particles particular problem.

I want the particles to do their thing three times.
on frames 40,55,& 70. (of 180 frames)
Can i ipo them ?
do i need three sets?

If I understand you correctly this is what you are trying to do:

Object a sits quietly (and probably invisibly?) until frame 40. At frame 40 object a emits particles, then stops. Then again at frame 55 object a emits more particles and then stops. Finally at frame 70 object a emits more particles then stops.

If this is correct there are two options available to you.

Option 1: duplicate your object twice and set the start and stop frames to 40 and 41, 55 and 56, and 70 and 71, respectively. Animate as usual.

Option 2: Use an animated texture to control emission. Click the TexEmit button and choose which texture channel you will use. In materials, click add new for that texture channel (they are numbered top to bottom, 1 to 10). Then in the texture buttons select the texture type as image and load your avi (or whatever) to control the texture. Click the movie button there on the right and play with the controls until satisfied.

Mind you, I’ve never personally used this feature before, so you’ll have to experiment a little to see whether white or black colors emit. If it is opposite of what you want, just click the TexEmit button again.

Oh yeah, your avi texture should be something like pure black on every frame except frames 40, 55, and 70, which should be pure white.

Hope this helps.

I will stick to simple duplicates - for now.