1G DSM front k-member and tubular control arms

[talonkev]

I'm interested in one for my 1g, excited to see some pricing info

 

[TSimage]

I supported you like none other on your cross bars and told you I'd be there to support you on this. My auto bar fits perfectly and I love the craftmansship.

Let me know what you come up with or if you need another test mule.

 

[Ludachris]

Would you say this k-member and control arm set up would be strong enough to hold up to the demands of road racing and autocross? Or is it meant more for straight line racing/loads? Lighter weight is important to me, but increased rigidity front to back and side to side are just as important, if not more so. Suspension geometry adjustment is a must too.

 

[talon91tsiawd1]

I will deff buy one too with manual rack mounts

 

[greddy_1700]

Glad to see that you are addressing the issue of single shear vs double shear at the lower control arm mounting points. I was going to express my concerns with that, but looks like you beat me to it!

However, I am slightly concerned with the use of 0.083" wall. I realize that 4130 has a yeild strength of 85Ksi, but with the extreme forces seen under road race conditions, is this adequate? Personally, I would like to see a quick stress calculation to verify. Has any sort of calculation been completed, or is this more of a "should be strong enough" sort of case?

I mean absolutely no disrespect in my post whatsoever, clearly there are extremely impressive fab skills here.

 

[dsmmack]

Vassil. Great fab work. Been wanting to make one of these at some point in the future myself but its one of those things that's always on the backburner.

PM me a price.

Thanks
Colin.

 

[blktalon3]

Will you have one for an auto too? As far as the rear motor mount. If so I would be interested. Pm me the price. By the way, love the Front crossmember just got it back from the powdercoater and it looks awesome.

Can yoiu also post some close ups of the a-arms.
Thanks

 

[vassil]

Hi Guys,

Thank you for all the positive comments. Here is a close up the the control arm. It's attachment points to the K-Member are a double shear. I ordered some more 5/8" and 3/4 heim joints and this weekend I will try to figure out a way to change the clevis that attaches the two control arms to a double shear attachment with a heim joint. It is a little tricky, since the tubing used for the control arm is 1.25" with 0.095 wall and the thickness of a 5/8 heim joint, two misalignment bushings and two tabs exceeds 1.25" by a little bit. So I will have to experiment a bit on that one. Once accomplished it would be extremely solid.

You must be logged in to view this image or video.

Once this is complete, I will only have to steering rack mount to figure out and then we should be all good. I am trying to have this done as soon as possible but, sometimes there are simply not enough hours in the day, between my family, full-time job and DSM parts fabrication.

As far as the racks go. Initially I will have provisions for the DSM manual rack, since this is what I have in my car. I will also make sure that a power rack can fit. It time permits, I am willing to experiment with a mustang II, dodge ommi rear steer rack. Those are really nice and they aren't that expensive.

There was a question on how I came up with the various parts for fabbing this up. I haven't had time to draw everything in Solidworks yet and test it. So far I have my car up on a hoist and basically I make a part work, then jig it and move on to the next. My old tube chassis has 1.25 0.095 tubes with 3/4 heim joints for the 4-link. That was enough for a 1000+ HP RWD door car, so I figured that two of those in the front should be plenty. The 1.625" 0.083 tubing is the same as what I build my rollcage with and the same tubing that I used for a 25.1e tube chassis which is certified to 6.50 ETs. It should be more than plenty for a k-member.

Ludachris, to answer your question about adjustability. There is all sorts of it. You can change camber, caster and toe. I would recommend it for road-race use only once I figure out the swaybar situation, unless you're feeling brave. For drag racing and regular day-to-day, it should be fine. I have driven my car w/o swaybars for a long time and it really isn't that bad.

So, long story short ... I will have more updates this weekend. Thank you all for your input and support thus far. I appreciate it very much. If you can think of anything you want or anything I am missing out, don't hesitate to post here or let me know via a PM.

--Vassil

 

[Ludachris]

Very nice. I would definitely have to wait for the swaybar part of the project to be addressed.

Another suggestion - I'll have to dig up the info on this again for part numbers, but it would be awesome to be able to use Chrysler ball joints which have the same taper but are available with longer stems to address roll center when lowering the car. It's something we've been talking about in the road race forum for a while. I know they're available in the press-in style versions but not sure about the screw-in type like you're using.

 

[red94gsx]

About the screw in-type of ball joint. This does place bending forces on a threaded rod end, especially in braking.

From my experience with FSAE cars, this is usually a bad thing. The threaded sections of the rods are very prone to fatigue, because all of the stress on them is concentrated at the base of the threads. This means they won't break right away, but might catastrophically fail at some point down the road.

Now, this does happen more often when designing parts to be light (Formula cars), but isn't much of an issue if you overbuild the crap out of it. What you are essentially doing at that point is designing the parts for "infinite life".

There is a way to check this, if I dug out my machine dynamics text. It involves analyzing the maximum oscillating stress on the part (loading and unloading), and then checking to make sure that this stress won't bend the part to form surface cracks which lead to failure.

However, I really like the way this is going, especially the mounts in double shear. It is definitely useful for road racing to have a completely adjustable suspension. It does put you in a very serious class in autocross if you have custom suspension arms. But for those people who want to go there, this would be awesome.

 

[96awd]

Any updates on this, Vassil?

 

[RipperXX]

This looks sick! I personally would love to have this for autoX style racing. I don't even care about class though as I doubt i'd ever actually enter a real race with my car. I just want the ability to set the car up to handle the best it can for DD driving. Not as in going to work and back, but as in playing on moutain roads etc. The weight reduction would also help balance out our front heavy cars (obviously).

Keep this up, I hope you end up with a drag option and a roadrace option. I have been wanting to see something like this for 1g's for a LONG time. Once you finish the refinements of your K-member, throw a nice powder coat on that thing and you got a REAL sharp product there!

 

[igopoopy]

im in love with this i have a 91 tsi awd with a manual rack
its a drag car so weight is the only thing i care about
so im in please pm me about price

 

[SHEARER_TSI]

Very Interested, please pm me pricing.

 

[91stocker]

Any progress with this? Would love to see this with the mustang 2 rack.

 

[96awd]

Yeah for real. I have money waiting for this right now.

 

[agentorange313]

Yeah for real. I have money waiting for this right now.

Same, please update. I am definitely down for some 300+ lbs of weight reduction.

I wrote 300, that would be awesome, 30 lbs

 

[Lil' Shaun]

I have wanted one of these for about 5 wears now. ibut no luck finding one.

 

[96awd]

Same, please update. I am definitely down for some 300+ lbs of weight reduction.

I wrote 300, that would be awesome, 30 lbs

I've taken out almost 340lbs so far. This will be great and end my weight reduction!

 

[cioc]

I have found an expensive alternative.

Tubular Control Arms Mitsubishi EVO 5-6 - PeeBee Motorsport
EXTREMELY lightweight. Provisions for roll center adjustments, sway bar mounts, spherical bearings and bumpsteer spacers. They use only top notch materials. I would be willing to send my arms out for them to make prototypes. Cost drops to $1150/set if we can get 5 buyers. I'm doing this no matter what...who wants to jump on the bandwagon?

 

[96awd]

Not me... I want the WHOLE K member as Vassil has started building.

 

[agentorange313]

I just sent him a PM, hopefully he responds, last activity was on the 5th I think.
'

Here's Bulfab's website:

http://www.bulfab.com/index.html

 

[96awd]

I've sent about 3 PM's since he's posted this and have not heard back each time.

 

[DsMWookie]

Absolutely. I have the one on my car and I have to redo my jig since I had to make a couple of small changes. I will be redoing the jig next weekend and will post some pics. I have been swamped with all sorts non-DSM related things. Sorry it's taking so long.

Quote:
Originally Posted by dsmwookie
Vassil,

I m sure your busy man, but are you intending to make one of those K members still?

^ The above was from last week. He just seems busy, so relax and I m sure he will get to it.

 

[91stocker]

Absolutely. I have the one on my car and I have to redo my jig since I had to make a couple of small changes. I will be redoing the jig next weekend and will post some pics. I have been swamped with all sorts non-DSM related things. Sorry it's taking so long.

Quote:
Originally Posted by dsmwookie
Vassil,

I m sure your busy man, but are you intending to make one of those K members still?

^ The above was from last week. He just seems busy, so relax and I m sure he will get to it.

That is some good news.