Home Forums General Discussion Technical Questions Hydraulic Elevator Dove Tail

Can someone explain in detail what the dove tail measurement is for and why the inspectors always perform them? I can't seem to find a clear explanation for this measurement. Why are the springs removed and the car lowered all the way down on spring stands? What is the min. measurement to achieve? What is the code on this procedure? Thanks!

When you take the springs out, you are attempting to find out how far down the elevator can go, before the piston bottoms out in the cylinder. Of course, you would never want it to impact, because it could rupture the cylinder.

Lets say this comes out to 11" below bottom floor level. Piston is touching bottom of cylinder. This is the dovetail measurement.

Then you check the distance from the buffer strike plate to the buffer, when the car is at floor level. Say, it's 6". ("bottom runby")

What is the stroke of the buffer? 4"? ok, now-

Add 6" + 4", which equals 10". That's obviously less than the 11" of dovetail-

So now you know that when the elevator fully compresses the buffer, the piston will never be able to impact the bottom of the cylinder. In this case, there would be 1" of clearance between the piston and cylinder, on a fully compresssed buffer.

Dovetail must be a larger figure, than stroke + runby. Some inspectors say 1/4" more is a minimum. IDK what the code says about it.

Thanks Vic, very good explanation. You explained it much better than the inspector.

Glad it was understandable.

Inspectors are not always the most communicative people. But look at it this way- If they had the time to explain everything, they would be talking constantly.

Anybody know Woody Wright?

woody was the elevator code...I have never met anyone else that knew the code book front to back without looking at it.

i had a old US car without any dove tail because someone cut the spring stands for some reason. it blew out the bottom of the single bottom jack. think about a 4000# dead blow hammer hitting the bottom of the cylinder at 100fpm. i believe 1" is the minimum by code.

I should have said this:
After checking the dovetail, put the buffer springs back in their stands.