Hydraulic vise from car jack

[warsztatOdZera]

My old vice isn't work as good as it should be so I decided to make new one.
I took materials from the scrapyard. The jack has capacity about 5 tonnes.
I suppose that it hasn't so much capacity but it should be sufficient for my needs.
The whole vise weighs about 40 kg/90lbs.
If you have a question to me about this vice, just let me know in the comment section.

[Altair]

Thanks warsztatOdZera! We've added your Hydraulic Vise to our Vises category,
as well as to your builder page: warsztatOdZera's Homemade Tools. Your receipt:

Hydraulic Vise by warsztatOdZera

tags: vise

[Johannasp]

very nice planning on building one myself

[Crusty]

That's a badass vise!

[Paul Alciatore]

I am curious about the reasoning behind this. First, it must take longer to close it than a screw vise so there is one negative. And the opening seems to be about average for the jaw size (width) so that is neither a positive nor a negative. It looks like the base is made from steel instead of cast iron and it has an extended height, probably anticipating bending due to the forces of closure. I have seen vises that have bent bases so I wonder, will it hold up over time?

What are the positives? Can it actually exert more force than a screw vise? And is that really needed? For what?

Are there other advantages?

And I have to wonder why you beefed up the movable jaw to the same extent as the fixed jaw, but the post at the end that the jack bears against is built more lightly? It would seem that this post would need the strength more than the movable jaw. So, why on that?

I am trying to understand why it is designed as it is. Frankly, I do not see the design as being optimal.