesel fuel and the exhaust fumes from an Oliver Tiger are just heaven!

[Tom Major]

I am not so enthusiastic about smell of diesel fuel, but totally enjoy glow. D2000 smells like them tiny green flies that are present everywhere during summer

[thomas oliver 1]

A method I used in past was to introduce a wee bit of thicker oil like motor engine oil through the exhaust and flick over with a largish prop. Saved dismantling the engine.

[Tom Major]

Little P.A.W. is back in one piece and all seems to work well. I can adjust the compression any way I want now, all that was inside was previously mentioned tiny amount of gunk.

Do I need a compression locking screw to be on? I had a look at few pics and I saw same engines without this device and now am not sure if it was there originally or was added later. While it's on, the adjustment is very limited. If I put the washer back on as well, I can't feel any changes in compression at all...

Test run tomorrow, hopefully I'll get it right

[Jon H]

I don't have a lock lever on my 149 but you might need it. I would leave it off until you see evidence that you cant get away without it.

[Tom Major]

Thanks Jon.

[onetenor]

Re diesels and motorhomes. You mentioned a shed.Why not keep fuel in shed and work in there.? Make sure that cyl liner goes back the right way round too

The lock lever should be backed off to adjust the compression then turned to lock the comp screw in place once the correct setting has been found. It too may be gummed up and that is why you have limited movement. A bit of heat and two pairs of pliers will shift it. Then a drop of oil on it..

[Tom Major]

By limited movement I mean lack of thread, lever itself is nice and smooth but I have about half a turn movement when any effect actually can be felt...

[Bill Wood]

All this talk of diesels and contra pistons reminded me of when I had the opposite problem with a PAW 1.49. The c.p. was riding up and down on top of the piston i.e. too slack. The cure was to put the c.p. on a lump of wood then place a ball bearing of similar diameter as the c.p. on top and whack it with a hammer. Very crude but it worked. Think its called "peening" in engineering terms. Splays out the contra piston a bit.

[Mike Etheridge 1]

Unless the engine is clapped out you should not need the compression screw lock so as others have suggested I would remove it initially and see how you get on. I have had an ED Racer MK 2 for over 50 years and it's never needed a compression screw lock. I also have a PAW 19D ball raced Combat Special bought new in 1976 by a mate of mine, and as far as I remember it never needed a compression screw lock. Because it is ball raced I gather from my nephew that it did not qualify for combat! . The other PAW's I have which I have not started are a 29 RC and a 1.49 the same as yours Tom. That said I have started 1.49's loads of times firstly in a control line Simple Simon. An excellent engine the 1.49 that PAW produced in a more powerful version the 'Blue head' that my nephew won his first combat competition with.

[onetenor]

Do you mean you have insufficient thread length on the comp screw.If so reduce the thickness of the boss of the lock screw to free of a bit of thread length. A few strokes of a file or a slice with a Dremel type tool. Either that or use an allen screw for the comp screw . This has an additional advantage of being adjustable with the cowling in place through a hole in the cowling.