Just throw some cinder blocks in there so the boys dont get their panties in a bunch. Proven by car thieves since 19xx.

 

holy **** I would never get under that. I've taken plenty of materials classes for my engineering degree, and I understand that wood has a very high compressive strength for the material, but like someone else has mentioned, what is to keep the entire assembly from twisting?

Only way to try and describe what I mean is like if you have ever built the pyramid out of playing cards, and you get to a certain point and the bottom cards decide to fold left or right, and the whole thing collapses...

Basically with this design you seem to be hoping that the sheer strength of whatever screws you used is greater than the moment created by the boards under load. That being said, hopefully we don't read about you in the news

 

You better go back to class as what you said makes no sense. The screws are not under any shear or would not be under any shear loads no matter what you do with the car. For the structure to buckle the screws would have to pull out of the wood or break under a tensile or bending situation. Hopefully your not designing anything i may use in the future

 

Im very interested if he could post a video of him going onto the ramps/platform. That should squash any doubt of its instability. Take video from a side angle where you can see the car going onto the ramp and platform as well as the vertical pieces of wood to see if there is any movement when the car moves to its final position.

 

you missed the whole point, what is to keep the boards from rolling over? What's keeping the structure from rolling over is the strength of the screws.

hard to convey through words, imagine building the shape of an I, which is what his structure is like. Now put a lot of weight on top of the I and tell me what that middle board wants to do under compression.... it's going to want to twist left or right, now what is going to keep that board from folding over on itself?

 

i think what everyone is trying to say is what if one day it goes from | | | | to \ \ \ \ then _ _ _ _ with u under and i figure the screws won't break maybe bend but the wood can crack leaving the screws behind. No matter what, i think adding something in the middle to keep the wood vertical is worth the xtra few hours rather than ending up crushed.

I will always remember from middle school tech triangles triangles triangles = strong (i kno circles honeycombs and other shapes work also but triangles are easier)

 

I dont mean to pick on you, but I feel like everyone is being very dramatic. I feel like you guys have never taken woodshop , or did anything with wood. This wood will not collapse, unless you do it COMPLETELY WRONG. Its not gonna randomly split. Its not gonna get a little bit of oil on it, and then decide that its going to fall. It is going to hold. Many very very stable structures are made of wood, and our cars arent THAT heavy.

 

I understand completely, it just erks me when people use big words to try to sound smart when they really don't know what they are talking about. Check back in when your finish your program and take statics and dynamics.

 

Yes, that is what everyone is talking about, i was just pointing out that that situation had nothing to do with the shear force on a screw.

 

I think that anybody that wants to post on here and state that the ramps are unsafe needs to back up their statements by posting a free-body diagram and some stress analysis calculations. LOL sorry, the nerd engineer in me is trying to bust out. :P

 

already graduated, but thanks

 

I completely agree, haha.

Being a nerd isn't all bad, i don't know about you but it sure pays well for me

 

Back in the day, Truck ramps were made of wood but never went higher then a foot. Also they used some seriously thick Oak with X braces and plenty of cross braces. Now most places use aluminum cause of the wieght factor. imagine trying to move one of the oak ramps around that was 2 feet wide and 7 feet long, although most had handles to carry them on both sides LOL.

I would never get under a wooden ramp, i agree with never knowing if its gunna give away, i use jack stand and always have a fork lift under it for safty just in case. but thats me and i usualy over engineer everything cause ive seen stuff go wrong that should not have.

 

funny but i argee with the title i woke up with some wood this morning....

 

Everyone is insisting on cross bracing the boards etc etc. Well the fact is, he already did that with the plywood.... That is what the plywood on the outside is for, NOT for looks. There is no way it is going to fall like dominoes as you described assuming he assembled it properly. That is what is stopping the ramps from doing that. So enough with the its going to fall like dominoes ideas.