Author Topic: 20 cc Horizontal 2 Stroke Diesel  (Read 54481 times)

Online Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #300 on: June 03, 2020, 06:03:48 PM »
I made up the fuel tank support which was actually quite fun as I was not working to sub mm tolerances, could happily blast 10mm holes through things  :) and use taps I was not scared of breaking  ::)
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Roger

Online Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #301 on: June 04, 2020, 07:58:07 PM »
Having assembled the tank I tried to prime the system with the new 10░ injector. No success  :( I worked my way back through the system and tried to check the pump for leakage with light machine oil, nothing  :headscratch: I measured the plunger and to the best of my measuring ability it had worn 3-5 microns. Using a new 1.98mm pin gauge In the pump body I couldn't build any pressure so that was also worn. I don't have a 1.99mm pin gauge to check with so I can't judge the wear but I need to get back to a known point with the pump before I can continue experimenting.
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Roger

Online Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #302 on: July 20, 2020, 07:29:14 PM »
I am starting to sort out how to fit the new fuel pump onto this engine. As I dismantled the old system I found that the cam follower bearing had failed again  ::) It seems that at least two of the balls had cracked in half  :headscratch: Maybe a solid follower on a bronze bush or a complete bronze follower will be better  :thinking:
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Roger

Offline Admiral_dk

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #303 on: July 20, 2020, 09:39:59 PM »
I suppose that you have "a shock load" from the way the pump work, on the bearing and axle ....

If this is the case, there are some very different bearing data that you need to peruse ...!

Another reason might be a slight angle that shouldn't be there ...?...

Per

Online Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #304 on: October 11, 2020, 07:18:57 PM »
This thread tends to merge/spilt with the fuel injection thread.

I had some success with a stainless steel injector body and decided to make some more. I had also found that my compression tester tended to leak off far to quickly so I would make a new body/valve seat. The operations required were quite similar so I made them together. The compression tester still is not working as expected. The low range (15 bar gauge) goes off scale easily but the high range (315 bar gauge) barely reads. I think I may need to buy a new ~100 bar gauge. My current gauges are from an old gas bottle regulator.

Whilst I was playing with the compression gauge I noted that the injection pump cam follower bearing broke again  :( This is strange as there was no fuel and no injection pressure  :headscratch: I think I will try a bronze roller.
« Last Edit: October 12, 2020, 07:28:38 AM by Roger B »
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Roger

Offline Brendon M

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #305 on: October 15, 2020, 05:43:05 AM »
Hello Roger

What material is the bearing? Looks to be a ball bearing?

Probably not standing up to impact loading. As you surmised, you will may get better longevity out of a solid roller.
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Online Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #306 on: October 16, 2020, 05:20:48 PM »
Hello Brendon, Yes it is an RC car ball race which has failed several times already  ::) I have made a bronze version however the end of tappet is looking somewhat abused due to the various failures so I may remake that as well.
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Roger

Offline Admiral_dk

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #307 on: October 16, 2020, 09:57:55 PM »
I think I can explain Roger.
That very tiny ball bearing can probably easily 'carry the load' of the spring in your system, but I'll be very surprised if it can withstand the shock load when the cam hits ...!
I'm almost alway surprised on how fast the load capabilities of a ball bearing rises with size when reading the tables -> it must be very small with a bearing the size you use here ....

I have never seen the inside of a full size injection pump and only a few drawings (curiosity) and I seem to remember that they use a solid roller and not a ball bearing - I can be totally wrong here ....

Great to see that you haven't given up  :ThumbsUp:   :cheers:    :popcorn:

Online Roger B

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Re: 20 cc Horizontal 2 Stroke Diesel
« Reply #308 on: October 22, 2020, 11:22:25 AM »
Thank you Per  :ThumbsUp:

The small ball race was a quick solution at the start but as expected will need to be re-engineered  ::) As the bronze roller will be running on the pivot rather than an inner race I will need to improve that as well.

I put the compression tester back together with the new valve and gauge and had a quick trial.


At low speeds it will read 20 bar and at high speed (~3000rpm, max. for the drill) over 30 bar. There is still unfortunately a leak somewhere which I think is partly responsible for the speed dependancy of the readings. I may be able to lap the valve seating if I glue a ball bearing onto the end of a rod  :thinking:
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Roger