Recommended caster

[bharmon77]

I am a new guy! I am building a Lakester, the rule book implies 20 max. caster. What would be a recommended caster angle for this set up? How about a minimum?

Thank you,
bharmon77
bharmon77@yahoo.com

[doug odom]

You need just enough for directional stability. That means it will go straight ahead without any input from the driver. You need enough so it will resist tracking in ruts. Long wheelbase, narrow tread cars should be fine with 5 to 9 degrees. Some people run a lot more than that but I could never see the need myself.
Doug Odom in big ditch

[bharmon77]

Doug,

Thank you for your response, my experience is all going in circles so I have alot to learn about LSR. My car has a 130" wheel base and I have 2.5 wide dragster front wheels and tires.  I feel that aero wise they are probably a good idea I hope that the car wants to go straight because I don't think that you could do much driving with those front tires? The car is motorcycle powered and should be around 1200 lbs. Thanks again for the advise, now I can finish the front end.

Bruce Harmon

[hitz]

Bruce,
  If you use over 20 degrees of caster, you are required to have steering stops. I couldn't see running with out them in any case. The rule is 3.T, on page 34 in the 2006 rule book. Some cars have over 30 degrees and they may be trying to get rid of some of the tire scrub. I am pretty new to LSR myself and this forum is very helpful to aquire information.

  The best thing to do is to get in contact with the specal construction chair:
  John Bjorkman
  (714) 546-8142
  jbjorkman@comcast.net
 
  You will find him very helpful with your questions and it may save some problems at inspection.

  I'm in the third year of building a small engine lakester and hope to make this years Speedweek 

  You'll find a place on this web site to let everyone know how you are coming along on your project and keep track of some of the one's that are being built by others. Let's get some pictures on there!

  Welcome!

  Harv

     

[jimmy six]

John is the correct one to contact. When I inspect any car I would like to see positive stops no matter what the caster is. It could be tough on your wrists during the spin. Roadster guys know what I mean..Good Luck

[bharmon77]

Thanks to Harv and Jimmy Six, I will install stops and I do have some questions for John Bjorkman.

Thank you, again,
Bruce Harmon

[John Nimphius]

When using positive steering stops, how is the ideal point to limit steering determined?

[836dstr]

Does the use of a Rack & Pinion have any effect on the need for steering stops?  (Mustang II type unit)

Tom

[hitz]

  John,
The most common (best )steering stop is at the wheel spindle and is mounted on the axle or an A frame.

  Tom,
Rack and pinion also should have a steering stop.

  Link steering should have additional stop at any link that could possibly go over center!

Harv

[836dstr]

Thanks Harv,

Another thing to add to the list for this year. Now the important question. How many degrees of steering should the stops allow for a 107" wheelbased Roadster with a top speed of say 190 MPH. The car has an I-beam axle with 12 degrees of caster?

Tom

[Peter Jack]

Why not make the stops adjustable using a threaded boss (i.e. a nut) welded on with a bolt and jam nut for the actual stop. That way you don't end up cutting, grinding and welding several times to get it right. If the head of the bolt is used as the stop you won't have a mushrooming problem when you go to take it out.

Pete

[JackD]

The steering stops are designed to limit the wheel steering to the point that you expect to use them while underway.
They should take all the stress at the spindal and not put a limit stress back through the steering linkage.
Steering wheel rotation and ratio should go from the right to left limit within 180 deg. so when you go round and around and around the steering wheel doesen't go round and around and around also.
Too much rotation of the steering wheel in a spin won't help get you out of it , particularly if your white knuckels are on the ground.
The end result of all of this is you don't want too much steering travel for what you are doing.
You can forget parrallel parking and it might also mean a couple of passes to get it lined up withthe trailer.
Or so I am told.

[Richard Thomason]

Anything less than a 1/8 mile radius turn is more than you need or will use anyplace other than the pits. Course to return road is 1/4 mile.

[Bob Drury]

BH, although I have posted this before, I believe it is worth reprinting.  When I built my car (CFALT) ten years ago, I was trying to find a way to slow the steering down, and thereby take some of the natural herky jerkey motion caused by our natural tendency to over-correct (think driving in snow or ice).  While searching for a slower steering, I came across a roundy-round parts catalog and discovered a steering increaser gear box that fits in the steering shaft between the box and the steering wheel.  They are available in 1.5 or 2.1 ratios.  I inverted a 1.5 ratio box, and mounted it right below the steering wheel, attaching it to a roll cage cross bar.  The result is a reduction in steering speed of aproximatly 1/3.  Several other competitors have since tried it, and I have yet to hear any negative comments.  Good luck, and remember, this only works with the rubber side down.  Bob

[836dstr]

Bob,

I had a similar situation. I had a Mustang II R&P mounted behind the axle that required some way of reversing the steering direction. My solution was to fabricate a little gear box that used 2' and 1 &1/2' gears. At first I had the gears set up to slow down the steering. Then someone mentioned how reversing them would make it better for manuvering in the pits, etc. After a wind assisted spin @ Bonneville (with overcorrection) I am going back to the slower steering this year.

I think the plan will be to add steering stops that are adjustable and that can also be disabled for use in pits, driveway etc.

Tom