That was a very interesting little tidbit Roger - do you have any reference, or was it just told verbaly to you ?
Per
I found this by a number of routes. L C Mason refers to a carb with two butterflies, one before the jet and one after and the relationship between them. I have a couple of commercial carbs that I have modified for my engines and noted that the air intake bore was bigger that the bore in the barrel and the engine side bore. If you go to the extreme and make the inlet side bore bigger than the air intake side you will end up drawing neat fuel and no air. For a high volume production finding the optimal bore can be done by experiment. For a one off as soon as you open the air intake past the optimum you have to make a new body
Hi Roger,
a very interesting discussion.
May be also the reason, why I have avoid it so far, to make a carb by myself.
There are so much different information available, all in relationship to very special applications.
The first idea was always to follow a recommendation and to use a carb of the shelf where somebody else has done the approval already.
Now I feel it is time to go deeper and try to understand the contex a bit better.
Good to know that there is some information in the book of L C Mason, I do have it and will try to find the part about the carbs in there.
Just seen, that Malcolm Stride also has a chapter about carbs in his book, also something to read very soon again.
In then meantime R&D was busy too yesterday.
Coolant was given into the system and surprise no leakage so far, also not later with 90°C.
And also this morning after resting a night it seems to be fine.
The main intention was get the cooling working to make a longer running stint possible.
I have started with the 3 mm carb same as has been used so far for running.
Same behavior, running with fully open throttle only no chance for and control of the revs.
By the way, next thing to do, to fix a small piece of reflector tape at one flywheel, so a measurement of the revs will be possible.
The adapter with the O.S. 2A carb was prepared some days ago has find its way to the intake manifold now.
The bore in the barrel is 4,5 mm. See pictures below.
By try and error the best coolant level has to be find, because if the engine stalled, some fluid comes back from the engine into the reservoir.
The water jacket in the heads is much higher than the coolant reservoir.
Generally it was checked if the coolant circle does work as it should be.
A lot of different effects are coming together now.With every minute run time, the engine seems to go smoother
It is reacting to the barrel position now a bit.
Over all I could write something about 5 minutes run time into the records.
Here are nearly 50 sec of run time captured by another video with steaming coolant.
[youtube1]https://youtu.be/qEhwXJJ4of4[/youtube1]
Max temperature measured was 90° C, when the fuel cell was empty.
I took this as a sign to stop it for that day and make a plan for further experiments.
So it seems we are going into the right direction now.
The to do list shows now:
To start the engine with half open throttle and to find the right nozzle jet position for it, if possible.
To measure the revs in accordance to the throttle.
As Jeff suggested, to measure the intake and exhaust timing.
Generally to get more run time for better evaluation.