Custom Tubular K Member, Tubular Control Arms, etc

[97eclipseNT]

i don't mean to take any of your thunder away because i do like your subframe alot but someone previously said that they didnt think anyone else made a tubular kmember but polk does make one but it is by no means cheap. but that can be expected i'm sure a lot of work went into it. nice work on your kmember though i definetly looks like a quality piece and i am also interesed on what you would want for one.

-gombos

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[topstreet]

No prob, everything is Driveshaft Shop. I remember seeing your car at GLD this spring. I believe it was the first time you hit 9's! Congrats!! You have one badass car. I was there in a white EVO. I know you were part of the inspiration for my friends build and very helpful. Thanks!

Hey Thanks Man!

I thought that yoke looked different than normal. The part that threw me off is that I have only seen this with the Carbon shaft.

You or your friend every need any thing hit me up!

Jake

 

[eclipsh]

Pardon my ignorance but are either of these setups significantly stiffer than the factory AWD bracing with good bushings or are they just for weight reduction?

I guess what I really want to know is if there is a big handling difference.

 

[topstreet]

The factory 1G system will significantly stiffen up with a good set of urathane bushings. Back in my GT35R days... I dropped the K-member and replaced the mounting bushings, and lower control arm bushings with plain jane urathane. At the same time I switched to a manual steering rack. The handling difference was very nice. My car had about 145k on it at the time.

Since then, the car has become more of a weekend warrior / drag car. I have done alot more weight reduction and chassis strengthening and the handling has only gotten better. If at this time, I could have easily taken close to 70 extra lbs out of the frontend and been left with a heim joint system it would have been that much better. But this is by no means the cheap "bang for the buck" setup that those bushings give you. This is more one of those "I did every thing else for weight reduction... What now?" kinda things.

If you notice in some of the other pictures, this car doesnt have a whole lot of anything in it. I would have to say, the stripping has gone BY FAR more than I have ever brought myself to do in my own car.

But as far as this setup goes... If you have the cash and the dedication, This would REALLY help the handling of a 1G. The amount of sprung and unsprung mass that is being removed is going to allow the suspension to react to the road very quickly and is going to make driving very nice.

 

[GSXNXS]

Pardon my ignorance but are either of these setups significantly stiffer than the factory AWD bracing with good bushings or are they just for weight reduction?

I guess what I really want to know is if there is a big handling difference.

This was only designed for drag racing at this point. I would say between the custom motor mounts and rest of the pieces it will be noticeably stiffer.

 

[GSXNXS]

Ok, so the rear bar of the a-arms has the typical ball joint and attaches to the upright. Then the front leg of the 'a-arm' attaches to the rear leg via the tab. The heims end on the front leg, at the upright, is in single shear. Obviously, you're driving a fast car on the strip and braking becomes critical.

If it was me, I'd question the safety of that. With that heims end in single shear, it'll be see a bending load or axial load (ie through the ball) for which the load rating is significantly lower.

My suggestion would be to either:
A. Make it a double shear joint.
B. Make it a fixed joint, removing the heims end at that end. Leave the adjustment to the inboard end. In all reality, the amount of adjustment on the inboard side of the arms is more than enough.

After talking to the fabricator more about this he clarified that there is a clevis on the control arm side that makes that mounting point double shear. He said it is the same setup he uses on super late models and one of those guys has also done some open track with his car. Other things he threw out at me that I jotted down where 95 wall chromoly and 3/8" cold steel plate.

 

[steel_3d]

Is that Polk piece for a 1g or 2g? It seems to have the weird 2g-like angled trailing link that would force the travel of the control arm to arc fore and aft. Don't even know how well that would work with a mcpherson strut... I guess it would... It does seem to do its job better than one mounted coaxially with the front inboard link, now that I think about it.

 

[topstreet]

After talking to the fabricator more about this he clarified that there is a clevis on the control arm side that makes that mounting point double shear. He said it is the same setup he uses on super late models and one of those guys has also done some open track with his car. Other things he threw out at me that I jotted down where 95 wall chromoly and 3/8" cold steel plate.

Just as a refference point to anyone who is unaware... The rule book says for roll cage mounting points... They must be at least 1/4" thick. As far as roll cage tubing... When using chromoly, you must use at least .083".

I threw that one out there because it just goes to show how good something like this really is. The rule book also says that cars faster than ( I Believe? ) 8.49 MUST be chromoly.

As far as the single shear thing goes. Yes the double shear may be a more sound design... BUT, I will back you and the fab guy up on this one. In the truck world... These single shear rod ends replace failing ball joints all the time... AND TRUST ME!@! These guys know how to break stuff. I though DSMers were bad... The single shear will work well in this situation because it is being held by a grade 8 bolt.... I highly doubt that is going anywhere!

Jake

 

[Morphius]

As far as the single shear thing goes. Yes the double shear may be a more sound design... BUT, I will back you and the fab guy up on this one. In the truck world... These single shear rod ends replace failing ball joints all the time... AND TRUST ME!@! These guys know how to break stuff. I though DSMers were bad... The single shear will work well in this situation because it is being held by a grade 8 bolt.... I highly doubt that is going anywhere!

Jake

I don't question the quality of the overall part. It looks to be built well. However, I still question the particular heims end on the outboard end of the front arm. It looks to be on the small side for one, like half the size of the inboard one. I don't think you realize the forces that are running through that joint. Grade 8 or not, someone should analyze it. The "they've done it like that before" really means nothing. Maybe they were lucky.

 

[Morphius]

It looks to be on the small side for one, like half the size of the inboard one.

I looked back at the last pic you posted and it looks like the end that threads in the arm may be the same size, however the bolt in single shear is rather small.

Just voiceing my concern.

 

[topstreet]

The "they've done it like that before" really means nothing. Maybe they were lucky.

I think you should take alittle more consideration for this one. Your right in a sense... If I put my entire car together with heims and said "it worked for me" (with out ever having tested it in the real world) I would totally agree with you. This is why I brought up the truck example because, We will snap steering shafts, rack and pinions, ujoints, collapse axle housings, break frames... I could keep going BUT!... I have never yet seen a snapped heim joint rod end. (worn out but not snapped)

Offroad, you will find every limit of the parts you are running. Compressed, flexed, impacted, jolted and put at wierd angles. ON TOP of it... There Are guys that I go up with that will run wheel/tire combos that are over 400lbs a PIECE. with a 7,000 lbs truck making 600+lbs/torque.

I know every one is allowed to an opinion and I am not going to attack that at all. I am entirely convinced though.

Jake

 

[GSXNXS]

Thanks for the added information Jake it is sincerely appreciated.

I have the upmost faith in this fabricator as I have been in this area for 32 years and have not ever heard one bad word about him. He has done everything from super late model Nascar, drag chassis, road racing chassis, and also street rods. Anyone who has that broad of experience in racing, I have been working with for three or four years already, and never heard a complaint about can definitely build me a chassis or custom parts...in fact I am still toying with the idea of doing a 4G63 rail car too

 

[Morphius]

I have never yet seen a snapped heim joint rod end. (worn out but not snapped)

I have seen many, many snapped heims ends in Forumla SAE and Solarcar racing. Thus, my concern.

 

[Morphius]

What size is the suspect 'grade 8' bolt for that joint?

 

[eclipsh]

^^^ Professional automotive engineers might be worth listening to. Yes your guy is too, but he doesn't have to design street cars \with safety issues in mind.

If nothing else, making it double shear is just added protection at a minimal weight gain and cost.

I have no experience as an engineer but personally, I'd rather over-engineer something than take an unnecessary risk, especially with something that critical. If that spot fails on an 80-100mph sweeper or a stop from 130 mph, chances are you're not walking away from the accident unscathed. That's if you can walk at all.

That said, I'm still jealous.

 

[GRNDSM]

It cracks me up when people are calling this mod "not popular in the DSM community". It isn't done much because it is so expensive! IIRC, Polk's set-up was (is?) around $1200 with the A-arms. Consequently, very few people could afford it. I have a suspicion that it would have been a much more popular mod if someone could sell it for $300 .

 

[SBstar]

I have a feeling I would buy one if it was $300...

 

[almostquick]

well the thing was, like stated earlier, if a product like this could be had for roughly the same amount as the f-body/fox body community, this would be a VERY popular product. As far as money was concerned I was thinking in the ballpark of anywhere between $300-$600. For example you could pick up a tubular mustang K-member for $250 right now.

 

[topstreet]

I can respect where you guys are coming from. In the same sense though... I would run this design or one very similar. This is just my opinion though.

 

[GRNDSM]

The difference is that those $250 Mustang frame weldments have been engineered to be mass produced at a factory. I highly doubt that you will see something comparable for a DSM, because the numbers will never support it . Something hand made, in a small fab shop will never reach the same economy of scale... Which is why Polk frame was as much as it was.

Trev, I would love you to prove me wrong .

 

[GSXNXS]

I am not a vendor and will not discuss anything regarding possibly selling them or a price here with respect to Chris and the site. If you want to make positive/negative comments, suggestions, etc, keep them coming. I appreciate the postive ones and for the negative ones...you know the saying "opinions are like...eveyone has one". With that said, the design will stay the way it is for this drag racing application and we will be torturing the car all this year attempting to put the small 16g deep into the 10's. After that a built motor and 42R will torture it some more.

For those like Jake and the others, thanks again

 

[nitrouskris]

S E X Y

+1...........................................................................................................

 

[GSXNXS]

Well progress on the car has been much slower than expected. We did however get one of our team mates street cars in this week and are working on a k member with the stock steering rack. Our fabricator has been beyond swamped.

Here are some more pictures for those that are interested in checking out a 1G with a full rear tube frame, moser 4 link rear end and some more pics of the custom K member up front.

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[absolute_DSM]

Our fabricator has been beyond swamped.

Aint that always the truth. Not an easy job there.

Everything looks great

 

[GSXNXS]

Aint that always the truth. Not an easy job there.

Everything looks great

Thanks!

I should have also mentioned the car is running a custom spool and not a locker rear end. It is the only other one besides Shep's in an AWD that I know of.