Author Topic: Hoglet- breaking in a new assembly  (Read 1130 times)

Offline Trevorc

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Hoglet- breaking in a new assembly
« on: December 17, 2017, 10:06:22 PM »
Hello, i have just completed the mechanical build of my Hoglet engine. I can turn the engine over but it is extremely tight with some squeaks. Before attempting to run it i need to free it up somewhat. I plan to drive the engine with a small electric motor with plenty of oil in cylinders to break it in.
Am i doing right? Does anybody have any other advice to offer?
I will upload some photos when i can fathom out how  do it!!
Regards
Trrevorc

Offline Brian Rupnow

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Re: Hoglet- breaking in a new assembly
« Reply #1 on: December 17, 2017, 10:48:47 PM »
Trevor--I run in all of my small motors to loosen them up before trying to run them. Make absolutely sure that you CAN turn the engine over at least two or three times by hand. Coat everything that moves with medium weight lubricating oil, take out the sparkplug, and don't turn it over any faster than about 200 rpm. If you have a look at my thread titled "Model compressor--maybe" on this forum, there is a video of my set-up for running in engines. An hour is not too long.
« Last Edit: December 17, 2017, 11:05:18 PM by Brian Rupnow »

Offline Jasonb

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Re: Hoglet- breaking in a new assembly
« Reply #2 on: December 18, 2017, 07:43:01 AM »
Personally I have never "Motored" an engine. I would suggest stripping it down back to the 4 pieces that make up the frame and checking they are all lined up correctly and then building it back up checking the fit of each part as you do which should indicate where any tight spots are, could be the fit of two parts, one part off line, part sitting at an angle, etc.  As you find an issue deal with it as needed by easing, adjusting or remaking. With the plugs out and no rings you should be able to turn the engine over with out binding, squeaks etc.

Offline b.lindsey

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Re: Hoglet- breaking in a new assembly
« Reply #3 on: December 18, 2017, 12:57:36 PM »
Trevor,
The above two replies kind of define the two camps of thought on this. I know Brian has used this effectively in many of his builds and with apparently no ill effects. I must admit however to being more in line with Jason's line of reasoning...find the binds and eliminate them first. Yes, things will "wear" in but if there is some mis-alignment (crank journals for example) then my thinking is that the wearing in process could result in some eventual "looseness" at some point. If such mis-alignment is very minor it may not be a big deal, but real binding may have more implications including damaging something during the wearing in process. I recall way back on this forum there was a discussion of this but the author now eludes me. Maybe someone else can put their finger on it. At any rate, I think this is a useful discussion and I an interested in others' responses.

Bill

Offline Roger B

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Re: Hoglet- breaking in a new assembly
« Reply #4 on: December 18, 2017, 03:39:58 PM »
I can see this in two different ways:

With 'homemade' piston rings, cylinder bores, valves and valve seats motoring will give these a chance to bed in and give a better chance of the engine starting.

If parts are misaligned or the clearances are insufficient motoring may be an initial solution, but it is likely that there will be an increased rate of wear and problems in the future. Having said that very few of the engines made on here are run for extended periods or under high load so it is probably a theoretical problem

My zwei Rappen  :)
Best regards

Roger

Offline Jasonb

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Re: Hoglet- breaking in a new assembly
« Reply #5 on: December 19, 2017, 08:17:33 AM »
One of my issues with motoring is that the forces are all in the wrong direction as the flywheel is moving the engine parts and not the engine moving the flywheel so points of contact in say the big and little ends will be wrong, also there is no gas behind piston rings to expand them and no explosive gas pushing the valves into their seats.

By motoring out of line parts you will only wear the weaker of the two into sub mission so on a bent crank for example the crank will likely stay bent and on size but the bearings will be worn into a sloppy fit until things rotate smoothly. To me it is far better to sort the bent crank and scrape the bearings to get things turning by hand and then there will be minimal bedding in once you start to run the engine. In both cases the engine will likely run but one will have a sloppy fit and may knock as well as a bent crank and wobbly flywheel the other will run with closer fitting bearings, straight crank and true flywheel.

I won't post a link to a recently completed engine that was posted here which shows the less desirable of the two results after having been motored. On the other hand this part made one came to me and the crank could not be turned when the bearings caps were even loosly tightened, I spent the bast part of a day straightening the crank and scraping the bearings and another half day on the big end shells and it ran reasonably straight first time, hate to think what it would have been like if I had left the 0.045" of run out in the crank and let the tight bearings wear themselves in.

<a href="http://www.youtube.com/watch?v=TC4qyRpw0UY" target="_blank">http://www.youtube.com/watch?v=TC4qyRpw0UY</a>


Offline Roger B

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Re: Hoglet- breaking in a new assembly
« Reply #6 on: December 19, 2017, 08:58:43 AM »
Jason, I see a blank space above the picture of a crankshaft being straightened with a pair of Stilsons. Should there be a something there? I have found that I can't see YouTube videos that are embeded with the Icon above but I can see them if just the URL is pasted in.
Best regards

Roger

Offline Jasonb

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Re: Hoglet- breaking in a new assembly
« Reply #7 on: December 19, 2017, 09:24:28 AM »
Video link remove the gap in the HT TPS as otherwise the forum just embeds it.

ht tps://www.youtube.com/watch?v=TC4qyRpw0UY

Offline Trevorc

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Re: Hoglet- breaking in a new assembly
« Reply #8 on: December 20, 2017, 08:28:13 PM »
Many thanks for your replies. I am fairly confident that the tightness comes from piston ring and cylinder bore. The bores were left 0.0002 undersize and the rings are for a dead 1 inch. However, i will do a partial strip down to confirm that it isnt tight in other areas. I plan to run in using my lathe. Will let you know how i get on. Engine takes back stage for  a week or so but i hope Santa got my mesage asking for ignition system this year!!

Happy Christmas

Regards
Trevorc