would it be possible to get the link to the treb sim that you use in lots of videos and i respect that you show us your failures without extreme bitterness thanks for your honesty
234 m isn't catastrophic, but breaking the arm sure is... This failure led me to contrive a different release mechanism for the CW. See 120lb Counterweight Baseball MURLIN
Have you ever tried adding a piece of metal were the rope goes in the throwing arm in case the ball slips out of the sling so you don't have to keep replacing the throwing arm every time it breaks.
I have two ropes to reduce the load on the rope, and to keep the forces on the throwing arm more symmetric. It wouldn't do to have the throwing arm twisting due to 2000lb loads just before release - 1000lb on each side is much better. Regarding the rope/spring comment, you are correct. I am redesigning the release mechanism to hold the CW at the top of the frame so that there's no tension on the CW cord when the trigger is pulled.
Instead of having two ropes on either side of the machine why don't you just have one. And one more question do think as soon as you release the arm the rope acts like a spring thereby jerking the arm forward and having the rope jump the notch in the sprocket.
@Idvance01 what do you plan to do overall do you plan to build something to fling pumping like in punkin chunkin or do you just want to see how efficient a trebuchet could be.
@ACDC5968: Hard for me to see exactly what you're thinking, but I do have a 'stopping sprocket' on the base of the throwing arm , which absorbed the great majority of the energy by bending nearly into a semicircle.
My analysis tools tend to come up with about the same radii for the longer sprockets. I think this is because it keeps total arm inertia down. Smoothing can be important, however between the two final (smallest) sprockets.
Well, I'm hoping so. I've got some design problems to sort out. I think I must figure out how to suspend the CW without holding it by the arm. The resulting spring in the cord immediately following release is the dominant source of the cord and projectile jumping out of their respective places.
Atkist: I guess I could rig up larger sprocket channels - probably make them out of aluminum stock to supplement the fender washers. I'm pushing the weight ratio up deliberately high in hopes of applying the lessons to a pumpkin tosser someday. Looks like I can keep decent efficiency up to mass ratios of about 400.
@spunkyprep: The jury is still out on that one. Both devices are capable of very high efficiencies. I also don't know how high a FAT can push the CW mass before efficiency rolls off. One thing is known. Variants of the FAT are very popular at the Chunk, but there are no MURLINS, yet.
120 pounds is just an awful lot to throw a baseball with. Hope it's just the arm that needs rebuilding. Deeper retaining channels on the sprockets? The kilofoot is a great goal. Hope you can reach it.
I am working out the kinks in this device so that I can apply those lessons to larger projectiles, ie pumpkins. Not sure exactly how to do that with my small garage, but that's my eventual goal.
My little F2K couldn't get past 850' on a calm day dropping 108.5 lb. The arm broke at 111 lb. 5oz base balls do not fly well. I'm going to make another attempt with the 5oz then go to the 10 or 12 oz x 9" practice ball. I don't know if I can get there with a 5 oz ball. I have seen the "efficiency roll off" ld spoke of. It may have to do with sling length as the arm speed increases.
would it be possible to get the link to the treb sim that you use in lots of videos and i respect that you show us your failures without extreme bitterness thanks for your honesty
Good-humored, courageous, and improvement-oriented to share your failure. Thanks.
234 m isn't catastrophic, but breaking the arm sure is... This failure led me to contrive a different release mechanism for the CW. See 120lb Counterweight Baseball MURLIN
Have you ever tried adding a piece of metal were the rope goes in the throwing arm in case the ball slips out of the sling so you don't have to keep replacing the throwing arm every time it breaks.
I have two ropes to reduce the load on the rope, and to keep the forces on the throwing arm more symmetric. It wouldn't do to have the throwing arm twisting due to 2000lb loads just before release - 1000lb on each side is much better.
Regarding the rope/spring comment, you are correct. I am redesigning the release mechanism to hold the CW at the top of the frame so that there's no tension on the CW cord when the trigger is pulled.
Bearach:
I actually don't give out any simulations. It runs in MatLab, but it's all my own code and represents thousands of hours of work.
I wonder, would this design be capable of out-distancing a FAT of a comparable size?
Instead of having two ropes on either side of the machine why don't you just have one. And one more question do think as soon as you release the arm the rope acts like a spring thereby jerking the arm forward and having the rope jump the notch in the sprocket.
@Idvance01 what do you plan to do overall do you plan to build something to fling pumping like in punkin chunkin or do you just want to see how efficient a trebuchet could be.
@ACDC5968: Hard for me to see exactly what you're thinking, but I do have a 'stopping sprocket' on the base of the throwing arm , which absorbed the great majority of the energy by bending nearly into a semicircle.
My analysis tools tend to come up with about the same radii for the longer sprockets. I think this is because it keeps total arm inertia down. Smoothing can be important, however between the two final (smallest) sprockets.
Well, I'm hoping so. I've got some design problems to sort out. I think I must figure out how to suspend the CW without holding it by the arm. The resulting spring in the cord immediately following release is the dominant source of the cord and projectile jumping out of their respective places.
Atkist: I guess I could rig up larger sprocket channels - probably make them out of aluminum stock to supplement the fender washers.
I'm pushing the weight ratio up deliberately high in hopes of applying the lessons to a pumpkin tosser someday. Looks like I can keep decent efficiency up to mass ratios of about 400.
@spunkyprep: The jury is still out on that one. Both devices are capable of very high efficiencies. I also don't know how high a FAT can push the CW mass before efficiency rolls off.
One thing is known. Variants of the FAT are very popular at the Chunk, but there are no MURLINS, yet.
120 pounds is just an awful lot to throw a baseball with. Hope it's just the arm that needs rebuilding.
Deeper retaining channels on the sprockets?
The kilofoot is a great goal. Hope you can reach it.
I am working out the kinks in this device so that I can apply those lessons to larger projectiles, ie pumpkins. Not sure exactly how to do that with my small garage, but that's my eventual goal.
My little F2K couldn't get past 850' on a calm day dropping 108.5 lb. The arm broke at 111 lb. 5oz base balls do not fly well. I'm going to make another attempt with the 5oz then go to the 10 or 12 oz x 9" practice ball. I don't know if I can get there with a 5 oz ball. I have seen the "efficiency roll off" ld spoke of. It may have to do with sling length as the arm speed increases.
How about a smooth Fibonacci spiral cam instead of the arms? I have some ideas...
You call 234 metres catastrophic with a an that small?
So, _not_ 1000 feet, then?
Nope, not with this model, but lookup THMPR golfball trebuchet. I got over 1200 feet with that one.
hmmmmm