LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently March 29, 2024, 4:17 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 155 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7 ... 11  Next
Author Message
PostPosted: May 21, 2018, 1:00 pm 
Offline
User avatar

Joined: March 19, 2011, 10:22 am
Posts: 2386
Location: Holden, Alberta, Canada
Good to know, I did not realize the rule of thumb works with the UCA also.

_________________
Perry

'If man built it, man can fix it'
"No one ever told me I couldn't do it."
"If you can't build it safe, don't build it."

Perry's Locost Super Che7enette Build
Perry's TBird Based 5.0L Super 7 L.S.O
Perry's S10 Super 7 The 3rd
Perry's 4th Build The Topolino 500 (Little Mouse) Altered
Perry's 5th Build the Super Slant 6 Super 7
Perry's Final Build the 1929 Mercedes Gazelle


Top
 Profile  
Reply with quote  
PostPosted: May 31, 2018, 5:18 pm 
Offline
User avatar

Joined: May 29, 2015, 6:09 pm
Posts: 120
Location: Charlotte
Miatav8,MstrASE,A&P,F wrote:
Interesting build. Have you looked into what it will take in your area to get this registered for use on the road? It seems nearly every state has their own hurdles/walls.


Actually, I have built 2 other cars and registered them in NC as a "Specialty Construction Vehicle". This one may be more of a challenge since its based upon an ATV. Some states will not register a home built if there are any ATV parts in it.

I've been afraid to call my local NC DOT to ask :puke:


Top
 Profile  
Reply with quote  
PostPosted: May 31, 2018, 5:56 pm 
Offline
User avatar

Joined: May 29, 2015, 6:09 pm
Posts: 120
Location: Charlotte
horchoha wrote:
Hey Rumbles
I find this interesting with the rack perched high.
I aren't no mathematician, so I have simple rules of thumb when designing my front ends for minimal bump steer.
First - the UCA, LCA, and ITR pivots must all line up in plane on the PS and DS.
Second - the LCA and ITE, adjusting tube if used, and OTE of the rack assembly must be parallel to each other
Third - go have fun, no bump steer

Please explain your steering geometry with the rack perched high, I'm interested. Is it parallel to the UCA? :cheers: :cheers:


Before I started this project, I did quite a bit of research on suspension and steering engineering. I read 4 books on it and they all seemed to saying the same thing about the front end geometry. Then I used the VSUSP tool to design and tune my suspension and steering design to what I learned in my research.

Once you have your spindle and A-arm pivot points loaded in VSUSP, it tells you where your steering rack rod pivot points should be.
  • The steering rods that go to the spindle are parallel to the A-arms
  • The universal joint between the steering rods and the rack is inline with the inboard pivot points of the upper and lower A-arms.
  • The rack is located about 10mm (0.5") rearward from being in line with the spindle pivot points. That's not optimum, but that dimension is not as critical to bump steer, so I think it should be OK.

I think the reason the rack looks high, is that the steering rod ball joint is mounted high on the spindle.

To see my VSUSP suspension model -> Click Here


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
Reply with quote  
PostPosted: May 31, 2018, 5:57 pm 
Offline
User avatar

Joined: May 29, 2015, 6:09 pm
Posts: 120
Location: Charlotte
TRX wrote:
His steering arms are that high already... when you put the rack coplanar with the upper or lower A-arm pivots, you eliminate rack height as a source of bump steer.


Correct!


Top
 Profile  
Reply with quote  
PostPosted: May 31, 2018, 6:36 pm 
Offline
User avatar

Joined: May 29, 2015, 6:09 pm
Posts: 120
Location: Charlotte
I finished the cantilever sprung portion of my front suspension.

I wanted to reuse the front coil-overs from the donor Raptor 700, but I didn't want them to be visible in the finished car. So I came up with a cantilever spring design. Well, maybe I should say I did 3 cantilever designs, because that's how many iterations it took to get it right. Once I started my fabrication, several important aspects of my front suspension design went out the window.
  • Once I mounted my spindles in their jigs, the track width seemed too wide, so I narrowed it from 1374mm to 1274mm.
  • When I started building the front subframe, I quickly realized that the design was far to complex and difficult to build in a precise manner, so I simplified it
  • While simplifying the subframe, I realized the narrower track width allowed the Raptor coil-overs to be mounted lower and reduce any racking of the subframe

I also built the cantilever arm that connects to the lower A-arm.
  • I fabricated a temporary clamping bracket which attaches the lever arm to the lower A-arm. I'll start my setup with no weight on the suspension and adjust the clamp to where it should be at full drupe.
  • The next step is to set the lever arm length to adjust the spring force to get the correct ride height. However, I don't really know how long the lever arm should be because I don't know how much spring force the Raptor coil-overs have nor do I have an accurate estimate of how much I'll need to suspend the car. Here too, I left the arms a little long and fabricated a temporary adjustable coil-over bracket. Once the car is sitting on its own weight, I can adjust the arm length to find the right amount of spring leverage.
  • I'll probably go through several iterations of ride height and lever adjustments to get it dialed in. Once I'm happy, I can weld the clamp and coil-over bracket permanently in place.

To see the video -> Click Here


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
Reply with quote  
PostPosted: May 31, 2018, 9:57 pm 
Offline

Joined: March 15, 2018, 6:03 am
Posts: 160
Hi Mr Rumbles
I'm not a qualified engineer so I just wanted to query your suspension design, which seems to be massively strong, but the UCA is fastened to the chassis by what looks like a couple of 1/4" bolts, which also hang way out... and 'looks' odd to me.

Was this deliberate, as an immediate weak-link (so you know where to check first), or am I just worrying unduly.

Not criticism - just curious. Best wishes, MangPong.


Top
 Profile  
Reply with quote  
PostPosted: June 1, 2018, 8:00 am 
Offline
User avatar

Joined: September 22, 2005, 8:12 am
Posts: 1879
Location: 4AGE in S.E. Michigan
I would 2nd MangPong's motion. You do not want to put bending loads into threads. You need a solid frame block as an attachment point, so the threads are in tension. Davew


Top
 Profile  
Reply with quote  
PostPosted: June 1, 2018, 5:16 pm 
Offline
Automotive Encyclopedia
User avatar

Joined: December 22, 2006, 2:05 pm
Posts: 8037
rumbles wrote:
Miatav8,MstrASE,A&P,F wrote:
Interesting build. Have you looked into what it will take in your area to get this registered for use on the road? It seems nearly every state has their own hurdles/walls.


Actually, I have built 2 other cars and registered them in NC as a "Specialty Construction Vehicle". This one may be more of a challenge since its based upon an ATV. Some states will not register a home built if there are any ATV parts in it.

I've been afraid to call my local NC DOT to ask :puke:


I would be too. The rotors are a dead giveaway imho. Otherwise could be older, grey market kei car parts? Designed to clear mud to grab I suppose. If the calipers are two piece you might machine a spacer and fit thicker, mostly solid rotors in steel for a more auto appearance and less pad wear.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


Top
 Profile  
Reply with quote  
PostPosted: June 2, 2018, 8:38 pm 
Offline
User avatar

Joined: May 29, 2015, 6:09 pm
Posts: 120
Location: Charlotte
MangPong wrote:
Hi Mr Rumbles
I'm not a qualified engineer so I just wanted to query your suspension design, which seems to be massively strong, but the UCA is fastened to the chassis by what looks like a couple of 1/4" bolts, which also hang way out... and 'looks' odd to me.

Was this deliberate, as an immediate weak-link (so you know where to check first), or am I just worrying unduly.

Not criticism - just curious. Best wishes, MangPong.


MangPong, Thanks for the comment.

The rod bolt that attaches the Upper Control Arm (UCA) to the frame is actually a hardened 3/8" bolt. You are correct, if there is a weak point in the design, that rod bolt is it.

However, I took my queue from the Yamaha engineers who designed the donor Raptor 700. The Raptor upper A-arms were very lightweight aluminum and the attachment point on the frame was a .060" steel tab, that is weaker than my 3/8" rod bolt. The donor Raptor was built to withstand rock hopping and jumping the whoopees, where I will be using it on more civilized streets with an occasional speed bump. If my calculations are correct, the weight on the front end should be close to the donor Raptor as well.

All that said, I admit that I also looked at the rod bolts thinking they seemed less than beefy. I still have quite a bit of adjust-ability remaining on the upper A-arm ball joints, so I could thread-out the ball joint and thread-in the rod bolts to reduce the stress on them. However, that will change my front end geometry.

I plan to keep an eye on the rod bolts as I test the car. If there is a problem, I can replace the rod bolts with a beefy bracket.


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
Reply with quote  
PostPosted: June 2, 2018, 9:05 pm 
Offline
User avatar

Joined: May 29, 2015, 6:09 pm
Posts: 120
Location: Charlotte
Miatav8,MstrASE,A&P,F wrote:
Interesting build. Have you looked into what it will take in your area to get this registered for use on the road? It seems nearly every state has their own hurdles/walls.

Actually, I have built 2 other cars and registered them in NC as a "Specialty Construction Vehicle". This one may be more of a challenge since its based upon an ATV. Some states will not register a home built if there are any ATV parts in it.

I've been afraid to call my local NC DOT to ask :puke:

I would be too. The rotors are a dead giveaway imho. Otherwise could be older, grey market kei car parts? Designed to clear mud to grab I suppose. If the calipers are two piece you might machine a spacer and fit thicker, mostly solid rotors in steel for a more auto appearance and less pad wear.


MV8,

Yes, I agree that the brakes will need to be beefed up.

I was careful to keep the diameter of the front wheel/tire package the same as the original donor Raptor 700. I looked high and low for the lightest DOT wheel/tire combination I could find, but each corner ended up being about 10lbs heavier that the Raptor. My overall vehicle weight will be close to the donor Raptor (with 2 passengers), but the rotating mass of the DOT wheel/tire package will require more braking power.

Before I destroyed the Raptor, I did some braking tests with the DOT wheel/tires at low speeds (~30MPH) and all the brakes were able to lock up. The real challenge is to lockup the increased rotating mass at higher speeds like 75MPH.

I plan to work up my speed slowly when testing the brakes. At a minimum, I will upgrade the brakes with performance pads an rotors. There are lots of suppliers of performance pad/rotors on the market and they aren't expensive.

If that is not enough, the solution could empty my wallet :ack:


Top
 Profile  
Reply with quote  
PostPosted: June 2, 2018, 9:33 pm 
Offline

Joined: March 15, 2018, 6:03 am
Posts: 160
Thanks for the detailed response re. your 3/8" bolts.
It interests me (in the design stage) that, if these bolts are strong enough (and I'm certainly not saying they aren't...) then we all seem to be building way over-strong wishbones.
I would be interested to know if others on LocostUSA have used smaller diameter control arms, and not suffered failure - i.e. failure because of just being too slim - not because of other design anomalies.

For example: my current design has 3/8" heims in 5/8" tubes for the UCA, and 1/2" heims in 3/4" tubes for the LCA...
Maybe I can drop to even 1/2" & 5/8" tubes respectively... But would I want to risk it...? lol.

Thanks, MangPong.


Top
 Profile  
Reply with quote  
PostPosted: June 2, 2018, 11:35 pm 
Offline
User avatar

Joined: March 30, 2011, 7:18 am
Posts: 1615
Location: central Arkansas
There have been several cases of 3/4"x16ga lower control arms bending, usually near the shock mount. Probably avoidable with changes to lower mount design, but I bought some 1"x16ga, then decided I liked Kinetic Vehicles' 1x2 rectangular lower arm better, and I'll use the 1" for the upper.

You're talking about thinwall tubing. I haven't looked up the difference in weight per foot, but the arms don't weigh much to start with.


Top
 Profile  
Reply with quote  
PostPosted: June 3, 2018, 11:37 am 
Offline
User avatar

Joined: July 17, 2008, 9:11 am
Posts: 6414
Location: West Chicago,IL
I would reinforce those forged eye bolts with a hand fitted sleeve to reduce the bending issue. Just saying.....

As for MangPong's issue, Woah there partner. "1/2" heims in 3/4" tubes for the LCA" I would repeat the advice that TRX gave. 3/4" 16 ga tubes has a known history of failures here and elsewhere. I ran 1" 0.083 wall tubing because of that and had no problems. 1/2 heims, if good quality should be fine. Check out Jack's Kineticvehicles.com and consider his LX series heims.

The UCA's do see less stress. They see about 1/2-1/3 the forces of the lowers, not including the shock mount issue mentioned. You might get by with a smaller dia upper and maybe smaller heims. But to simplify the purchased/service parts, I'd recommend staying with 1/2 heims and the same tube as the LCA's

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766


Top
 Profile  
Reply with quote  
PostPosted: June 3, 2018, 12:02 pm 
Offline
User avatar

Joined: March 30, 2011, 7:18 am
Posts: 1615
Location: central Arkansas
The larger the rod end, the lower the loading on the ball, and hopefully the longer their operating life before they start getting clickety.

You can safely run smaller rod ends than 1/2", but they'd have a short life.


Top
 Profile  
Reply with quote  
PostPosted: June 3, 2018, 1:22 pm 
Offline

Joined: March 15, 2018, 6:03 am
Posts: 160
"As for MangPong's issue, Woah there partner. "1/2" heims in 3/4" tubes for the LCA" I would repeat the advice that TRX gave. 3/4" 16 ga tubes has a known history of failures here and elsewhere. I ran 1" 0.083 wall tubing because of that and had no problems. 1/2 heims, if good quality should be fine. "

Hello again, Chuck. I am honoured to have you as a 'pardner' and rest assured I have Woah'd myself in.
In an ideal world (wherever that is) that's what I would have liked to do, but, as they say North of that other border: "I hae me doots..." - but I have no engineering knowledge about this. Therefore I hoped that by being a trifle provocative I would get a response... and so, many thanks...

However, while I have your attention... (with Rumble's permission): What if I use solid 3/4" bar, drilled to a little under 1/2" with just the ends drilled and tapped for 1/2" heims...? Hmm... It'll be a bit heavier but will have the looks that I desire.

Best wishes, MangPong.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 155 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7 ... 11  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 9 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
cron
POWERED_BY