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Ognib
Ognib New Reader
4/20/19 5:22 p.m.
Ognib
Ognib New Reader
4/21/19 12:06 p.m.

Nice & stiff & snug, just like new ball joints should be.   Waiting for a top rail.

noddaz
noddaz SuperDork
4/21/19 3:13 p.m.

That looks like fun.

What is going to keep the rear knuckles from pivioting on the balljoints?

Ognib
Ognib New Reader
4/21/19 5:21 p.m.

In keeping with the f1 concept, it will be fitted for adjustable toe on the back.  A tie rod will be fitted to position everything & provide adjustments.

Ognib
Ognib New Reader
4/23/19 2:09 p.m.

A matched set.  Everything is level on all axis.  With angle clamped across the bottom of the lower control arm, I'm able to get an accurate outside to outside dimension for building the top rail on the frame.  My variation in measurements from one suspension set to the other is less than 1/64 in.  So, good to go.

Ognib
Ognib New Reader
4/24/19 7:32 p.m.

Mock ups inspire me.

Ognib
Ognib New Reader
4/25/19 9:09 a.m.
Robbie said:

Very cool! Can't believe I haven't seen this thread before today.

1 - I'm also building a motorcycle engined car right now, but starting with a Fiat x1/9 of sorts.

2 - you've read the book "how to build a motorcycle engined race car"? I'd suggest it if you have not. If you'd like to borrow my copy I'll mail it to you.

Good luck, it is looking awesome so far!

 

Hey Robbie, is there a thread on your build?  I've looked & didn't find anything.  I'd like to check it out.

Ognib
Ognib New Reader
4/25/19 10:31 a.m.

Beginning the layout of the upper rail.  In the first pic, you'll notice that the housing on the side of the engine is in the way of the upper tube.  I mentioned outrigger tubes earlier, this is where they will be necessary.  Want to be able to get the engine in & out quick so gotta get that upper tube out of the way.  Will also give extra room in the seat area. 

The fitting jig on the table is dimensionally correct.  I can fit all the uprights here at one time & know that everything is exactly the same length.

Ognib
Ognib New Reader
4/25/19 4:09 p.m.

I want the engine as far back in the frame as possible & still be able to fit certain components in place.

For center of gravity I'm attempting to have all the major weight down between the wheels.  This will go a long way towards eliminating body roll in the corners.

For polar moment of inertia everything is to be placed between the front & rear axles & as close as possible to cog.  This affects how quickly the car will respond to steering input.

Battery down low with box representing about a gallon of fuel cell.  

Short upright tubes will tie the frame into the engine cradle at motor mount points front & rear which are gusseted & otherwise re enforced.

This first pic is a good representation of the overall profile I'm aspiring to for this build.

 

 

AWSX1686
AWSX1686 SuperDork
4/26/19 9:37 a.m.

This thing is awesome! I hope someday I have time/space/skills to make awesome stuff built from scratch like this!

Ognib
Ognib New Reader
4/26/19 1:13 p.m.

AWSX, thanks for taking a look.  Really appreciate the comments!

It's just a matter of doing it, making & learning from your mistakes & wanting to do it strongly enough to do it again.

Old Chinese proverb:  fall down 7 times, pick self up 8 times...

Dusterbd13-michael
Dusterbd13-michael MegaDork
4/26/19 1:21 p.m.

This thread is making me really, really want to finally build a street version of a 50s indycar....

Ognib
Ognib New Reader
4/26/19 1:34 p.m.

Here ya go...not an indy but a very cool sprint car...street legal.

 

Ognib
Ognib New Reader
4/26/19 2:15 p.m.

Kind of a slow start today.  Got another cross member fitted & scratching my head on the best angle to use.

Ognib
Ognib New Reader
4/27/19 9:22 a.m.
Ognib
Ognib New Reader
4/30/19 1:21 p.m.

As this is my first attempt at building with round tube, I have no previous experience to draw on when doing the layout & fitting of the components.  Thus, my progress is quite slow at times.

On the uprights for the front of the engine cradle, for example, I want them to lay in to the cradle at matching angles from the crossmember tube.  I began thinking how I could jig them up in a manner that would allow me to dress both angles at the same time for sameness between the two...quickly.

This is what I've come up with.  See how it works.  Cross tube at the bottom keeps the base notches in alignment & the cross strap prevents movement as I'm dressing the tapered ends with the grinder.

I try to be innovative in situations like this & accomplish things in a simple, straightforward manner.

Ognib
Ognib New Reader
5/9/19 3:07 p.m.

To help with the unsprung weight factor, I've decided to go with a rocker arm suspension design which mounts shocks & springs inboard on the frame rather than out on the control arms.

A few examples...

Ognib
Ognib New Reader
5/10/19 8:50 a.m.

Some nice looking exhaust fab on a formula sae engine.

Cad drawing for chain drive differential concept.

SkinnyG
SkinnyG UltraDork
5/10/19 10:45 a.m.

Initially I thought "you're not going to get very much steering angle out of that setup." Then I figured some steering angle would probably be bad idea there.

I love this. Kinda want to build one now.....

Ognib
Ognib New Reader
5/12/19 1:33 p.m.

Skinny, it's proving to be a worthy challenge & I'm diggin it!

Ognib
Ognib New Reader
5/17/19 12:28 p.m.

I got the first 4 uprights in place, joining the engine cradle to the frame.

I'm doing some layout for the outrigger tubes.  With the seat templates in position I gain a better visual perspective as to how I want everything to fit.  I'm a big guy...6'2" & 200 lb...the outriggers will allow some shoulder room & cockpit space for steering wheel, gear selector etc.

I've drawn the outrigger in several different widths for consideration...want to have a good visual balance for the car.

The main rails were purposely set closer together in order to be able to use a longer control arm for better suspension geometry and still keep the track width where I want it.

Track width considerations were important, relative to the wheel base dimensions, for the track to wb length ratio.  The ratio on this car, as it's laid out now will be in the 1.65 - 1.7 area.  This has a lot to do with the quickness of steering response.

A dirt track sprint car with a 1.6 ish, or maybe shorter, ratio is very quirky in a straight line but quick to kick the rear end out for drifting through the corners under throttle.  Watching a sprint race & noticing how the drivers have to work the wheel in the straights gives insight into this.

On the other hand, a AA fuel dragster with it's 300" wb & very narrow track is much more stable at very high speeds, but ya gotta have 40 acres to turn one around, so to speak.

SkinnyG
SkinnyG UltraDork
5/17/19 7:06 p.m.

With the inboard pivots in the same Z plane, you're going to have very minimal camber curve.  Is that going to be alright for you?

SkinnyG
SkinnyG UltraDork
5/17/19 7:07 p.m.

Oh.  I see you have fron A-arms on now too.

I'll say it again - you're not going to get much steering angle out of that (you didn't need any on the back), and you will not have much camber curve.

Ognib
Ognib New Reader
5/18/19 9:41 a.m.
Ognib said:

I've opted to go with equal length & parallel  A arms.  As described by Carroll Smith in his book, there are more exotic configurations, but the equal/parallel set up, when in bump or droop, becomes a parallelogram & the camber settings that I  have dialed in on  the car stay consistent throughout the suspensions movement.  I figure since this my first scratch susp build, it would be a good idea to keep it as simple & basic as possible.

In body roll there is some camber change but with bars & springs & very low CG, body roll can be greatly minimalized...just look at how flat the F1 cars corner.

The down side to this set up is that there is some change in track width during movement.  This can be minimized by the use of long links on the a arm tubes, because the arc traveled is flatter.  Long arms were a major requirement during design.

The up side is that the instantaneous center distance is infinite from chassis centerline.  Thus, the roll center is at ground level & stays there.  That is good!

Have not built front A arms yet.  The one pictured in front is actually the left rear assembly placed there to aid in visualization while doing layout on the side bars.

SkinnyG
SkinnyG UltraDork
5/18/19 11:14 a.m.

Ah.  I did read that a while back, but since forgot (too much 60's during the acid).

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