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Learning how to build Lotus Seven replicas...together!
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 Post subject: Re: planing the G.T.R.
PostPosted: Thu Mar 15, 2012 11:30 pm 
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Driven5 wrote:
As speed increases, aerodynamic forces become much more significant in the amount of energy required to maintain that speed. Keeping this in mind, consider the following:

For argument sake, we'll use the aero numbers I came across for the the Boss 302 Mustang, with a frontal area of 24ft^2, and around a .36 drag coefficient. From best data I have been able to find for a Caterham we'll call the Locost a frontal area of 16ft^2, and around a .65 drag coefficient.

If anybody has more accurate numbers or formulas, please feel free to correct me.
The numbers I've seen for a Locost is that it has a Cd of 1. But cheer up, it's the same as the typical F1 car. :)

fastmonkey:
If you want good fuel mileage you don't want a high powered car. You aren't going to get high performance either. And the shape of a Locost is at the wrong end of the scale of what you need.

You want to get 40++ mpg the easy way?
My 1988 Honda CRX HF with a Cd of .29 and only 60 hp gets 42 to 48 mpg in town and 51+ mpg on the highway at reasonable speeds! The 1.5L engine was designed/tuned for max efficiency not hp. So you have to choose your engine accordingly.

One of the secrets is to have max torque (best efficiency) at the rpm your cruising speed will be. And don't expect that speed to be in the 75 to 80 mph range either with less than optimum streamlining. The CRX HF has max torque at 2000 rpm which equates to 64 mph.

Another secret if you're using a throttled engine (not a Diesel) is to have a vacuum gauge right in front of you and keep the vacuum as high as you can all the time.

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Completed building GSXR1000 CMC7, "Locouki"
http://dmr-architect.com/~locouki/


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 Post subject: Re: planing the G.T.R.
PostPosted: Thu Mar 15, 2012 11:48 pm 
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Quote:
But cheer up, it's the same as the typical F1 car.


It's just they generate downforce and we generate backforce. The power of Retro...

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 Post subject: Re: planing the G.T.R.
PostPosted: Fri Mar 16, 2012 12:48 am 
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this is a great forum. im not sure why but every time i read new posts :lol: . thanks again for all your help.


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 Post subject: Re: planing the G.T.R.
PostPosted: Fri Mar 16, 2012 9:15 am 
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fastmonkey, Here you go. Everything you need that will meet all of your MPG goals.....43 to 54 MPG.


It uses a small, inexpensive, commonly available 1275cc engine (MG Midget - OK - it may not be 200hp/ton) and an aero body style (the Lotus Eleven). There was an article written in R&T in 1984 about Peter Egan's journey cross country in a Westfield Eleven. You can read it here.....
http://members.toast.net/joerger/north.html

Even if this particular project is not for you right now, it will show you what it takes to get that kind of MPG. I'd drop that 43-54 MPG down to 40-50MPG with today's E10 fuels.

And here is the car, I mean, Project! Some assembly required.

http://cgi.ebay.com/ebaymotors/Westfield-Lotus-11-SCCA-Race-Car-/280844441924?pt=US_Cars_Trucks&hash=item4163a21944

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Chuck.

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

Check out my rotary build log: click here


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 Post subject: Re: planing the G.T.R.
PostPosted: Fri Mar 16, 2012 10:33 am 
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Location: Whitby, Ontario
Ahhh, A-Series. Hello old friend. I guess I won't be seeing much of you now I live over here :(

Actually, that should be a smiley face lol. It's a rubbish engine, but I guess I will always feel a kind of attachment to it :)


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 Post subject: Re: planing the G.T.R.
PostPosted: Fri Mar 16, 2012 10:46 pm 
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Posts: 23
rxlocost-thanks for the heads up on the aero car. i know that aero is the key to my mpg goal but aero cars are not my thing. so i would like to make the best plan that i can to get as near my goals as posible. so a light weight low drag drive train and a couple of engine options for the build is where im headed.

sence i started this thread my power train options have opend up some. if most gas engine are going to yeld 30 to 35 mpg then the f20 honda is tsill in the running. huge power for a relatively small fuel comsumption differants. the cons that i know of are few and short right now. 1-wiring and then more wires and a couple more wires and a few mor to wire the engine and componets 2-cost could be high if i dont find the right deal(missed the first one) 3-engine size, realy tall and wide at the bell housing. The pros 1-POWER and tons of it !!!!! 2-honda reliabilty 3-parts and wiring harness from donnor. all the gauges and lights and do dads plug in if the stock harness is re used 4-apparently as efficent as most gas engines

now the vw 1.9 td aaz pops in to the eqation, stock 75hp easly modded to 120hp and apx 200lb of torque modded. if the milage is there and its not to big its a stong contenderand. the deisel thing is cool. mates to either a toyota 22r or suzuki samari trans. The pros 1-simple, it doesnt get much simpler to hook up a motor than a mechanicl diesel. 2-ive read about these engines at apx 200,000 miles. thats a long life 3-milage, in the car these things get great milage (i know aero, aero, aero but its still a huge improvment over the gas model) 4- its a diesel, dont know why but this fact is just cool to me for what ever reason The cons 1-the power is down compared to my 200hp per ton goal 2- have to get trans and adapter from a different sources 3- this is just a little thing but its a diesel, fuel isnt always at the pump when you need fuel 4- likely hood of a donner is low and that could me more costs for the build

if any one has any thoughts or info on these or an engine that they think may be a better mach please jump in. some one said they had some vw 1.9 drawing. that would be great

:cheers:


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 Post subject: Re: planing the G.T.R.
PostPosted: Fri Mar 16, 2012 11:41 pm 
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just decided to reread thread after my last post.

rxlocost- march 15 you said you were doing some BOE calculating. whats that?


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 Post subject: Re: planing the G.T.R.
PostPosted: Sat Mar 17, 2012 2:06 pm 
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Well heck! I've got the dimensional drawing of the TDI as an Adobe doc, apparently the forum can't upload it. PM me your email and I'll send it to you.
Here's the flywheel measurements. ..

outer diameter 281mm
overall thickness 43mm
clutch diameter 231mm
clutch surface depth 12mm
teeth (for starter) width (top) 2.5mm, gap 4mm, depth 4mm
recess for crankshaft mounting surface 14mm
6 bolt unidirectional mounting
approx weight 9kg

I've got more somewhere. :cheers:

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 Post subject: Re: planing the G.T.R.
PostPosted: Sat Mar 17, 2012 2:39 pm 
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Quote:
you said you were doing some BOE calculating. whats that?


Sorry -- BOE is Back Of the Envelope or rough approximation. Not accurate enough to design a car from but certainly enough to know if one is in the right ballpark. I have a habit of making reality checks on my work and others. Sometimes on the back of a real envelope or any other sheet of scrap paper, sometimes even paper napkins. In that case, I was checking my MPG against some theoretical value. I used that website with published CdA & weight of a '90 RX7 to get "their" number. I then compared those results with some reported MPG results from RX7 owners to find some "correction factor" for rotary BSFC, driving habits, website calculator assumption errors, etc all lumped into one number. I then applied that correction factor to the results I get when entering my Locost to the same calculator. I came up with a number that exactly matched my experienced 20 MPG. So it told me that my tuning is about right and that any improvement will have to be either aero, or a complete engine swap; neither of which is in my future.

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

Check out my rotary build log: click here


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 Post subject: Re: planing the G.T.R.
PostPosted: Sat Mar 17, 2012 4:06 pm 
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rx7locost-thanks

was over a pop house lending a hand to day and had a crazy idea. we have a couple early A body chrysler and was thinking about using the spindles and rear end out of one. hopefully i can get some pics and post this week. nine inch drum brakes front and rear i beleave. the spindles are small and light looking. the arms that the steering hooks to bolt on. the car stock is rear steer spindle but it looks as if you could just swap the arms side to side to make it front steer. the lower ball joint is in the spindle. the rear end is a 7.25. i have a couple of diffs, im thinking some thing like 2.73, 3.08, 3.55 and 3.90 gears. i also have a single pot master cylinder and distribution block. not sure how wide the rear end is from ms to ms or bp to bp but the car is 43 inches across from innner wheel well to inner wheel well. these arent very comon any more but weve got a bunch of this stuff. any thought?


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 Post subject: Re: planing the G.T.R.
PostPosted: Tue Mar 20, 2012 12:14 am 
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heres what i came up with for the front spindels and the rear end width.

does any one see any thing that might keep these from being ok for the job?

so if my math is even close. ill need lower control arms that are 16.75 long. is that way to wide? thinking this would give me about a half inch wider front than rear.

but wait theres more!!! if this is all in the ball park could some one help me with the front end geom. or do i need more info?


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spindles and brakes 250.JPG [ 583.98 KiB | Viewed 683 times ]


Last edited by fastmonkey on Tue Mar 20, 2012 9:26 pm, edited 1 time in total.
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 Post subject: Re: planing the G.T.R.
PostPosted: Tue Mar 20, 2012 9:22 pm 
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i dont think my plan well work. when i reversed the steering arm it moved the lower wall joint forward about 1.5 inches. really looks funny! here are a couple pics.


Attachments:
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no worky 001.JPG
no worky 001.JPG [ 723.74 KiB | Viewed 654 times ]
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 Post subject: Re: planing the G.T.R.
PostPosted: Tue Mar 20, 2012 9:33 pm 
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These are not your typical uprights. Of course you know that already. But from what I see from your photos, especilly that last one, things are not nearly as bad as you are trying to show. Look down the upper BJ hole directly at the lower BJ, then move the lower BJ taper directly at the upper hole. See if the lower BJ taper is now perpendicular from its mount. Also look at the upper hole and see if it is now on the same axis. From what I can tell, they line up.

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Chuck.

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

Check out my rotary build log: click here


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 Post subject: Re: planing the G.T.R.
PostPosted: Tue Mar 20, 2012 10:07 pm 
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fastmonkey wrote:
the car stock is rear steer spindle but it looks as if you could just swap the arms side to side to make it front steer. any thought?
If you reverse the arms I'm pretty sure you will end up with extreme anti-Ackermann unless you bend the arms outward quite a bit. Is there room to bend them that much without hitting things like the backing plates or rims?

_________________
"My junk is organized. At least is was when I put it wherever it is." -olrowdy
Completed building GSXR1000 CMC7, "Locouki"
http://dmr-architect.com/~locouki/


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 Post subject: Re: planing the G.T.R.
PostPosted: Wed Mar 21, 2012 8:37 pm 
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had a chance to measure the lower ball joint. the ball joint is off set a quarter of an inch. so when i reverse the arms it moved a half inch forward. a couple more pics and a better drawing. so i had to rotate the spindle to get the upper mount center and ball joint pivot to line up. so does this end the plan or could they still be used? how would the ball joints pointing different directions affect the front end geom? another posible issue with this is that the pivots are now just infront of the snout instead of passing threw the snout.


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reversed steering arm 003.JPG [ 451.22 KiB | Viewed 616 times ]
reversed steering arm 001.JPG
reversed steering arm 001.JPG [ 680.19 KiB | Viewed 616 times ]
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