2016 SM (Street Mod) Autocross Discussion
May 21, 2016, 01:12 PM
#93
Im constantly working on getting these tested and continuing designing and improving (cost and performance). So that along with a full time real job isnt leaving a lot of time to keep they hype up. So here a some pics after my successful weekend of testing.
Here you can see the steering arm is much beefier. Also note the bolted on strut mount. This is how im keeping costs down. As is im machining a 3" thick block of 6061 that weighs 22lbs down to 4.5lbs. Thats a lot of waste material to remove and time. Without this approach, the block would need to be 5.5-6" thick.
One thing Im changing on the next version is to increase the size of the strut mount bolts to match the ball joint bolt and increasing steering arm bolts from M8 to M10. Why? These have proven strong enough for at least one weekend but the change is for reduced number of different bolts and increased margin. Its kind of an important part, if I was a customer I would want some warm fuzzy feelings this wasnt a fragile thing.
More beefy arm shot and other side of strut mount. Oh hi ABS sensor, no issues with ABS or ACD at a sopping sunday event. Ignore the lack of double jam nuts on the steering sleeve, it was a temporary fix to get things going but has proven to not be an issue so far.
Lower control arm angle on a car lowered ~2.25". Oh is that steering arm parallel?
Here you can see the steering arm is much beefier. Also note the bolted on strut mount. This is how im keeping costs down. As is im machining a 3" thick block of 6061 that weighs 22lbs down to 4.5lbs. Thats a lot of waste material to remove and time. Without this approach, the block would need to be 5.5-6" thick.
One thing Im changing on the next version is to increase the size of the strut mount bolts to match the ball joint bolt and increasing steering arm bolts from M8 to M10. Why? These have proven strong enough for at least one weekend but the change is for reduced number of different bolts and increased margin. Its kind of an important part, if I was a customer I would want some warm fuzzy feelings this wasnt a fragile thing.
More beefy arm shot and other side of strut mount. Oh hi ABS sensor, no issues with ABS or ACD at a sopping sunday event. Ignore the lack of double jam nuts on the steering sleeve, it was a temporary fix to get things going but has proven to not be an issue so far.
Lower control arm angle on a car lowered ~2.25". Oh is that steering arm parallel?
The following 3 users liked this post by Dallas J:
May 21, 2016, 04:13 PM
#94
My thoughts: I'm not a huge fan of separated pieces mounting to the strut but I get your point. In my environment if it's gonna shake loose it will usually so maybe even a || slot that a special jam nut fits in so it can't shimmy loose. Also the 'black coated' bolts will rust (as they did on my 1.0 AP brake kit) so go for stainless everything. And as much as allen key is cool, if you've ever had those on the top mounts they tend to strip. Elsewhere especially when air tools are used so stainless hex preferred.
I'm in for testing once your happy with the design
.
I'm in for testing once your happy with the design
.
Last edited by Balrok; May 21, 2016 at 04:18 PM.
May 21, 2016, 07:46 PM
#95
My thoughts: I'm not a huge fan of separated pieces mounting to the strut but I get your point. In my environment if it's gonna shake loose it will usually so maybe even a || slot that a special jam nut fits in so it can't shimmy loose. Also the 'black coated' bolts will rust (as they did on my 1.0 AP brake kit) so go for stainless everything. And as much as allen key is cool, if you've ever had those on the top mounts they tend to strip. Elsewhere especially when air tools are used so stainless hex preferred.
I'm in for testing once your happy with the design.
I'm in for testing once your happy with the design
.. There also isn't that much load in that area, most load is down in ball joint to wheel bearing and the steering arms. I am changing that bolt to a 12mm for a bit more clamping and there is also an M10 on the outside pulling it tight face to face. That screw is hidden by the rotor (also blocked access to re-tighten by the rotor though) so I used red loctite on it. Im not 100% sure what you mean by a jam nut though. Those black oxide bolts were a rush order to get something that was the right length and dia. McMaster didn't have everything in stainless I needed so I figured not a big issue on this prototype set. Also stainless doesn't have the tensile strength that alloy steel does so I'll have to see what I need and what I can get in the fine pitch thread I want.
The socket heads for some areas aren't really needed so I may switch some back to hex screws. The ones I currently don't have much latitude to change is on the steering arm. Those are closed into aluminum threads so shouldn't corrode and should never need to be removed. I need the socket head for small diameter head since the rib surrounding it does carry load. I am switching those to M10s to increase thread area for safety factor but the arm will still bend before those can pull out and that would take more force than it would to bend the stock hubs steering arm (in other words, you'd have to crash).
May 26, 2016, 12:10 PM
#96
If you go stainless, go different grades (harder on the bolt) to avoid galling. Can't tell you how much I have to deal with this issue at work and how no engineers EVER think about it.
The OEM hardware is actually really good stuff if you can find OEM bolts that meet your needs. It's all fine thread and much of it is 12.9 zinc-cadmium coated so it doesn't corrode or gall up.
Good stuff man. What you are seeing is in line with what I would have expected. You have been able to lower the roll bar stiffness up front because now the springs are giving you more of the roll stiffness. The front wheels now react more independently of each other which is why the turn-in improved. Total roll stiffness of the front has actually increased though so now the rear end is doing less work so it follows along blindly without much attitude.
In the end, you have more available front grip but have also created more total roll stiffness up front. Now to figure out how to move more roll stiffness to the rear while also gaining total rear grip.
The OEM hardware is actually really good stuff if you can find OEM bolts that meet your needs. It's all fine thread and much of it is 12.9 zinc-cadmium coated so it doesn't corrode or gall up.
Good stuff man. What you are seeing is in line with what I would have expected. You have been able to lower the roll bar stiffness up front because now the springs are giving you more of the roll stiffness. The front wheels now react more independently of each other which is why the turn-in improved. Total roll stiffness of the front has actually increased though so now the rear end is doing less work so it follows along blindly without much attitude.
In the end, you have more available front grip but have also created more total roll stiffness up front. Now to figure out how to move more roll stiffness to the rear while also gaining total rear grip.
May 26, 2016, 02:45 PM
#97
Interesting, as an engineer that doesn't deal with material testing that's good to know. I'll may end up getting stuck with what ever is available on the M12s because of fine thread and nut may not be available with any choice of grade other than 12.9. Also McMaster has a pretty small selection of m12x1.5 or 1.25 screws so I'll probably use whatever is the right size and pitch for the next iteration and talk with Fastenal about getting something a bit more weather proof.
Update on progress though, I did finish the model to make the next iteration. Changed the steering mount geometry just a little bit and switching to M10s for that extra bit of margin and increased strut mount bolts from M10 to M12 plus a little self inflicted DFM. I have the material in the garage just need to start cutting parts out and install to make sure its all good. The tight fit parts are the only real areas of concern. The wheel hub to upright and the ball joint to upright. Getting the right amount of interference was trial and error to match the fit of stock parts but I was still a little too tight on the ball joint.
Now I'm starting to think about Anodizing and finishing. Because these are under the car I'm thinking a rough texture from a media blast might be good to hide scratches and clean up tool marks. Tumbling a part of this size would probably take too long and cost more than its worth. Also curious what level of Anodizing people would want or what color to make them. I prefer orange but its such a polar color that just having them done in a darker grey (titanium grey maybe?) or black would be the safe bet. Is it worth getting pricing for Hard anodizing and what does that do to my interference fits. Coating thickness will need to be taken into account on the design so would have to have done before pulling trigger on making a batch.
Update on progress though, I did finish the model to make the next iteration. Changed the steering mount geometry just a little bit and switching to M10s for that extra bit of margin and increased strut mount bolts from M10 to M12 plus a little self inflicted DFM. I have the material in the garage just need to start cutting parts out and install to make sure its all good. The tight fit parts are the only real areas of concern. The wheel hub to upright and the ball joint to upright. Getting the right amount of interference was trial and error to match the fit of stock parts but I was still a little too tight on the ball joint.
Now I'm starting to think about Anodizing and finishing. Because these are under the car I'm thinking a rough texture from a media blast might be good to hide scratches and clean up tool marks. Tumbling a part of this size would probably take too long and cost more than its worth. Also curious what level of Anodizing people would want or what color to make them. I prefer orange but its such a polar color that just having them done in a darker grey (titanium grey maybe?) or black would be the safe bet. Is it worth getting pricing for Hard anodizing and what does that do to my interference fits. Coating thickness will need to be taken into account on the design so would have to have done before pulling trigger on making a batch.
May 26, 2016, 02:53 PM
#98
EvoM Guru
iTrader: (1)
I wouldn't want anodize, it scratches too easy. I would offer powder coating, but that's it. That also may be difficult to find a coater who will properly mask the part. Personally,
I would order them bare. I realize that wouldn't work for people that live in a more corrosive environment though. Although, aren't the OEM control arms just bare aluminum?
I would order them bare. I realize that wouldn't work for people that live in a more corrosive environment though. Although, aren't the OEM control arms just bare aluminum?
May 26, 2016, 03:35 PM
#99
True, and these aren't an "On Road" part. Its certainly a race only part not tested to the levels of a road worthy car seeing 100k+ miles. There's just no way for an individually to realistically test something like that.
Still need to figure out if I'm going to have them media blasted then. That would at a minimum clean up some leftover tooling marks.
Still need to figure out if I'm going to have them media blasted then. That would at a minimum clean up some leftover tooling marks.
May 26, 2016, 04:15 PM
#100
EvoM Guru
iTrader: (1)
They look beefy enough. You really think they don't have enough margin built into them for road use? I may end up building a chromoly set if you really feel that way lol
May 26, 2016, 04:27 PM
#101
I certainly feel they are beefy enough for road use, race use is far more extreme in loads. The thing I cant test for is long term fatigue and corrosion life. That's just something I could never predict. Track miles would never hit the same lifetime testing as a new York car daily driven on ****ty roads with salt spray every winter.
I'm not too concerned about the aluminum at all though. There are plenty of cars running cast aluminum uprights or other suspension components.
I'm not too concerned about the aluminum at all though. There are plenty of cars running cast aluminum uprights or other suspension components.
May 26, 2016, 08:57 PM
#105
EvoM Guru
iTrader: (1)
Originally Posted by Dallas J
I certainly feel they are beefy enough for road use, race use is far more extreme in loads. The thing I cant test for is long term fatigue and corrosion life. That's just something I could never predict. Track miles would never hit the same lifetime testing as a new York car daily driven on ****ty roads with salt spray every winter.
I'm not too concerned about the aluminum at all though. There are plenty of cars running cast aluminum uprights or other suspension components.
I'm not too concerned about the aluminum at all though. There are plenty of cars running cast aluminum uprights or other suspension components.
What are your thoughts on how you've raised the front roll center, but the rear is still the same? Is the roll center of the rear suspension more consistent thanks to being multi link?