LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently Tue Jul 29, 2014 8:55 pm

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 408 posts ]  Go to page 1, 2, 3, 4, 5 ... 28  Next
Author Message
PostPosted: Sun Dec 04, 2011 6:26 pm 
Offline
User avatar

Joined: Thu Oct 13, 2011 9:19 am
Posts: 342
Location: Denver Co
Posted some suspension numbers but it looks like it got tons of views but no replies... ; (

Any way I thought I would post the car build and get inputs on the look as of now. I am leaning towards the second design. Let me know which design you guys like best.

Chassis is 4130 and is about 95% complete from a design stage. The uprights etc are custom designed 7075 with carbon A Arms. I have two engines a B20Vtec and a B16 turbo (light pressure for quick spool)

Thanks,
Mo


Attachments:
Design3.jpg
Design3.jpg [ 206.73 KiB | Viewed 7640 times ]
Design2.jpg
Design2.jpg [ 267.06 KiB | Viewed 7640 times ]
Design1.jpg
Design1.jpg [ 240.47 KiB | Viewed 7640 times ]

_________________
My build: viewtopic.php?f=18&t=13096
Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Mon Dec 05, 2011 8:56 am 
Offline
User avatar

Joined: Wed Nov 12, 2008 6:29 am
Posts: 3306
Number 2.

Use mild steel not 4130 and go for the B20 as you will have a lot more fun.

You might get more response for the suspension in the suspension thread but you are pretty much asking people to take the times to do all the work as well - not too many are going to do that. Pictures would get a better response I'm sure as would offer your input as well into a community.


Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Mon Dec 05, 2011 9:53 am 
Offline
User avatar

Joined: Thu Oct 13, 2011 9:19 am
Posts: 342
Location: Denver Co
Yeah i was just looking for little comments on the suspension like, your camber looks off, account for more roll, etc. No biggie though since i changed the geometry anyway and every one on here seems really cool.

Yeah i like #2 too and the B20 will be a blast. The B20 has a full race port and polish (vague i know) with all titanuim uppers and dual valve springs good to 9500 rpm with the current set up. The block is slighly oversized with shot peened rods and 11:5 compression pistons. Probably good for 250whp (high altitude... 130whp)

Why mild steel might i ask? The FEA calulations were done using 4130 however i can chage that if there is a good argument. My main reason is that if the carbon suspension sees a side load of lets say 2klbs, the mild steel with a FOS 1.45 would bend causing damage to the chassis where as the 4130 would not and the suspension would take the load. I also would pay the extra $200 for a peace of mind.

This is the picing I got from Dencol down the street for 4130
2.5 x .083 = $3.12
2.0 x .083 = $2.50
1.5 x .063 = $1.95


as also thinking of running the fuel tank up front. Any reason not too?

Has any one ran across a way to run the rod shift linkage in the rearon the Honda B series? I saw something where two guys ran extended rods under the transmission but this seems like hokey way of doing things. I have been working on a electromechaical shifter but packing looks to be a hurdle.

Here is the suspension test part that i am taking to the lab for testing. Rod ends will be nice i just wanted to get something together.

Thanks for your imput guys!


Attachments:
DSCN1207.JPG
DSCN1207.JPG [ 201.5 KiB | Viewed 7569 times ]

_________________
My build: viewtopic.php?f=18&t=13096
Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Mon Dec 05, 2011 12:33 pm 
Offline
User avatar

Joined: Wed Nov 12, 2008 6:29 am
Posts: 3306
The 4130 Vs Mild debate is done to death on the net but comes down to you ain't going to hit a wall at 200mph so you don't need the extra yield strength which is all it offers, no other advantages.

The modulus of elasticity is much the same so your FEA won't change much.

In specific race classes the higher yield of ChMo allows you to go a half size down in the tube in some areas and that's where it gets the false myth that it's lighter than mild, it's not (but a lighter race chassis can be built to the specific rules when they apply), nor is it any safer for the speeds and builds that we generally do.


Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Mon Dec 05, 2011 1:24 pm 
Offline
User avatar

Joined: Tue May 08, 2007 9:50 am
Posts: 601
Location: Minnesota
I would suggest skipping the carbon suspension too. We did some on one of the FSAE cars we built and while we had good luck with it bonding the carbon bits to the metal bits is trickey for structural parts, and the failure mode isn't very pretty. However, the weight of the suspension arms (even steel) is pretty small, there are probably better places to save weight.


Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Mon Dec 05, 2011 2:29 pm 
Online
The voice of reason
User avatar

Joined: Thu Jan 10, 2008 4:47 pm
Posts: 5516
Location: Massachusetts
I think you need more practical experience before going to all the exotic materials. You also need a budget that says what the exotic materials are buying you for their cost. So how much lighter for how much money, and did you land up with something safer when it's elasticity before breaking is less then %10 compared to %40 percent for the square 1010 mild steel. These are not simple questions and you could probably build and start driving the car before you understand all the different exotics and their individual plusses and minuses. Which says build your first car the normal way people have experience and then use your own experience you have gained and consider the impact of the exotics.

Something I would note on the Carbon arm you are looking at is that the material it is made from is inappropriate for it's use. It may or may not contain unidirectional fibers inside. What I can see though is woven cloth. Half of the fibers are not going in a direction that you need ( you need some circling, but not nearly %50). THe fibers that travel lengthwise are woven so they are already buckled by nature, how much compression will they stand? I assume you have done the thing of standing on a beer can and then tapping it with your finger. Please do that if you haven't, it's one thing to hear that story and another to do it yourself.

Proper carbon materials are not woven and contain unidirectional fibers in one or more layers which are either lightly stitched or bonded together. I'm glad your doing testing, if you off the beaten path that's what you need to do to be responsible for yourself and other people. It's a lot of fun too. Remember to be careful when testing. I did some of this a long time ago and it quickly became obvious that fiberglass pieces of any size produce large loads and a lot of flex. Pretty quickly you are in a situation of being in a room with a hunter's bow pointed in random directions.

Having a desire to do better is what brings most of here to begin with. If you really want something better and are willing to do the extra work, you could consider building with round DOM 1020/1025 tubing. It's yield is considerably higher with reasonable failure modes etc.

There are good reasons to do things like custom uprights, if you can it would be great if the problem you solve here is useful to a wider community. It's fun to build your own stuff, it's really satisfying to build something a bunch of other people use too. Again, consider building with something like 6061 instead of the fancy stuff. Things like corrosion and fatigue life are real world issues. A car will not likely see the maintenance that an airplane or rocket will and it's exposed to more abuse and salt too.

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Mon Dec 05, 2011 3:12 pm 
Offline
User avatar

Joined: Thu Oct 13, 2011 9:19 am
Posts: 342
Location: Denver Co
Yeah i cant find DOM cheeper than the 4130 from Dencol. The best price i found online for 2.5x .065wall is $6+ per foot which is 2x that of the 4130.

Yeah i lost 5lbs to save weight in other places ; )

A couple of reasons for the carbon
1) Lighter
2) my welding sucks so the less the better (actually the frame will be welded by some high end mountain bike guys) and yes i iwll test each joint
3) I can always swicth back to steel
4) looks cool
5) Part of the bet ; (

_________________
My build: viewtopic.php?f=18&t=13096


Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Mon Dec 05, 2011 3:51 pm 
Offline
User avatar

Joined: Thu Oct 13, 2011 9:19 am
Posts: 342
Location: Denver Co
horizenjob wrote:
I think you need more practical experience before going to all the exotic materials. You also need a budget that says what the exotic materials are buying you for their cost. So how much lighter for how much money, and did you land up with something safer when it's elasticity before breaking is less then %10 compared to %40 percent for the square 1010 mild steel. These are not simple questions and you could probably build and start driving the car before you understand all the different exotics and their individual plusses and minuses. Which says build your first car the normal way people have experience and then use your own experience you have gained and consider the impact of the exotics.

Something I would note on the Carbon arm you are looking at is that the material it is made from is inappropriate for it's use. It may or may not contain unidirectional fibers inside. What I can see though is woven cloth. Half of the fibers are not going in a direction that you need ( you need some circling, but not nearly %50). THe fibers that travel lengthwise are woven so they are already buckled by nature, how much compression will they stand? I assume you have done the thing of standing on a beer can and then tapping it with your finger. Please do that if you haven't, it's one thing to hear that story and another to do it yourself.

Proper carbon materials are not woven and contain unidirectional fibers in one or more layers which are either lightly stitched or bonded together. I'm glad your doing testing, if you off the beaten path that's what you need to do to be responsible for yourself and other people. It's a lot of fun too. Remember to be careful when testing. I did some of this a long time ago and it quickly became obvious that fiberglass pieces of any size produce large loads and a lot of flex. Pretty quickly you are in a situation of being in a room with a hunter's bow pointed in random directions.

Having a desire to do better is what brings most of here to begin with. If you really want something better and are willing to do the extra work, you could consider building with round DOM 1020/1025 tubing. It's yield is considerably higher with reasonable failure modes etc.

There are good reasons to do things like custom uprights, if you can it would be great if the problem you solve here is useful to a wider community. It's fun to build your own stuff, it's really satisfying to build something a bunch of other people use too. Again, consider building with something like 6061 instead of the fancy stuff. Things like corrosion and fatigue life are real world issues. A car will not likely see the maintenance that an airplane or rocket will and it's exposed to more abuse and salt too.


The carbon arms are unidirectional with an outer layer of 45°. I have not built or designed anything without extensive testing. I have even put the Carbon under compression and did a break test (weighted drop) to test the real world situations like an object hitting them. They will also have an aramid lay up over the outside due to that testing. The pre gap for the epoxy is set by using a stepped custom made rod end. The tube id is gauged after sanding and the step is then matched. E120-HP is the epoxy.

7075 makes sense from a strength aspect. I can reduce the weight by 1/2lb+ by going with it instead of 6061. We dont have Saltspray issues here in Colorado but if we did I would test that too. They are going to be Hard Annodized too so that will cut down a bunch on the corrosion issuse. I am more worried about the HAB-8T bearings but i am accepting the fact that i will watch them and replace them as needed. No winter driving either

Yeah i like your guys idea to switch to DOM 1020 but i still cannot find it cheaper. The frame is actually on revision 16 so chaging material won’t make that big of a difference.

Thanks though. Added insight is always useful. I promise more pics once i get to the other computer tonight ; )

_________________
My build: viewtopic.php?f=18&t=13096


Last edited by mjalaly on Tue Dec 06, 2011 5:42 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Mon Dec 05, 2011 10:09 pm 
Offline
User avatar

Joined: Mon Apr 12, 2010 5:40 pm
Posts: 1817
Location: san francisco bay area
Regarding CF control arms. ..
Somewhere around here (I just can't seem to find it at THIS moment) is the video from an F1 in car camera showing what happens when a CF arm lets go.

I'd like to point out that the McLaren MP4-12C uses a CF tub and forged aluminum control arms. .. and they definitely have the resources to do all the research they want.
Not that I don't think there can be some advantages to using CF for a few things, fitting a glued in gusset somewhere I can't comfortably get my torch is one that comes to mind for me (there's a CF shop down the road from me that has a dumpster. ..).

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett


Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Tue Dec 06, 2011 12:50 am 
Offline
User avatar

Joined: Wed Nov 12, 2008 6:29 am
Posts: 3306
mjalaly wrote:


If i told you guys that the entire body was carbon would you think i was crazy?


No, but I would only view it with mild interest, my nick is cheapracer for a reason and the same reason I come to the Lo(w)cost forum. I have been toying with a CF tub myself but only because I can by pre-fab standardised box and tube structures in various sizes cheap.


mjalaly wrote:


Yeah i like your guys idea to switch to DOM 1020 but i still cannot find it cheaper.


Then use 1010 erw like the bulk of us do successfully and 1000's of race cars have/do (and handle well and crash with complete safety) - of course the roll cage has to be DOM for legal racing.

You know why you have to have a test hole in a roll cage? - because no one can tell from the outside if a (painted) chassis is made from 4130, 1010, Ti or DOM or not.


Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Tue Dec 06, 2011 12:52 am 
Offline
User avatar

Joined: Wed Nov 12, 2008 6:29 am
Posts: 3306
oldejack wrote:
Regarding CF control arms. ..

I'd like to point out that the McLaren MP4-12C uses forged aluminum control arms. .. and they definitely have the resources to do all the research they want.


And so do GM and thats why Pook uses those forged arms and uprights as I would if I could get them here...,


Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Tue Dec 06, 2011 4:12 am 
Offline
User avatar

Joined: Sun Jul 22, 2007 10:58 pm
Posts: 387
Location: Zagreb, Croatia
I would say that 4130 is not a bad choice for one reason... choice of thin wall tubing... from my experience you can get some nice thin walled tubing and make a more complex and stiffer frame than with 1020.. however, that advantage might be lost on a simpler larger walled tubed frame..

One thing if you are using 4130... in FEA, use the values for Normalized 4130, not heat treated.. :) Also, I'd like to see the torsional stiffness values for that frame...

best of luck..

v.

_________________
Building a single seater middy BEC with GSXR 1000 power :)
build log: http://locostusa.com/forums/viewtopic.php?f=36&t=5899

day job: http://smg.photobucket.com/albums/v723/turbolimac/portfolio/


Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Tue Dec 06, 2011 10:03 am 
Offline
User avatar

Joined: Thu Oct 13, 2011 9:19 am
Posts: 342
Location: Denver Co
cheapracer wrote:
I would say that 4130 is not a bad choice for one reason... choice of thin wall tubing... from my experience you can get some nice thin walled tubing and make a more complex and stiffer frame than with 1020.. however, that advantage might be lost on a simpler larger walled tubed frame..

One thing if you are using 4130... in FEA, use the values for Normalized 4130, not heat treated.. Also, I'd like to see the torsional stiffness values for that frame...


Thanks and i think i am going to stick with the 4130 sice i still cannot find DOM cheeper. I also ran the heat treated FEA too. There is options for that in cosmos and Anysis
Attachment:
Materials.jpg
Materials.jpg [ 169.17 KiB | Viewed 7419 times ]


cheapracer wrote:
No, but I would only view it with mild interest, my nick is cheapracer for a reason and the same reason I come to the Lo(w)cost forum. I have been toying with a CF tub myself but only because I can by pre-fab standardised box and tube structures in various sizes cheap.



Attachment:
IMAG0257.jpg
IMAG0257.jpg [ 705.35 KiB | Viewed 7419 times ]


Attachments:
File comment: One FEA
Upright FEA.jpg
Upright FEA.jpg [ 213.45 KiB | Viewed 7419 times ]
Upright Back.JPG
Upright Back.JPG [ 80.53 KiB | Viewed 7419 times ]
Upright front.JPG
Upright front.JPG [ 77.72 KiB | Viewed 7419 times ]
Chassis.JPG
Chassis.JPG [ 102.63 KiB | Viewed 7419 times ]

_________________
My build: viewtopic.php?f=18&t=13096


Last edited by mjalaly on Tue Dec 06, 2011 5:44 pm, edited 1 time in total.
Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Tue Dec 06, 2011 10:28 am 
Offline
Always Moore!
User avatar

Joined: Fri Nov 09, 2007 3:40 pm
Posts: 3285
Location: Pittsburgh, PA
I still don't see why using 4130 is such a no-no. The thinner available wall thicknesses make it desirable and even in the normalized state it is still stronger than 1020.

I ran into the same issue with cost on a few occasions. Finding mild steel below 0.065" wall thickness is difficult and its price always seems to be significantly more than the same stuff but in 4130. It makes the chromoly (dare I say it) economical.

Nice looking uprights. As long as you get to use the schools machine shop enjoy it - you'll be stuck using whatever is available in your garage like the rest of us at some point. ;)

What are your plans for wheel hubs and what loads are you using for the upright FEA?

I assume the grooved surface is where you will be attaching a steering arm - shouldn't the grooves be going vertically?

_________________
-Andrew
Build Log
Youtube


Top
 Profile  
 
 Post subject: Re: New Build
PostPosted: Tue Dec 06, 2011 11:01 am 
Offline
User avatar

Joined: Thu Oct 13, 2011 9:19 am
Posts: 342
Location: Denver Co
a.moore wrote:
I still don't see why using 4130 is such a no-no. The thinner available wall thicknesses make it desirable and even in the normalized state it is still stronger than 1020.

I ran into the same issue with cost on a few occasions. Finding mild steel below 0.065" wall thickness is difficult and its price always seems to be significantly more than the same stuff but in 4130. It makes the chromoly (dare I say it) economical.

Nice looking uprights. As long as you get to use the schools machine shop enjoy it - you'll be stuck using whatever is available in your garage like the rest of us at some point. ;)

What are your plans for wheel hubs and what loads are you using for the upright FEA?

I assume the grooved surface is where you will be attaching a steering arm - shouldn't the grooves be going vertically?


I am actually using my companies machining equipment and some of my buddies machining machines. I am trying to get a CNC Bridgeport but there is no more room in the garage and the wife is fighting me.

I planned on using a stock Civic front hub all the way around since i was doing inboard brakes (that was shot down once i found out how much dust it would create) but once i got a new hub in my hand and weighed it... i have had second thoughts. FEA is a loaded question. I attempted to package the Dynamic loads into the static loads. I assumed a 2/2/3G's layout (braking - lateral - bump). That’s all assuming correct weight transfer and CG with an FOS min of 2. It is over built but that is fine with me eventhought it puts a slight damper on my unspring mass. The caliper was loaded torsionally about the hub.

Correct. The grooved surfaces are for the steering arm. That design will allow for bump steer change. The Groves will hold the arm in the vertical position and 4 bolts through slots on the arm will hold it in the lateral direction

Hopefull all cacluations are right and it wont twist like the At-om's :BH:

Thanks a.moore

Mo

_________________
My build: viewtopic.php?f=18&t=13096


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 408 posts ]  Go to page 1, 2, 3, 4, 5 ... 28  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 0 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

Search for:
Jump to:  
POWERED_BY