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MANUAL TRANSMISSION AND DIFFERENTIAL NEED HELP.

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tushar962 View Drop Down
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    Posted: Jun/24/2012 at 7:14am
hey guys.. i am new to this site so hello everyone
i need help regarding manual transmission its first time we are participating in sae baja
i have done quite a research but not able to stumble upon any answer.
we have a 11hp Lombardini 340LGA engine and the weight of our car is around 320kg including driver.
the specs are 
Bore x Stroke : 84 mm x 64 mm, Single cylinder, Air Cooled
•Swept Volume : 338 cc
•Compression ratio : 8:1
•Rated Power : 8 kW @ 4400 rpm
•Max Torque : 19 Nm @ 3000 rpm
•Valve Timing System : Belt Driven Single Overhead Camshaft
•Lubrication : Forced Lubrication Vane Pump
•Luboil : 15W40 CF4 multi grade oil
•Luboil Capacity : 1.7 ltrs
•Starting System : Electric Start with Auto-Decomp on Camshaft
•Electric System : 12V, 18 amps flywheel mounted alternator,
•Recommended Battery : 12 V, 44 Ah
•Weight of Engine : 30.5 kg
Engine Specifications LGA-340
plzz help me to chose a manual transmission as i dont wanna go for an cvt.
also when i was looking for the differential i found limited slip differential to be quite good for
for off road racing.. tell me whether i am going in the right direction for diffrential,if yes then plzz suggest me one. 
<HELP GUYS>..............
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AndyRIT Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2012 at 11:41am
Lombardinis are great engines (look at my sig below Wink, Kohler owns that company)
 
BUT they are not the standard engine for baja, Briggs and Stratton intek 20 is required. Read the rules.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tushar962 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2012 at 12:48pm
hey i am participation in SAE BAJA INDIA in this lombardini 340lga ENGINE IS PROVIDED.
can you plzz help me out with some manual transmission 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote sandres913 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2012 at 1:04pm
Originally posted by tushar962 tushar962 wrote:

hey i am participation in SAE BAJA INDIA in this lombardini 340lga ENGINE IS PROVIDED.
can you plzz help me out with some manual transmission 


You do have to state if you're not competing in the USA, this forum is predominantly North American competitions.

What exactly are you asking for help on? You'll need to figure out the gear ratios and everything yourself, no one is going to tell you what to make, we all have our own cars to design, but if you have a more specific question, we might be more willing to help out.
Shaun
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tushar962 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2012 at 1:25pm
we are thinking of using Piaggio Ape transmission or an mahindra giyo transmission
the gear ratio of piaggio ape are:
first gear-1:55.08
second gear 1:32.72
third gear-1:19.95
fourth gear:1:13.40
rev:1:31.48
gear ratio of mahindra giyo are unavailable right now.help me which one to choose plzzz
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sandres913 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2012 at 1:29pm
Originally posted by tushar962 tushar962 wrote:

we are thinking of using Piaggio Ape transmission or an mahindra giyo transmission
the gear ratio of piaggio ape are:
first gear-1:55.08
second gear 1:32.72
third gear-1:19.95
fourth gear:1:13.40
rev:1:31.48
gear ratio of mahindra giyo are unavailable right now.help me which one to choose plzzz

Okay, what you're asking is for the forum to do the (simple) calculations for selecting gear ratios. Figure out if you want to go for high torque or high speed, or heck, even balanced, then make your selection from there.

An FYI, posting max torque/power and gear ratios and asking the forum to select for you will generally get you ignored. Look into Shigley's Mechanical Design book, or online. If you get stuck, THEN ask. The forum is NOT somewhere you can "outsource" your engineering to.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tushar962 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2012 at 1:43pm
pardon me for that but i am just new to drive train or power train.i was in steering department for my team but due to the recent shuffle in my team i have landed into this drive train.i just know a little about this power train i.e just about the mechanism of all transmission like manual or cvt and differential and all. i really wanna learn from you guys i really have no idea about choosing gear ratios and differential for my car.what we do is just use our Google skills to find a transmission fits the best with our engine can you help me out by suggesting me any site or book that helps us to understand this plzz help
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Shaun
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tushar962 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2012 at 1:52pm
is this the book you are talking about?
shigleys mechanical engineering design
does it have every thing that i need to know???
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Post Options Post Options   Thanks (0) Thanks(0)   Quote abenn Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2012 at 8:03am
I think you should look into some transmissons available and do some research on their ratios, what you have up there isn't going to get you much over 8mph. Keep in mind the revs only go up to 3800 at least in North America. But since we are a team that uses a manual I can tell you that our internal ratios are 

1st - 3.400
2nd - 2.077
3rd - 1.444
4th - 1.050
5th - 0.833

From then on you can do the research and select your sprocket ratios and what you want for your final drive. But you will want a transmission with a wide ratio. BAJAs are really limited on power and revs so an evenly spaced wider 5 or 6 speed is what your going to want.
Andy Benn
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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2012 at 8:34am

This is definitely the wrong subforum for this thread...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tushar962 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2012 at 1:59pm
thanks guys.but i still have few doubts

i know that   v_c = \frac{c_t \times v_e}{gr_t \times gr_d}  :ct-circumference of tyre;ve-engine rpm i.e 3600 rpm in my case
grt-gear ratio of transmission and grd-gear ratio of differential.this formula gives me the speedof my car at that gear.
we are thinking of choosing the transmission of mahindra gio
we are not able to get gear ratio for its transmission but the engine used in this is quite similar to 
lombardini 340LGA as it has same rpm as lombardini of 3600rpm but has a torque of around 21.5nm while in lombardini its 19nm.is there any way we can get the the gear ratio of this car?
am i using the right formula for determining the speed for specific gear ratio?
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Post Options Post Options   Thanks (1) Thanks(1)   Quote sandres913 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2012 at 2:11pm
Now this is where I'll be happy to help. Discussing equations as opposed to just telling you what to do. It's better to figure out why you need to do something than to just do something and take someone's word for it.

You are on the right track with that equation, but you can make your life a little simpler. Figure out what you want your top speed to be. I.e. if you want to go 5mph, or 50mph, just make an initial assumption. From here, convert that speed to wheel rpm, by using circumference, and subsequent conversions from mph to feet per minute. This will give you the rpm you need to reduce from the engine in your highest gear. Then determine what you want the engine revs to be at that speed, you noted 3600 rpm here, so I'll go with that. Divide 3600 rpm by the wheel rpm and you will get your OVERALL reduction. Now if you're using a differential and know its reduction, that's a constant reduction, so divide your overall reduction by your differential reduction and that will give you the ratio you need between your engine and your differential.
This is one of the ways I've come to use. You could do the same thing in Excel with the equation you have up there, but I just prefer the way I just laid out.

As far as finding the gear ratios from this Mahindra, I really can't help there, I'm not sure if Indian automakers provide repair manuals the way American automakers do. Your best bet would be to look for an assembly and identify the number of teeth on the gears and do the calculation. Or call the company and explain what you're doing.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tushar962 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2012 at 2:46pm
thanks mate i really appreciate your help. i would limit the top seed of my car around 35 to37 mph.because i think that's enough.what i am looking for is better acceleration and torque values.still i have few doubts to ask.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sandres913 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2012 at 3:00pm
You would select your gear ratios based how quick or slow you want to accelerate. It's all in Shigley's. Or searchable through Google.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2012 at 3:58pm
I'm not sure there is a baja car on earth that goes 37 mph... that would certainly limit your acceleration.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote abenn Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2012 at 4:20pm
With our wide ratio 5 speed manuals we can. With the right sprocket ratios, a set up that we change for different races, and enough flat land a handful of our cars will do that speed according to the transmission gearing. For the Auburn race the sprocket set up we ran was set to top out at 36.5mph. 

In the past with a flat straightaway we have driven a quad next to it and reached 35 and 36 mph. Then one of our alumni swapped in a 30 horse v twin with the same manual transmission/sprockets and supposedly that will do like 60. That is an entirely different story though....


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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2012 at 5:24pm
According to the transmission gearing is one thing... I never saw one of my cars go the theoretical speed, especially during a race.  Just saying.
 
My personal design philosophy was to be fast out of the hole, and quick out of turns. 
 
I'm also one of those people that would rather drive a slow car fast than a fast car slow.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sandres913 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2012 at 5:24pm
Originally posted by abenn abenn wrote:

With our wide ratio 5 speed manuals we can. With the right sprocket ratios, a set up that we change for different races, and enough flat land a handful of our cars will do that speed according to the transmission gearing. For the Auburn race the sprocket set up we ran was set to top out at 36.5mph. 

In the past with a flat straightaway we have driven a quad next to it and reached 35 and 36 mph. Then one of our alumni swapped in a 30 horse v twin with the same manual transmission/sprockets and supposedly that will do like 60. That is an entirely different story though....



SWEET! Thumbs Up

Out of curiosity, with a 5 speed, how much does your car weigh, like in the 500 range? We're putting our car on an extreme Weight Watchers diet this year and drivetrain got restricted pretty severely, and rightly so haha
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Post Options Post Options   Thanks (0) Thanks(0)   Quote abenn Quote  Post ReplyReply Direct Link To This Post Posted: Jun/26/2012 at 7:41am
Our car was 449 in Auburn. The tranny doesn't really weigh that much. I'd say 25-30 pounds. It's the rest of our car that has issues. Our frame was like around 100 pounds alone. We overbuild too many things so we don't have too worry about breaking. One of our cars was actually hit by a full size Chevy Tahoe at 40 mph causing at least 10 grand in damage to the Tahoe and it still ended up pulling another car out of the pits the same day. 
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Hahaha I hear that! Our car was/is a tank! Nice on the Tahoe damage! Thumbs Up
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/29/2012 at 1:25am
Originally posted by collinskl1 collinskl1 wrote:

I'm not sure there is a baja car on earth that goes 37 mph... that would certainly limit your acceleration.

We have been over 40 mph consistently without a firewall and right in that territory with one as a benchmark. I am sure Laval is hitting those speeds or even higher as well.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/30/2012 at 5:25pm
Originally posted by Soccerdan7 Soccerdan7 wrote:

Originally posted by collinskl1 collinskl1 wrote:

I'm not sure there is a baja car on earth that goes 37 mph... that would certainly limit your acceleration.

We have been over 40 mph consistently without a firewall and right in that territory with one as a benchmark. I am sure Laval is hitting those speeds or even higher as well.
Unless you can provide proof; I'm calling B.S. on a 40 mph SAE Baja car w/ ATV tires & legal engine.
At least ducktape a GPS to the car and snap a picture.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/30/2012 at 5:35pm
40 mph is easy for a light fast car with no firewall, like I said. You lose around 4 or 5 mph with the firewall but it shouldn't be all that shocking. I'm graduated now and out in California so I can't get you a picture. I think the highest speeds we were recording in auburn were like 35 or so on the smoother straights when we were really hauling for the first hour.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/30/2012 at 7:54pm

I had my champion car out on the street w/ the govern set over 4,000 RPM and the GPS only said 30 MPH (which was disappointing but inline w/ previous testing).  Granted its geared to spin the tires but if it had the HP to do so the CVT should allow for 35 MPH and it just didn't happen.  I'm not going to dismiss that a car could be faster w/ different tires ect. but 40 MPH needs documented proof otherwise it B.S. (I'd still suspect some trickery).  I'll urinate on the engineering degree of anyone who says the lack of firewall makes a 5 MPH difference (maybe 1 MPH if any notable difference).

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/30/2012 at 8:22pm
Well I unfortunately don't have any proof I can share other than first had knowledge of top speed runs on pavement with a handheld gps and our data aq both showing up to 41.5 if I remember correctly. If you don't believe me that's fine, but your champion car is a dinosaur that followed different tech rules and was completely different. Don't believe me if you don't want to but I'm saying we have done it and there are a handful of other cars who may have as well.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zglazer Quote  Post ReplyReply Direct Link To This Post Posted: Jun/30/2012 at 9:46pm
I can definitely see a well-tuned 300 pound car hitting 40mph in ideal conditions. I also see no reason to doubt what Danny says given what I've seen of Cornell's car and its performance this year.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/30/2012 at 11:23pm
Originally posted by Soccerdan7 Soccerdan7 wrote:

Well I unfortunately don't have any proof I can share other than first had knowledge of top speed runs on pavement with a handheld gps and our data aq both showing up to 41.5 
I'm guessing you had your system in KPH and not MPH.  Happens to the best of us.  (41.5 KPH = 25.8 MPH). 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 12:40am
You must really think I am an idiot. We have wheel speed and gps speed on the car and the handheld garmin. They were all mph.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 12:55am
Originally posted by Soccerdan7 Soccerdan7 wrote:

You must really think I am an idiot. We have wheel speed and gps speed on the car and the handheld garmin. They were all mph.
 
Fine, your #1 car is 50% faster than my #1 car!!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zglazer Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 11:51am
Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

Originally posted by Soccerdan7 Soccerdan7 wrote:

You must really think I am an idiot. We have wheel speed and gps speed on the car and the handheld garmin. They were all mph.
 
Fine, your #1 car is 50% faster than my #1 car!!!
Looking back at the results, your #1 car (in the 2002 midwest competition) scored less than 1000 points total and didn't even make it into the top three cars in the top speed event. Aside from the fact that many things have changed in the intervening ten years, it doesn't look like that car was much of a speed demon to begin with.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 1:51pm
Originally posted by zglazer zglazer wrote:

Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

Originally posted by Soccerdan7 Soccerdan7 wrote:

You must really think I am an idiot. We have wheel speed and gps speed on the car and the handheld garmin. They were all mph.
 
Fine, your #1 car is 50% faster than my #1 car!!!
Looking back at the results, your #1 car (in the 2002 midwest competition) scored less than 1000 points total and didn't even make it into the top three cars in the top speed event. Aside from the fact that many things have changed in the intervening ten years, it doesn't look like that car was much of a speed demon to begin with.
 
Your right, I never had the absolute fastest car.  Thanks for pointing out absolutly nothing that substantiates the existence of a 40 MPH legal SAE BAJA car!
 
To my knowledge, no car ever got a recorded top speed over 30 MPH at any of the competitions were top speed was measured.  The highest I've found was 2005 Brazil 29.3 MPH, which was the first year engines went to 3,800 RPM and maybe the last time Top Speed was scored (even that speed is suspiciously high!).
 
What the F@#$ do you think has changed in the last 10 years?  Did they repeal the requirement to drag a hog tied freshman behind the car or something?  You think because your smart phone has an APP to measure G-force and cameras mounted to your helmets that you are super high tech now!  Are you using elf magic to form composites out of adamantium?  Are you under the impression that my car has square tires?  Do cars levitate now?
 
Do you have any proof of a legal SAE Baja car going anyways near as fast as you're claiming? Because it has not been recorded in any competition results etc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 2:05pm
Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

Originally posted by Soccerdan7 Soccerdan7 wrote:

Originally posted by collinskl1 collinskl1 wrote:

I'm not sure there is a baja car on earth that goes 37 mph... that would certainly limit your acceleration.

We have been over 40 mph consistently without a firewall and right in that territory with one as a benchmark. I am sure Laval is hitting those speeds or even higher as well.
Unless you can provide proof; I'm calling B.S. on a 40 mph SAE Baja car w/ ATV tires & legal engine.
At least ducktape a GPS to the car and snap a picture.

We ran our '09 car on pavement behind a truck once and got 36MPH.  Not exactly scientific testing methods, but it should be fairly close.  That car weighed 396 race ready.
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Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

Your right, I never had the absolute fastest car.  Thanks for pointing out absolutly nothing that substantiates the existence of a 40 MPH legal SAE BAJA car!
 
To my knowledge, no car ever got a recorded top speed over 30 MPH at any of the competitions were top speed was measured.  The highest I've found was 2005 Brazil 29.3 MPH, which was the first year engines went to 3,800 RPM and maybe the last time Top Speed was scored (even that speed is suspiciously high!).
 
What the F@#$ do you think has changed in the last 10 years?  Did they repeal the requirement to drag a hog tied freshman behind the car or something?  You think because your smart phone has an APP to measure G-force and cameras mounted to your helmets that you are super high tech now!  Are you using elf magic to form composites out of adamantium?  Are you under the impression that my car has square tires?  Do cars levitate now?
 
Do you have any proof of a legal SAE Baja car going anyways near as fast as you're claiming? Because it has not been recorded in any competition results etc.

What kind of proof would satisfy you?  With the resources some of the top schools have, I'm sure they could accommodate you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 3:22pm
Originally posted by dillon_b12 dillon_b12 wrote:


What kind of proof would satisfy you?  With the resources some of the top schools have, I'm sure they could accommodate you.
 

Why did they stop measuring top speed at competition?

 

Honestly, I would probably never believe a 40 MPH legal SAE Baja car is possible unless they did something they probably wouldn't do at competition (like formula slicks on asphalt etc.)  Some explanation of how they got such an awesome speed would be warranted.

 

But at the very least snap a picture of a radar gun, GPS, or something calibrated to back up your claims.  I wouldn't trust the speedometer in your truck because they are notoriously off by 5 MPH. 

I had a $2,000 STALKER ATS radar gun with PC interface..................................AND THEY'VE GOT NOTHING!!!  Here a graph with engine at 3,600 RPM Max GOV.


Edited by Akron 1998 to 2004 - Jul/01/2012 at 3:28pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 3:48pm
PROOF

This is all I have on my computer. It is a plot of wheel speed of our first lap of Auburn where we got the holeshot off the line and had no one in front of us for the entire lap. Our driver wasn't going full out since it was the first lap, but it certainly gives you an idea of the speeds we were seeing in the straights on dirt / grass etc in full on racing conditions with everything according to tech. I don't have anything from our top speed testing on pavement from before competition (with and without firewall testing) but this should at least clearly say our car is faster than what you were claiming was the fastest and under ideal conditions it gets even better.


For the record that pavement testing was done on worn down 22" atv tires but nothing like slicks or anything unreasonable just to get the high top speed other than no firewall.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 4:03pm
That is what I'm talking about.  35 MPH, I could see that being possible.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 4:17pm
My point is we did that on a (fairly rough) endurance track. We can go faster (obviously) on pavement and break 40 easily without a firewall. I'm not sure why you think that graph proves your point. I said we can do 37 no problem and gave you the best proof and argument I have. Conversation over.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 5:12pm
Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

Originally posted by dillon_b12 dillon_b12 wrote:


What kind of proof would satisfy you?  With the resources some of the top schools have, I'm sure they could accommodate you.
 

Why did they stop measuring top speed at competition?

 

Honestly, I would probably never believe a 40 MPH legal SAE Baja car is possible unless they did something they probably wouldn't do at competition (like formula slicks on asphalt etc.)  Some explanation of how they got such an awesome speed would be warranted.

 

But at the very least snap a picture of a radar gun, GPS, or something calibrated to back up your claims.  I wouldn't trust the speedometer in your truck because they are notoriously off by 5 MPH. 

I had a $2,000 STALKER ATS radar gun with PC interface..................................AND THEY'VE GOT NOTHING!!!

It wasn't my truck we used to approximate the top speed.  GPS in my truck usually runs +/- 1MPH of my speedo.  I guess they are both off the same amount.

I don't think I saw anyone in this thread claim to be running 40 MPH in a legal car on an endurance track.  Your say your car ran 30MPH on asphalt with a governor set  to 4,000.  Cornell has provided proof that they hit ~35 on an actual endurance track in a race trim car.  You don't think it's even conceivable that moving that car on to asphalt would put it pretty close to 40?

If any invitational race ever has an open class, you should bring your car out and see how it stacks up against newer cars.  They aren't the turds you make them out to be.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ErikHardy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/01/2012 at 6:54pm
Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

 
What the F@#$ do you think has changed in the last 10 years?  Are you under the impression that my car has square tires?  Do cars levitate now?
 

Transaxles and CVT's have to be the biggest contribution. But can you verify your car does indeed not have square tires? Are you really surprised that cars have gotten better over 10 years? Not just in Baja, but in fsae, F1, Gt1, etc. etc. Time to wake up buddy.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JeremyB Quote  Post ReplyReply Direct Link To This Post Posted: Jul/02/2012 at 12:58am
As another datapoint. The 2012 Auburn event test mule got up to 36 mph on the NCAT asphalt test track. Mule is Auburn's olds 2004 car with full firewall, old Briggs governed to 3800, poor CVT tune, and nondescript off road tires. Speed taken with GPS. I'm sure Cornell's 2012 car is faster!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote taukea Quote  Post ReplyReply Direct Link To This Post Posted: Jul/02/2012 at 10:56am
30 mph at 4000RPM? Iowa State's 2012 car consistently did 30 during CVT tuning with governor set at 3800.  I would believe that some of the faster cars like Cornell could pull off 40 mph with no firewall.  I am a firm believer that that sucker slows us down a lot, have toyed with the idea of a rear engine enclosure >=]
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/02/2012 at 12:15pm
Originally posted by dillon_b12 dillon_b12 wrote:

If any invitational race ever has an open class, you should bring your car out and see how it stacks up against newer cars.  They aren't the turds you make them out to be.
 

I'd absolutely love to get into a race.  Can't really justify the trip from WA to MI for a friendly invitational.  Almost happened last year against OSU, if I can beat them I fair very well against any team. 

 

If OSU doesn’t hold an invitational this year, I might try to set something up. 

 
The aero drag for the entire car accounts for like 0.2 HP, don't worry about the firewall.


Edited by Akron 1998 to 2004 - Jul/02/2012 at 12:23pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote taukea Quote  Post ReplyReply Direct Link To This Post Posted: Jul/02/2012 at 12:41pm
It may never happen and you may be right, but its thinking like that that puts a severe damper on progress.  You can calculate things all day long but until you get out there and test it you will never know.  There is a lot to be said for engineering behind the desk but it can really put the blinders on. That is what Baja is all about.  That is what gives us the professional edge in the job market.  We have the technical knowledge AND we know how to properly apply it.  Deep down there is always some guess work and intuition!  

- I tend to think more this way being in Industrial Technology major.  But that is why I work well with engineers.  I get to tell them when they are being stupid and over-thinking things and then offer a simple solution that they can optimize and they get to tell me when my ideas aren't possible/ effective. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote taukea Quote  Post ReplyReply Direct Link To This Post Posted: Jul/02/2012 at 12:48pm
Also .2 HP sounds pretty nominal but are we foregetting that we are playing with at MAX 10 hp which i think is generally accepted to be a bit less that 10?  Thats 2% power loss! More if its windy lol.  Look at your sport bikes, from model year to model year they get excited if they drop 2 pounds and add a horsepower at the rear wheel! Why should we overlook the little things?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/02/2012 at 1:50pm
Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

 
The aero drag for the entire car accounts for like 0.2 HP, don't worry about the firewall.

Proof?  You can't complain about people making unsubstantiated claims and then make one yourself.
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At the risk of making myself look like an idiot (so please check my math)...
density of air: 4.42554E-5 lbm/in^3
Velocity at 32.5 mph: 572.03 in/sec
cd: 1.0 (very unknown)
Area: 1189 in^2 (41in*29in)

Drag equation:
F = 0.5*den*vel^2*cd*A
  = 8609.12 lbm-in/sec^2
  = 22.30 lbf

Speed above correlates to 63.33 rev/sec at a CVT ratio of 0.8 and a final drive ratio of 10:1, with a 23" diameter tire.  I believe assuming 168 in-lbs of torque, this results in an output of 116.9 lbf to the ground.


If we change ratio to 8:1, force to the ground drops to 93.5 lbf, and aero drag goes up to 35 lbf, at a speed of 40.6 mph.  I would assume the other drags are due to tires / bearings / ect. account for the rest to keep you from accelerating.

Edited by Waffles - Jul/02/2012 at 3:07pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blitz1321 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2012 at 12:11pm
Are u sure these are the correct ratios for ape??
cz we too are ultimately thinking of using pia ape gearbox
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Paritosha Quote  Post ReplyReply Direct Link To This Post Posted: Feb/27/2020 at 12:03am
I am too participateing in Baja SAE.
Can u pls tell piaggo gear boxs each gear rpm.
We need to do rpm deduction. So need to buy shafts.

So pls tell each gear rpm or toque in each gear.??
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