Dutchman IRS for 427.Teckie help needed.

[Prof]

(Similar post to the lengthy one I placed on Lonestar's forum)

Dutchman Axles sells an IRS unit that can be adapted to any frame. I ordered it and they forwarded the instruction manual. Several of the locating points for the forward arms look to be tricky--no, technical in their attachment to the frame. Anyone "game" to glance over the PDF file and tell me your thoughts on the forward mounting arms? Angles and offsets and bobs and fractions and holesaws are involved, so please be ready for the challenge of simplifying this.



My Lonestar frame is bare and upside down on a lift for convenience of this installation.

Thanks,
Paul
(Dallas)

paulmay1 [at] msn [dot] com

[Three Peaks]

Your information says this is to be a full time track car. With that information, I would give serious thought to taking this set up to a shop that sets up race cars and let them take a look at it. A race set up can be completely different from a street set up and installation may be a different ball game.

I would put the frame right side up so you can take measurements. It will be difficult enough understanding the geometry and taking measurements with it in the standard position. Doing it with the frame upside down will be downright confusing. Once you determine what needs to be done and where all the attachment points need to be welded on, you can always turn it upside down for the welding- though I don't think you will gain much.

Also, without seeing your frame and a link to the PDF file, it is difficult to determine what would need to be done to install this rear differential properly. I live a few miles from Dutchman and I've seen these rear ends in person and they are gorgeous. But after looking at them for awhile I realized it would be nearly impossible to adapt it to a Cobra frame given the dimensions from the seats to the rear axle. There just isn't enough room for the link arms to be mounted properly in the configuration they show and still use your seat. At least on my original style frame they wouldn't.
Your milage may vary.

Bob

[Prof]

Thanks, Bob. I am glad you suggested a racing operation's opinion. I have one scheduled to come look at this before I tack anything together.

Here's the setup for the outer arms. IF (big if) the arms are 7" and 9" long, then the 4-link's holes will help guide the install. I can go forward 2" for longer rods (9" and 11") and better suspension articulation at the hub.



Regards,
Paul

[mickmate]

Hi Paul. I'd be glad to look at your PDF of it. I would as Bob suggest put it right way up. I would also if you could get the body on and get the wheel/tire combo you're going to use and get that in place, at ride height. Then take some measurements relative to your frame where the wheel needs to be. If you can bolt the wheels to the rear end and fit it in there even better. Hot rods are built around the wheels and tires. Now get your body off and start ciphering where you're going to have to reach out to for the mounts. It looks like the diff hanging plate could go between the 1 x 2"? tubes and the four bar links may be able to go to your radius rod links although it looks like the lower may need extending forward and the upper extending back. If that doesn't look feasible you might have to go to inside or outside of the 2x4"? outside rails. Looks like a fun project and nice hardware. You'll like an IRS ride in one of these things.

[mickmate]

I just stumbled on this as I was looking for some IRS 9" parts
http://www.kitcarmag.com/howto/rcc_s...ica/index.html
I see it uses an upper and lower arm where yours uses a 4 link but a good install read.

[Ralphy]

That setup looks very similar to a Guldstrand C3 5 link conversion. Using non splined half shafts. Notice he (Guldstrand) moved the link mounts behind the wheel centerline. Shorter the link the more wheelbase change you will have during suspension movement.

http://www.guldstrand.com/scripts/pr...p?idproduct=80

The forward links I think you will never get the length shown.

Now looking at it more the forward links are mounted well in front of the half shafts, that will shorten the forward links even more. I think you will struggle to get 14" from your wheel center forward. Just guessing, your wheel well goes forward next to the seats. betting again from seat back to center of wheels is maybe 13" at most. Look at a C4 Corvette setup also.

[Ralphy]

Also, this setup stresses the third member housing in turns. Forcing the half shaft at the third member. Can be a problem with racing.

[FUNFER2]

Think about cutting off the rear frame section behind the rear seats, and using the Dutchman for the entire rear frame clip. It may prove a easier & better job than adapting the LSC frame.

[Prof]

It will work. Met with top-notch builder of one- offs and high speed competition cars. He said the directions were written for a first-timer. He said this is a great setup for my LoneStar.

The forward arms will mount on Dutchman's plates attached to the side rails of the frame. This will allow me to keep the arms long.

[FUNFER2]

That's fantastic buddy !

Have they said what torque it will handle ?

When you you want to pick up my LSC and install one for me ?

[Ralphy]

Paul, if you can get a longer lower link under the body and keep it raised at the front. You may be able to stretch it out to 20" or so. Then for the upper use a watts link, giving you more control over for and aft. Another issue I see with unequal forward links is that they will move in different radius's. Which will cause the outer bearing carriers to rotate in relation to the chassis. Now if this happens, your camber rods rotate moving one downward and one up. Seems to me this will effect the toe angle. How much not sure!