advice from hooley or any of you other men of the salt

chimp koose · August 24, 2009, 09:23:07 PM

I may be building the front end of the jet car we are fixing. My friend phoned and asked if I would do it. I have a good Idea about how much caster to dial in but would like some advice from others. The car went 251mph and is probably capable of more. It rolls on bias ply tires I believe. What do you guys who run at those speeds use for alignment specs.I am not sure what the scrub radius comes out to for setting toe in but that can be adjusted. The front axle is fixed (no suspension) and likely has little or no adjustability so I want to get it right . There is a fixture being sent to the shop to set caster and camber before the axle (actually two tripods ) is welded up.Suggestions please?

WZ JUNK · August 24, 2009, 09:41:50 PM

Quote from: "chimp koose"I may be building the front end of the jet car we are fixing. My friend phoned and asked if I would do it. I have a good Idea about how much caster to dial in but would like some advice from others. The car went 251mph and is probably capable of more. It rolls on bias ply tires I believe. What do you guys who run at those speeds use for alignment specs.I am not sure what the scrub radius comes out to for setting toe in but that can be adjusted. The front axle is fixed (no suspension) and likely has little or no adjustability so I want to get it right . There is a fixture being sent to the shop to set caster and camber before the axle (actually two tripods ) is welded up.Suggestions please?

My thoughts are lots of caster.

I would go to the landracing board and ask your question. There are lots of knowledgeable people on that board who have experience building cars that handle well at high speed. Most people on this board have low speed experiences under 200 mph

John

chimp koose · August 25, 2009, 01:41:37 AM

thanks wz junk, do you have a web address for the land speed site? I was thinking around 25degrees of caster myself. and about 2degrees of camber, but camber will depend on scrub radius as well.

WZ JUNK · August 25, 2009, 10:14:46 AM

http://www.landracing.com/

John

kb426 · August 25, 2009, 12:40:38 PM

I can only relate to drag racing. Funny cars are 7 degrees. Slow dragsters are 15 degrees and fast ones are 22 degrees.

chimp koose · August 25, 2009, 10:57:29 PM

kb426, this car has a 130" wheelbase ,I had dragster alignment stuck in my head and probably shouldnt have . Thanks for the tip.wzjunk, thanks for the site address, I will go there right away.

kb426 · August 26, 2009, 06:40:28 AM

There's several factors to consider in deciding how much to put in the front end. Is it possible to make multi hole mounting plates with a 7 degree starting and 22 degree ending point? The amount of weight on your front axle, the tire size, the steering box ratio. Those factors all will influence what the end result will be.

chimp koose · August 27, 2009, 12:00:02 AM

kb426, the axle will likely be axle stubs bolted to either side of the frame. there will likely be one strut going from just under the king pin to the bottom rail of the frame and one going back from the king pin to a point on the frame horizontal to the king pin. It should look like a solid mounted funny car front end. the caster would have to be built in to the axle stubs. For setting caster to eliminate scrub radius I will be building a long shaft with a point on the end that will fit in place of the king pin. If I project a line forward parallel to the frame along the center of the tire contact and intersect it with the fabricated pin placed in the king pin hole when fabricating the axle stubs, I will eliminate the scrub radius. If that caster setting falls within reasonable limits the car should handle fine.Total vehicle weight with fuel is 2300 lbs. The engine sits where a driver and lenco would in a funny car.I dont know front axle weight but I would think it to be less than a similar weight wheel driven funny car as the driver and fuel sit nearer the rear than the engine in a funnycar and there is 5" more wheelbase. This should allow for more caster than a funny car if necessary without causing excessive steering effort.wz junk thank you again for the link to the land speed site , it confirmed my thinking on eliminating scrub radius.I will be leaving town to build the front end on friday ,if anyone has more suggestions or feels I have not considered some important aspect of this job, please chime in. I want to build this the best it can be.Top speed with the old chassis was 251mph. I would love it if I could build something that would allow it to go faster .