Author Topic: 20 cc Horizontal 2 Stroke Diesel  (Read 41608 times)

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #270 on: February 02, 2019, 03:15:57 PM »
The temperatures eased a little today so I had a play  :)

In the first video I slowly raised the fuel rack until it started and then gradually lowered it until the engine stopped. In the second clip I tried the same but the fuel didn't shut off and I had to choke it. I also did a quick speed check and it seems to settle down around 4 000rpm  ::)



So it will have to sit in quarantine in the garage for the next week before I can investigate the fuel pump again  :headscratch:
Best regards

Roger

Online Kim

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #271 on: February 02, 2019, 08:43:56 PM »
So, what's the quarantine for?  Is your shop inside, and the engines smell too bad after they've been run?

Just curious,
Kim

Online yogi

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #272 on: February 02, 2019, 09:50:39 PM »
Progress!!! It's fun to watch how that project came along.  :popcorn: :popcorn: :popcorn:
Looking forward to the next step... Thanks for sharing Roger.  :ThumbsUp: :ThumbsUp: :ThumbsUp:

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #273 on: February 03, 2019, 10:19:44 AM »
Thank you both  :ThumbsUp:

Kim, my workshop is in a communal cellar so I have to be very careful not to upset the neighbours, checking my shoes for swarf before going out etc. The diesel does smell quite strongly at the moment after running but hopefully that will improve as I improve the combustion.

Looking back at yesterdays runs I think I will make another cylinder head with a further reduction in volume. The theoretical compression ratio is already high, around 28-1, but being a two stroke the cylinder filling is probably not that good  :headscratch: I will also go back a try the larger injector nozzles again. It seems that the original lack of combustion was due to insufficient compression temperature rather than poor atomisation  :thinking: I may also need to think about limiting the lift of the injector needle as the needle opening increases the fuel volume in the injector.

However after a couple of Fohn days the snow has come back so the R+D department is closed again.
« Last Edit: February 03, 2019, 11:59:05 AM by Roger B »
Best regards

Roger

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #274 on: February 10, 2019, 07:38:21 AM »
I bought the engine into the cellar and dismantled the injection system. The cam follower bearing had failed, possibly as I had continuous contact for the last trials  :headscratch: The helix plunger was still ok  :thinking: I then removed the cylinder head, everything was black and oily but otherwise ok. I turned it over a couple of times and got a fine mass of black gunge that can only have come from the transfer port. That's probably why it wouldn't stop the last time  :facepalm:

Next steps:

Make an oil return line from the crankcase.

Skim another 1 - 1.5mm from the cylinder head.

Check the 0.5mm nozzle and make a new 0.35mm nozzle
Best regards

Roger

Offline bent

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #275 on: February 11, 2019, 06:12:27 PM »
Roger - did the bearing fail by losing a couple of balls, or did it gall/seize?

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #276 on: February 11, 2019, 07:06:34 PM »
It looks like it failed due to side pressure, I think one ball is missing and the cage looks distorted. Needs more investigation  :thinking:

I drained most of the gunge out of the crankcase and the started on the drain fixing. I could have completely dismantled the engine and clamped the crankcase to an angle plate or used a slightly risky setup  ::) With the engine held in my largest vise I started off, planning to minimise the amount of swarf in the crankcase. First a flat with my largest center cutting end mill, than center drill and drill 4mm, but not right through. Next a counterbore as it is guided/supported and finally right through with a 4.5mm drill.
« Last Edit: February 12, 2019, 07:23:41 AM by Roger B »
Best regards

Roger

Offline Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #277 on: February 11, 2019, 08:16:47 PM »
The last step was to tap M5x0.5 for a union, followed by carefully cleaning any bits of swarf from the crankcase. I made up short connecting pipe and started re assembling. It's interesting that a 2mm hole is sufficient to destroy the crankcase compression at low speeds in the same way that a 0.35mm hole in the injector was enough to destroy the compression in the cylinder  :thinking:
Best regards

Roger