A quick question Edward. It looks like it fires once when the points open twice. Is the engine missing every other firing stroke or is it a sound / optical illusion of the video. It's almost like it's starved of fuel.
Tony
Tony
Another Karl Benz 1886 Engine and Motor Wagon.
- Thread starter Edward Perera
- Start date
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Edward Perera
Active Member
Thanks for your question Tony.
You are wright. It is not producing the four stroke beat. I doubt the carburetor. The needle is at the optimum position, any variation immediately reflects on the rpm. While test running there were instances that I got the beat wright, only with the vapour carburetor, as I could remember.
I think the one you are designing would solve the problem.
I would like to wait and observe the results of your carburetor, before doing any further research by myself.
Edward.
Edward
You could try a quick test. Run the engine and gradually cover the venturi to choke it. It will show if you need a richer mixture.
On second thoughts it may well be something else.
There are a few videos on youtube and only one engine works well.
The rest all run with a misfire some worse than others but even the TS video show the engine running badly.
- TS video
The engine that runs well has had some mods which he says but I think he has also changed the cam to give better valve timing. Maybe also changed the inlet port.
You could try a quick test. Run the engine and gradually cover the venturi to choke it. It will show if you need a richer mixture.
On second thoughts it may well be something else.
There are a few videos on youtube and only one engine works well.
The rest all run with a misfire some worse than others but even the TS video show the engine running badly.
- TS video
The engine that runs well has had some mods which he says but I think he has also changed the cam to give better valve timing. Maybe also changed the inlet port.
Last edited by a moderator:
Edward Perera
Active Member
Thought this way it is better.
Last edited by a moderator:
Edward Perera
Active Member
Thanks, Tony,
Is there a way to overcome the situation?
Edward.
Is there a way to overcome the situation?
Edward.
![IMG_3694 [800x600].JPG](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/70/70942-IMG-3694-800x600-.JPG "IMG_3694 [800x600].JPG")
I was in contact with the guy who made the first engine. He has his valve timing set to TDC and BDC but the main change he made is to increase the compression ratio. If you go to his Youtube channel you will see the conversation. He said it took a long time to get it running that good and he thinks it's even better now.
Edward Perera
Active Member
I would appreciate if you could send me a link so that I could visit his channel.
Edward Perera
Active Member
Hi All,
Thanks very much for all your suggestions.. I'm really looking forward to try them all , but unfortunately due to a medical condition I need to keep away from any hand's on work for a couple of weeks. But I will be online.. Will get back to you with results once I try them.
Edward.
Thanks very much for all your suggestions.. I'm really looking forward to try them all , but unfortunately due to a medical condition I need to keep away from any hand's on work for a couple of weeks. But I will be online.. Will get back to you with results once I try them.
Edward.
Edward Perera
Active Member
That runs beautifully!
Ken Brunskill
Well-Known Member
I have followed and applied the drawings I've received and scaled them to 1/4 scale in inches vs. metric, however I observe that the 3D model has the piston ending up, seemingly quite a distance from the top of the cylinder at the top of the stroke. I know that you have a nicely operating engine (Congratulations!) Could you advise what the relationship is between the top of the cylinder to the top of the piston is a TDC on your engine? Obviously I need to correct my 3D model, just would like to get an idea of by how much.
Edward Perera
Active Member
I have followed and applied the drawings I've received and scaled them to 1/4 scale in inches vs. metric, however I observe that the 3D model has the piston ending up, seemingly quite a distance from the top of the cylinder at the top of the stroke. I know that you have a nicely operating engine (Congratulations!) Could you advise what the relationship is between the top of the cylinder to the top of the piston is a TDC on your engine? Obviously I need to correct my 3D model, just would like to get an idea of by how much.
I am very sorry for my delay in replying.
There is a gap of 33.5 mm from the top surface of the piston to the top end of the sleeve, @TDC.
Edward Perera
Active Member
Ken.
As you are making this from scratch at a smaller scale you should know that the design, as is, gives a very low compression ratio. Something like 2 - 2.5 : 1. This is insufficient to make the engine work consistently well. You should design the head with a spigot rather than a recess and maybe increase the piston length in order to increase the compression ratio to at to 4.5 - 5 : 1.
As you are making this from scratch at a smaller scale you should know that the design, as is, gives a very low compression ratio. Something like 2 - 2.5 : 1. This is insufficient to make the engine work consistently well. You should design the head with a spigot rather than a recess and maybe increase the piston length in order to increase the compression ratio to at to 4.5 - 5 : 1.
