Catapult beam ratio

[Akitist]

Tried to post this question before, but it disappeared. Wonder what happened.

Anyhow, it seems that many "catapults" use a trebuchet-style arm (class 1 lever). Is there a rule of thumb for calculating beam ratio similar to Phsstpok's Rule for HCW trebs? Any input will be appreciated.

[TeamHazard]

Is there a rule of thumb for calculating beam ratio similar to Phsstpok's Rule for HCW trebs? Any input will be appreciated.

i've been doing this for 5 years and i have no idea what he just said - my ratios were this piece fits and the other one will work - i'm probably not the best one to give technical advise -

[Akitist]

Phsstpok's Rule is a guide to balancing the leverage ratio of the arm with the amount of counterweight and the mass of the item being thrown. As much effort as goes into a big spring-powered rig I thought there'd be some numbers for optimizing the leverage versus motion-multiplier ratio.

[Hypertension]

It's funny I am fooling with this right now. Hypertension has worked for years on a 5/15 rule. 5' at the power end and 15 on the leaver.
It worked when we functioned more like a treb at treb speeds but I am convinced it's worthless once you exceed (Greatly) those speeds. I have said for years we function more like an Onager now with very sim limitations...

I am right now playing with cams like Chucky, Sir Chunks a lot and slayer use. The beauty of cams are that you can make up for stroke issues using the ark of the cam. The cam also allows for a change in power depending on the cam design and the placement of the peak.

Hypertension is getting a ratical makeover... Not Chucky ratical, but will move the towers to allow us to take advantage of a full stroke but much larger than most in our class. Power development is not our problem so a longer stick will be no big deal.

I now think that because of the stroke limitations we are not going to do much better than 1600-2000' With a full range of motion we should gain a ton of speed. Hyper T is now 10 years old on her existing frame and I guess it is time we look like something new.

I do agree with you that once you start speed ball pitching the traditional treb look is very limited.

Hypertension as it sits now is very much like a top fuel dragster that just can't seem to hook up a massive amout of power and make it mean business. The limitations of the beam design are a huge part of those problems.

The new project is forcing a second 7000lb axle under the trailer to hold it all... It never ends. The new mag wheels and tires showed up today, the new fenders tomorrow and Axle system tomorrow. We just got the steel for the new beam and new towers 2 weeks ago. So we are committed. Need to get it built before Spring.

The King of Spring