Bungi wrote:
1.) If you design anti-squat into the rear IRS by tilting the inner pivots of the a-arms, won't this create a binding of the bushings on the uprights as the a-arms swing at different angles?
If you don't keep the a-arm pivot axis parallel to each other, yes you'll have binding. Regardless, IRS doesn't have very strong anti-squat anyways, so I wouldn't put too much effort into it.
Bungi wrote:
2.) I have all the energy suspension bushings to replace the original Ford rubber bushings in the uprights, what is a good size bushing set to use for the inner pivots on the a-arms?
If going poly bushings, I'd look a the energy suspension universal bushings (
http://energysuspension.com/universal-products/link-flange-type-bushings-universal-mounts-isolators.html) and pick it by a combination of outer tube size (diameter larger than a-arm tubes, easily sourced DOM wall thickness in that diameter, and long enough that a-arm tubes at necessary angles won't overhang) and fastener size (1/2" or maybe 5/8").
Bungi wrote:
3.) Has Stu at IRS Machining closed the business? The website has disappeared?
Unfortunately, I have recently come to the same conclusion, even though I've found no mention of it on the Factory Five (or other) forums.
Bungi wrote:
4.) What are good lengths for the a-arms to start with?
I too have Factory Five axles, and believe that with careful planning they
should result in a close, but acceptable, clearance on up to a +2 width chassis with up to 40mm (or was it 45mm?) offset wheels. Of course, this is all still just math based, and has not been physically built/confirmed, so don't trust anything in this reply to work 100% at face value. In this setup though, I was looking at the outer (spindle) pivots being ~24.5 outboard of the centerline and ~10 vertical from the ground for the lowers, and ~23.75 outboard of the centerline and ~17.75 vertical from the ground for the upper for the ~25" OD tires I'm planning for. If I were to go with a conventional IRS, my early design work was narrowing in around the inner pivots being ~9 outboard of the centerline and 10 vertical from the ground for the lowers, 12-12.5 outboard of the centerline and 16.5 vertical from the ground for the uppers. But the compromises in a suspension design are very individualistic, so numbers that I found appealing you may find less so.