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    Posted: Nov/11/2010 at 1:18pm
Much to the disagreement of my team, I would like to run a chain drive reduction, instead of our double reduction gearbox .  My main reasoning behind this is that our gear box has ALOT of rotating mass.  Also it is very heavy.  I think that with a chain drive we could reduce the weight considerably.

I need some help convincing them that this might be a good alternative to the double reduction.  I have done some research and I have found that most quads are running a 520 chain and that we could run a maximum of a 7:1 single reduction.  Our current box is a 8:1.  What I am thinking is that the chain would come straight off the CVT and then link down to the drive axle.  

What advise do you guys have far a team that has never done this before?  What has worked for you?  Is it possible to pull a 8:1 single reduction?  Where is a good place to buy sprockets? ( me and Google aren't getting along right now)  

Thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SDTech Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 1:25pm
Even with the reduced rotating mass, that seems kind of like a step backwards, especially in the efficiency department.  We ran a double reduction chain setup for a long time and it did work.  But there was a lot of messing with chain tensioners, and blown master links and sprocket hubs.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red_Beard Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 1:30pm
Originally posted by Minnesota Minnesota wrote:

Much to the disagreement of my team, I would like to run a chain drive reduction, instead of our double reduction gearbox .  My main reasoning behind this is that our gear box has ALOT of rotating mass.  Also it is very heavy.  I think that with a chain drive we could reduce the weight considerably.

I need some help convincing them that this might be a good alternative to the double reduction.  I have done some research and I have found that most quads are running a 520 chain and that we could run a maximum of a 7:1 single reduction.  Our current box is a 8:1.  What I am thinking is that the chain would come straight off the CVT and then link down to the drive axle.  

What advise do you guys have far a team that has never done this before?  What has worked for you?  Is it possible to pull a 8:1 single reduction?  Where is a good place to buy sprockets? ( me and Google aren't getting along right now)  

Thanks!


We did the chain case thing for a couple of years and worked well for us, but I'm glad we got away from it.  Everyone on our team realized chains belong on farm equipment or industrial equipment.  As far as running a single reduction your going to have an abortion of a final sprocket; we did this one year and it looked like an abortion on the back of the car.  The 420/520 combo worked pretty well for us if I remember correctly.

http://lmgtfy.com/?q=Chain+Sprockets Wink

Since you came here asking for opinions I would put my effort into lightening your gear box and optimizing that system than building a chain case.  Last year was our first year with a gear box and it worked excellent, and there was minimal weight difference between our gear box and chain cases.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SDTech Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 1:49pm
Hah, beat ya by 5 minutes Tongue
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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 2:00pm
At my school, all of our cars were double reduction chain systems.  We had tension issues, but nothing that was unbearable or impossible to work out.  We had a tensioning system that took care of things fairly well.  I liked chains because they were simple, strong, and it was easy to fine tune ratios.
 
I can't speak to single reductions from personal experience, but 7:1 or 8:1 is a pretty big jump. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 2:02pm
If i remember correctly, TTU had a single 9:1 reduction in 2009...I took prictures while they were explaining it to some people, looked REALLY great, really good engineering
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 2:44pm
Ohio State made the jump to gearbox from chains for the 2006 car and never looked back. A gearbox is a much more, running the risk of sounding like a professor, elegant solution in my opinion. Chains are exposed and can break if not setup perfectly. A solid gearbox design protects everything and keeps it all clean and lubed. Plus, I think packaging a gearbox is much easier than a chain drive. For our 2009 car, our rear brake caliper bolted straight to the box.

I'm not saying chains can't be done, obviously some very good teams have used them. But I'm not a fan.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 3:11pm
Originally posted by adrive7 adrive7 wrote:

Ohio State made the jump to gearbox from chains for the 2006 car and never looked back. A gearbox is a much more, running the risk of sounding like a professor, elegant solution in my opinion. Chains are exposed and can break if not setup perfectly. A solid gearbox design protects everything and keeps it all clean and lubed. Plus, I think packaging a gearbox is much easier than a chain drive. For our 2009 car, our rear brake caliper bolted straight to the box.

I'm not saying chains can't be done, obviously some very good teams have used them. But I'm not a fan.

All valid points.

However, depending on design, replacing a broken chain can be much easier and quicker than replacing a gear.

We've had chainboxes for the last 3 years and have bolted our brake calipers directly to the box so that's not a feature that's limited to only gearboxes.

If you do go to a chainbox, use a dynamic tensioner.

Just because the gearbox you currently run is heavy doesn't mean a chainbox is better.  It just means you need a lighter gearbox.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ErikHardy Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 3:21pm
+1 what joe said about packaging. The gearbox should be much smaller than the chain reduction.
How much does the current gearbox weigh vs. how much do you think a chain reduction will weigh, don't forget about all of the protective guards as well. Hopefully weight isn't your biggest argument as they should be very similar in the end as a combined system.
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red_Beard Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 3:23pm
Originally posted by SDTech SDTech wrote:

Hah, beat ya by 5 minutes Tongue



Well that's what happens when your workingWink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Minnesota Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 3:32pm
Originally posted by ErikHardy ErikHardy wrote:

+1 what joe said about packaging. The gearbox should be much smaller than the chain reduction.
How much does the current gearbox weigh vs. how much do you think a chain reduction will weigh, don't forget about all of the protective guards as well. Hopefully weight isn't your biggest argument as they should be very similar in the end as a combined system.
 
 

If I remember this right the gears are rated for 300-hp.  They do have some of the center part of the gear milled out to reduce weight, but they are still heavier then sin.  If I had to make a guess off the top of my head I would say it weighs somewhere in the neighborhood of 30 lbs.  

When you guys have used chains in the past have you used oil or no?  

I may need to review the rules but if oil is not used, we should be able to build a guard out of plastic.  This would be lightweight and give me some time to play around on the lazer to make fancy designs/air vents.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 3:41pm
I'll qualify any statements I have about chains by saying that our cars are all swing arms, and are limited to using chains in some fashion to get to the axle...
 
We don't use any lubrication other than oiling them every once in a while, i.e. there is no bath that the chain runs in.  We make all our chain guards out of plastic and they're very light.  We have packaged the shafts and sprockets on frame tubes, so there isn't really a chainbox/case.
 
I assume you're designing an IRS car?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ErikHardy Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 3:42pm

30lbs for a reduction unit is impressive. Any failures with it? If you haven't had any failures with the system and it only weights 30lbs it would be silly to change it. Also a litle chain lube does the trick for sprockets.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote dillon_b12 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 3:47pm
I think he meant that one single gear was 30 lbs.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Minnesota Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 3:56pm
Originally posted by ErikHardy ErikHardy wrote:

30lbs for a reduction unit is impressive. Any failures with it? If you haven't had any failures with the system and it only weights 30lbs it would be silly to change it. Also a litle chain lube does the trick for sprockets.


Take that 30 lbs with a grain of salt, I'm really really bad at guessing weights.  

Yes we do have some problems with it.  The gears rub against each other in the box, which creates a nice vibration that travels through the chassis.  One of the bearings is riding directly on the shaft, and last year at nationals that bearing failed and took us out of the race with 20 minutes remaining. The box leaks like a, well a gear box that doesn't seal.  At nationals we ended up pouring about 5 quarts of oil through it, it was getting so hot that you couldn't touch it.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ErikHardy Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 4:03pm
Originally posted by Minnesota Minnesota wrote:

Originally posted by ErikHardy ErikHardy wrote:

30lbs for a reduction unit is impressive. Any failures with it? If you haven't had any failures with the system and it only weights 30lbs it would be silly to change it. Also a litle chain lube does the trick for sprockets.


Take that 30 lbs with a grain of salt, I'm really really bad at guessing weights.  

Yes we do have some problems with it.  The gears rub against each other in the box, which creates a nice vibration that travels through the chassis.  One of the bearings is riding directly on the shaft, and last year at nationals that bearing failed and took us out of the race with 20 minutes remaining. The box leaks like a, well a gear box that doesn't seal.  At nationals we ended up pouring about 5 quarts of oil through it, it was getting so hot that you couldn't touch it.  
Well fix those problems with a new iteration of the design. It could have been much worse, as in it could have broke right before comp and you couldn't go. Those problems all sound pretty minor to me, everyone loves a screaming gearbox anyways. This is a good engineering problem, don't give up now.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Waffles Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 4:25pm
Originally posted by Minnesota Minnesota wrote:

I may need to review the rules but if oil is not used, we should be able to build a guard out of plastic.  This would be lightweight and give me some time to play around on the lazer to make fancy designs/air vents.  


That's an interesting contradiction.  For all exposed chains, you are required to have guarding with equivalency, but for a chain box, are you required to prove that your box meets equivalency?

What are peoples experiences with chain boxes, are you required to prove guarding equivalency?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 4:43pm

Yes.  In previous iterations our "box" was plate sides with plastic around the periphery, it was required to mee the powertrain guard spec.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/11/2010 at 9:25pm
I've had this argument discussion with other members of the team and I've boiled my points down to this:

A gearbox is the right answer for a "real" vehicle of this type.  They last longer, require less maintenance, and generally have a better "toughness" to weight ratio.

BUT...

The time and resources it takes to make a "real" gearbox are on  a whole 'nother level compared to a chain drive.  A lot of teams do, but we don't have the resources and talent to pull of a sweet ass gearbox.  We did build, IMO, a sweet ass little geartrain last year, barely.  It took more time, effort, and cost than I like to think about and was the main reason that we were only able to accumulate 3 hours drive time before Rochester.

In contrast a chain drive is easy to build, easy to design, and will work just fine.  (Note that we know some people just up the road that do awesome work with custom sprockets: Rebel Gears.  They are a family business that manufactures top quality sprockets in the heart of Tennessee. http://www.rebelgears.com/) They are typically adjustable in ratio and can be pretty dang small.  Our 2011 chain case should have the same footprint as our 2010 gearcase which itself couldn't get smaller because the cvt guard would run into the CV if the C-C got any shorter.

The one Jeremie referred to was a single reduction system that had an integrated adjustable engine mount, integrated brakes, and a huge f'ing sprocket.  The whole package tipped the scales at just over 16 pounds ready to bolt into the car.  That's been my favorite drivetrain we've done, but it was (and is) kinda finicky and very sensitive to chain alignment.  It is probably a little too light and has a little flex that doesn't help things.

So, after all that rambling and incoherent ADHD talk I say go for the gearbox if you've got the tools to pull it off.  Think it all through, there is a crap ton of work that we perhaps didn't realize.  Chains are fairly straightforward and easy to pull off and not at all bad.  We're doing a chain box this year and we don't suck?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asims Quote  Post ReplyReply Direct Link To This Post Posted: Nov/12/2010 at 12:09am
Originally posted by Minnesota Minnesota wrote:

If I remember this right the gears are rated for 300-hp.  They do have some of the center part of the gear milled out to reduce weight, but they are still heavier then sin.  If I had to make a guess off the top of my head I would say it weighs somewhere in the neighborhood of 30 lbs. 

....

Yes we do have some problems with it.  The gears rub against each other in the box, which creates a nice vibration that travels through the chassis.  One of the bearings is riding directly on the shaft, and last year at nationals that bearing failed and took us out of the race with 20 minutes remaining. The box leaks like a, well a gear box that doesn't seal.  At nationals we ended up pouring about 5 quarts of oil through it, it was getting so hot that you couldn't touch it.  


It sounds like this is all relatively minor things to fix if you already have the means to build a gearbox.  The heavy gears can be solved by proper gear strength analysis.  Figure out the maximum torque each gear will see, and design around that, plus a safety factor.  Check out Shigley's Mechanical Engineering or your equivalent design of machinery/component design textbook.  Shigley's steps you through the AGMA recommended gear calculations in a relatively painless way.  We designed our first gearbox last year with the methods in that book and it turned out pretty well.

If your gears are as heavy as you say, I'm betting you got a pretty big face width, right?  Our gears are pretty dang skinny, but if you make them out of a proper alloy (8620, 4340) and case harden them, they work just fine.  Last year we modified some stock gears from Martin Gear to our desired face width and had them case hardened.  They were made from an unspecified carbon steel, and lacked in strength due to the poor alloy, but they did survive competition.

The gears rubbing just sounds like a design oversight.  Put some spacers in between the gears, and make sure they don't wobble on their shafts.  The bearings sound like they could also benefit from a proper strength analysis (again, see Shigley's).  Don't cheap out on bearings, get something with a load rating that matches you needs.  And finally, the leaking things can be resolved many ways - good shaft seals on all input and output shafts, and an o-ring for the case joint would be my advice.

As a point of comparison last year's double reduction, forward-reverse gearbox weighed only 19 pounds dry.  This year we're adding a locking differential and it should still come out under 25 pounds


Edited by asims - Nov/12/2010 at 12:50pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Nov/12/2010 at 1:27am
You know, last year a car that had a single reduction chain drive here in brazil, was not only the fastest, but was better than FEI and the other teams that competed this year in traction.. (UFMG is the car, 2007 they competed in RIT, was the lightest baja i ever seen that could take the endurace. they did crazy things like nylon wheel hubs.)

not saiyng chain drive is good, but i can achieve a good performance, if done right.. also you don't need a double reduction,  if you choose the right sprockets,  with the great advantage of the possibility to change reductions.

 Chains can give a you a headache if you dont have a good tensioning system... and if the system is not well aligned.

you also have the problem of the sprocket hitting rocks or something like that... every choice have downsides.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote J.Cremer Quote  Post ReplyReply Direct Link To This Post Posted: Nov/15/2010 at 9:57am

For designing a chain & sprocket reduction, has anyone tried building the "case or support structure" in a way that each jackshaft is independent of the others.

For example, the jackshaft from the secondary to the first sprocket remains a rigid mount because it needs to be in order to keep the correct relationship for the cvt belt.  But the second jackshaft could be made in a way that the mounts slide along a groove in the mounting plate, creating a built in chain tensioning system. 
 
In the case of a double chain reduction the final sprocket (jackshaft) could possibly have the same style mount, but maybe this wouldn't be a good idea being that the axles are coming into connection at this point.
 
Has anyone tried something similar to this?  What are your thoughts?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red_Beard Quote  Post ReplyReply Direct Link To This Post Posted: Nov/15/2010 at 10:57am
Originally posted by J.Cremer J.Cremer wrote:

For designing a chain & sprocket reduction, has anyone tried building the "case or support structure" in a way that each jackshaft is independent of the others.

For example, the jackshaft from the secondary to the first sprocket remains a rigid mount because it needs to be in order to keep the correct relationship for the cvt belt.  But the second jackshaft could be made in a way that the mounts slide along a groove in the mounting plate, creating a built in chain tensioning system. 
 
In the case of a double chain reduction the final sprocket (jackshaft) could possibly have the same style mount, but maybe this wouldn't be a good idea being that the axles are coming into connection at this point.
 
Has anyone tried something similar to this?  What are your thoughts?


If you model the chain correctly and design your center distances correctly you shouldn't need to do this.  The last 3 iterations of our chain cases didn't use any tensioning devises and those cases had the fewest failures of all our cases. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote J.Cremer Quote  Post ReplyReply Direct Link To This Post Posted: Nov/15/2010 at 12:45pm
You mean to tell me you didn't get any stretching from your chains, causing them to loosen up? 
 
What type of chain are you using?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red_Beard Quote  Post ReplyReply Direct Link To This Post Posted: Nov/15/2010 at 3:09pm
Originally posted by J.Cremer J.Cremer wrote:

You mean to tell me you didn't get any stretching from your chains, causing them to loosen up? 
 
What type of chain are you using?


I didn't say anything about the chains not stretching or wearings, they did just like normal and when it was time they were replaced.   We've used 40, double 40, triple 40, 50, 420, 520, non O-ring and O-ring chain.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wishin4snow Quote  Post ReplyReply Direct Link To This Post Posted: Nov/15/2010 at 4:03pm
Originally posted by J.Cremer J.Cremer wrote:

For designing a chain & sprocket reduction, has anyone tried building the "case or support structure" in a way that each jackshaft is independent of the others.

For example, the jackshaft from the secondary to the first sprocket remains a rigid mount because it needs to be in order to keep the correct relationship for the cvt belt.  But the second jackshaft could be made in a way that the mounts slide along a groove in the mounting plate, creating a built in chain tensioning system. 
 
In the case of a double chain reduction the final sprocket (jackshaft) could possibly have the same style mount, but maybe this wouldn't be a good idea being that the axles are coming into connection at this point.
 
Has anyone tried something similar to this?  What are your thoughts?


Here is a little set-up I saw in one of our older designs. The rear Axle bearings were contained in a small housing with 4 bolt holes round the outside. The bearing was however not centered in the housing. The housing was then bolted to a box frame. The frame however had 8 holes for mounting. You could then rotate the bearing housing to different holes to change the center to center distance just enough to tighten the chain. Just design the housing to be offset enough to change the same amount as one link in your chain.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote J.Cremer Quote  Post ReplyReply Direct Link To This Post Posted: Nov/18/2010 at 12:51pm
wishin4snow - Sounds very interesting.

Any pictures available of the setup?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/18/2010 at 1:11pm
We did the same thing in our two stage reduction, except slots.  The cvt secondary/chain input shaft was fixed, but the other shaft could move to tension the system.  It worked well, but wasn't as good as a springloaded tensioner because you had to stop the car to go through the change.  Eccentric bearing housings work in the same manner.  We ran those on our axle last year. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wishin4snow Quote  Post ReplyReply Direct Link To This Post Posted: Nov/18/2010 at 5:36pm
J. Cremer,
  I don't have any actual pictures of the setup but I drew up this model represent what I mean.


Edited by wishin4snow - Nov/18/2010 at 5:36pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote J.Cremer Quote  Post ReplyReply Direct Link To This Post Posted: Nov/19/2010 at 8:52am
That's a really good idea, thanks for posting the pics.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wolverine Quote  Post ReplyReply Direct Link To This Post Posted: Jul/13/2013 at 10:12am
The doubt is related to the max input rpm for the smaller sprocket of the chain drive.
I am thinking to put a chain drive directly after the CVT for the reduction purpose. We are using CVTech CVT. Its overdrive ratio is 0.43:1. Though my research tells that it cant be reached we can still achieve an overdrive of 0.50:1 which makes the maximum output of driven pulley and hence the input of smaller sprocket 7600 rpm. The books i am referring to right now suggest that the input rpm can have a maximum value of 4000 rpm which makes my design invalid. Does anybody have any solution regarding this?
The plan for the drive train:
engine -cvt - chain reduction(3.6:1) -reverse and differential equipped gearbox with 4.17:1 forward ratio.
We ruled out the custom made gearbox because of time and money constraints.
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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/15/2013 at 4:28am
High ratio in baja never passes 1:1 even in the best designed powertrain. Hi ratio is not a worry, but the low.

The last car i worked on was a CVT + chain directly drive, ran well.








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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/15/2013 at 4:35am
note, that car uses GAGED and really small tires. With CVTech and larger tires you may need a huge sprocket.
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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/15/2013 at 6:08pm
We ran a CVTech for '13. Managed a GPS recorded top speed of 32.5mph with 23" tires and a 13.867 reduction. Doing the math that's a 0.58 low ratio assuming we made it all the way to 3800rpm which I doubt since it was running the legal governor setup. So less than 1:1 low is definitely possible. That said I wouldn't use a CVTech with a single chain reduction. You'll need a beyond huge final drive sprocket that will force you to raise your axles up pretty high killing ground clearance. Unless you're willing to sacrifice having a low ratio that will generate plenty of torque.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cujdubs Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2013 at 6:59pm
In our storage unit we found a drivetrain from '07 (if i remember right) that a was double reduction 
with the first reduction being a small gearbox and the second being a chain with the final drive sprocket mounted to an aluminum case housing a torsen diff.  with the excetion of a really heavy mounting structure the assembly was pretty light and compacts and fabrication was probably pretty easy. (oh and a CV-Tech came off the engine)
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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/16/2013 at 1:12pm
Something to keep in mind about chain drive; it might not be as efficient or fancy as gears but if you want to change the overall gear ratio for any reason its easy w/ chain.  If your gear reduction has the wrong overall ratio, even by a little, forget about the efficiency gain over chain.
 
Snapped chain = $10 and a few minutes
Stripped gear box = done
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/16/2013 at 1:38pm
Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

Something to keep in mind about chain drive; it might not be as efficient or fancy as gears but if you want to change the overall gear ratio for any reason its easy w/ chain.  If your gear reduction has the wrong overall ratio, even by a little, forget about the efficiency gain over chain.
 
Snapped chain = $10 and a few minutes
Stripped gear box = done
 
 
 
I whole heartedly agree.  It is super easy to tune ratios, and replacing broken parts is easy too.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Rivera Quote  Post ReplyReply Direct Link To This Post Posted: Jul/16/2013 at 2:08pm
Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

Something to keep in mind about chain drive; it might not be as efficient or fancy as gears but if you want to change the overall gear ratio for any reason its easy w/ chain.  If your gear reduction has the wrong overall ratio, even by a little, forget about the efficiency gain over chain.
 
Snapped chain = $10 and a few minutes
Stripped gear box = done
 
 


This is what we did the first few years we had a team. Once we were more confident in the ratio we wanted, and more confident in our machining skills we moved on to a gearbox
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RLM Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2013 at 5:24pm
just to put in our 2 cents, we ran a gear box in '12 and ran the same reduction in '13 but in a chain case and we saved 18 lbs off the car, most of which was rotating. This gave us much better acceleration, the box was smaller, and the ratio is now easy to change. the cost difference to us was about $600 which for a relatively low budget team is a lot as well. We run a large ratio tho so with a smaller ratio, the changes wouldn't be quite as drastic.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote StasS Quote  Post ReplyReply Direct Link To This Post Posted: Nov/04/2013 at 9:09am
did you find an answer to that?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote justin_6649 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/13/2013 at 2:30pm
ive always like the idea of machining a casing that you could assemble (in case you cant get your hands on a big enough piece of billet) and running a dual reduction chain drive. dont overlook double or triple strand chain.

The end result can have great performance...it will be compact, you can adjust ratios easily, the reliability is very good, it might weigh a very little bit more than most gear boxes but for any start up team (or already existent team for that matter) i think its a good idea (due to reliability and lets face it, how many bajas dont finish endurance..)

i am not saying that it is better than a properly designed gearbox though
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RLM Quote  Post ReplyReply Direct Link To This Post Posted: Nov/13/2013 at 4:42pm
What you are describing is essentially what we have. the weight savings over gears we have calculated are quite significant if designed properly. the one tip i have about these though (cant say too much to protect our design) is to keep your tolerances tighter than you normally would. We had some trouble with snapping master link clips, this was corrected with a 2 thou spacing shim on one of the shafts. The closer the center distances of the shafts, the tighter the tolerances need to be. other than that it's easy to design and build a super light reduction case very cheaply and that is easily serviceable and very reliable.
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