Jump to content
SAU Community

My Own Pistons And Rods...

nissan200sx.dk
 Share

Recommended Posts

nissan200sx.dk Community Regular

nissan200sx.dk

Posted
Posted

Hi.

Have just finished my education, FINALLY!!! And have gotten a new job with acces to much more "fun" machines. hehe.

Its basicly just draw it in solidworks, CAD/CAM, and make the part.

Sooo, i wanna make my own pistons and con rods.

Have thought of 7075 aluminium for the rods, but dont know what material for the pistons.

Rods are much more beefy than std rods, as they are aluminium so need to be bigger.

This design has been tested in COSMOS (in solidworks, with very high test loads) and it have been redesigned some times to get to this. In solidworks, with correct material inputted they can withstand over 2000nm of force down on them, and also in pull and twist.

They are not too wide so they will touch pistons when engine is turning, have measured and tested. The chamfer in the top hole for lubrication is a little bigger than std.

On picture the big ends bearing caps are not cut out.

Are there anything I should be aware of when building my own rods??

Now to the pistons... What material?

How about design?

post-24535-1212584875_thumb.jpg

Link to comment
https://www.sau.com.au/forums/topic/222391-my-own-pistons-and-rods/
Share on other sites
Roy Grand Master

Roy

Posted
Posted

Also, be careful with the modelling. Are you allowing for the lateral loads, intertia, cyclic stresses, heat etc etc Also how do you propose to make them, machinging from a billet i suppose? A set of aftermarket rods are already cheaper then the price you will pay for the billet you require to make the things :P

nissan200sx.dk Community Regular

nissan200sx.dk

Posted
  • Author
Posted

I want to make them, because I can make them myself. :) This is one long learning process..... So they will be tested in a engine on a test stand first. hehe.

I know alu expans more, but there is ALOT of different alu.. Some expand more than others, and how hot is the rod going to be???? Recon it wont be hotter than the oil its covered with? Then its faily easy to calculate how much it will expand.

We have a danish dragster team, they have over 6000hk and have seen one of thier homebuilt rods. Its alu, and just much much more beefy. thats it. Like the one i have drawn, but mine is going NO WERE near 6000hk, its maybe going to take 1000hk. (This is far out in future dreams, if rods and pistons are made by me, and tested etc etc etc.)

Ï know aftermarket rods usually are somekind of steel... But they can be made in alu also.

My new company I work for make ALOT of aluparts for the military.. (also carbon parts for that matter)

Could rods be made in carbon? <-- crazy thougt?

If the say the lenght of the rod, this is way way overrated, would expand just 0.1mm. How much influence does that have???? Would recon nothing, as the squish is more than 0.1 mm, and piston to valve clerance is also bigger. (pistons could just be made with cut outs for valves if an issue)'

One more thing I havnt really gotten clearified is the design of pistons. They are not completly round, but how much?? I recon this has some corolation to how much it expans.?

(Sorry for bad english, some technical words im not sure of in english)

Adriano Grand Master

Adriano

Posted
Posted

The rods will definately get a lot hotter than the oil, the oil cools them. they are also a lot longer than a piston is wide, i would expect to allow .25mm for thermal expansion, which effects squish and comp ratio. I would get a forged piston and measure how much "barrel" shape it has. How do you plan on forging the blank?(ps you can buy forged blanks)

**RB2530** Proficient

**RB2530**

Posted
Posted
Hi.

Have just finished my education, FINALLY!!! And have gotten a new job with acces to much more "fun" machines. hehe.

Its basicly just draw it in solidworks, CAD/CAM, and make the part.

Sooo, i wanna make my own pistons and con rods.

Have thought of 7075 aluminium for the rods, but dont know what material for the pistons.

Rods are much more beefy than std rods, as they are aluminium so need to be bigger.

This design has been tested in COSMOS (in solidworks, with very high test loads) and it have been redesigned some times to get to this. In solidworks, with correct material inputted they can withstand over 2000nm of force down on them, and also in pull and twist.

Dood,

You are keen!!

Just a couple of things though...2000Nm (always need to pay respects to Isaac Newton and use a capital N) is a torque or torsional force. Linear force is measured in Newtons or (N) Anway just wondering how you got this number....Is it from a static or dynamic calc...

When I was at uni I did a conrod design project and found that the dynamic stresses far outway stresses caused by gas pressure on the rod from the piston...These stresses increase with rpm and the relationship is pretty much a squared one...ie if you double the engine rpm, the conrod stresses increase by a factor of four...I also worked out that the highest stresses are tensile and experienced just after TDC on the inlet stroke...The reason for this is that the rod has to accelerate the piston mass, overcome piston friction and also draw in the air fuel mix...This force is by far the highest when engine is at full rpm and the throttle is closed suddenly producing high cylinder vacuum. This is why good rod bolts are so important cause the tensile stress in the rod bolts can be absolutley huge and get much much higher as rpm increases...

On the power stroke the mass of the piston causes a tensile stress in the rod but the gas pressure produces a compressive force...these forces then start to cancel out and the resultant force is less....

You also need to consider bending in the rod...the angular acceleration of the bigend compared to the little end is huge as well so the rod has to be stiff enough resist fatigue due to cyclic bending..eg the use of H-beam rods that have high stiffness across them...

Anyway mate good luck with it but I would really recommend you try the rods and pistons out in a crap engine first...

**RB2530** Proficient

**RB2530**

Posted
Posted

Just remembered that you also should use a material that has a relatively high elastic modulus because conrods stretch elastically due to the high tensile load and which means they come higher up in the bore with increasing rpm....they also get shorter at bdc but this has less impact...obviously...the hisgher the elastic modulus, the less they stretch...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • EndZee
      Fuel Pump Control Module & Dropping Resistor

      By EndZee · Posted

      Guys since i bought r33 gts25t coupe 1994 automatic a/t(manual swap 350z gearbox)  all i got is problems, always problems. Lets start with that when i turn key into ignition(ON) fuel pump doesnt always works. Sometimes i have to turn key twice Off/on/off/on until it primes. Its new, dw300 - 340lph. My gearbox broke so i did gearbox swap, install different intake manifold, injectors and i take pipes. Car was sitting in garage for more than half a year. I did assembly all not that long ago and when i turn ignition cant hear prime. All of sudden it stopped working. Theres many videos on YouTube how to make relay mod on r33 straight from battery so i did and it doesnt work! 😰 30 - battery positive  87 - positive from fuel pump to relay 85, 86 - one of two wires from original fuel pump wires(light blue, grey) and it didn’t work. so I check on ignition and took original BLUE relays wires from trunk, next to fuses. (I believe it’s IGN+ and ECU pin 18. it didn’t work…  tried connecting (IGN+ from og relay) and (ECU 104 from 1of4 FPCM wires) to my new relay 85/86 and it didn’t work.  I unplug FPCM. Didn’t work. im thinking what’s wrong   fuel pump is working, if I leave IGN+ on 85 and 86 straight to ground it works but it’s just nonstop. Since it getting constant 12v after key in ON. light blue wire gives me 6-8v.  so how this should be connected? What causing ECU not giving — on pin? Or I did sth wrong and that’s why it doesn’t work? I need negative signal on ECU that control fuel pump. What this should be?
    • Duncan
      M35 Brake caliper replacement

      By Duncan · Posted

      You can use your VIN to look up the factory part number somewhere like amayama, and then look to order new if necessary. https://www.amayama.com/en/genuine-catalogs/nissan Depending on price you might want to rebuild instead. @GTSBoy I had an interesting insight into US market parts when the Titan rear calipers were sticking. New calipers were dirt cheap, about 20% more than a rebuild kit....they are just considered throw away maintenance items
    • Duncan
      Most women will agree that parking is the most taxing part of driving

      By Duncan · Posted

      Funny, but really not funny. Thank god (most) f the world has moved on since then
    • Duncan
      Jacks that fit under GTR lips that can reach the subframe?

      By Duncan · Posted

      Lots of votes for driving onto a plank first; that is the quickest way I've found, 25mm is enough for my case but that will vary by car It also depends where you are going for. On the 32 I can get to the rear diff with my floor jack if I do that end first, and get it up on stands. Then I lift the front from either front tow hook as high as needed, also onto stands. Sometimes I need a small lift on the other tow hook to get it level enough If I do the front first I can't get to the rear diff because of the angle of the car Other options are getting to the front mount of the rear subframe from in front of the wheel (if only lifting one side, or just do both which is a bit of a pain compared to one lift from the diff), or also the gearbox cross member mount on the driver's side if you are  just trying to lift the driver's side. I This is the jack I use; it says 75mm clearance but of course that is only on the lower section so if you have to reach too far in like the diff you still get stuck. https://www.snapon-bluepoint.com.sg/category/Floor-Jacks/product/Floor-Jack,-2-Ton-Low-Profile
    • Duncan
      NC MX5

      By Duncan · Posted

      On the bright side, the weather will turn much nicer for working outside shortly....sounds like you might need to start on a neighbour's garden next
×
×
  • Create New...