# Search results

1. ### I wanted to know that what exactly is Knocking in an engine cylinder.

http://en.wikipedia.org/wiki/Engine_knocking
2. ### Tensil or compression?

Ok i'll give this one more try. Previous post is not a calculation example, you dont really calculate, just assume stresses. Say you have those as your principal stresses, they are all negative. As you change the orientation, shear stresses will appear within the planes along that...
3. ### Tensil or compression?

My guess?What are you talking about? The negative positive is BY DEFINITION compressive and tensile. I told you these are tensors, stress will be like this in one direction, like that in other direction. Why dont you do a calculation instead of speculating? Solve a problem with a cylinder under...
4. ### Tensil or compression?

You do have to know it very well to do advanced analysis like FEA, etc. Anyway, if you know the six stresses sigmaxx,sigmayy,sigmazz,sigmaxy,sigmaxz,sigmayz (if isotropic, they define the stress state) at any orientation, you can calculate the principal stresses using the formula in wiki. Then...
5. ### Tensil or compression?

Wikipedia? http://en.wikipedia.org/wiki/Stress_(mechanics [Broken]) From your stress state, find the principal stresses and then calculate 3d mohr circle, its there in wiki. Like i said, positive values mean tensile, negative means compressive.
6. ### Single Stroke Engine with two cranks

No there is a fundamental difference here. The only reaction force to the piston expansion is the inertia of the piston itself.Unless you make it super heavy, you cant use the power cycle effectively. If its that big, its useless anyway. It will tend to quickly settle in the middle and try to...
7. ### Simple mechanisms to measure joules output?

Just use a microphone touching the spring (just stick its face on the spring) and record the sounds at 44khz you can easily resolve milliseconds. The engine sounds will be background compared to that. So in the recording, you'll have some background followed by some large peaks (main) followed...
8. ### Single Stroke Engine with two cranks

I dont think this engine would run any cycles at all. It will just settle in the middle and start violently shaking.
9. ### Web service/person that solves engineering/maths r

How critical is your application?If its not gonna kill anybody :) , you can probably find some ME grad student here if you offered money.
10. ### Tensil or compression?

Can you elaborate more on what you are trying to do?So you're running finite element analysis(3d element?) or you're referring to something else? Basically, if you know the stress state, you still need to define an orientation to find stresses; stress is a tensor, it varies with angles. After...
11. ### Simple mechanisms to measure joules output?

Can you explain your system in more detail? For now I think you can use a coil spring which has some marker like a pen on it, so you can measure the maximum compression distance and calculate the variation in force within the spring. At the same time, you can use a microphone to pick up the...
12. ### Extrem precission

Micrometers are used to measure down to 0.0001 in, so in theory they can be used to move linearly that much as well. You can buy one as low as \$37, hook up a motor at the end with limiters(something that will keep it from rotating further), then you can move anything that much back and forth. Or...
13. ### Cheap Continual Motion Linear Actuator?

Why dont you use something like this? http://www.youtube.com/watch?v=poDwOv3unD8&feature=related
14. ### Pet project. Sane or not?

Hi Jim Unfortunately what you describe is perpetual motion. The power you produce from the falling mass will never be enough to power the winch system to raise it back to the same height, it will be slightly lower. So this machine will run some cycles and eventually stop. I wouldnt waste too...
15. ### Stress strain and tensile strength diagram

The load falls off because the amount of area reduction in the necking area is faster than the work hardening in the material. So although stress increases, the load still drops. Engineering stress doesnt take the area decrease into account so it shows a decrease whereas true stress relates to...
16. ### Stress strain and tensile strength diagram

necking means your sample gets much thinner at some point than the rest. Imagine most of the cylindrical sample diameter is say 1 inch, length is 5 inches, there's a region which is 1 inch wide in the middle thats only half an inch in diameter. that region is said to show necking, deformation is...
17. ### Two wheel non-balancing robot

The extra weight wouldnt work. Your wheels will turn but also the cylinder, their velocities proportional to moment of inertias. The wheels have esp high mom of inertia because most of the weight is on the outside. In the end, you would get little velocity. To get reasonable acceleration, the...
18. ### Gear v/s roller drive

The bearing (the hole) where the shaft of the gear goes is also important, if its too loose it will be noisy. Also lube the gears well.
19. ### I was wondering is there a way to connect two rotating cicrcles

Do you want a rigid connection or flexible one?What are the desired degrees of freedom?