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Old 01-11-2017, 11:12 AM   #31
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Beginners question here.
Seeing that it is a 2 cylinder will you need twice as big flywheel to carry the momentum? or how do you calculate that?

Jon


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Old 01-11-2017, 10:36 PM   #32
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Originally Posted by Blogwitch View Post
I do hope you are not using oilite bearings in your con rods.

There is a reason for it.

Oilite bearings are not solid, but sintered, made up of tiny balls compressed together, great for rotary bushes but I doubt if they will stand up to explosive forces pushing down onto them mounted into the con rods in your engine, they are liable to just shatter into tiny pieces.
I had enough trouble carefully parting them off to make thrust washers for rotary tables, they just disintegrate before your eyes.

John
John--are you speaking from personal experience, or just posting what you "think" you know? I have used oilite sintered bronze bushings in con rods on engines that I have built. I do have personal experience with them. They work fine. I wouldn't want to run the engines at 18000 rpm with sintered bushings, but for low speed engines they work very well, and their ability to retain oil seems to give them an advantage over solid bushings.---Brian


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Old 01-12-2017, 03:53 AM   #33
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Brian,

No experience using them like you are doing, just many years experience of using many types of bearings and materials for bearings, including Oilite in a vast array of circumstances. In other words, the right ones for the job.

They are not designed to be used with shock loads because of their build structure, they are very fragile when used in shock compression, which is the state you are using them in. Maybe you are just lucky.
I know this isn't definitive, but it does show that solid bronze is preferable to Oilite due to their relevant strengths

http://www.getyourbearings.co.uk/oil...horbronze.html

Take note of the shock loads and maximum load.

If it was me in that situation I would use something like these polymer bearings or their steel or bronze counterpart. In fact, I would most probably make my own out of something like ali bronze.

http://uk.rs-online.com/web/p/linear...rings/6671434/

One of these bagged sets would last a lifetime in the smaller sizes.

John
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Old 01-12-2017, 07:27 AM   #34
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Hi All,
Made a start on the con rods.

John,
Like Brian, I have had no problems with the Oilite bearings in the big end, as long as they are not machined. They fall apart if you machine the ends(brake The seal so to speak) if they are too long. I order to size. With the con rods for the twin, I have will have to make them out of some bronze that I have as my supplier can not supply the width of bearing that I need.

Barnbikes, Jon, the fly wheel does not need to be twice as big, could use the same as for the single, could even use a lighter one. How do you calculate is a lot of maths that I don't have handy.

Cheers
Andrew
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Old 01-13-2017, 03:36 AM   #35
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Hi All
Got the con rods done, started the assembly.

Cheers
Andrew
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Old 01-13-2017, 05:46 AM   #36
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Hi All,
Getting close now, have to work out a fuel tank, and a flywheel. May have a contact with someone who has there own forge, may be able to make my own flywheel blank.

Cheers
Andrew
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Old 01-13-2017, 06:35 PM   #37
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Really aced Andrew on your design of offset (to block) cylinders and overhang crankshaft. I have a couple engines using that concept I'm happy with.
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Old 01-16-2017, 05:12 AM   #38
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Hi All,
Sneaky little fuel tank made and fitted. Just waiting on some more magnets for the ign system.

Cheers
Andrew
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Old 01-18-2017, 12:08 AM   #39
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I'm interested in seeing this run. Everything I have read about twin cylinder engines indicates that if the cylinders are not diametrically opposed, or side by side, that the engine will "lope" because of the angled configuration. I don't know if this is a concern for model engines or not. I have seen videos of the Hoglet engine that seemed to work alright. I have no doubt that it will run. It is an interesting adaptation of the original design.---Brian
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Old 01-18-2017, 01:28 AM   #40
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Originally Posted by Brian Rupnow View Post
I'm interested in seeing this run. Everything I have read about twin cylinder engines indicates that if the cylinders are not diametrically opposed, or side by side, that the engine will "lope" because of the angled configuration. I don't know if this is a concern for model engines or not. I have seen videos of the Hoglet engine that seemed to work alright. I have no doubt that it will run. It is an interesting adaptation of the original design.---Brian
Thank Brian, I am looking forward to running it as well.
Got the magnets today. Fitted the twin pickups, and then set the timing(5 deg BTDC) very easy with the ign test module.
Got a reply on a price of 6" dia brass today, will be in next week I hope, will make a very nice flywheel.

Cheers
Andrew


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