Strength of wood and lumber

[mmg5782]

Hey guys,

I'm looking to design a car platform to drive up onto in order to perform maintenance. And the big thing is going to be for removing a transmission. Yes, I could use jackstands, but am looking to alternatives to stands.

Below is a preliminary design. Lumber in my area is Douglas Fir, and from what I've found it has a high compressive allowable when loaded parallel to the grain. I've seen around 7000psi, but am not sure if that is a realistic number or not. The diagram below has the red lines if the grain would be running parallel to the ground and green if perpendicular to the line. I would like to build three separate segments so as to be able to remove the middle segment. The splice boards I would use 3/8' or 1/2' bolts going through the entire top boards of the structure. I'm looking for insights to using lumber for such an application, as I haven't dealt much with lumber at all, other then making some cable trays. Any inputs are appreciated.

Thank you,
matt

 

[MiketheEngineer]

Doug fir usable is more in the 1,000-1,500 psi range depending on grade.

BUY the jacks - safer and CHEAPER and if it falls on your pretty little head - your wife will have someone to sue instead of saying "That DS did it again and killed himself" and runs off with your neighbor.

Or maybe that's what she wants.

 

[Xera]

Will this be indoors or outdoors?

What about old RR ties?

 

[JAE]

Do you know how to design with wood? If you don't I'd suggest you get someone who does just to protect yourself. Someone laying underneath a vehicle with that vehicle supported by wood members designed by someone who doesn't understand wood design makes me nervous.

 

[mmg5782]

I haven't not done much with wood before at all. I'm looking for advice on design.

Xera, this would be used in the garage, and stored in the garage as well. I haven't thought of old RR ties. I think it would depend on the condition of the ties though.

Thanks,

matt

 

[Artisi]

Why wood?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[pmover]

take your vehicle to a reputable and qualified mechanic for transmission removal . . . then again, if you are living in very rural areas, a tow would be costly.

we cannot design your system, we can only provide guidance/suggestions. your statements of "not dealt with lumber" imply that you ought to consider keeping matters simple and utilize proven supports. i would think the cost of metal ramps or jack stands are less then the cost of building an unproven wooden structure. definitely less risky . . .

your proposed design is vague and lacks details for us to provide guidance.

why not use varying lengths of roughcut 2 x 12-inch or 1 x 12-inch boards and stack them - wood on wood with no open gaps between the boards.

at one or both ends, cut the boards at a 45-degree angle to ease the wheel rolling up the board to the desired height. need to be sure of no rolling of stacked boards. many years ago when we traveled using the RV, we had roughcut 2 & 1 x 12-inch boards for leveling the RV. we placed them in front of the tires and drove the RV up on the stacked boards. back then, there were no automatic leveling systems. it worked perfectly and safely.

you need to keep matters simple . . .

good luck!
-pmover