Bore vs Stroke vs Displacement

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Old 09-21-2006, 11:49 PM
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Originally Posted by hav_lova
Are you kidding? i'm not trying to be a smart ass or question your experience but, my dad and i both run TZ's and have not had one single problem. his, i think has done around 14+ litres and mine around 7-10 litres (its hard to know mine exactly, as we share fuel) and both engines perform like they did out of the box, both have incredible compression and i run mine hard, and its the original conrod in mine, although i believe my dads was replace after a couple litres. so i wonder, how the hell do you blow up an O.S. after
?????

Come to think of it, he still uses both of my old os tr engines and i know for a fact one of them has run about 20 litres! the other around 8 and both go like an OS should!
I'm pretty sure that some of the early tz's had conrod problems, but they sorted them out.

If you break it and run it properly it should run for ages.
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Old 09-22-2006, 04:49 AM
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Originally Posted by hav_lova
Are you kidding? i'm not trying to be a smart ass or question your experience but, my dad and i both run TZ's and have not had one single problem. his, i think has done around 14+ litres and mine around 7-10 litres (its hard to know mine exactly, as we share fuel) and both engines perform like they did out of the box, both have incredible compression and i run mine hard, and its the original conrod in mine, although i believe my dads was replace after a couple litres. so i wonder, how the hell do you blow up an O.S. after
?????

Come to think of it, he still uses both of my old os tr engines and i know for a fact one of them has run about 20 litres! the other around 8 and both go like an OS should!
ok maybe not one day say about 3 but the two pistons did break the same way.i see guys run them for a long time but there not that fast and it wasent the con rods the pistons in 5 little peaces.
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Old 09-22-2006, 05:11 AM
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Originally Posted by wallyedmonds
ok maybe not one day say about 3 but the two pistons did break the same way.i see guys run them for a long time but there not that fast and it wasent the con rods the pistons in 5 little peaces.
Odd, ive never done that to an O.S.
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Old 09-22-2006, 06:59 AM
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Found this information that my shed some more light on stroke lenght


"Longstroke vs Shortstroke. Differently to four strokes, a short stroke is not higher power/higher revving in a two stroke engine. The port area available in a two stroke engine is proportional to the the cylinder wall area not the head area. This favours long stroke/small bore The limitation is friction/wear and inertial effects and so the best stroke/bore ratio seems to be between 1:1 and 1.2:1.
Rod/stroke ratios. A rod stroke ratio of 1.75:1 will give a good wide powerband. A rod stroke ratio of 2:1 will give a higher revving narrower powerband."


Dave Marles, Prestwich Model Centre, 1 Mill St., Golborne, Nr Warrington, England.


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Old 09-22-2006, 11:26 AM
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If anybody has a new (or relatively new) conrod, could you please measure points A and B as indicated below. Then I can put a engine matrix together for everyone to reference.

Thanks!


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Old 09-22-2006, 12:35 PM
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rmd, I think you should specify "GOOD" conrod or NEW, cause if the conrod is worn, then the data will be inaccurate.
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Old 09-22-2006, 01:00 PM
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Originally Posted by Warmac
rmd, I think you should specify "GOOD" conrod or NEW, cause if the conrod is worn, then the data will be inaccurate.
Thanks for pointing that out. Change made.
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Old 09-22-2006, 03:12 PM
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no prob rmd
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Old 09-22-2006, 08:53 PM
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Originally Posted by rmdhawaii
If anybody has a new (or relatively new) conrod, could you please measure points A and B as indicated below. Then I can put a engine matrix together for everyone to reference.

Thanks!

Novarossi conrod 25 mm between centers of the holes.
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Old 09-22-2006, 09:50 PM
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Originally Posted by afm
Found this information that my shed some more light on stroke lenght


"Longstroke vs Shortstroke. Differently to four strokes, a short stroke is not higher power/higher revving in a two stroke engine. The port area available in a two stroke engine is proportional to the the cylinder wall area not the head area. This favours long stroke/small bore The limitation is friction/wear and inertial effects and so the best stroke/bore ratio seems to be between 1:1 and 1.2:1.
Rod/stroke ratios. A rod stroke ratio of 1.75:1 will give a good wide powerband. A rod stroke ratio of 2:1 will give a higher revving narrower powerband."


Dave Marles, Prestwich Model Centre, 1 Mill St., Golborne, Nr Warrington, England.


AFM
hey AFM, you are getting really close to real info. I am aplause to you, and my hat off to you. Now calculate what is conod ration for 25 mm conrod lenght and 14 mm strock and 14.25 mm strock-then here is some answer. Keep going and I am sure you are pretty close to make some seriouse stament and I will support it. Please PM your email and I will send you some programm for help to play around.
BTW, Prestwich posted a lot of valuble info on the web. Just keep diging it-very interesting thing will find there as well as on other sies too..
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Old 09-23-2006, 05:11 AM
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Originally Posted by afm
Found this information that my shed some more light on stroke lenght


"Longstroke vs Shortstroke. Differently to four strokes, a short stroke is not higher power/higher revving in a two stroke engine. The port area available in a two stroke engine is proportional to the the cylinder wall area not the head area. This favours long stroke/small bore The limitation is friction/wear and inertial effects and so the best stroke/bore ratio seems to be between 1:1 and 1.2:1.
Rod/stroke ratios. A rod stroke ratio of 1.75:1 will give a good wide powerband. A rod stroke ratio of 2:1 will give a higher revving narrower powerband."


Dave Marles, Prestwich Model Centre, 1 Mill St., Golborne, Nr Warrington, England.


AFM
Good post this is the sort of stuff I was getting at above. This sort of analysis will really allow you to start seeing why certain engines react the way they do beyond merely the stroke/bore ratio.
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Old 09-23-2006, 07:06 AM
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Originally Posted by EdwardN
hey AFM, you are getting really close to real info. I am aplause to you, and my hat off to you. Now calculate what is conod ration for 25 mm conrod lenght and 14 mm strock and 14.25 mm strock-then here is some answer. Keep going and I am sure you are pretty close to make some seriouse stament and I will support it. Please PM your email and I will send you some programm for help to play around.
BTW, Prestwich posted a lot of valuble info on the web. Just keep diging it-very interesting thing will find there as well as on other sies too..
Thanks Edward

Lots of information available on the web, specially on R/C boating and airplane sites.

This is fun......reserching and learning beyond copying other modder's work.

Do you happen to have numbers on the Mega ZX 12 engine?? rod lenght, timing numbers, etc.???

BTW, I sent you PM

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Old 09-23-2006, 07:30 AM
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Yup! This is really awesome! Thanks AFM. .12 Knowledge Base

Trying to make an informed decision about what engine to get next has been pretty difficult for me. Based on the specs that manufacturers publish, it's next to impossible to determine what the real differences are between each engine and what exactly you're getting. That's why most of us just rely on other people's experience and opinion. Clutch and 2-speed tuning are really big factors in getting the most out of any engine of course, but if you select the wrong engine for the type of track you racing on to begin with, then you're just wasting your time.

This can't possibly be this simple. Crank out a bunch of formulas to help people choose an engine? Add on gearing info and then all of this becomes a no brainer.

I must be missing something...
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Old 09-23-2006, 07:52 AM
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I just did the rod/stroke calculation for the WASP Rev:

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Old 09-23-2006, 03:44 PM
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Originally Posted by EdwardN
Novarossi conrod 25 mm between centers of the holes.
Thanks Edward. Is the Axial conrod 25 mm as well?
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