Differential (Clutch type LCD)

[sachinpg]

http://s1-04.twitpicproxy.com/photos/large/512221753.jpg

this LSD is available to us...can anybody suggest someway to attach a sprocket to it??
I know it is little large in size and doesn't suit for FSAE car but still this is what we got here..
Else we have open differential and spool as other options..
please suggest best option :rolleyes:

[sachinpg]

http://s1-04.twitpicproxy.com/photos/large/512221753.jpg

this LSD is available to us...can anybody suggest someway to attach a sprocket to it??
I know it is little large in size and doesn't suit for FSAE car but still this is what we got here..
Else we have open differential and spool as other options..
please suggest best option :rolleyes:

[,4lex S.]

Do yourselves a favor and run a spool.

[Freddie]

I'm not in our drivetrain team, so I might get some of this wroung, but: We ran into the same type of problem, and before we decided to go ahead and buy a new, suitable diff we briefly looked into some sort of torsion bar differential. It's not very pretty, but it does help out a bit. Also, I suggested using a bevel gear on the gear box and having a drive shaft instead of the usual chain. I'm sure many people around here can explain why that is a bad idea.

[jordan.k]

I would just run a spool.

[Jon Burford]

If it's that or a spool, save yourself a LOT of weight and heartache and run the Spool.
If getting a nice Limited Slip is realistic do that.
Please Please Please think carefully and for a long time before you use that!

Expect a comment from Dewi Griff on this one, It will probably be insightful

[Dewi Griffiths]

Mr Burford is correct!

I believe my insight here could be of use. As you will see below I am from Cardiff University and we have used a spool drive for the last 4 years. If you want to save some weight and a lot of complexity I would recommend it.

Some see using a spool drive as a cop out from a design point of view. But I totally disagree. These cars we design aren't far from karts after all. So long as you can justify your design you can have whatever you like.

Also, I would like to point out that the world record for the skidpad is held by a car with a spool http://fsae.com/groupee_common/emoticons/icon_wink.gif

Spool's are simple to design, easy to manufacture, light, simple and effective. We prove that. It gets rid of complexities such as prop shafts (as you would need with your LSD), so IMO you should consider this. The one thing you may have to consider are slightly different suspension geometry's that allow one wheel to scrub. But that's another thread altogether.

If you would like any information on design etc feel free to PM me.

[Jon Burford]

Told you!!

[Kevin Hayward]

Dewi,

Monash recently broke their own record for skidpad this time using a LSD. That being said a spool may have helped them go even faster by maintaining drive wit both inside wheels up off the ground.

The run by Monash in Australia was amazing. If they end up in Europe this year I recommend everyone who is there making sure they watch them on the skidpad.

To the original poster - run a spool, not just as a fallback. With the increased grip of cars recently the load left on the inside wheel is becoming very low (or zero) during cornering. It is getting harder to justify the expense and effort of a LSD.

Kev

[Dewi Griffiths]

Hi Kevin

Thanks for the update! I heard Monash did amazingly well as FS OZ in December. With the decreasing weights in all FSAE competitions I'm guessing that having a spool is more beneficial in terms of the loads decreasing on the inside wheel as you said. It would be good to have a benchmark between both though. I can tell you that in the last year we took 30kg (220kg to 190kg) from the car and the improvement in skid pad was astounding.

I hear Monash are coming over to the UK for competition. I will make a note of ensuring I am there on the sidelines! Lets hope it's not raining or a wetpad like FSG last year...

Are you involved with Monash at all? Do you have any contacts there? I see Scott Wordley is very active on these forums so I could get in touch with him even though he seems to be more into his aero!

Here in Cardiff we are running a spool drive for the 5th yeah at Silverstone in July. However, we are considering purchasing a Drexler diff running them back to back and comparing times. Perhaps this is bordering on a new thread...

[Kevin Hayward]

Dewi,

Not involved with Monash, but have competed with Scott and his crew as both a student for 4 years and a faculty advisor for another 4. Monash are very friendly to other teams over here and hosted ECU at their Uni prior to the comp. I wouldn't worry too much about asking Scott about diffs. He may be extremely knowledgable about aero, but he knows a few other things about cars too.

Kev

[Dewi Griffiths]

Kevin,

Yeah, from speaking to some of them on facebook they seem really nice.
Not doubting his knowledge at all! Don't get me wrong.

Very much looking forward to see their car as Silverstone in July. Loving the massive wing look http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Mike Cook]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by dewigriff:
Also, I would like to point out that the world record for the skidpad is held by a car with a spool http://fsae.com/groupee_common/emoticons/icon_wink.gif

. </div></BLOCKQUOTE>

Spools are the fast way around circles. Not quite as good going through other manuevers.

[scotty young Taylor Race]

If those are your only options . I would suggest an open diff. A spool will be great if you have 750hp and can work your push out on corner entry with the long skinny pedal on the right. But you don’t . Either of these diffs you choose will have pros and cons…..you need to do some home and compare them
ATB , Salisbury or Torsen is the diff of choice . University of Maryland did not beat out 750 entries by 2 seconds at the SCCA solo nats running a spool. They did not set fastest skip pad in 09 with a spool. SDSM did not finish in the top 3 in auto cross with a spool either. Same goes with Missouri S&T and Oregon State and so on.
A spool is a good choice if you are out of budget, Or running on a dirt track with stagger.

[rjwoods77]

Epic Stagger....

http://www.youtube.com/watch?v...ed&fb_source=message (http://www.youtube.com/watch?v=g4vnEoml5ow&feature=related&fb_source=message)

[coleasterling]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by scotty young Taylor Race:
If those are your only options . I would suggest an open diff. A spool will be great if you have 750hp and can work your push out on corner entry with the long skinny pedal on the right. But you don’t . Either of these diffs you choose will have pros and cons…..you need to do some home and compare them
ATB , Salisbury or Torsen is the diff of choice . University of Maryland did not beat out 750 entries by 2 seconds at the SCCA solo nats running a spool. They did not set fastest skip pad in 09 with a spool. SDSM did not finish in the top 3 in auto cross with a spool either. Same goes with Missouri S&T and Oregon State and so on.
A spool is a good choice if you are out of budget, Or running on a dirt track with stagger. </div></BLOCKQUOTE>

Scotty, what about Monash's success running a spool for as long as they did? With the propensity for these cars to lift inside-rears, I can't imagine that an open diff would be a better choice.

[scotty young Taylor Race]

That is a good point, They took a spool and developed a car around it. I think going outside the box is great. It is a huge learning experience. They spent a lot of time and testing , not to mention sets of tires to get where they are with a spool.
But, a differential whether it is open , ramp style or torque biasing ( torque sensing ) is a faster set up in applications that include off camber turns as well as tight corners and long sweepers.If you can generate loads of down force at lower MPH. An open diff is magic.

[PatClarke]

Don't forget the little team from Uni of Queensland won the Dynamics at the first FSG in 2006 with a spool. It can be done.

Pat

[Z]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by sachinpg:
http://s1-04.twitpicproxy.com/photos/large/512221753.jpg
this LSD is available to us... </div></BLOCKQUOTE>
Sachinpg,

Before you go rushing off and designing and building a spool, look at what you have at your feet.

It looks like you already have one CV, and I guess the other three CVs and two half-shafts are nearby. Now open up the diff housing and look at what is inside. You will probably find a bolt-on ring gear, and a pinion and its bearings. You don't need these, but you might be able to use them elsewhere (eg. as the steering, after some lightening http://fsae.com/groupee_common/emoticons/icon_wink.gif).

You should also find the "diff cage" with its "spider" and heavy duty "tapered roller bearings", some "planet gears", two "half-shaft gears" with their splines that perfectly match the CVs, and the "LSD clutch packs" (assuming it has them?). All this stuff is useful, expensive to buy, difficult to design, even harder to make, but you have it at your feet!

So I suggest you toss the external housing, bolt a large sprocket to the ring gear flange, make up some chassis mounts to carry the main diff bearings, and then fabricate a light sheet metal housing to keep the oil inside the rotating part.

Lastly, you can now run it as;
1. An LSD with its clutch packs.
2. An open diff, by removing the clutches and locking up the ramps.
3. A spool, by locking up the planets.

(BTW, these first world kids don't really understand that in some countries you just have to make do with whatever comes to hand (or feet). http://fsae.com/groupee_common/emoticons/icon_biggrin.gif)

Z

[scotty young Taylor Race]

Z....

Well put...very well put. This is what is so cool about this forum...

[sachinpg]

Thank you all for your replies

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Z:
Sachinpg,

Before you go rushing off and designing and building a spool, look at what you have at your feet.

It looks like you already have one CV, and I guess the other three CVs and two half-shafts are nearby. Now open up the diff housing and look at what is inside. You will probably find a bolt-on ring gear, and a pinion and its bearings. You don't need these, but you might be able to use them elsewhere (eg. as the steering, after some lightening http://fsae.com/groupee_common/emoticons/icon_wink.gif).

You should also find the "diff cage" with its "spider" and heavy duty "tapered roller bearings", some "planet gears", two "half-shaft gears" with their splines that perfectly match the CVs, and the "LSD clutch packs" (assuming it has them?). All this stuff is useful, expensive to buy, difficult to design, even harder to make, but you have it at your feet!

So I suggest you toss the external housing, bolt a large sprocket to the ring gear flange, make up some chassis mounts to carry the main diff bearings, and then fabricate a light sheet metal housing to keep the oil inside the rotating part.

Lastly, you can now run it as;
1. An LSD with its clutch packs.
2. An open diff, by removing the clutches and locking up the ramps.
3. A spool, by locking up the planets.

(BTW, these first world kids don't really understand that in some countries you just have to make do with whatever comes to hand (or feet). http://fsae.com/groupee_common/emoticons/icon_biggrin.gif)

Z </div></BLOCKQUOTE>
n thanks Z,
We have decided to go with an open differential, which is available to us. We think it is the best choice considering all other circumstances of our team.
this is it..
http://s1-03.twitpicproxy.com/photos/large/515711805.jpg

[Dewi Griffiths]

I must say Z has made a very good point there. However I would just like to share this quote from Pats column on the FSG website (JAN 2008).

"To present a car with a spool at Design will cause questions to be asked. Generally, the Design Judges will see the application of a spool as something of a 'cop-out', but if the subject is fully researched and the choice can be defended logically, there is no reason why use of a spool will cost Design Points."

I see no downside if you can justify it. Simplicity is often the way forward!

[Jon Burford]

Everybody makes valid points.
But with respect to getting parts. Motorsport is not a cheap business, parts can be sourced from all over the world and short of not having a functioning postal system, getting any purchasable component should not really be a problem. We buy our tripod joints from America rather than file them from a block or cast them, we do it because it's CHEAPER and more time effective. which is better. What does sense say that you do. If you can't affoard a diff, thats fine, we can't affoard lots of nice stuff, you could make one, lots of teams have, we don't feel we have the amount of team members needed to design and manufacture our own diff along with the rest of the car. So we buy a diff, just like we buy our engine, and chain etc etc. A spool is something that we could easiky fabricate ourselfs yet we choose not to. So we should be able to justify that too.


I like to see cars running different types of drivetrain. It makes for an interesting competition. A well sorted spool car can undoubtedly be better than a LSD car, but can a spool car keep up with an equally well sorted LSD car? the only way of really knowing is to run both on one car, with one driver who has enough time to learn both setups before a decision is made.
Who does this??
would be interesting to know.

[Dewi Griffiths]

Well said, Mr Burf! As I may have mentioned to you a few weeks ago, we're planning on buying a drexler diff in the summer (When the new budget comes in!) with the aim to compare it to the spool with back to back tests. We'll take as much data from the car as possible and try to eliminate as many variables as we can also.

I'll design diff carriers that can be bolted onto this years car and make it so a quick changeover is possible. We'll try accelerations, skidpads, sprint style course and compare times and data. With a bit of luck my driving will be relatively consistent too http://fsae.com/groupee_common/emoticons/icon_wink.gif

If anyone is interested in the results you will be more than welcome to see data/speak to me about it. I may start a new thread on the subject. I'm sure teams like Monash already have data on this subject so it'll be good to speak/share data with some of those guys too.

[Jon Burford]

yes, if you can do it. It will be a brilliant experience for you to drive both cars!
Also the data might give an answer once and for all, for your car at least..

[Dewi Griffiths]

Indeed it will be a brilliant experience. I haven't driven an FS car with a diff before so may prove to be an eye opening experience!

The only issue is that the suspension is being designed with the spool in mind. I'm sure we can make tweeks to the suspension to allow it to be more suitable to a diff though.

If you're lucky you may get an invite to that pretty special testing venue we have http://fsae.com/groupee_common/emoticons/icon_wink.gif Actually would you guys want to come for a blast in the stadium too?