Pro/E Mechanism - Crank, rod and piston assembly main bearing loads

[asecker]

Hi all,

I posted this query at mcadcentral and the PTC forum at the weekend but haven't had a response as yet so thought I'd try here.

Sorry for the length of the post but I just wanted to describe how I've set up the assembly.......

I'm currently working in Pro/E Mechanism with a flat plane V8 crank, rod and piston assembly. Basically I want to be able to create measures which will give me results for the 5 main bearing loads.

I have set up Mechanism to analyse the system over one engine cycle (2 crank revolutions) and have applied combustion loads to the top of each piston as a function of the "crank_angle" measure I have set up.

I have applied "connection reaction" measures to the Mechanism joints between piston and rod little-end and between crankpin and rod big-end. I get good results from these measures. The forces are of the correct order and they vary as expected over the engine cycle. I have an excel spreadsheet I wrote a few years ago for a similar engine which I'm using as a reference to verify the results.

However, I'm struggling with the crank main bearing loads. Since I posted on the other sites I have assembled the crank in a slightly different manner. I have created 5 axis within the crank part through the 5 main bearing surfaces. I have also created 5 axis in the relavant positions within the skeleton part and used these as the pin joints to assemble the crank.

I have then applied a servo motor at the first of these pin joints to turn the crank assembly.

I have set up 5 "connection reaction" measures at each of these 5 pin joints but I'm not getting the correct results. 4 of the measures produce a constant 30N force while the first pin joint constraint within the assembly seems to give me results for the total forces applied to the crank. This does seem to vary with combustion load and crank angle so I seem to be getting somewhere. I just need to split this total load up along the 5 main bearings somehow.

I've tried moving the constraints around but the only thing I have found is that the total load on the crank is linked to the first pin joint constraint within the assembly.

If anyone has any ideas I'd be very grateful.

Many thanks in advance,

Adam

 

[JCReynolds79]

Sounds really interesting, sorry I can't be of much help as its over my head a little.

But my interest is because I have been doing some simpler analyses of a crank/rod/piston assembly, well just crank really, but just in a simple static load case. I.E. gas force down as a 'bearing load' on the crank journal and a mixture of constraints and rigid connections at the mains to try and get realistic stress results in the critical areas, i.e. crank pin fillets.

It was finding a suitable way of applying constraints to the mains that kept me going for a while but I think I have a suitable method now, but I would be really interested to know how you are constraining your mains.

Cheers

Regards,

Jon Reynolds