Planet Minis

chasetheface123

Jordan pm me back

cyclerider57

I had a little extra time today and the camera was handy...

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z50 chopper

I just skimmed over the thread as I am in a rush but from what I read and saw this looks very promising. cyclerider57 you do amazing work.

chrisc161076

Is it possible to carry out some FEA on a modified stock rod, drill holes, carry out some shaving as l assume Honda has allowed massive safety factors in their original design.

Then make a comparison cost verses gain.

cyclerider57

Absolutely, the shiny dimple on that stock rod in the picture is from a drill bit... Many of my rods have had holes drilled in them (minis and otherwise). The stock rod pictured actually already has two small pilot holes drilled (got side tracked before finishing the process on that rod) but they can't be seen very well. Modifying a stock component only takes cost in the form of hours to do the work so it is always a preferred method. Keep in mind safety factor almost cut in half with a double of hp... Stock 50 rods can take a lot of abuse because design has remained unchanged for 20 years but the material quality and consistency has increased. Think about it, there are 50 engines running a completely stock crank putting down over 10hp on a rod designed for 2.5hp with no failures. For reference, a stock crf450 rod won't take over 60hp for very long and 65+hp is a major no-no on a stock rod (stock engine is 48hp on my dyno). It took breaking a few (even ones without being modified in any way) before going to a Carrillo rod. The rod I made for this engine, I just wanted something a little more special as my 50cc build is all about using stock parts and modifying them.

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb

chrisc161076

"Stock 50 rods can take a lot of abuse because design has remained unchanged for 20 years but the material quality and consistency has increased. Think about it, there are 50 engines running a completely stock crank putting down over 10hp on a rod designed for 2.5hp with no failures."

Excatly my point, so there is at least a factor of 4 incorporated in the design (material strength, cast quality etc etc) that can be played with and what is not saying that factor can't go higher?

Lets see it drilled, shaved, reshaped and coated for durability and see where it goes (or doesn't go for that matter).

Grafixxs

I hope you made that rod from 7075 and not 6061.

Motarded

he used 6061

Grafixxs

cyclerider57

Don't worry Grafixxs, I've taken it into account. If it was anything more than 90cc I would need at least 500 MPa ultimate and would have been required to use high tempered 7075. I still have to do my pull test and hardness test at the university to make sure the material sample I was sold was of correct grade. I've been given marked 6061 that wasn't even 6061 before. I should have done it before I took the time to make the rod but I get all antsy in my pantsy. If it isn't the right material I'm ***ed and this rod will be a show piece.

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb

LongMooie

ok what the feck is FEA
and im guessing the drilling of the holes is to reduce rotating mass?
id like to see a modded stock rod as i plan on lightening and balencing my stock cranck for the 50cc screamer

thanks

cyclerider57

FEA: Finite Element Analysis. It is a tool built into a lot of modern computer design softwares (such as SolidWorks and CATIA like I use) that breaks a part into little sections and calculates the stress in little pieces within complex part based on the forces we input.

Drilling the holes in the rod is all about reducing reciprocating and rotating weight (depending on where you drill them). It seems there is quite a bit more interest in using more of the stock components (like my 50cc build). Perhaps people would be more interested in that? Or a combination of using stock parts on the 88? Ideas anyone? I'm open to some suggestions yet as long as I can fit them into my build design. If there is interest in that then I will do what I am doing on my 50cc build and cut and shorten a stock rod along with the other work to it.

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb

LongMooie

id love to know more about the stock components and your 50cc build as you know thats what im wanting
(you never did reply to the email i sent you on the work i wanted done)

BlackBeard

I say leave the build as directed. I dont want to see stock parts modified, I want to see your mind and talent unleashed on a custom minicycle engine!

zwieblekopf

Why did you pick 6061 when you could have taken off more weight (or some) from the stock rod weight? I know 6061 is cheap, but if it's about the same weight and susceptible to fatigue then what's the point?

LongMooie

im a little confused as if its not standard lenght then how is it still 88cc you might need to dumb it down a little for us non techy guys lol

cyclerider57

A few reasons. A) To my knowledge, an aluminum rod has never been made for a crf50 so if I am capable then why not. B) I prefer making my own components when I can. I am in this for fun and making something from scratch is more satisfying than just hacking up something somebody else has already made. C) I wanted a shorter rod and although I have made jigs and cut and welded rods for race engines in the past, I didn't feel like doing it for this engine. D) I have been wanting to make an aluminum rod to test with a composite wrist pin to see which can handle the most abuse. This may be the engine to test it because it is a lot cheaper to trash a crf50 engine then a crf450, Harley-Davidson XR750, etc. E) My project focus changes so quickly that when I'm in the mood to make something different I need to do it right away or it will get put on the back burner and I won't ever get around to testing it (A.D.D.). It is very possible that this build will change as it goes and this rod may never even make it into this engine.

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb

cyclerider57

The length of the rod is not to be confused with the length of the stroke. This will still have a stock stroke making it 88cc. The length of the rod itself changes other characteristics such as where the piston reaches maximum speed, when it gets to maximum velocity, dwell time at tdc and bdc, forces on the cylinder wall, etc.

I tried emailing you but it got sent back with a delivery status failure. It should still be in my box. I'll dig it up and try again.

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The wise understand by themselves; fools follow the reports of others. Goodness speaks in a whisper, evil shouts. -Tibetan Proverb

orracle

I sure hope your planning on running some nitro through this motor to take advantage of that aluminum rod.

50rider340

If the rod is shorter what piston are you planning on using? Wont the piston sit lower in the jug if you used a standard 88 piston? Although i had a 106 tak piston sent to me instead of a 88 and the pin heights were different. Putting it in with a stock crank it sat just a hair out of the jug hence why its still sitting on the shelf.

So the question is what kind of piston are you planning to use? Or your going to be making your own. And just to stir things up a little what ever happened to that 4 valve head for a 88 motor you had going on solid works. Boy would i love that to be going onto this build. I know you got a part printed/made out on a rapid prototyping machine. I had a chance at school to do the same. I made a takegawa super head cam cover to spec to even fit on my motor. Those machines are sick with what you can do with them.