FrontEngineDragsters.Org Forum
Technical => Roo Man's Room => Topic started by: hemidakota on October 29, 2015, 12:48:08 PM
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My fed is a 206" wb, motor is out 42". I need to either do some repairs to front end or replace. I like the a-arm look. I will loose 10-12" of wheel base (maybe a little more) and the steering tie rods will be in front of the axle center line. Will the steering be ok in front or should it be moved? I would like to leave it in the front due to fuel tank. Also will the narrower front effect how the fed handles? It all seems simple but was just wondering how others feel about it. I talked to Bruce a while back and he told me how to set up the torsion front end correctly but now I am leaning another direction. It is an addiction that never ends. Thanks Greg.
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Greg,
it the very least you will need to rework the steering geometry. When the tie rods are in front of the axle they will need to move in the opposite direction to what they did behind the axle if all else remains the same. Post some photos so that we can see what you have now.
Roo
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Couple things about a narrow track front end
You loose some stability or outrigger effect with it being narrower. If the car gets out of the groove/crossed upped, then the recovery angle gets smaller (tipping effect) compounded by not being 300" of wheelbase. The wider the front axle on a short WB car acts as an outrigger putting weight on the outside tire(of the turn) keeping the car flat at an increrased angle and makes the steering input not have to be as violent into the recovery. In other words a wider front end slows things down for eaiser control on a short wheelbase chassie when things go wrong.
Prefer rear steer over front steer, it just looks cleaner. If you run the steering rod out to the left front spindle then steering arms in front or back does not matter, but if you use a bellcrank then it does
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Thanks for all the input you guys give. Another Question is if the torsion front end was removed for a solid drop axle welded to the end of the frame rails would you still need radius rods or could you do it with out? I don't think the a-arm deal would work anyways now that I have looked the fed over again as the upper and lower frame rails are too close together. When I get a chance I will post a pic of the front of my car. Thanks again.
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If the distance from the axle mounting point to the king pin is less than 18" then radius rods are not required.
Roo
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A couple pics of my fed. Please Pick it apart. Any advice would be helpful. I do like the drop axle look but do not want to reinvent the wheel. I do have to replace radius rods as for one has been repaired and covered up well. If there is anything else I would like to catch it now. There are a few things I don't like but I would like a few thoughts from others. Thanks as always...
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I see some good things there--lock stops for the steering bell crank and the fact that the bell crank pivot is in double shear. If you keep the torsion bar I would suggest steering from the bell crank to one wheel and then back to the other with a single tie rod. As it is now, if the suspension actually articulates you will get some toe variation through the travel.
If you don't want suspension in the front just lock up the torsion bar and leave the steering as it is.
It also looks as if it has tabs for engine limiters--another good thing.
Roo
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Thanks Rooman. So you don't have a problem with all the rod ends mounted on single tabs the way it is? I always thought it should be a tab on either side or a solid rod end with the tabs in the center. I guess I'm overly concerned over the simple things... It all seems to work well. I would like to remount the steering arm along the side of the chassis with Teflon bushings of some sort instead of it being metal to metal, if that is necessary? Sorry for all the questions but going 175+mph I don't want any problems. Thanks again.
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Metal to metal works OK for the steering sliders--generally a 1/4" thick aluminum piece tabbed to the frame rails where appropriate.
Mounting rod ends in double shear is good practice as is a clevis on a single bracket but what you have will work OK.
Roo
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Any way to have the short steering rod from the steering box to the long steering (slider) rod straight instead of bent?
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A couple more things after having a closer look at the photos on a bigger monitor. It may pay to put a spacer behind the heim where the radius rods attach to the frame as it looks as if you are about out of radial travel there. I know that there is very little motion at that point but it is just good practice.
Also please lose the socket head cap screws in the steering and replace them with some good quality bolts--preferably AN or NAS. If cost or sourcing is a problem with that option the next best thing is to buy the appropriate length bolt that puts the shank through the mating parts and then cut off the excess thread. That can be difficult as the shank lengths are in larger increments than with the aircraft bolts which come in 1/16" splits. And please use fine thread bolts--coarse thread is for tractors and for threads in aluminum or cast iron.
Finally, the photos do not show if you have anti "pull through" washers on the steering heims as required in the NHRA etc rules. Chassis Shop/ Pro Werks have a good one that adds radial clearance and satisfies the rule. http://secure.chassisshop.com/partlist/15343/
Roo
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Something I just noticed,
Really?? spliced ty-rods??? OK for mock up or an emergency repair at the track , but not on a finnished piece.
Another reason for the straight steering rod---- have somebody hold the front wheels from turning and rock the steering wheel, that bent rod will flop as the heims find straight line adding play into the steering which would not be there if it was straight.
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This is why I like this site. Thanks for the input! So that being said, what size and thickness of tubing should be used on tie rods and steering rod down side of chassis? also for radius rods? I know its been said before but want to ask again. Will have to post better Pics on photo bucket so they can be easier viewed. Thanks again guys. Oh and one other thing, the steering rod down side of chassis has a long section in the front with no supports, is that for chassis flex so it wont bind up?
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Most threaded bungs are machined for .058 tubing
Ty-rods are mostly 3/4" dia.
Since the long rod is supported at both ends and extra slider is not needed unless the dia. is too small. I would make the long rod 7/8" min and the short one 3/4" min or 7/8" to match the long. Some dragsters require a bend in the short rod, but the bend is close to the steering arm and use a clevis instead of a heim to attach to the arm, that will keep the rod from twisting with steering input plus one goes with a larger dia (7/8")
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Sorry to revisit such an old thread. Now I am back to dragster front end. I want to cut torsion off of front of chassis, remove radius arms, steering bell crank and entire front end. I would like to have a 32" wide front axle(king pin to king pin) with a 4-5 inch drop welded to front of chassis and steering arm to spindle without bell crank. I think it would be simple and effective. What do you all think? And Bruce what all will you need from me to build me a axle? Spindle and king pin? Thanks again.
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"...What do you all think? ..."
Well... since you asked, what I think is that I love the look of classic FED's with wide front track like Bruce's digger pictured below.
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Now a days I would need the spindles since the KP angle if different on some
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Thanks for the help Bruce. I have spe spindles. This is kinda what I am after. Sorry stole the pic from rooman. My only concern is with a 36" wide, 5" drop axle @ 20 deg caster, the tie rod is going to be close to the top frame rail in my fed. Is there any options to get tie rods up a little higher, short spacers? bend in the steering arms? Or do I need to spend more time to figure exact drop that will work? Thanks guys for the input and sorry for the many questions.
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Just bend the steering arms to get the steering parts where they need to be. If you steer to the spindle (as in the photo) you will need to bend that arm as well so that the heim aligns correctly. When I bend that arm to drop it I follow Don Long's example and put the bends at an angle to the axis of the arm so that the end where the link attaches is pretty much parallel to the link.
Roo
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You should get spindles today Bruce. Thank you and talk to you soon.
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Here you go
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That is really going to clean it up and look good.
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Very cool. Thank you Bruce. I will give you a call today.
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Turned out perfect. Thank you Bruce. Tie rod is just mock up and very bent. all the steering rods were horrible, very glad I did the change.
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Turned out perfect. Thank you Bruce. Tie rod is just mock up and very bent. all the steering rods were horrible, very glad I did the change.
Looks great Greg!
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Wow that look great Greg
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Did you end up with 20 degrees of caster as originally planned? That seems a little excessive to me and may be problematic for backing up and wheel shimmy. I know I've seen this much on older cars but I think ten degrees would be perfectly OK.
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Did you end up with 20 degrees of caster as originally planned? That seems a little excessive to me and may be problematic for backing up and wheel shimmy. I know I've seen this much on older cars but I think ten degrees would be perfectly OK.
20 degrees is just about right for a front motor dragster. 10 is good for altereds and such.
Roo
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Thanks guys. Yes is at 20deg. Found bent rod ends, everything different sizes and just not anything good in the steering. I am very pleased with how it turned out. Will be mounting all new steering from the box forward soon.
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Did you end up with 20 degrees of caster as originally planned? That seems a little excessive to me and may be problematic for backing up and wheel shimmy. I know I've seen this much on older cars but I think ten degrees would be perfectly OK.
20 degrees is just about right for a front motor dragster. 10 is good for altereds and such.
Roo
I think old diggers were in the 30 degree ballpark (e.g.: that's what's in Mark Williams print). The wheels leaning on the sides when maneuvering the car in the pit looks cool, but if I were redoing my car, it'd stick with 20 deg.
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Newer style tires do not need as much caster as the moped tires did