Max safe height for ramps?

[Ponkotsu]

I'm going to make some car ramps for my SUV from wood. I'd love to make them out of steel but just don't have access to the equipment. I'm not worried about the strength of the ramps, I'll make the portion that the vehicle rests on out of solid 2x12's and just stack them up and hold together with carriage bolts. I'd trust a stack of lumber like that over almost anything else.

What I'm worried about is too much incline on the truck. I'd like to get it up at least 10.5" (7 layers of 2x12) so I can have plenty of working room for pulling a transmission in a couple weeks. I've never used ramps that were more than the normal 8" or so. And I think Ideally I might even jack up the back end and put something under the rear tires also. I'll build some type of solid chock into the ramp so it can't roll out without great force.

A lot like this but I'll make the ramp portion removable so it doesn't get in my way.
http://www.srtforums.com/forums/f75/how-build-homemade-car-ramps-568285/

Thoughts? Am I being stupid?

 

[mech-tech]

The lumber is trust worthy, but long ramps like the ones in the link would probably get in the way of pulling the trasmission.

 

[Ponkotsu]

The lumber is trust worthy, but long ramps like the ones in the link would probably get in the way of pulling the trasmission.

Yeah, that's not such a good design. The ramp portion definitely needs to be removable. They would make it impossible to get under the vehicle.

 

[e_d]

What's wrong with jack stands? I can see at times where the ramps would be more convenient but other than that,why.

 

[jetrep]

Why bother with ramps? Just jack the corner up to where you need and place a 10-12" block of wood under it...then remove the jack

 

[KinzeMech]

I can have plenty of working room for pulling a transmission in a couple weeks.

Ramps save a few minutes time, at best, over jackstands. That's great for 15 minute jobs, like oil changes, but on a transmission change, you're in it for the better part of the day, at least. Those few minutes just don't make the difference (just my opinion) on a job that large.

If you want plenty of room, jackstands let you remove the wheels, and have a much smaller footprint to work around than a ramp.

 

[Ponkotsu]

Ramps save a few minutes time, at best, over jackstands. That's great for 15 minute jobs, like oil changes, but on a transmission change, you're in it for the better part of the day, at least. Those few minutes just don't make the difference (just my opinion) on a job that large.

If you want plenty of room, jackstands let you remove the wheels, and have a much smaller footprint to work around than a ramp.

Yeah, I see your point. Just never felt totally safe under a car with small jack stands. Maybe I'll go find some nice old heavy duty ones on Craigslist.

 

[Ponkotsu]

Like these bad boys:

 

[KinzeMech]

When in doubt, put a stack of large wood blocks somewhere a major part of the frame will land on it if primary support goes down.

 

[KinzeMech]

The thing I don't like about jackstands is the tendency to teeter if one is using four of them (think of a table that needs one leg shimmed). On a rear wheel drive vehicle, I typically put the front stands on the frame, and the rear stands on the axle. Supporting one end solid to the frame, and the other end through the suspension, allows all four jack stands to have solid weight on them. Most jackstand problems I have seen are due to the fact they can move if they don't have weight holding them down. A vehicle on 4 jackstands that teeters diagonally actually has all of it's weight on only two of the four jackstands.

 

[Ponkotsu]

I used to have some chunks of railroad ties that I put under the frame of cars. Probably that is what I should do now that I think about it more. I'll have more time making the ramps as I will pulling the ******. For my oil changes, I only need to jack it up a couple inches to get under it. Unlikely I'll need to remove the front wheels for the ****** job, but I do need to look at the half shafts. Maybe just do it all at one time.

 

[alan camby]

My homemade ramps are 11.5" tall.
They are steel though.

 

[zkling]

My homemade ramps are 11.5" tall.
They are steel though.

Beautiful, fantastic work, just like your jack stands.

 

[Ponkotsu]

Beautiful, fantastic work, just like your jack stands.

Therein lies my problem. I'd need a huge jack and stands to get my truck up that high. And then I'd need to put some blocks of lumber or something under it to feel safe. Whereas the ramps are super easy to use and are safe to work under even without backup. (Although I'd still probably use some backup anyway...) I'd hat to drop this ****** and then not have enough room to slide it out from under the truck. That would really ****.

 

[zkling]

Therein lies my problem. I'd need a huge jack and stands to get my truck up that high. And then I'd need to put some blocks of lumber or something under it to feel safe. Whereas the ramps are super easy to use and are safe to work under even without backup. (Although I'd still probably use some backup anyway...) I'd hat to drop this ****** and then not have enough room to slide it out from under the truck. That would really ****.

Couple things.

1.) What exact vehicle are you working on. I'm going to assume (dangerous I know) that it is a high ground clearance vehicle? Therefore height added to contact patch is better than jacking and supporting from the frame?

2.) In theory you could make ramps as high as you want. Just keep in mind the CG vs base size to prevent tip over. Particularly in the axial direction of the axles. I don't know how to say that better, sorry.

3.) Max safe incline is not a super issue. You could pretty easily calculate the force exerted in all directions based on incline angle of the ramps. As you increase the angle between the ground and the vehicle, you will increase the horizontal (bad as it will cause sliding) force on a set of ramps. Alan's ideal is probably the best. If you had set of ramps that lead to blocks then have the block have stops both front and back to prevent the car from rolling off the block. After the car is up you can then remove the ramps to work around the blocks.

Example of what I was thinking of. If you wanted to be super safe, you could put temp lags in the floor for the "sides". That way even if they were kicked hard they wouldn't move.
http://corvettec3.ca/ramps.htm

 

[Ponkotsu]

Its a Lincoln Aviator. (Similar to Explorer). Not such high ground clearance. I can't get under at all without jacking up. If the front is up 10.5" that is only about a 6degree incline. Not much at all. If the supports are 2x12's (Actually 11.25" wide) and 24" long, then it's pretty stable. Make some integrated chock on both sides of the support structure and chuck front and back of rear wheels and it would take an earthquake to knock it off.

 

[Sureshot]

Stagger your 2x12 blocks with a long one to act as the ramp and top layer. You can do this with all 4 tires. Drive on top of them then use more blocks under your jack to lift as high as needed and block the tires. Takes less time than this thread. Find a construction site if you need more blocks. Skip the carriage bolts or ?????. Gravity will work fine. Some layers could be 2x4 or 2x6 beside each other.

 

[CNGsaves]

OP if your SUV has plenty of ground clearance, you can make those wood ramps and just backup onto ramps backwards. There will be no ramps in your way for transmission work.

I'm big believer of lots of blocks (solid wood or solid concrete blocks) so if whole thing falls down, you're not crushed underneath. Thus, I never just rely on jack stands.

Also, safety all around with wheel chocking and setting emergency brake.

With enough MacGyver ingenuity, anything is possible !!

 

[rsanter]

So you question was how tall can your ramps be and be safe
Geometry says that if the height is no more than the base dimensions then it hard to tip them over. So wanting to go 10-12" high, no problem.
Personally I would not do the ramps. I would do the wood stacks and then just use a jack to pick the truck up and place it on the blocks

Bob

 

[justanengineer]

The thing I don't like about jackstands is the tendency to teeter if one is using four of them (think of a table that needs one leg shimmed). On a rear wheel drive vehicle, I typically put the front stands on the frame, and the rear stands on the axle....A vehicle on 4 jackstands that teeters diagonally actually has all of it's weight on only two of the four jackstands.

Shortened to save space. JMHO, but if the vehicle teeters at all or there isnt significant weight on one or more stands then you have a serious issue with either the floor or the stands bc vehicle frames are designed to flex quite a lot. You should be able to put the vehicle on stands with one corner high/low by a full notch or two on that stand without a serious safety issue or anything teetering. Also, shop safety 101 - never support a vehicle via the suspension.

Personally, Id just put it up on stands and get on with the real work. No need to create work/waste space with ramps.

 

[neonnblack]

When in doubt, put a stack of large wood blocks somewhere a major part of the frame will land on it if primary support goes down.

Do what i, and alot of people do, jack it up and when you take the wheels off put them under the car, on the edge/pinch weld.

Beautiful, fantastic work, just like your jack stands.

He never made jack stands, he made a camera tri pod.

 

[Ponkotsu]

Shortened to save space. JMHO, but if the vehicle teeters at all or there isnt significant weight on one or more stands then you have a serious issue with either the floor or the stands bc vehicle frames are designed to flex quite a lot. You should be able to put the vehicle on stands with one corner high/low by a full notch or two on that stand without a serious safety issue or anything teetering. Also, shop safety 101 - never support a vehicle via the suspension.

Personally, Id just put it up on stands and get on with the real work. No need to create work/waste space with ramps.

About the frame thing, I think it depends on the vehicle. Probably my Aviator has enough flex to allow a good 1/2" of unevenness. But I remember years ago I had a Triumph TR7. That unibody was so stiff it would rock back and forth like a brick. I doubt if it flexed even 1/8".

You are right about the jack stand issue. I'm probably worrying and over thinking the problem. I just have a phobia about it because I had a friend crushed by a car years ago. He took reasonable precautions but still had an accident. Luckily wasn't killed but was really lucky. I don't remember the exact details but I think the vehicle rolled off the jack stands. When you work on a ****** you have to remove the drive shafts so are relying on the parking brake (bad idea) and wheel chocks only to keep it from rolling. My garage has a slight pitch to it and the jack stands will increase that, so it will naturally want to roll off the stands.

I'm almost thinking that for the ****** job the best and safest way is going to be to put some good sized jack stands or stack of railroad ties under the front frame member. Then I will have full clearance and nothing in my way.

 

[KinzeMech]

Shortened to save space. JMHO, but if the vehicle teeters at all or there isnt significant weight on one or more stands then you have a serious issue with either the floor or the stands bc vehicle frames are designed to flex quite a lot. You should be able to put the vehicle on stands with one corner high/low by a full notch or two on that stand without a serious safety issue or anything teetering. Also, shop safety 101 - never support a vehicle via the suspension.

You are correct, there *should* be enough chassis flex for it to rest on all four stands when set to uniform height, but what should be isn't what always happens. One notch to the next on a common jackstand is what, 3/4" inch? That's pretty coarse adjustment, and could require a frame to flex up to 3/8" to get to the nearest notch. You just can't count on that happening every time.

If support via the suspension is bad, well, that's exactly what ramps and wheel blocks do. I guess I should have clarified, I would never recommend putting a jackstand under most suspension parts, but a solid live axle is different. The axle tube fits perfectly in the jackstand saddle, and has enough give to ensure there is force on all four stands. Most other suspension components it would be a bad idea, but if there is a good reason it's a bad idea on a live axle, please share that information. Thanks!

 

[KinzeMech]

Do what i, and alot of people do, jack it up and when you take the wheels off put them under the car, on the edge/pinch weld.

I like this idea, and do so myself most of the time. It's just tough to find a place to put the wheels that isn't in the way when working on a transmission. Near the pinch welds is where my creeper goes in and out most of the time.

 

[firebox40dash5]

You are correct, there *should* be enough chassis flex for it to rest on all four stands when set to uniform height, but what should be isn't what always happens. One notch to the next on a common jackstand is what, 3/4" inch? That's pretty coarse adjustment, and could require a frame to flex up to 3/8" to get to the nearest notch. You just can't count on that happening every time.

If support via the suspension is bad, well, that's exactly what ramps and wheel blocks do. I guess I should have clarified, I would never recommend putting a jackstand under most suspension parts, but a solid live axle is different. The axle tube fits perfectly in the jackstand saddle, and has enough give to ensure there is force on all four stands. Most other suspension components it would be a bad idea, but if there is a good reason it's a bad idea on a live axle, please share that information. Thanks!

What are you working on with a frame that stiff? Regular cab Ford 1-ton where the bottom of the frame is shorter than the doors? I don't use stands much anymore, but I have never had anything 'wobble' on them. Hell, if I use a safety stand to relocate a lift arm I usually have to crank on it for the better part of an inch just to get the weight off that pad, let alone unweight another one.

I will gladly, however, jackstand a solid axle in the case of long trucks with short frames when possible. I want the longest, widest jackstandbase I can get.