Ramp thread. >Are there any ways to get materials cheaply?

>>1018045
>that's obscenely shady

yeah that's not theft at all

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>>1018048
Yeah that's what I was getting at.

Go to a construction site, where they dig water pipes, heating or sewers. Ask for the manager, and then ask for used materials.

They often use plywood to prevent soil from collapsing down in to the trench. Some plates might be scrapped even though they are fine.. I have salvaged 20 plates this way, often in 244x122cm

Otherwise ask where they mold concrete.

>can only have a reasonable incline by code that makes ramps useless
>Looks inviting to lazy cripples
>More material used because of incline required
RAMPS BTFO, STAIRS4LYFE

RAMPFAGS JELLY

>>1018057
not utility ramps you mong, I want to throw myself into the air at high speeds

>>1018058
>throw myself into the air at high speeds
You better know how to calculate dynamic loads.

>>1018052
>They often use plywood to prevent soil from collapsing down in to the trench.
sure, just jump in your time machine and pop back to a time before health and safety.

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>>1018070
I'm a college student. I have a working knowledge of moments and centroids from an engineering class I took. Do you have anything helpful to contribute?

>>1018045
>going to a construction site
sometimes they trow away (in a dumpster) a lot of good 2x4s and sometimes plywood... taking material out of a dumpster actually helps them. they pay for each dumpster load to be taken away. if you take stuff out that means they can put more in before having to pay to have it taken away - they shouldn't complain about that.

>>1018095
This

Just dumpster dive OP. Also go around to places that get shipments on pallets. Sometimes you can score some good shit. 2 weeks ago I got a 4x8 sheet of plywood with a 2x6 frame already attached. It's now a small porch. A month before that I scored 2 6x8x12 beams that were solid red oak. Gonna milk those down into something useful.

>>1018045
>Any general construction/woodworking tips
your diagram looks like it might be a bit flimsy but I guess it depends on what you are going to use it for (bike, skateboard, roller blades, motorcycle?)
this isn't rocket science; I'd build strong frame out of 2x4 (or 2x6) then maybe thin strips of plywood on top to get the rough curve then maybe a layer or two of masonite over the ply for super smoothness on the curve. but note that masonite doesn't do well getting wet. painting it will help but if this ramp is outdoors in the rain you may need to replace the masonite periodically. that said I once used a piece of masonite as the deck surface of a tree fort and it lasted for many years totally untreated/unpainted in the rain and snow. the edges got a bit rough over the years but the rest of it stayed strong. I had the smooth side up.

>>1018100
*mill

>>1018101
masonite is thin and tough and will bend to a [gentle] curve nicely...

>>1018102
"milk" DOH! ;o)

>>1018091
Are you really bragging about taking an engineering class while asking for help with something teenage stoners have been doing since the 80s?

>>1018103
there is also a material called 'sintra' or 'cintra' (often used in sign making)... it is a highly compressed foam board. that might work as long as it is over a good ply base for support. it bends to gentle curves easily and is kind of 'plastic' like which means it is water proof - won't be ruined by getting wet in the rain. it might be expensive in large sheets though. whereas masonite is pretty cheap.

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>>1018091
>moments and centroids
Those are structural considerations, not load considerations. How many Gs will you be pulling? Once you figure out what you want the ramp to do (speed, dimensions, what you'll be riding, and the total weight involved), you can figure out what the load on the ramp will be. When you know that, you can do structural calculations to figure out how beefy the ramp has to be. THEN you can figure out what materials will economically give you what you need. What step have you completed?

>>1018134
too much BS for a simple ramp... if you are doing this for a car or motorcycle then yes maybe a little more 'figuring out the science' should be taken. if for a bike or skateboard; nigga please. just built it with 2x4s and it will be fine. as other post said: kiddies been doing this for a looooong time with just scrap wood and old bent nails. I made one for my BMX bike waaaay back when without any math or engineering BS. worked fine never broke. no problems. thanks for trolling. please try again soon.

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>>1018108
You might notice that none of my questions would be answered within the scope of an elective. These are all things I would want to know when I try to apply the mathematical concepts irl.
>>1018100
>>1018095
will probably do this
>>1018101
thanks for the input but I just entered the word "ramp" into google images and used the first image that seemed appropriate for the thread. more succinctly, I'm not actually using that diagram.
>>1018109
I wonder if this would cause weird traction problems like plastic ramps.

>>1018134
this >>1018160 was kind of my reasoning also. thank you for articulating in a way I probably couldn't.

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>>1018160
OP hasn't said what he wants to jump with. Just "throwing himself into the air at high speeds". That sounds like something where it would be prudent to do the math (which is engineering, not science). You know, so as to avoid the kinds of accidents that kids get into all the time doing things like this. If OP is an adult, a ramp strong enough for a kid might not be enough, and then he gets to catch a broken masonite edge with his face "at high speeds".

>>1018180
>OP hasn't said what he wants to jump with
true.
regarding the gif. -- looks like user error not an issue with the (strength of the) ramp.

just watch some MythBusters episodes. on one episode a while back they built a HUGE ramp for a rocket car using 2x4 trusses meant for a building roof. they laid (one layer of) plywood on top. I suspected with the mass and speed of the car hitting the leading edge of the ramp just one layer of ply wasn't going to be strong enough. it wasn't. but the car still jumped the ramp. just the first several feet of the ramp's deck got torn up really bad as the car adjusted to its new upward trajectory.
just saying that if OP is riding a skateboard, a bike, even a mini motorbike as in the gif, a 2x4 base with cross supports blah blah blah and a nice layer of ply plus something smooth on top of that will in all likelihood be fine. even for an adult. do not need a degree in engineering to build an easy DIY ramp.
regarding the plastic like sintra - yes, it might be a bit slippy for use on a ramp.

>>1018180
he leaned back WAY too far and the bike shot out from under him!

>>1018073
While not ideal, you can still use plywood sheets in shoring, you don`t even need to use hydraulic posts for load. Though it`s a hell of a lot easier than wedging 4x4s into place. The only thing the plywood itself has to do is help transfer load to either the load bearing post/structure.

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>>1018399
>looks like user error not an issue with the (strength of the) ramp
>>1018402
>he leaned back WAY too far and the bike shot out from under him!
Yes. The ramp was apparently strong enough for the rider and bike to run as intended, and the guy fell off instead. However, that's not what I posted it for. See how the guy catches on the ramp and stops dead? That indicates that the impact of the guy falling off the bike overcame the strength of the thin sheeting used for the ramp surface, so the guy caught on the frame instead of sliding off. Had the ramp been designed with possible unintended impacts like that in mind (and been made with a stronger surface), the guy would have had a gentler landing on dirt, with some of the kinetic energy dissipated by sliding along the ramp.

>>1018399
>on one episode a while back they built a HUGE ramp for a rocket car
See pic related. It was a straight ramp, which produces a sharp acceleration at the base and none along the length. It also used A LOT of framing. A curved ramp like what OP talked about is better for jumping, and it produces acceleration over its whole length. So it needs to be strong enough to take the extra force of the acceleration along its entire length.

For a reasonable design and a skateboard / bicycle / light motorcycle, you're right that a 2x4 frame and plywood would probably work just fine. The problem is that if you don't use math (or established designs that have been engineered or tested), it's easy to come up with unreasonable designs that aren't anywhere near as strong as they need to be, even if the materials are capable of taking the load if arranged differently. How many people have enough intuitive understanding of Newtonian dynamics that you would trust your life to something that they built according to what just looks right? Because at "high speeds" where you catch decent air, your life really is on the line.

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>>1018703
(continued)

And math is cheap. This isn't what you go to an engineering school for. This is high school physics. No calculus or tensors, just arithmetic and vectors. We're talking probably around a hundred dollars in raw materials for the ramp, a vehicle that probably cost more than that, a few hours for construction, and some risk of injury with consequences ranging from negligible to death, with broken bones plausible (thousands of dollars if you don't have insurance). So I think that a few minutes at the start to check if things will actually do what they're supposed to is a reasonable step.

>>1018704
yup that is the Mythbusters ramp I was talking about. I wondered why they used a straight ramp rather then one with a slight curve to it (to ease the transition from the level ground to "flight") and seeing the straight ramp and the one layer of ply I figured that car/rocket is going to tear up at least the first part of the ramp... and it did.

anyway, OP still not being specific as to what he's doing/riding...

Build it, and they will come!