Author Topic: james coombes.  (Read 8348 times)

Offline kellswaterri

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james coombes.
« on: June 09, 2015, 10:53:20 PM »
Hi  folks...back  in the shed and finally have the Coombes finished...the little compressor unit is  basically only for tyres or air beds and has not   the power to turn over the  engine,   although it did give a few kick overs about half a rev...a few questions if I may ask...what pressure will i need to turn it fast enough ...   2nd  &  3rd  questions are related to the drawings...I started the build with the original first drawings...then a long break of a few years...when I got back in the shed the first drawing had faded with the sun new drawing had some valve gear linkage problems....so current situation ...not enough air pressure   (run on steam)???...valve gear dimensions ...or possibly the occillator dimensions ...please can any one supply those dimensions from an engine which has been running...Cant be all that wrong if it tries to start???
                                                              all the best for now,
                                                                            John...lancelot.

Online Jo

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Re: james coombes.
« Reply #1 on: June 10, 2015, 08:07:26 AM »
 :pics:

We don't accept excuses  ;)

Sorry I don't have a copy of the Coombes drawings  :disappointed:

Jo
Usus est optimum magister

Offline Ian S C

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Re: james coombes.
« Reply #2 on: June 10, 2015, 01:03:28 PM »
Sounds as though you just need a compressor with a bit more capacity,  I found that the Stuart Turner S9 would just give a bit of a kick when hooked up to the 12v car tire compressor.  My home made workshop comperssor had a job keeping up with the volume of air required, it only needed 10/20psi, just quite a bit of it.  The James Coombs should only need about that pressure, maybe a fraction more until it frees up.
Ian S C

Offline kellswaterri

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Re: james coombes.
« Reply #3 on: June 10, 2015, 03:21:32 PM »
Hi Jo and Ian...thank you for the speedy reply...I ran it on steam this after noon ...not a blooming twitch!!!It turns over quite freely I am beginning to believe that the throw dimension for the valve gear con rod is wrong and the steam valve is not getting enough movement in either direction...
a little bit of further work still...
                             John.                                                                                                                                                                                                                                                                                                   

Offline kellswaterri

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Re: james coombes.
« Reply #4 on: June 13, 2015, 07:14:52 PM »
hi folks...on further checking I got loan of larger compressor...made up a set of fittings for inlet.... checked for linkage looseness to valve gear applied pressure...the flywheel whipped round about just over 1/2 way...no amount of fiddle with eccentric sheave helped ...the problem I am fairly certain is the throw dimension in the new drawing I am working to supplements all previous ones including the build book ...(giving   11/64'')...THE NEW DRAWING HAS IT AT 9/64''   which is what I made the part to...I can now see that 11/64 '' is the more likely measurement  so I will have to make a new one ...could anyone confirm 11/64''as the right dimension...
                                                         this would be most appreciated...
                                                                           John.
                                    Sorry  Jo   the photo machine is not playing fair at moment will keep trying...

Offline smfr

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Re: james coombes.
« Reply #5 on: June 13, 2015, 09:54:04 PM »
My 1977 plans for the James Coombes show the eccentric throw as 9/64". I haven't built it yet, so I can't verify that this is correct!

But if you throw is wrong, it should just affect the valve travel. Is the valve fouling the inside of the valve chest, or is there interference on the outside? A bit of inspection while turning it over by hand should tell you why it's not running.

Simon

Offline kellswaterri

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Re: james coombes.
« Reply #6 on: June 14, 2015, 08:33:37 PM »
Hi Simon...my drawing is 1993 issue and still gives 9/64'' as throw... the valve s are ported in the cylinder already when kit was supplied  inlet valves   3/32''   with 3/8'' between top and bottom...the exhaust port is 3/16''   (careful...right on centre line of centre two stud holes for the valve chest...
                       LOVELY......cheers...John.

Online AOG

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Re: james coombes.
« Reply #7 on: June 14, 2015, 11:14:46 PM »
Hi Simon...my drawing is 1993 issue and still gives 9/64'' as throw... the valve s are ported in the cylinder already when kit was supplied  inlet valves   3/32''   with 3/8'' between top and bottom...the exhaust port is 3/16''   (careful...right on centre line of centre two stud holes for the valve chest...
                       LOVELY......cheers...John.

have you checked that there is no moulding sand in the passage ways? Pull the end covers off and try to blow air into the ports and see if you can feel it come out the cylinder. If not the ports are probably blocked with sand. Get a piece of wire and clean them out.

Tony

Offline smfr

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Re: james coombes.
« Reply #8 on: June 15, 2015, 12:27:55 AM »
Hi Simon...my drawing is 1993 issue and still gives 9/64'' as throw... the valves are ported in the cylinder already when kit was supplied  inlet valves   3/32''   with 3/8'' between top and bottom...the exhaust port is 3/16''   (careful...right on centre line of centre two stud holes for the valve chest...

Those dimensions agrees my my plans too. Any luck?

Simon

Offline kellswaterri

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Re: james coombes.
« Reply #9 on: June 15, 2015, 10:43:57 AM »
Hi Folks...just off  the phone to Stuarts ...picking their brains  ...after checking what was done and my description of how the engine reacted to pressure    he said it should work just fine on 9/64''.....but he thought same as you Tony      sand possibly partly ckocking the port passages.
back soon...with good news I hope...John.

Online Jo

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Re: james coombes.
« Reply #10 on: June 15, 2015, 10:52:52 AM »
back soon...with good news I hope...John.

AND PHOTOs  ;)

Jo
Usus est optimum magister

Offline Stuart

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Re: james coombes.
« Reply #11 on: June 15, 2015, 12:44:20 PM »
John

If you are a win doze user ( I am not )

This site will help with the valve gear dims

First lot are DOS. But the windoze  :toilet_claw: files are lower down

They will show with reversing ,but put in the dims and see if it will work try both sets and look at the difference

Stuart
My aim is for a accurate part with a good finish

Offline kellswaterri

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Re: james coombes.
« Reply #12 on: June 17, 2015, 12:03:12 PM »
not possibly the correct thing to do ...having some difficulty ...latest photo  to go.....

C:\Users\John\New folder (2)ME ONLY\2015-05-17\Phone\DCIM\Camera\20150426_170825_2.jpg

Online Jo

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Re: james coombes.
« Reply #13 on: June 17, 2015, 01:05:58 PM »
John you need to insert that link into the add attachment box below the box where you type in your messages before posting. The we will be able to see the Photo  ;D

Jo
Usus est optimum magister

Offline kellswaterri

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Re: james coombes.
« Reply #14 on: June 17, 2015, 02:19:27 PM »
trying this''......head sore now ...think I will go and lie down...... :noidea: