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Differential Design

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breazy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Topic: Differential Design
    Posted: Jul/24/2014 at 9:59pm
I've taken on the Drive-train design for our team this year and through the last two years at competition i've noticed that our packaging is alot larger than most teams.  Now I understand that alot of those teams with the small form factor gear boxes are actually using spools while we are using an open differential.  So i'm trying to take on the task of designing a 1 way differential that will provide a form factor approximately the size of a spool  and will act like a spool under accelleration but will allow differentiation between the wheels while coasting or braking .  So. With that in mind, I've read alot on the internet about clutch type differentials and other diffs.  

My primary issue/question..without giving out my idea/design..Is there any reason for spider gears if you can find another method to transmit torque to the axles?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Jul/24/2014 at 10:52pm
Use this:

Ausssie cutting edge diff:



From Drexler motosport. very small and fully adjustable LSD.
Open diff for off roading is worse than spool.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/24/2014 at 11:08pm
I agree pedro on the necessity of a differential thus my designing one, that will hopefully have the characteristics i laid out in the initial post.  couldn't you theoretically eliminate the spider gears? if so that would eliminate a large section of the middle of the differential.

I'm also not looking for a product recommendation so much as trying to have a conversation about how clutch type diffs work and re-engineering one without the spider gears..Thats about 2 inches worth of space i want back for packaging and materials reasons.


Edited by breazy - Jul/24/2014 at 11:12pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FredC Quote  Post ReplyReply Direct Link To This Post Posted: Jul/24/2014 at 11:57pm
There's few types of differential that you could use/design, here's a little something where you could read more about different diff types. http://www.offroaders.com/tech/limited-slip-lockers-differentials.htm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2014 at 1:29am
I think you misunderstood me. I meant, if you will not run with a proper designed LSD/torsen you will have better results with spool in a baja sae. 
Open diff is the worse choice for a baja sae, close followed by the sh*ttness of an locker on-off.

The working principle of a LSD is using the axial component of the gears to create friction. Setting a preload and the clutch discs locking forces will will keep the car running like a spooled on straight track but progressively distribute the torque between the both wheels during the turns.

This already was thoroughly discussed in late topics, search for it.

I assuming that you know how a diff works, if you are not using a Torsen or gearless automatic locker and dont have spider gears, than thats not a differential.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote njgedr Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2014 at 8:47am
Take a look at the GKN Visco-Lok. It is a very cool viscous diff. It is used in the front axle of the CAN AM Renegade. It is a speed sensing diff that lends itself very well to baja. Weighs a ton, but it can be lightened up, I think it would be worth it. Unlike almost every other LSD, it can provide torque when a wheel is completely off the ground, just with a bit of latency. You don't want that Drexler diff for baja, it is crazy expensive, and will not lock when a wheel is the air, unless you add a ton of preload... but that would defeat the purpose. Drexler is super popular in FSAE though, because of the tunability and weight. For baja I would stay away from a Salisbury in general.  

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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2014 at 10:38am
Pedro, What i'm wondering is if someone were to develop another way to axially load clutch packs for a clutch type differential, would the spider gears be necessary.  

NJGEDR, I'm not just planning on removing the spider gears from a differential i know that won't work.  I'm designing my own concept that will not require the spider gears
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Post Options Post Options   Thanks (0) Thanks(0)   Quote njgedr Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2014 at 12:45pm
Interesting, will it be a true differential that balances torque or just a slipper clutch?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2014 at 2:39pm

In theory it will. But that is to be seen. Im looking at.doing a combination of a 1 way clutch type automotive diff and a ball differential seen more commonly in radio controlled.cars
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paasch Quote  Post ReplyReply Direct Link To This Post Posted: Jul/28/2014 at 4:00pm
Originally posted by Pedro UFPBaja Pedro UFPBaja wrote:

Use this:
Ausssie cutting edge diff:

Drexler is in Germany.

Quote
From Drexler motosport. very small and fully adjustable LSD.

The Drexler diff is a very fine unit, we've used it on our FSAE car for 4 years. But it's not a good choice for Baja simply because of the price, 2000€. That's about a 20 point hit in cost.

Quote Open diff for off roading is worse than spool.
Originally posted by Pedro UFPBaja Pedro UFPBaja wrote:

I think you misunderstood me. I meant, if you will not run with a proper designed LSD/torsen you will have better results with spool in a baja sae. 
Open diff is the worse choice for a baja sae, close followed by the sh*ttness of an locker on-off.

We've already had that debate Pedro. You lost.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote rasmuet Quote  Post ReplyReply Direct Link To This Post Posted: Jul/28/2014 at 4:43pm
I'm LOL'ing at the fact he is trying to start this debate again... LOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote njgedr Quote  Post ReplyReply Direct Link To This Post Posted: Jul/28/2014 at 4:52pm
My favorite setup: 

Wide Solid Axle + Really Stiff Swingarm = Torque Vectoring 

Very predictable, consistent and fast cornering. Articulation is over rated, especially for Baja. 

Salisbury makes no sense for baja even if you could afford it. Salisbury can only transmit whatever the preload torque is as soon as one wheel is off the ground, something that happens quite a bit in the woods. 

I have seen the OSU Cutting Brakes, which are clever, but I bet that car struggled in Mud and Sand. Still, Cutting brakes make the open diff or LSD seem plausible.





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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richie_Dagger Quote  Post ReplyReply Direct Link To This Post Posted: Jul/28/2014 at 5:31pm
Originally posted by njgedr njgedr wrote:

My favorite setup: 

Wide Solid Axle + Really Stiff Swingarm = Torque Vectoring 

Very predictable, consistent and fast cornering. Articulation is over rated, especially for Baja. 

Salisbury makes no sense for baja even if you could afford it. Salisbury can only transmit whatever the preload torque is as soon as one wheel is off the ground, something that happens quite a bit in the woods. 

I have seen the OSU Cutting Brakes, which are clever, but I bet that car struggled in Mud and Sand. Still, Cutting brakes make the open diff or LSD seem plausible.

OSU didn't seem to have a problem in the mudpit at Illinois maneuverability. I don't think anyone could round that cone on top of the hill as fast as OSU without a cutting brake. Not to mention that rock crawl run... I think they've proven that an open diff with a cutting brake is an extremely viable option. But I agree that a swingarm works great as well. I noticed a lot of cars having trouble at the mud pit/hill donut at Illinois maneuverability, but our swingarm car with poor ackerman/turning radius could just slide through it without any issue.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aztec Warrior Quote  Post ReplyReply Direct Link To This Post Posted: Jul/28/2014 at 7:14pm
What do you guys mean by "swing arm"? I'm picturing a swing arm and solid axle like the back of a quad?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richie_Dagger Quote  Post ReplyReply Direct Link To This Post Posted: Jul/28/2014 at 7:32pm
Originally posted by Aztec Warrior Aztec Warrior wrote:

What do you guys mean by "swing arm"? I'm picturing a swing arm and solid axle like the back of a quad?
Yes.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aztec Warrior Quote  Post ReplyReply Direct Link To This Post Posted: Jul/28/2014 at 10:19pm
Hmmm, wouldn't be my first choice...seems like it would be a bit of a rough ride (side to side) through natural terrain with off camber whoops an rocks. But is simple, and would probably do ok on a groomed M/C style track. To each his own...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Jul/29/2014 at 2:16am
Originally posted by paasch paasch wrote:

We've already had that debate Pedro. You lost.



well, lets just list the number "open-diffed" champions x "spooled" champions
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zglazer Quote  Post ReplyReply Direct Link To This Post Posted: Jul/29/2014 at 10:11am
That doesn't mean anything. The fact that only one team seems to have done it well doesn't diminish the fact that they did in fact do it well.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote njgedr Quote  Post ReplyReply Direct Link To This Post Posted: Jul/29/2014 at 10:46am
With a swing arm, you can sometimes "tricycle" your way over gaps, and things. The ride is questionable at best, but that has more to do with the unsprung weight than lack of articulation. I have yet to see a baja course that specifically punishes cars without articulation.

If your front suspension is set up right, the car doesn't roll very much on moguls.  

The weaknesses I found with the swingarm include: .
Weight, Ground Clearance, and getting it stiff enough. 

I think I have posted this before, but we ended up putting a sway bar of sorts onto our swingarm to make it even stiffer than it already was. Made a huge improvement!

Also, Chain guard is a nightmare to keep light and strong enough to be the bottom of the car. 

Still, I would definitely run the Swingarm again if I had the chance. In fact I am begging my Formula team to let me do it.... CVT too of course haha. 

As for the Open Diff with cutting brakes, I have to admit, I would love to try it, and no one is debating it is an advantage for Maneuverability. We had two separate brake pedals one for the front and one for both front and back. It added quite a bit of control for tight turns, but I imagine cutting brakes were at least twice as good. 

I remember the sand in the woods at Tennessee Tech, or maybe Auburn (they all blend together now) specifically I remember pushing diff cars out of the sand. I don't specifically remember OSU, or if OSU was even there, but I imagine the open diff would have struggled. 

Does Oregon still use cutting brakes, I remember them from 2011.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aztec Warrior Quote  Post ReplyReply Direct Link To This Post Posted: Jul/29/2014 at 7:10pm

"If your front suspension is set up right, the car doesn't roll very much on moguls.  "


That is sort of my point. If you are in "moguls" with a well working front suspension, the chassis will stay flat and stable while the wheels oscillate independently, both staying on contact with the ground, maintaining steering in the rough stuff. A well designed independent rear suspension will follow suit with both rear tires staying in contact with the ground and driving forward. Once you have a rigid swing arm, you are either forcing the chassis to rock back and forth with the terrain, or will always have one tire off the ground at all times. If the later is the case, then the rear suspension would be forced to cycle twice as fast, and probably result in a less that comfortable ride.  

Anyways, Sorry for going the wrong direction with this thread. just had a couple thoughts brought up earlier in this thread, none of which were worth starting a new thread.

Bob and Pedro, carry on...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/29/2014 at 9:59pm
Originally posted by rasmuet rasmuet wrote:

I'm LOL'ing at the fact he is trying to start this debate again... LOL

Hahahahaha. Paasch is very protective of the holy grail OSU lockable open diff / cutting brakes / reverse combo. 

It does work and they do it very well, but it is not what I would do and I would love to see them try something else since this is an SAE Collegiate Design Series. I personally liked getting to try something different every year and make it my own. Sometimes it worked for us (2010 and 2012) and sometimes not as well for any number of reasons, but it was always a blast and I could not have learned more.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote njgedr Quote  Post ReplyReply Direct Link To This Post Posted: Jul/30/2014 at 9:19am
I agree, a swingarm will never be as good as IRS for Moguls. My point is that you can make it acceptable by tweaking the front suspension. 

Besides, with IRS unless you run a diff you have to choose between mogul performance or ability to turn. I have seen plenty of cars with IRS that worked beautifully in a straight line, but under steered like pigs on the lawnmowing, I mean maneuverability course.... next comes the stiff rear springs or the roll bar, both of which make for a less than level mogul experience, but allow the thing to turn.

Also, for whatever reason, moguls are rare in baja, making articulation just unnecessary. 

The single best thing about the swingarm.... no CVs. 

 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Jul/30/2014 at 9:35am
Our suspension works like swing arm on straight and like a semi trailing in turns.
No matter what situation, the rear wheels are always perpendicular to the ground.








Edited by Pedro UFPBaja - Jul/30/2014 at 10:10am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Jul/30/2014 at 9:53am
You can make a spooled car turn well just making it overteer a lot.




Edited by Pedro UFPBaja - Jul/30/2014 at 10:28am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote njgedr Quote  Post ReplyReply Direct Link To This Post Posted: Jul/30/2014 at 10:21am
Pedro,

Video doesn't work for me. However, I am picturing a semi trailing arm car with little to no suspension droop in the rear unloading or lifting the inside tire so it can drift. It works great for turning, but it sacrifices mogul performance. 

Basically, to "make it oversteer a lot" you increase the rear roll stiffness. AKA Roll bar or stiff springs. Your other option, move your rear RC really high and drive a car with a ton of jacking that flips unpredictably.

My point is that IRS for Baja with a spool will always have to sacrifice articulation to make the thing turn. Which isn't that bad, because baja doesn't require or reward lots of articulation.

I think a lot of teams settle on IRS and spool, thinking that articulation is necessary, when really they would be just fine with a dependent rear suspension. The teams that just get their car together often have understeer problems, and it is usually because they haven't had time to learn that increasing the rear roll stiffness is how IRS makes turns. By the time the car starts to corner the RRS is so high it is coming up on typical swingarm stiffness anyway. 

I am not saying IRS is the wrong choice, I just don't want people making illusions about why it is an advantage.

BTW I have always loved the ufp cars, they look fast, simple.... and stiff.  

Maybe we should move this to the IRS vs. Swingarm thread... sorry Breazy



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richie_Dagger Quote  Post ReplyReply Direct Link To This Post Posted: Jul/30/2014 at 11:31am
Originally posted by Pedro UFPBaja Pedro UFPBaja wrote:

Our suspension works like swing arm on straight and like a semi trailing in turns.
No matter what situation, the rear wheels are always perpendicular to the ground.






Looks like the trailing arm torsion beam used on the first 5 or so generations of the VW Golf/Jetta. Still behaves like a beefy sway bar limiting your articulation.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Jul/30/2014 at 11:38am
It's not a twist beam,.
It's a DeDion tube variation, rolls freely.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RLM Quote  Post ReplyReply Direct Link To This Post Posted: Jul/30/2014 at 11:47am
Originally posted by breazy breazy wrote:

My primary issue/question..without giving out my idea/design..Is there any reason for spider gears if you can find another method to transmit torque to the axles?

how does suspension design have anything to do with whether you need spider gears in a diff or not????? 

Thread Hijack. 
if you would like to discuss suspension designs and argue all day about which is best, please start a new thread so I can ignore it. The simple answer is, Make everything work for your car and your driving style. There is no Right answer. 

I for one am curious about breazy's Idea and would like to hear more about it in his thread. Not listen to you guys back and fourth about IRS vs non IRS.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/30/2014 at 4:29pm
When watching this video while doing research  https://www.youtube.com/watch?v=ujsxq9WBllU
i began to wonder if i could replace the spider gears and use another method to create the added axial force to the clutch packs under acceleration.  As it is now the forces are transferred via differential case to the shaft that the cross spider gears run on.  This is kinda the basis of my question.  In this particular case I believe that one could remove the spider gears and with a redesign of the case/gear area be able to dramatically reduce the size of the differential.  

As for the other topic about suspension designs, I'm inclined to believe that the type of suspension you choose to deploy can determine what kind of diff you should run for optimal performance however it really all boils down to preference

about the open diff and cutting brake, If you have competent drivers with alot of time in a car, one can use a cutting brake to make an open differential lock up in instances where a tire is off of the ground or one tire is stuck in the mud.  This however is like i said predicated on good drivers with experience with the setup because to be truly successful with this method it needs to be second nature to the driver.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aztec Warrior Quote  Post ReplyReply Direct Link To This Post Posted: Jul/30/2014 at 8:56pm
Cool design Pedro. I haven't seen that setup before. Nuff said, don't want to upset RLM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/30/2014 at 9:04pm
Aztec, I don't mind the peripheral conversation, at least there's some discussion going on that doesn't envolve the stupid m12 whatever golf cart transmission that has like 4 threads on the first page.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paasch Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 1:12am
Originally posted by Soccerdan7 Soccerdan7 wrote:

Originally posted by rasmuet rasmuet wrote:

I'm LOL'ing at the fact he is trying to start this debate again... LOL

Hahahahaha. Paasch is very protective of the holy grail OSU lockable open diff / cutting brakes / reverse combo. 

It does work and they do it very well, but it is not what I would do and I would love to see them try something else since this is an SAE Collegiate Design Series. I personally liked getting to try something different every year and make it my own. Sometimes it worked for us (2010 and 2012) and sometimes not as well for any number of reasons, but it was always a blast and I could not have learned more.

Dan, I don't consider the lockable open diff a "holy grail", and in fact for teams not consistently in the top-10 I wouldn't recommend it, as they have other areas (project management, stress and fatigue analysis, suspension kinematics) where they can make more gain.

But done right, it does give the car a lot of versatility, and I'm not going to let Pedro spout out a bunch of uninformed opinion as fact without some challenge.

As for design, yes, it's the same basic layout, but every year our transaxle has gotten lighter, smaller and/or cheaper. Getting good reliable locker and reverse actuation is also a design challenge. Suspension design also gets more complicated as the car has to run well both open and locked. Did you get a chance to see Otto's 5 link rear last year?

Originally posted by njgedr njgedr wrote:

I have seen the OSU Cutting Brakes, which are clever, but I bet that car struggled in Mud and Sand. Still, Cutting brakes make the open diff or LSD seem plausible.

Low traction situations we lock the diff and run like a spool.

Originally posted by RLM RLM wrote:

I for one am curious about breazy's Idea and would like to hear more about it in his thread. Not listen to you guys back and fourth about IRS vs non IRS.

Is the main design goal just losing weight and smaller size? There's probably more that could be done with their spider gear current design. I see two potential downsides to breezy's design: reliability and power losses. I'd be leery of transmitting torque through friction. Lose friction and you lose torque. Also, BajaSAE cars don't have much power to begin with, so you don't want to waste any where you don't need to, and friction is wasted power. That's one reason, IMHO, that I don't think limited slip diffs make sense in a BajaSAE car: too much friction loss.


Edited by paasch - Jul/31/2014 at 1:57am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 2:06am
Originally posted by paasch paasch wrote:


Dan, I don't consider the lockable open diff a "holy grail", and in fact for teams not consistently in the top-10 I wouldn't recommend it, as they have other areas (project management, stress and fatigue analysis, suspension kinematics) where they can make more gain.

But done right, it does give the car a lot of versatility, and I'm not going to let Pedro spout out a bunch of ignorant opinion without challenge.

As for design, yes, it's the same basic layout, but every year our transaxle has gotten lighter, smaller and cheaper. Getting good reliable locker and reverse actuation is also a challenge. Suspension design get's more complicated as the car has to run well both open and locked. Did you get a chance to see Otto's 5 link rear last year?

We had a 5 link also, but only competed at El Paso.

Originally posted by paasch paasch wrote:

Originally posted by RLM RLM wrote:

I for one am curious about breazy's Idea and would like to hear more about it in his thread. Not listen to you guys back and fourth about IRS vs non IRS.

Is the main design goal loosing weight and smaller size? There's probably more that could be done with their spider gear current design. I'd be leery of transmitting torque through friction. Lose friction and you lose torque. Also, BajaSAE cars don't have much power to begin with, so you don't want to waste any where you don't need to, and friction is wasted power. That's one reason, IMHO, that I don't think limited slip diffs make sense in a BajaSAE car: too much friction loss.
 

It's a bit of both, primarily size though as if i can get the system to work properly, It would allow me to mill my transmission out of 2-12"x12" aluminum plates .  As for the lack of torque in the baja cars, I had thought of that and it is my assumption that if i were to make the ramps shallow enough in their inclination that it would be easier for the weaker engine to create the required axial forces.   The system would also have some amount of preload on it to ensure a minimum level of friction.


There's also a bit of a curiosity to it to see if i can make the design work and work well.  I'll be building some simple versions to test the friction/preload components when we return to school in late august before wasting money/sponsors time on machine work.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 5:51am
Well, the rear suspension is intimately related to transmission system, so i don't see many problems in this topic.

With a open diff very low power is lost to friction, but this power is transmitted for the wrong wheel during turns, and transmitted in a very unstable way on bumpy tracks.

About the spider gears, if don't use a OEM set, proper sizing it for Baja loads, using a good material such cemented 8620, you will get very small diff. 
With that ball diff concept i'm sure will be a lost friction-battle unless you use that special oil for toroidal cvt which becomes a polymer on pressure.


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Post Options Post Options   Thanks (1) Thanks(1)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 6:25am
P.S.

This is a badass good topic, very rare to see today here. 
It has almost all, crazy innovative ideas defended with technical argument, light off-tracks on the subject, guys defending the ideas they used in their projects. Dr. Paasch's tantrum. No bumb Indian questions. 
It's just missing Akron 98 2004 saying that we are talking bullsh*t and that he did much better and much simpler at 98 without doing any calculations. 
Wish all the topics were like this
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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 12:44pm
Pedro, It's not simply just a ball differential, It started off that way, My uses principles from clutch type differentials.  

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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 4:22pm
Originally posted by Pedro UFPBaja Pedro UFPBaja wrote:

Well, the rear suspension is intimately related to transmission system, so i don't see many problems in this topic.

With a open diff very low power is lost to friction, but this power is transmitted for the wrong wheel during turns, and transmitted in a very unstable way on bumpy tracks.



maybe i'm looking at things as to simplistic or just imagining them under ideal conditions, but if using a clutch type differential, when under load the axial force should be high enough to prevent friction losses at the clutch plates as they should be under static friction conditions.  Given this, Aside from bearing friction, where else would there be friction losses?  

This is the crux of my issue though is determining if i can with the engine we have access to  provide enough axial force through a ramp mechanism to create this 'static' scenario without having to preload the system so much that it is completely locked while under no load conditions.

the picture below is kinda how i plan to add the axial load, this uses the hardened shaft of the spider gear to add axial load via wedges, I just want to get rid of the spider gears.  Now I'm not talking about just taking spider gears out of a diff, i mean design one to work without them 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 7:02pm
Originally posted by paasch<div><br></div><div>Dan, I don't consider the <span style=font-size: 12px; line-height: 1.4;>lockable open diff</span><span style=font-size: 12px; line-height: 1.4;> a holy grail, and in fact for teams not consistently in the top-10 I wouldn't recommend it, as they have other areas (project management, stress and fatigue analysis, suspension kinematics) where they can make more gain.</span></div><div><span style=font-size: 12px; line-height: 1.4;><br></span></div><div><span style=font-size: 12px; line-height: 1.4;>But done right, it does give the car a lot of versatility, and I'm not going to let Pedro spout out a bunch of uninformed opinion as fact without some challenge.</span></div><div><span style=font-size: 12px; line-height: 1.4;><br></span></div><div><span style=font-size: 12px; line-height: 1.4;>As for design, yes, it's the same basic layout, but every year our transaxle has gotten lighter, smaller and/or cheaper. Getting good reliable locker and reverse actuation is also a design challenge. Suspension design also gets more complicated as the car has to run well both open and locked. </span><span style=font-size: 12px; line-height: 1.4;>Did you get a chance to see Otto's 5 link rear last year?</span></div><div><br></div>
[/QUOTE paasch

Dan, I don't consider the lockable open diff a holy grail, and in fact for teams not consistently in the top-10 I wouldn't recommend it, as they have other areas (project management, stress and fatigue analysis, suspension kinematics) where they can make more gain.

But done right, it does give the car a lot of versatility, and I'm not going to let Pedro spout out a bunch of uninformed opinion as fact without some challenge.

As for design, yes, it's the same basic layout, but every year our transaxle has gotten lighter, smaller and/or cheaper. Getting good reliable locker and reverse actuation is also a design challenge. Suspension design also gets more complicated as the car has to run well both open and locked. Did you get a chance to see Otto's 5 link rear last year?

[/QUOTE wrote:



I have seen many pictures of the 5 link and it is very nice. I may have even contributed a few thoughts during the design phase. I am not trying to put down what OSU does. Most of the consistently top teams make small incremental changes every year around the same basic architecture and concepts and Cornell is now to that stage too. 2012, 2013 and 2014 were built around the same winning setup with a few focused big changes and incremental improvements and adjustments on everything else.

I am just nostalgic of the days where we ran completely different cars every year where everything was done from scratch and looked nothing like the previous vehicles. This spawned the hydraulic rear steer, carbon fiber driveshafts, data acquisition, active antiroll bar, hybrid CVTs and vehicle dynamics that were comically different from car to car. Some of them worked great and some didn't, but I enjoyed that more than honing in on a winning configuration and picking and choosing a few limited major changes. Obviously the cars are all different but you don't see changes like a 6" wheelbase shrink or a frame that is front braced / rear braced or has a footbox or not happening every year.

I have seen many pictures of the 5 link and it is very nice. I may have even contributed a few thoughts during the design phase. I am not trying to put down what OSU does. Most of the consistently top teams make small incremental changes every year around the same basic architecture and concepts and Cornell is now to that stage too. 2012, 2013 and 2014 were built around the same winning setup with a few focused big changes and incremental improvements and adjustments on everything else.

I am just nostalgic of the days where we ran completely different cars every year where everything was done from scratch and looked nothing like the previous vehicles. This spawned the hydraulic rear steer, carbon fiber driveshafts, data acquisition, active antiroll bar, hybrid CVTs and vehicle dynamics that were comically different from car to car. Some of them worked great and some didn't, but I enjoyed that more than honing in on a winning configuration and picking and choosing a few limited major changes. Obviously the cars are all different but you don't see changes like a 6" wheelbase shrink or a frame that is front braced / rear braced or has a footbox or not happening every year.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 10:19pm
Does anyone know/happen to have a handy dandy list of atv's that have a clutch type differential?  I'm trying to figure out what i'm going to use for my clutch discs?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RLM Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 10:52pm
Don't know about atvs but you could try and find a motorcycle wrecker. The bikes I've torn apart all had several clutch discs in the clutch pack. A wrecker should be able to sell a used pack to you cheap or donate to at least try out your design then if it works search around for something new that meets your specs. Could also try a pick your own car yard. I believe audis with Quattro use multiplate clutches in the haldex coupling that sends torque to the rear wheels.

Here is a link to what they look like. Sorry can't post the photo from my phonecbr600 clutch pack

Edited by RLM - Jul/31/2014 at 10:57pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 11:14pm
I had totally forgotten about motorcycle clutch packs.  There's a Harley dealership around the corner from my house and they may have some in stock for me to at least get measurements off of. The Honda place in town may have that stuff also so I will check with them as well.  Thanks RLM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aztec Warrior Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 11:19pm

Bob, Is the Beaver's diff able to lock and unlock on the fly, under load? Or does the car have to stop? Also, is the turning brake integrated into tranny, or a basic turning brake plumbed in line that works with the existing brake rotors and calipers?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/31/2014 at 11:25pm
I know i'm not bob, but our turning/cutting brake was plumbed in with the regular brake system that way there's only one system to bleed.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paasch Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2014 at 12:21am
Originally posted by Aztec Warrior Aztec Warrior wrote:

Bob, Is the Beaver's diff able to lock and unlock on the fly, under load? Or does the car have to stop? Also, is the turning brake integrated into tranny, or a basic turning brake plumbed in line that works with the existing brake rotors and calipers?


We can lock and unlock on the fly, and in fact did so several times a lap at El Paso and Peoria. No secret to the design, it's similar to that of the Polaris Ranger front diff, with a sliding internally splined collar that locks the two sides together.

The turning brake is plumbed in line.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FredC Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2014 at 12:56am
Originally posted by breazy breazy wrote:

Does anyone know/happen to have a handy dandy list of atv's that have a clutch type differential?  I'm trying to figure out what i'm going to use for my clutch discs?

When we did our diff in 2012, we designed our own clutch pack made of layers of steel discs and bronze discs glued to those, I'll try to find a picture of it so you understand what we did.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richie_Dagger Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2014 at 3:28am
Originally posted by breazy breazy wrote:

I had totally forgotten about motorcycle clutch packs.  There's a Harley dealership around the corner from my house and they may have some in stock for me to at least get measurements off of. The Honda place in town may have that stuff also so I will check with them as well.  Thanks RLM
It won't be small enough for what you want, but it might get the gears in your head churning. The clutch used in my KDX200 is probably around 6" in diameter and almost 3" thick.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RLM Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2014 at 7:22am
The motorcycle clutches are large, but as a proof of concept they should do the trick. then I would go about designing and making your own. friction material is relatively cheap and easy to get. McMaster Carr has it available. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote breazy Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2014 at 12:32pm
Richie/RLM I agree that the're too large, however they're just large enough to see whats going on easily.  I think i'm going to have to look further into atv/automotive differentials as their clutch discs would have a more appropriate size for  what i'm after.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2014 at 12:43pm
50cc motorcycles has a perfect sized clutch set for this.
Not sure if is available in US, but you can buy easily in internet from China.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richie_Dagger Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2014 at 2:12pm
Or you can buy 2 Yamaha Blaster clutches from us. I think one may have been the culprit for our extremely smelly, gritty black transmission oil at Illinois, but it wasn't slipping!
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