IRS in a gmt400

[Pinger]

My opinion - and it is just an opinion. I'd leave the coilover in its original/intended location. Because, one, the damper will more easily be cooled there and two, cantilevered it will be much higher - to the detriment of the overall centre of mass.

 

[Alteca]

My opinion - and it is just an opinion. I'd leave the coilover in its original/intended location. Because, one, the damper will more easily be cooled there and two, cantilevered it will be much higher - to the detriment of the overall centre of mass.

Thanks for the reply, both of those were a concern when I started doing the cantilever. The coilover is extremely light being an aluminum body so I’m not concerned with the increase in height of the center of gravity. But I am still concerned about the exhaust heat. Maybe there’s something I can do to combat the heat? I will take a look at everything Monday and reconsider my options.

 

[0xDEADBEEF]

You're like the mad scientist of suspension.

 

[Alteca]

You're like the mad scientist of suspension.

I wouldn’t say that, there’s still a chance the front suspension sucks in real world scenarios. I designed it based on math which only gets you so far when something like driver preference can completely change a suspension setup.

 

[Alteca]

I don’t doubt this question has been answered on here before but can anyone tell me how to wire in a second alternator? Both are going to one battery. Both are cs130 although one is a 200 amp and the other is a stock replacement. The factory plug on the truck is 1 wire. The plug is the only part I don’t understand. Some people talk about a resister on the wire?

 

[Shwa Kid]

Here’s a sneak peak of what I got going on. Still getting everything figured out but it’s coming together. I made the cantilever with the original intention of having the coilovers towards the front of the truck but decided I’m gonna put them towards the rear and I now need to remake this cantilever to correct some geometry. I will try and make the new cantilevers a bit prettier.

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This is a really cool project, cantilever suspensions always look rad. In your revisions I think you should adjust your pivots to be in double shear, that lower mount especially will have a hard time with the full weight of the truck on it.

Also what secrets is that third gen hiding that you managed to pick it up so cheap??

 

[Pinger]

Thanks for the reply, both of those were a concern when I started doing the cantilever. The coilover is extremely light being an aluminum body so I’m not concerned with the increase in height of the center of gravity. But I am still concerned about the exhaust heat. Maybe there’s something I can do to combat the heat? I will take a look at everything Monday and reconsider my options.

If we go back and consider the origins of cantilever front suspension - called 'inboard' at the time, we find that the primary reason was to get the spring damper unit out of the airstream on single seater race cars to benefit aerodynamics. Then, as aerodynamics improved and more downforce was sought, the cantilever nature made a rising spring rate possible which was of use to counter increased downforce while maintaining correct ride height and an initial spring rate for slower speed corners. In one sentence - packaging benefits for improved aerodynamic performance and adjustability to cope with downforce.
None of the above relates to a truck and while race car engineers ensured there was ducting for cooling the dampers it was an additional aspect to cater for compared to them being in the airstream previously.
I just don't see any benefit (only complication) from you going inboard at the front - and as you're already aware - increased cooling difficulties.

 

[Alteca]

This is a really cool project, cantilever suspensions always look rad. In your revisions I think you should adjust your pivots to be in double shear, that lower mount especially will have a hard time with the full weight of the truck on it.

Also what secrets is that third gen hiding that you managed to pick it up so cheap??

Those mounts are not done they will be supported better soon. The third gen sat in someone’s yard for 15 years, previous owner(a family member of mine) was able to pick it up for free. He put a few parts on it and then sold it to me. It has a large number of issues but most are cosmetic. Besides the engine being due for a rebuild. It runs but has a misfire and smokes.

 

[Alteca]

If we go back and consider the origins of cantilever front suspension - called 'inboard' at the time, we find that the primary reason was to get the spring damper unit out of the airstream on single seater race cars to benefit aerodynamics. Then, as aerodynamics improved and more downforce was sought, the cantilever nature made a rising spring rate possible which was of use to counter increased downforce while maintaining correct ride height and an initial spring rate for slower speed corners. In one sentence - packaging benefits for improved aerodynamic performance and adjustability to cope with downforce.
None of the above relates to a truck and while race car engineers ensured there was ducting for cooling the dampers it was an additional aspect to cater for compared to them being in the airstream previously.
I just don't see any benefit (only complication) from you going inboard at the front - and as you're already aware - increased cooling difficulties.

I appreciate the lesson on that. I may not benefit from the geometry but I did design it to be a rising rate. It will be close to 50% stiffer at full compression. I don’t think cooling will be an issue since I rarely drive the truck for more than 20-30 minutes at a time. Yes it’s more complicated but it’s just for looks at this points.

 

[0xDEADBEEF]

The other benefit of cantilever is you move the mass of the shock and spring inboard. In a race car, you would normally mount them low in the chassis (pull rod).