Rotesserie Action...on an early chassis

[Britain Smith]

Although spent the greater part of the weekend gathering the materials, tools, bribing the neighbors, and sweet talking the wife...everything was cut to fit, most of the holes drilled, most of the welding done neighbor who is a professional welder (I cut his lawn for him). I took the drawings a fellow Pelican member sent me, modified them a bit where I saw fit, and laid it all out as a proper engineer would do...on engineering paper.

The biggest problem that I have had to work out is the fact that the early ('69) 911/912's did not come with ANY crash protection as the laters car did. All the pictures that I have seen of 911's on rotesserie's have the ends mounted to the reinforced bumper mounts which are sturdy enough to do just fine. I mounted the rear using the engine mounts. Keep in mind that this is a 912 chassis so the engine mounts are further in.

So...my question...take a look at the pictures posted below and let me know if you think that it is going to be enough support my car. The entire car is stripped out except the dash, windows, and doors...the suspension, drivetrain, fuel tank, interior, etc. is all gone. My only concern not is the distance from the engine mounts to the rear pivot causing increase amount of torque on the engine mounts. Take a look and let me know what you think.







Here is a picture of me standing on the rear support piece...I was jumping up and down on it...



Here is a pic of the front support:


And the sandwitch plate on the inside of the front trunk:


I am still going to add additional supports to the bottom:


And to the two rotating parts:


My neighbor is a professional welder and for using a 110V Miller Welder, they don't look bad:

[carmaneddy]

looks good to me. I assume you have a strong backing plate at the motor mount.

[Britain Smith]

Well, actually the motor mounts are threaded. I am going to get a long M8 bolt to fit through the threads and then make a backing plate on the bottom.

-Britain

[KevinP73]

Any chance you might share the drawings with those of us who would be interested in building one for ourselves?

[Series900]

Britain, the front is fine, the rear is going to torque. You need to make a strap from one of the rear bumper mount captured nuts down to your horizontal square tube on both sides. This will give you 4 point mounting, no torque twist. My rotiss mount that utilizes the engine mount is 911, not 912. the 912 mounts will twist the way you have it now. Easy fix, great job!

[Tim K]

Here is what I did to avoid the mounting problem with the pre 74 tubs. This is an 83SC, but I've since removed the bumper isolator brackets.
The cantilever setup requires quite a bit more strengh, but was worth the effort.
This is also nice because the tub isn't bridging as long a span, and if the front pan is rotten,
it can be replaced while on the rotisserie.
Enjoy your rotisserie, you'll love the ease of access.

Tim K

[Britain Smith]

Originally posted by Series900
Britain, the front is fine, the rear is going to torque. You need to make a strap from one of the rear bumper mount captured nuts down to your horizontal square tube on both sides. This will give you 4 point mounting, no torque twist. My rotiss mount that utilizes the engine mount is 911, not 912. the 912 mounts will twist the way you have it now. Easy fix, great job!

Thanks for your comments. I will stop by the steel place at lunch and pick up a few more peices to make those mounts. My original design had the rear support peices mounting solely to the bumper mount locations, but after bolting up that I determined it wasn't strong enougn. I like the idea of have all four locations though...that would provide support when the engine mount locations want to twist under load.

-Britain

[Britain Smith]

Originally posted by Tim K
Here is what I did to avoid the mounting problem with the pre 74 tubs. This is an 83SC, but I've since removed the bumper isolator brackets.
The cantilever setup requires quite a bit more strengh, but was worth the effort.
This is also nice because the tub isn't bridging as long a span, and if the front pan is rotten,
it can be replaced while on the rotisserie.
Enjoy your rotisserie, you'll love the ease of access.

Tim,

Can you send me a couple more pictures of your set-up. That was one of the early designs I was playing with, but I determined that the front mount would be sufficient...we shall see. I appears that you have springs on this ends of the support, but the picture is hard to determine.

-Britain

[Tim K]

Hi there. I don't seem to have any good pictures of the rear attachment. Here is what I've got. I'll see if I have any others that might be helpful. The two pics from the front and rear might give you a good Idea of where the axis needs to be for good balance. As it is, the axis of my rotisserie is just a tad high. I used the 911 shop manual blueprints as my starting point. They allowed me to ensure the car would be level on the rotisserie, but I had to guess at where the center of mass would be. I built in some adjustment if I was off. The "springs" you see are just a bunch of washers. The mounting bolts for the front cross member are not fully threaded. They are also a goofy pitch for their particular diameter and the appropriate bolts were not readily available (read: Lazyness). Let me know if you have any other questions.

Tim K

[Tim K]

[Tim K]

[Tim K]