Airframe's Mid BEC LMP
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Author:  airframefixer [ May 21, 2007, 3:06 pm ]
Post subject:  Airframe's Mid BEC LMP

I figure its about time I share some of my progress with everyone here. Ive been greatly motivated by the ideas and projects of others here and on the other forum, so Ive decided to share, in the hope of getting some constructive feedback, and hopefully inspiring others.

My names Andrew and Ive dreamed about building my own car to my own specs since I was about 17 years old. I grew up helping dad on the weekends restore 60-70's muscle cars since i can remember. these were "by the book, number matching restorations to correct factory condition". It was lots of fun and i still enjoy helping out, but these cars are not driven, and theres seems to be a lack of creativity in it that just doesn't appeal to me, never mind the cost. then i discovered locosting. But i wanted the engine in the back.

So Ive settled on using the Miata as a donor for suspension and brake components, and the Yamaha R1 engine as a power plant driving the rear wheels.

I officially started collecting donor parts last august and started making parts this past January. The most time consuming part of the project has been measuring suspension components and drafting the chassis in DeltaCAD, a basic drafting program, in which I'm still using the demo after 6 years.

I work 3 weeks on away from home which most of the design work is accomplished, I only have one week per month to fabricate. so progress is slow and steady, but well thought out by the time i cut metal.

drawing nov 07.jpg
drawing nov 07.jpg [ 82.92 KiB | Viewed 59441 times ]
File comment: this part was the source of major delay in the design of the front suspension. after trial and error by myself and a few other locostusa members and annoying lots of auto parts store clerks, i discovered that the ES2074R is a perfect match for the miata u
ES2074R.JPG [ 120.73 KiB | Viewed 62285 times ]
File comment: Once all the pivots were located and the Geometry was settled upon, i could start fabbing parts. these are the unfinnished lowers
arms.JPG [ 182.63 KiB | Viewed 62069 times ]
File comment: I initially bought 92 miata brakes but later found out about the 94 caliper brackets, seen here. i may install the larger brakes, but i really dont think that there necessary on a 1000 lbs car.
brakes.JPG [ 133.51 KiB | Viewed 61881 times ]
File comment: Accurately measuring the uprights and the ball joint pivots took alot of time. there were cleaned and primed using Endura epoxy primer.
uprights.JPG [ 114.64 KiB | Viewed 61752 times ]

Author:  airframefixer [ May 21, 2007, 3:22 pm ]
Post subject: 

my most recent progress. front subframe and suspension work in progress. the shocks will be QA1 82 series acutated by pushrod, still waiting for delivery from racetech motorsports in portland. wheel ratio is 1:1. steering rack is a miata manunal unit. later to be swapped out for a depowered rack with the faster ratio, 2.8 turns to lock instead of 3.3, but thats after inspection and its road legal. pushrods are mockups for now, while i wait for rodends from racetech also. the steering column is mazda 323, the shaft is gen 2 RX7, with matching splines and keyways.

File comment: mockup was created to check binding in the steering system.
mockup2.JPG [ 73.29 KiB | Viewed 61606 times ]
mockup.JPG [ 70.33 KiB | Viewed 61497 times ]
File comment: triumph spitfire bushings
left corner.JPG
left corner.JPG [ 121.51 KiB | Viewed 61419 times ]
corner.JPG [ 98.93 KiB | Viewed 61357 times ]
File comment: that hole is there to install the bellcrank bolt. the bushing is bronze oilite on a .5 od crush tube. hardware is all AN, a few grade 8 pieces for mockup and MS21042L6 nuts.
bellcrank.JPG [ 100.92 KiB | Viewed 61289 times ]
File comment: front subframe was built using a jig to square things up, not seen here. theres minimal warpage as i was careful so remove the heat after welding. still some bracing and gusseting to be added
frontsub.JPG [ 132.7 KiB | Viewed 61243 times ]

Author:  sodamninsane [ May 21, 2007, 5:24 pm ]
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nice work!

Author:  robertwa [ May 21, 2007, 5:34 pm ]
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Some great looking fabrication there!

Author:  JonW [ May 21, 2007, 6:49 pm ]
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Nice welding and fab work.

But, what exactly are you building? Single seater? 75" wheelbase?

Can you show us the entire frame isometric or rendering of the car?

Author:  sodamninsane [ May 21, 2007, 7:24 pm ]
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Andrew, one thing, since I too plan on using miata parts for my suspension, I was wondering if you could send me the dimensions for the uprights as well as ball joint centers for your control arms.

I am still early in the design phase and since I do not have any parts myself I am trying to get the most accurate dimensions possible.

Also, what does the underside of you lower control arms look like? have you fixed the lower balljoint into position so it does not pivot?

Thanks and keep up the great work!


Author:  airframefixer [ May 21, 2007, 8:30 pm ]
Post subject: 

JonW wrote:
Nice welding and fab work.

But, what exactly are you building? Single seater? 75" wheelbase?

Can you show us the entire frame isometric or rendering of the car?

thanks. you bet guess i forgot to say. 55.5 track front, 56.2 rear, same as a miata, wheelbase is 95 inches. two seat mid engine rear drive

heres my work in progress drawing.

sodaminsane, i will send you the delta cad file tonight of my front suspension. you can download the demo on the delta cad website, its easy to learn.

thanks for the comments.

lm6.JPG [ 254.99 KiB | Viewed 61119 times ]

Author:  KB58 [ May 21, 2007, 8:46 pm ]
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Wait, I see a "real" differential on the drawing. How are you going to drive that with the R1's output sprocket? Or is that just temporary for the drawing?

Author:  GatoEnFuego [ May 21, 2007, 9:03 pm ]
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Nice work so far. How is that RHS tube going to hold up on those control arms?

Regarding the drive system, it would be really trick to find a way to somehow turn the R1 drive sprocket into a CV joint and then run a real driveshaft back to the real diff. Hmm... What direction does a bike motor rotate?

Author:  KB58 [ May 21, 2007, 9:14 pm ]
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Haha, think about it... you already know the answer! It turns in the direction needed to make the bike move forward, which is CCW.

Author:  airframefixer [ May 21, 2007, 9:34 pm ]
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[quote="GatoEnFuego"]Nice work so far. How is that RHS tube going to hold up on those control arms?[quote]

thanks. the square tubing is 1x1 .100 HSS, much stronger than erw, with larger radius corners.

the drive train will be much the same as Jeff's, but the drive shaft will only be about 16 inches, custom made obviously. engine will be aquired next spring. i just spent this years budget on shocks and springs. sprocket adapter is available from peter d motorsports.

Author:  airframefixer [ May 21, 2007, 10:03 pm ]
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KB58 wrote:
Wait, I see a "real" differential on the drawing. How are you going to drive that with the R1's output sprocket? Or is that just temporary for the drawing?

mount the engine along the longitudinal axis, exactly the same way as every other BEC, but with a much shorter drive shaft. or if your familiar with the turner LMP, much the same as that.

Author:  airframefixer [ May 21, 2007, 10:13 pm ]
Post subject:  re: lower balljoint

here some pics of the lower bj. i needed to grind two sockets down in order access the fasteners. there is a .187 spacer welded into place under plate. the socket fits between the lower pushrod mount tabs.


sockets.JPG [ 56.55 KiB | Viewed 60977 times ]
bjointbolt.JPG [ 87.78 KiB | Viewed 60917 times ]
bjoint.JPG [ 40.74 KiB | Viewed 60818 times ]

Author:  R1 Seven [ May 22, 2007, 8:38 am ]
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Cool project, and nice work so far. The R1 should work nicely in there. Depending on how rigid your rear diff housing is monted you might could make a real short drive shaft sans u-joints using Guibos (sp) like are found on BMW driveshafts. Dennis used this type of arangement on the DP1 car.

Anyways, I look forward to your progress. Thanks for sharing.

Author:  Glen [ May 22, 2007, 10:35 am ]
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Could have used 12Pt drive MS hardware and avoided the socket grinding. Nice to see the Jetnuts though :thmbsup:

Actually, isn't there enough room to get a box end wrench on there?

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