VD Fragile pushrod adjusters, rear toe adjusters

[4mulaGuy]

I have a 99 Van Diemen and broke 2 of the barrel adjusters that are used in 6 places on the suspension. One each at the inboard end of the 4 pushrods - to allow you to adjust the length of the pushrod. One each side that allows you to adjust the rear toe.

I just had a race at Laguna and ever so slightly kissed the wall during practice with my right rear - breaking that toe adjuster - OK, my fault - I am glad it was an inexpensive part - relatively.

Then during the race, the adjuster on the front left pushrod bent and then broke as I came over the top of the Corkscrew. I hit nothing - it just broke.

Does anyone have experience with these components being fragile? I can see it breaking when you hit something - saving the rest of the car - but I can't it just breaking due to the stresses of racing. I have only had the car since June, so I don't know what kind of abuse on the track (or in the garage) it might have experienced.

Any help would be appreciated. At this point I am going to replace all of the remaining ones, but I wonder if this is common - and if it is, has anyone made a better one?

Thanks!

- Rob

[Douglas Brenner]

Rob
The problem is that you are just going to darn fast! Slow down a couple seconds a lap and it should be fine! Great job!! Douglas

[Charles Warner]

I can see it breaking when you hit something - saving the rest of the car - but I can't it just breaking due to the stresses of racing. I have only had the car since June, so I don't know what kind of abuse on the track (or in the garage) it might have experienced.

- Rob

Rob,

Why can't you see it breaking due to the stresses of racing? It's a 6 year old race car! And, as you point out, what abuse has it suffered at the hands of previous owners? Race cars undergo much higher stresses than you imagine. Race car parts are not intended to last a lifetime. You got off lucky. There could have been many other stress-induced failures that might have taken tghe car, and you, out.

I am constantly amazed at how many racers get a new (but used) car and assume all parts are perfectly whole. No crack checking, no inspection of bearing or rod ends, or even the tub/chassis, etc. Then they wonder why parts break.

[sarrcford]

I had a right front pushrod adjuster bend on me this year at Lowes Motor Speedway. Like you, no contact with anything. My best guess was that it was taking a pounding on the transition from the infield to the banking at Nascar Turn 1. I always bring a spare one now.

Rob Poma

[PK]

We had a couple front pushrod adjusters break, but both were traceable to on-track incidents (one a real accident where other suspension pieces were bent and one nailing a pothole inboard of the apex of a corner.)

Don't take this failure lightly! If the front pushrod adjuster breaks, you become a passenger. One of our cars broke on turn in for the carousel at Nelson Ledges. Obviously it had fatigued from the initial accident damage because this turn in isn't at all severe. But, the frame dropped down onto the track, and the car went straight off into the tires at 80+ MPH. Not pretty.

The other failure occured coming out of the bowl at Grattan, and again the car went straight off, fortunately not hitting anything. A little earlier in the corner, and it would have gone into a wall.

So, we replaced all the pushrod adjusters and threw the old ones away.

[RobLav]

My right front steering adjuster broke at NHIS on my RF99 last month. But I believe that it broke because the front wing endplate hit it when I went too wide and went over a fairly high curb.

I lengthened the stock steel front pushrod adjusters so I can use standard rod ends rather than those expensive original Van Diemen ones. I cut the threaded part of the original Van Diemen rod ends and used that piece between the adjuster and a new threaded rod welded to that adjuster.

[formulasuper]

18 years of formula car racing experience has made me believe these are the most fragile formula cars in SCCA club racing, & therefore the fastest for the HP they have. After seeing SARRCFORD'S pushrod failure earlier this year with no previous contact to cause it, I would have to advise the owner/drivers of these cars to modify the pushrods as ROBLAV has or some other method of beefing them up, unless they are replaced on a regular interval. I don't think a few ounces is going to make a noticeable increase in lap times. Crack checking is good, but how do you know they won't bend or break during the next session after being checked? These suspensions were designed to be as light as possible & therefore are time limited, not unlike aircraft parts.

[Scotty Segers]

If I remember correctly the 98 and 99 push rod adjusters bent and broke all the time. In 2000 VD did a redesign and corrected the problem. Use a 2000 push rod and adjusters. The rear toe link had to be abused sometime it's it life. Replace everytime it gets dinged.

Scotty

[R. Pare]

One big issue overlooked by most people when building a pushrod is just how perfectly (or not) in line all the companents are after welding. It doesn't matter how good your fixturing is, the welds will draw the threaded ends off center to some degree as they cool. You have to remember that a pushrod is a column where the slenderness ratio ( diameter vs length) is in the critical range for buckling.

If everything is not as close to perfectly in line as possible, an offset load will be created, with a bending stress being the end result.

If the offset is small enough, you'll never know - it will probably work fine darned near forever. But, if large enough, either the adjuster or the rod end can have enough bending stress put on it for it to bend and break - I've actually seen a brand new car have a pushrod rod end break while in the trailer on its way to the track!

To minimize this problem, the threaded ends really should be drilled and threaded AFTER welding. Yea - it's a bit of a pain in the ass to grip non-round tube and center it correctly in a lathe ( 4-jaw chucks are the easiest way), but if you want to minimize this sort of buckling, this is the only way to do it.

Another problem everyone overlooks is the jamb nut being used. In this application, it is the threads of the jamb nut that are supporting all the load, NOT the threads inside the threaded end of the pushrod. Quite often, you will get a nut where the faces are not square to the centerline of the threads. So what happens? In tightening the nut, you automatically introduce a bending load on the rod end shank, AND skew it slightly out of line. Add the stresses from the load, and things can quickly get out of hand.

[Paul LeCain]

Adding to Richard's post:

An easy way to see if your adjusters are lined up properly is to look for movement of the pushrod or rod end as you turn the adjuster. If either the pushrod or rod end moves in a small circle, the adjuster is not lined up and/or bent.

[greg pizzo]

call Doug Learened

he has made some turnbuckles out of a better (tougher)steel material I think 300M same as used for his axles

it will bend alot more before it SNAPS ...

if he still has some buy those ...


Doug Learned can eb reached at Fast Forward

831.899.3636

[Bob Wright]

Listen to Scotty- the problem was fixed in 2000-throw out all the '98-99 stuff. I broke more than one of them at inappropriate times.

[4mulaGuy]

Ok. Lots of really good advice. When I bought the car, I did do a reasonably thorough checking of it and found numerous issues that I resolved including replacing the rod ends on the pushrods and the track/steering rods. I didn't magnaflux the suspension bits though. I spoke with both the 2 previous owners and was told the car had never been crashed and from the records had been to the track 6 times (it sat for 2 years between owners). But

The place on the track where the pushrod adjuster broke was a pretty slow part of the track (1st gear). When I got back to my pit and discovered what happened, I got a bit of a chill thinking about what would have happened if it had broken 30 seconds earlier at turn 4 (90+MPH). So yes I will definately go through the suspension carefully this winter.

Some questions for Scotty and Bob...
Do I need to replace the pushrods as well as the adjusters with 2000 hardware? Did the pushrods change too? I will have the push rods magnafluxed to make sure they are solid. Also, I have the narrow track, are the 2000 cars narrow track? I will also look into the FastForward parts (Doug lives 5 miles from me).

Thanks everyone for your great advice.

- Rob

[Scotty Segers]

The push rods are different lenghts than what you have to accomodate the redesigned adjusters, so yes you have to replace the pushrods and adjusters, but you won't have a problem again, without damaging the parts.

[Mark Blythe]

I would like a confirmation, are the turnbuckles failing or the threaded part of the pushrods failing or is it either or?

Thanks

[RobLav]

turnbuckles

[4mulaGuy]

The threaded end of the turnbuckle itself broke - between the pushrod jamnut and the turnbuckle.

[Larry]

We've faced this problem for years in aviation. Components often fail due to fatigue. I'm certainly not disputing Richard's comments about reasons for failure or how to improve the life of the component, but you need to recognize when components have a useful life (as in 83/4 Reynard wheel spindles). I recommend that front spindles on these cars be replaced every 20 races (or 10 races if you run on ovals). In other words, you should replace these known, weak components on a time basis before they fail. Estimate how many races you had before the failure (call this the life limit), and then track the life of the component and replace it when you have reached 50% of the life limit.

By doing this kind of preventive maintenance, you'll avoid the expense and problems of associated corrective maintenance.

Larry Oliver
International Racing Products