Tractor pulling a trampoline - GIF

**Jon** · Mar 29, 2019, 12:53 PM

When you're a farmer, but your real love is demonstrating the laws of physics.

Also, are those guys stomping on the trampoline to heighten the other guy's bounce? I didn't know you could do that. Perhaps because that's the sort of information that people hide from their children.

Previously:

Tractor-mounted irrigation pump - GIF
Tractor plays percussion in bluegrass band - video
Tractor-powered wood chopper - GIF
John Deere tactical tractor

**12bolts** · Mar 30, 2019, 11:19 PM

Didnt you ever double up on the trampoline as a kid Jon?

Originally Posted by Jon

Also, are those guys stomping on the trampoline to heighten the other guy's bounce? I didn't know you could do that. Perhaps because that's the sort of information that people hide from their children.

If you get the timing right, and especially if, say, your older, heavier brother was with you, then he could pretty much catapult you out of the backyard!

**Scotsman Hosie** · Mar 31, 2019, 01:18 AM

That's always been the trouble with them farm boys. No appreciation of the hazards they're screwing around with — while tempting the Gods.

**ranald** · Mar 31, 2019, 06:28 PM

Originally Posted by 12bolts

Didnt you ever double up on the trampoline as a kid Jon?If you get the timing right, and especially if, say, your older, heavier brother was with you, then he could pretty much catapult you out of the backyard!

Reminds me of my previous (late) partner. She loved her cats but had an allegy to them. One seemed to love lying on her side of the bed. I would try to encourage it to not get on the bed by carefully removing it but every day I would come home & there it was on the bed again. One day I kicked down on the water bed and bingo; I dont know who got the biggest shock. The cat was propelled out the second story open window. That cat kept coming back to lie there so I gave up & watched my wife suffer while continually rubbing her eyes & taking medication.

**JTG** · Mar 31, 2019, 08:00 PM

Despite initial appearances, these people actually know what they're doing (they have some level of gymnastic training), and they are using professional equipment -- that's a competition trampoline, which you won't often find outside of a gym because they cost anywhere from $6-12k.

The technique is called double bouncing, and in this case it's the only reason the person can keep bouncing while landing on his stomach, which doesn't let you add any more energy into the bounce. Without the double bouncing, he would get five or six bounces of decreasing height. It can also be used to get insanely high off the deck of the trampoline if done correctly.

They're doing a partial version, where two people use one leg to put their weight onto the deck as the third person comes down, such that you effectively have the weight of three people loading the springs. As the rebound begins, the two people at the sides shift their weight onto the frame and bend their other leg, such that they don't take any of the energy they put into the springs -- it is instead transferred to the third person, who goes proportionally higher.

This can be done with two (or more) people at full bounce, with one bending their knees and crouching on rebound to stay on the deck, while the other goes soaring. Back when I was training, I once hit the drop ceiling over the trampoline at my gym, which was 25 feet over the deck.

Note: double bouncing shouldn't be done on consumer-grade trampolines (the round ones), because it is very hard to control the direction of the doubled bounce, and you can find yourself far away from the intended landing zone. Enthusiastic double bouncing can also cause the deck to bottom out on the ground, and I know someone who sprained an ankle because of this.

**Big Sexy** · Apr 1, 2019, 09:47 AM

I was 300lbs and my 10 year old 60lb daughter use to jump on her trampoline together. Launching her higher than the safety net was my favorite thing to do with her on it. She loved it too after she learned to expect it. The first time she got hysterical from it. But after calming down, it’s all she wanted me to do with her on the trampoline.

**JTG** · Apr 1, 2019, 01:27 PM

I'm glad that you and your daughter had fun on your trampoline -- my point was more to emphasize that the forces involved in trampolining can be much higher than anyone would rightly expect, and that a certain level of caution is necessary, especially on consumer trampolines. For example, a 165-lb gymnast bouncing 12 feet off the deck will experience a (brief) peak force of ~11 bodyweights (1815 lbs), and the trampoline suspension system will see a peak force of ~25 bodyweights (4125 lbs). Here's the reference, for anyone interested, though be warned it's a 164-page pdf of master's thesis.

With that in mind, most consumer trampolines have weight limits of 200-300 lbs. There's an ASTM guideline stating that a trampoline should withstand four times the rated weight limit, but the test is done with a static load -- the springs can permanently deform on a 200-lb rated trampoline when an 800-lb load is placed on it, allowing the deck to bottom out. They can also deform when a single 150-lb person is bouncing more than ~8 feet, or when two high-school students are trying to double bounce at 4-5 feet.