Welcome to the North American Subaru Impreza Owners Club Tuesday December 12, 2017
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Transmission (AT/MT) & Driveline

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 01-04-2009, 03:40 PM   #226
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default

Good deal. Sorry I haven't been posting much recently. I have 5 plates completely finished and I got a call from my bolt supplier that my bolts came in, so all I have to do is go pick them up Monday and get each plate packed into a nice box be to ready for shipping.

I'll still have to figure out how Dylan wants to handle ordering standard plates or plates with the addtional full bolt kit. I'd have to order the additional bolts for the bolt kits, but it won't add much time. Things were a bit sluggish with the holidays in the way, but from here on out, I should be able to get those bolts pretty quickly after ordering, so that would only make it about a 3-5 day backorder for folks who want the full kit.
* Registered users of the site do not see these ads.

Last edited by jhargis; 01-05-2009 at 12:29 PM.
jhargis is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 01-04-2009, 06:06 PM   #227
DrewDeezy
Scooby Specialist
 
Member#: 160279
Join Date: Sep 2007
Chapter/Region: NWIC
Location: Richland, WA
Vehicle:
2004 STi
Crawford Performance

Default

looking good. not looking forward to having to drop my transmission though to put this in..
DrewDeezy is offline   Reply With Quote
Old 01-04-2009, 09:14 PM   #228
thejaredhuang
Scooby Specialist
 
Member#: 86206
Join Date: May 2005
Chapter/Region: SCIC
Location: Irvine
Vehicle:
2006 WRX Wagon
Blue

Default

Are you going to test fit the bolts to make sure they fit?
thejaredhuang is offline   Reply With Quote
Old 01-05-2009, 03:34 AM   #229
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default

They'll fit... Already measured everything. And the 4 bolts that go through the plate have been confirmed, I actually ordered a set a while back and they fit perfectly. I will do a quick test fit though just to make sure on the full bolt kit.
jhargis is offline   Reply With Quote
Old 01-05-2009, 12:58 PM   #230
skimobile
Scooby Specialist
 
Member#: 92114
Join Date: Jul 2005
Chapter/Region: NESIC
Location: Westerly, RI
Vehicle:
03 WRX (NAVY Camo)
in"Special Ed." Run Group

Default

Got any pricing yet?
...just getting ready to pull the tranny so the timing would be perfect : )
skimobile is offline   Reply With Quote
Old 01-05-2009, 05:24 PM   #231
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default

Quote:
Originally Posted by skimobile View Post
Got any pricing yet?
...just getting ready to pull the tranny so the timing would be perfect : )
Sorry, but since I am not a vendor, I technically can't discuss pricing. Though DS1 Motorsports is aware that I have some plates ready to send, so it shouldn't be too long before they set up a thread.
jhargis is offline   Reply With Quote
Old 01-05-2009, 05:27 PM   #232
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default

I figure some of you guys might get a kick out of this. I wasn't aware of it until now when I got a full labeled package of bolts in, but the bolts are made in Italy. No wonder they're so expensive, being made in the land of Ferraris and Lamborghinis and such.

jhargis is offline   Reply With Quote
Old 01-05-2009, 10:08 PM   #233
skimobile
Scooby Specialist
 
Member#: 92114
Join Date: Jul 2005
Chapter/Region: NESIC
Location: Westerly, RI
Vehicle:
03 WRX (NAVY Camo)
in"Special Ed." Run Group

Default

Did you make sure they are the proper hardness rating for the application?
skimobile is offline   Reply With Quote
Old 01-06-2009, 08:17 AM   #234
drkramm
Scooby Specialist
 
Member#: 159156
Join Date: Sep 2007
Chapter/Region: Tri-State
Location: catasauqua, pa
Vehicle:
2007 wrx
wrb

Default

maybe just the sticker was made in Italy lol
drkramm is offline   Reply With Quote
Old 01-06-2009, 12:37 PM   #235
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default

Quote:
Originally Posted by skimobile View Post
Did you make sure they are the proper hardness rating for the application?
These are metric class 10.9 which are stronger than the stock class 8.8 hardware. Yield strength is quite a bit higher. In other words, these bolts are not prone to stretch/flex as much as the stock bolts would. You'd often see class 10.9 hardware on higher end cars (I noticed in the past that my Mercedes 190E used a lot of 10.9 on the engine and transmission). A lot of less expensive cars do not use such high grade hardware though... Class 10.9 bolts can often be double or even triple the cost of 8.8s (depending on size/type) and if you add a couple of dollars in hardware cost over thousands and thousands of units produced, I'm sure you can see how that can add up very quickly for a manufacturer.

A close comparison would be a domestic manufaturer using SAE grade 5 bolts instead of grade 8... Most of you are probably more familiar with SAE grades than metric grades. BTW metric class 8.8 is pretty close to SAE grade 5 and class 10.9 is a tiny bit stronger than SAE grade 8 if that helps.

Now I don't blame Subaru specifically, their engineers and bean counters probably got together and did a cost analysis... In which case, the bean counters asked "Where can we cut costs without conspicuously affecting quality, can we use cheaper bolts in the driveline and still be ok with 227hp?" to which the engineers replied "Yeah, it'll hold together well enough for the level of power that will be applied to it." Remember that these cars are engineered to stay alive for a while with an average point A to B driver and without modification. But then crazy reckless folks like you and me come along and start bolting on bigger turbos or cranking up the boost on a car that we drive spiritedly and other parts start failing under the added stress.

Quote:
Originally Posted by drkramm View Post
maybe just the sticker was made in Italy lol
Haha, now there's an idea. I should have the logo that goes on the plate printed in Italy to make my product more exotic

Last edited by jhargis; 01-07-2009 at 02:43 AM.
jhargis is offline   Reply With Quote
Old 01-07-2009, 01:55 AM   #236
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default



jhargis is offline   Reply With Quote
Old 01-07-2009, 09:13 AM   #237
axelthrasher
Scooby Guru
 
Member#: 144779
Join Date: Mar 2007
Chapter/Region: MWSOC
Location: In the land up over
Vehicle:
200X ZOMG a car 100%
crabon fibre girlfrendorz

Default

Looking good. And I'm looking forward to getting my hands on one of them.
axelthrasher is offline   Reply With Quote
Old 01-07-2009, 11:54 AM   #238
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default

Quote:
Originally Posted by axelthrasher View Post
Looking good. And I'm looking forward to getting my hands on one of them.
Thanks Dustin, they do look really sharp with the clearcoat on there... really shiny (I like how you can see the relfection of the cross bracing on the plate).

I remember you mentioning that you'd like to get all of the braces at one time... Shouldn't be too much longer on those diff braces. Now that I have the first run of the plates down, I'll move on to making a production jig for the driver side diff brace in the next couple of days so I can start pumping those out. The holidays really held me up more than I had expected, so I still have to get a design firmed up for the passenger side diff brace, but it shouldn't be too huge an undertaking. Every time I make a plate, I get a little quicker at it too, so that helps free up a little more development time (in the pie chart of time that is my life).
jhargis is offline   Reply With Quote
Old 01-14-2009, 02:50 AM   #239
Mr_Snips
Scooby Specialist
 
Member#: 152117
Join Date: Jun 2007
Chapter/Region: SCIC
Location: Hills Have Eyes
Vehicle:
2012 Ford F150 ECO
White

Default

will these fit the RS trans?
Mr_Snips is offline   Reply With Quote
Old 01-14-2009, 11:19 AM   #240
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default

The main reinforcement plate will, though I'm not 100% sure on the diff brace, I haven't had a chance to test fit on to a push-clutch trans yet.

Update for the rest of you that are waiting: Sorry it's taking so long, I'm just waiting on Dylan to get some free time together so we can discuss the last little details and get the first 5 sold, but I know those guys are pretty swamped over there @ DS1 and they're probably sick of me bugging them anyways

Also, I should have the production jig for the diff brace finished today so I can start a run of those soon as well + the full bolt kit option for the main reinforcement plate is put together and all of the bolts fit nicely... In fact, I have a full bolt set holding my spare trans together

Last edited by jhargis; 01-14-2009 at 11:26 AM.
jhargis is offline   Reply With Quote
Old 01-19-2009, 07:46 PM   #241
Dave_RalliSpec
Scooby Newbie
 
Member#: 45702
Join Date: Oct 2003
Default

In 2003 we developed a test rig for measuring case distortion and worked with some Drexel engineering students doing their senior design project. The transmission was attached to an engine block in normal fashion and the input shaft fixed to the crankshaft. The whole assembly was solidly bolted into the test rig and the output shafts were fixed to the rig so they could not rotate. Also the center diff was replaced with a spool that directly connected the output shaft to the front pinion. Input torque was via a torque wrench and a special socket which allowed the torque wrench to apply force directly to the crankshaft.

The case was strain gauged at several critical locations and the the torque applied in fixed steps while case distortion was measured. The limit of the torque wrench was 450 ft-lbs. Even at the maximum torque the case distortion at the areas we measured was minimal (<.0005"). We did not measure the areas of the case forward of the front support bearing (i.e. the bellhousing) because it didn't seem to be relevant.

After this we drilled a hole in the side of the case and built a fixture to allow a dial indicator to be placed on the main shaft at a point approximately centered between the support bearings. The test was repeated. At 250 ft-lbs the shaft had deflected sufficiently to put the 3rd gear separation outside the recommended range by most gear manufacturers for this type and size of gear. At 450 ft-lbs the deflection was more than 4 times the recommended gear separation.

Granted these deflections were under a static condition and under dynamic conditions are most likely a good bit lower. But with sufficient traction and high enough shockloading the deflections probably peak fairly close to these levels.

My personal opinion is that the real issue lies in several areas:

1. Main shaft rigidity.
2. Undersized shaft support bearings not designed for the loads people are subjecting the transmission to.
3. Insuficient rigidity of the bearing support locations in the case. I think the bearing races are capable of moving within their supports and possibly the supports themselves distort somewhat (but not enough to create a measurable distortion on the outside of the case).

On some of the higher power level cars where we've torn down the transmission we have found evidence of fretting at the bearing supports which seems to indicate that the bearing races are moving relative to the case.

Without addressing the above issues I think the only real option is to make the gear teeth strong enough and less affected by significant gear separation that they will support the particular torque loadings. Also something like the Isotropic Superfinishing process, which reduces the friction between the teeth and therefore lowers the tooth bending loads and the torque reactions can be beneficial in allowing the gears to operate at increased torque levels without increasing the gear deflections.

I am not saying that these braces are not going to help. But I did want to share the research that we had done and the conclusions we had come to. I have thought a lot about what type of modifications or improvements could be made and the conclusion I came to was that the only way to make serious improvements would involve substantial and complex machining of the internal parts of the case in order to be able to install a steel bearing support plate in place in or in combination with the aluminum structure of the case. A less effective but more realistic option was to dowel pin the case halves at the bolt locations near the bearing supports.
Dave_RalliSpec is offline   Reply With Quote
Old 01-19-2009, 07:52 PM   #242
Unabomber
👏 Big Ron 👏
Moderator
 
Member#: 18062
Join Date: Apr 2002
Chapter/Region: MAIC
Location: I can save you a ton of cash
Vehicle:
on car parts so PM
me b4 j00 buy

Default

Thanks for your quality input Dave. I just wish you'd hang out here more often.
Unabomber is offline   Reply With Quote
Old 01-19-2009, 07:59 PM   #243
Unabomber
👏 Big Ron 👏
Moderator
 
Member#: 18062
Join Date: Apr 2002
Chapter/Region: MAIC
Location: I can save you a ton of cash
Vehicle:
on car parts so PM
me b4 j00 buy

Default

Thanks for your quality input Dave. I just wish you'd hang out here more often.
Unabomber is offline   Reply With Quote
Old 01-19-2009, 09:21 PM   #244
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default

Quote:
Originally Posted by Dave_RalliSpec View Post
...The case was strain gauged at several critical locations and the the torque applied in fixed steps while case distortion was measured. The limit of the torque wrench was 450 ft-lbs. Even at the maximum torque the case distortion at the areas we measured was minimal (<.0005"). We did not measure the areas of the case forward of the front support bearing (i.e. the bellhousing) because it didn't seem to be relevant.

...

Without addressing the above issues I think the only real option is to make the gear teeth strong enough and less affected by significant gear separation that they will support the particular torque loadings. Also something like the Isotropic Superfinishing process, which reduces the friction between the teeth and therefore lowers the tooth bending loads and the torque reactions can be beneficial in allowing the gears to operate at increased torque levels without increasing the gear deflections.

I am not saying that these braces are not going to help. But I did want to share the research that we had done and the conclusions we had come to. I have thought a lot about what type of modifications or improvements could be made and the conclusion I came to was that the only way to make serious improvements would involve substantial and complex machining of the internal parts of the case in order to be able to install a steel bearing support plate in place in or in combination with the aluminum structure of the case. A less effective but more realistic option was to dowel pin the case halves at the bolt locations near the bearing supports.
Great input Dave, I never realized that anybody outside of maybe Subaru actually did any strain-gauge testing. I messed with strain gauges in a lab for an electrical metrology class during the semester before my last class... very cool stuff. Also nice to get some input from somebody that did this with the trans actually bolted to the engine block, that could potentially make a difference.

Out of curiosity, in which direction did you orient the strain gauges and at which spots (this is quite important)? Best I could think of doing it would be to place 2 rather near each other at each point of measurement... One aiming front to rear and one top to bottom. That would actually give you the direction in which the material is stretching (if it's stretching along only one "axis" of measurement, you'd have one high measurement from the gauge that is being stretched lengthwise, and a much lower measurement from the gauge that is oriented 90 degrees off). Torsional distortion would be measured most prominently with the gauge applied diagonally (think candy cane). Whereas placing only one gauge at each point could miss a lot of distortion if the matarial is stretching in a different direction. I'm really curious on this one because I measured a relatively small amount of distortion along the top of the trans, much more twist that showed itself in measurements along the bottom. The other shortfall of strain gauge testing is that it only gives you a snapshot of how much distortion you get right under the footprint of the gauge... so for a smaller strain gauge, .0005" of stretch under the footprint of a small strain gauge spread over the legnth or height of the transmission in it's entirety sounds like something that's right about in agreement with my measurments. Torsional flex is rarely focused in one spot, but rather found as a cumulative amount of distortion over a larger portion of the material, in other words the material doesn't neccesarily have to stretch very much in one spot to see a fair amount of twist in the assembly as whole. Take for a example a peice of paper, you can distort it rather agressively without actually stretching the paper... Strain gauges primarily measure stretch, so the measurement from the strain gauge would be fairly small even though the piece of paper to which it is fixed could be quite aggressively distorted... The top surface of the gauge compresses while the bottom surface stretches, and you don't get a huge change on the ohm meter since the overall change is the gauge's resistance is relatively small.

Funny thing is, the largest point of distortion in the case appeared ahead of the front support bearings, where the pinion gear is applying pressure to the ring gear up front, which is in turn putting a tremendous amount of load on the driver's side of the case in that area. I'm kind of bummed that you guys didn't measure that part, seems to be where a couple of people have actually managed to crack the case

I too noted a large amount of input shaft deflection... It sure twists a lot... At 300 ft./lbs. it had twisted to a point that I really didn't feel comfortable going beyond that level of input torque. I was trying not to destroy the gearbox as it is my personal back up.

I agree with you completely that it's not going to be a giant increase in strength... When it comes down to it, the gear teeth are just too small in a stock transmission to handle the kind of shaft deflection that we've both noted in our respective test sessions. I do personally think the diff brace will make a difference for the high power guys, just because the case seemed to really expand there. As for the plate, it's there simply to further strengthen the gear's foundation and it comes with better hardware that should at least to some small extent decrease in flex near those front bearings.

Again really good professional input and really well said, BTW I'm jealous that you got to mess with those strain gauges

Last edited by jhargis; 01-19-2009 at 09:52 PM.
jhargis is offline   Reply With Quote
Old 01-19-2009, 09:26 PM   #245
Dave_RalliSpec
Scooby Newbie
 
Member#: 45702
Join Date: Oct 2003
Default

Quote:
Originally Posted by Unabomber View Post
Thanks for your quality input Dave. I just wish you'd hang out here more often.
I know....just too dang busy! Its 8:30PM and I am still at work and really should be out in the shop finishing something.

I got a call today asking me about the "RA gears made in China" rumor so I was trying to find the thread they were talking about. Instead I've been sidetracked reading all these other threads I've missed out on the past year!
Dave_RalliSpec is offline   Reply With Quote
Old 01-19-2009, 09:56 PM   #246
Dave_RalliSpec
Scooby Newbie
 
Member#: 45702
Join Date: Oct 2003
Default

Quote:
Originally Posted by jhargis View Post
Out of curiosity, in which direction did you orient the strain gauges and at which spots (this is quite important)?
Well to be honest, I was more a sponsor and facilitator of this project than anything. One of the students is a good friend of mine and also was an original founder of RalliSpec together with his brother and myself. He left the business and went back to school to finish his degree (now works for Lockheed). I supplied the transmission and helped build the test rig and gave some input. But he and his partners took responsibility for deciding how to perform the actual tests. It was their project after all. If I recall correctly there were at least 4 strain gauge locations if not more. I know that one or two were located across the seam between the case halves. I am half guessing on the actual measurements and I don't know whether they looked at the cumulative measurements to estimate how much torsional twist there was. But I did discuss it with them afterwards and at the time there was rampant speculation about case flex and all that so they were expecting something substantial and they told me it was barely measurable and that they did not feel case distortion was a major contributor to the failures. They were pretty shocked by the severity of the main shaft deflection, though.

Improving the hardware...especially the 10mm dia. becauase of their location...is definitely a small but worthwhile incremental upgrade. I had considered at one time having ARP make a bolt set but decided the cost to benefit ratio probably wouldn't be worth it. However, if I were building a cost-no-object 5-speed for someone I would definitely put the idea out there for the customer. Most times people willing to spend big bucks on transmission upgrades are simply going to step up to a 6-speed. To really take advantage of a high tensile bolt set, though, I suspect that re-line boring the bearing saddles would be necessary if you increased the torque values by any significant margin. Similar to the problems associated with the ARP block bolt set that really requires line boring the mains back to spec.
Dave_RalliSpec is offline   Reply With Quote
Old 01-19-2009, 11:22 PM   #247
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default

Quote:
Originally Posted by Dave_RalliSpec View Post
Well to be honest, I was more a sponsor and facilitator of this project than anything. One of the students is a good friend of mine and also was an original founder of RalliSpec together with his brother and myself. He left the business and went back to school to finish his degree (now works for Lockheed). I supplied the transmission and helped build the test rig and gave some input. But he and his partners took responsibility for deciding how to perform the actual tests. It was their project after all. If I recall correctly there were at least 4 strain gauge locations if not more. I know that one or two were located across the seam between the case halves. I am half guessing on the actual measurements and I don't know whether they looked at the cumulative measurements to estimate how much torsional twist there was. But I did discuss it with them afterwards and at the time there was rampant speculation about case flex and all that so they were expecting something substantial and they told me it was barely measurable and that they did not feel case distortion was a major contributor to the failures. They were pretty shocked by the severity of the main shaft deflection, though.

Improving the hardware...especially the 10mm dia. becauase of their location...is definitely a small but worthwhile incremental upgrade. I had considered at one time having ARP make a bolt set but decided the cost to benefit ratio probably wouldn't be worth it. However, if I were building a cost-no-object 5-speed for someone I would definitely put the idea out there for the customer. Most times people willing to spend big bucks on transmission upgrades are simply going to step up to a 6-speed. To really take advantage of a high tensile bolt set, though, I suspect that re-line boring the bearing saddles would be necessary if you increased the torque values by any significant margin. Similar to the problems associated with the ARP block bolt set that really requires line boring the mains back to spec.
Ahh... I would not expect much stretch across the seams as those spots have the greatest concentrations of bolts holding them together. To be honest, the outcome of my testing was different from what I was originally expecting, rather than finding much expansion of the case near the bearing locations, my data showed a much more pronounced twist to the case as a whole, and the only spot that I suspect would really clearly show up on a strain gauge would be where the case actually expands under the front ring gear... Strain gauges aren't always great at sensing a twist or bend in a material, but they can be quite good at measuring where the material is expanding or stretching along one plane.

Very good point on higher bolt torque specs. The guys at DS1 and I discussed this as well. I wouldn't recommend more than maybe a 10% increase over stock torque specs, and I'd only recommend an increase when using the full bolt kit to ensure that increased clamping force is evenly spread throughout the case. It's not uncommon to see a +/- 10% tolerance on bolt torque specs even in many modern manufacturing processes, so I think that's a fairly safe figure... Going beyond that could be possible, but that's navigating into uneasy waters. I definitely don't want to qoute a spec that is really likely to put the bearing bores out of round. Measuring bolt stretch is actually a better way of going about it, the relationship between bolt torque and actual claimping force can be surpsingly different from bolt to bolt, but short of the space program and the aviation industry, how many manufacturers are really willing to measure bolt stretch (not many)?

I suppose that if a customer was willing to have the case line bored and take every ounce of advantage out of the class 10.9 full bolt kit, they could probably take the bolts right up to the max (or at least nominal) recommended torque, which is just shy of 40% higher than the stock hardware's max recommended spec.

Thanks for the quick reply, and again, great input. It's really cool to have had some very reputable Subaru guys chime in on this thread!
jhargis is offline   Reply With Quote
Old 01-20-2009, 08:08 PM   #248
Dave_RalliSpec
Scooby Newbie
 
Member#: 45702
Join Date: Oct 2003
Default

I am sure the loads on the case are quite complex. The case has to absorb at least the following reaction forces if not many more I am overlooking:

1. There is a torsional rotation around the axis of the crankshaft/main shaft/propshaft which is mostly absorbed by the drivetrain mounts. I suspect any twist in the case caused by this is negligable when the mounts are rubber. A solidly mounted drivetrain would be another story all together.

2. There is a significant separation force between the engaged gear pair. This is what we measured by placing a dial indicator on the main shaft. I am sure whatever forces are not lost in the deflections of the shaft components are being directed into the bearing supports and surrounding case structure.

3. There is an axial load component when the gears are helically cut and this is directed along the shaft. Depending on the helix angle it could be a fairly high percentage. This is why the rear support bearings on both shafts (at least on turbo applications) are double row tapered roller bearings.

4. There is some twisting load on the case as the gear teeth try to walk up each other. This could manifest itself in a distortion of the bellhousing since the bearing support structure probably stiffens the center part of the case quite a bit while the bellhousing has less material and is much less rigid.

5. The front diff and the rear transfer gears also subject the case to various reaction forces generated by those engaged gear teeth. In the case of the ring and pinion most of the forces are in the direction of the sides of the case. I don't think you would see the bellhousing twisting but there may be substantial forces causing the bellhousing to egg-shape. The side axles also generate a reaction force which must be controlled by the drivetrain mount although in a fore-aft direction along the axis of the transmission.

6. As you commented the shafts, particularly the main shaft which is long and slender, will twist like a torsion bar although I don't know that this would create any significant load on the case itself.

As for the seam...any bolted connection is going to be the weakest link from an engineering standpoint. If the case were to expand or twist by any measurable amount, I don't care how much torque you apply to those 8 and 10mm bolts, the two halves of the case will move relative to each other at this bolted joint. Bolts (at least ones without a machined shoulder on them for a tight fit) do not locate or align components, their only purpose is to provide a clamping load. They won't keep the alignment of the case halves under conditions that cause case distortion. So I would actually expect most movement at the seam as opposed to anywhere else. This is partly my reasoning for suggesting the use of additional dowel pins in certain key locations. A tight fitting dowel pin will do a lot more to maintain the case half alignment and therefore create a more rigid structure overall. Downside may be that it becomes very difficult to get the case apart for service.

Last edited by Dave_RalliSpec; 01-20-2009 at 08:13 PM.
Dave_RalliSpec is offline   Reply With Quote
Old 01-21-2009, 10:17 AM   #249
axelthrasher
Scooby Guru
 
Member#: 144779
Join Date: Mar 2007
Chapter/Region: MWSOC
Location: In the land up over
Vehicle:
200X ZOMG a car 100%
crabon fibre girlfrendorz

Default

This is on somewhat of a tangent to what you guys are talking about, but how many ft lbs of torque would be seen when launching on a set of helical gears? I know everyone always says that transmissions fail due to high amounts of shock load, but how can that even be measurable?

Has anyone done any research on how much pressure is applied in the worst "shock load" situations of drag launching? I was just wondering if anyone could predict any numbers that might be seen in those extreme conditions.
axelthrasher is offline   Reply With Quote
Old 01-21-2009, 12:33 PM   #250
jhargis
Scooby Specialist
 
Member#: 110304
Join Date: Mar 2006
Location: Crestline, CA
Vehicle:
2004 Volvo S60R
No more Subie

Default

Dave,

Great points as always. Actually the idea of using additional dowel pins or something along those lines is certainly intriguing. I would think that movement between the case halves would be in more of a shearing motion (halves sliding past each other) rather than expansion. The potential miss I see here when using strain gauges is that only a tiny percentage of the gauge's surface would be placed over a point where it would see distortion. Since only maybe .001"-.002" of the gauge's overall legnth would experience any deformation directly over the seam in the case halves, the gauge would show very little resistance change on an ohm meter... Also depends on the gauge itself, they come in lots of different sizes and different resistor film layouts, and rates of resistance change per unit of expansion. The larger the gauge, the less deformation it would register.

As a side note, 7/16" SAE bolts are almost a press-fit in the holes for 10mm bolts, and 3/8" would nearly fit in the holes for 8mm bolts. So they'll go in with just a little bit of drilling using a really long drill bit. While it's sort of bad form to use SAE bolts on a metric car, it does work nicely. In fact, I've been playing with the idea of offering these as a full bolt kit in grade-8 as well, not only would they be a slighty larger diameter than stock on top of being of a higher grade, they would also act like dowel pins to keep the case halves better aligned.

I agree with you that too much emphasis was put on case flex early on, I really don't think it's the main factor here... However, there is one bit of evidence that kept me from dismissing case flex as a complete myth and this drove me to do a little testing of my own: That is, Subaru themselves beefed up the case design in 1998. The changes they made strengthened the case a bit over the old 4-bolt models, but their changes were obviously limited by cost. These changes were within a fairly cost effective scope, rather than making radical changes to the case that would require major re-tooling in the manufacturing process, they added material where it would be fairly inexpesive to modify the castings. I think Subaru wouldn't have put any effort into changing this design at all if there would be no benefit in doing so. Because of this, my guess was there could still could be some level of gain with further reinforcement.

Quote:
Originally Posted by axelthrasher View Post
This is on somewhat of a tangent to what you guys are talking about, but how many ft lbs of torque would be seen when launching on a set of helical gears? I know everyone always says that transmissions fail due to high amounts of shock load, but how can that even be measurable?

Has anyone done any research on how much pressure is applied in the worst "shock load" situations of drag launching? I was just wondering if anyone could predict any numbers that might be seen in those extreme conditions.
http://www.botlanta.org/converters/d.../flywheel.html

I used this online calculator as a quick reference to show just how much energy is stored in your flywheel @ 6,000rpm.

The figures are kind of off the top of my head and only approximate a stock subaru flywheel. I used 21 pounds (336 ounces) over a 12" diameter @ 6,000rpm... I don't have a flywheel in front of me, but the clutch disc diameter is 230mm (about 10"), and another inch or so on either side sounds about right. Now this calculation is assuming a uniform spread of weight throughout the fylwheel, so these figures will only be a ballpark estimate.

At this speed the energy stored in the flywheel is 21,846 Joules. The conversion factor is roughly 0.73 ft-lb to every joule... So you're looking at about 15,946 ft-lbs stored up in that flywheel... In other words, if you could stop the flywheel instantly, it would exert almost 16,000 ft-lbs into whatever is stopping it.

Now, when a clutch engages, a lot of this energy is lost to friction/heat, and some of it is spread out over the period it takes for the clutch to fully engage (slippage). The car is also able to roll, so the gears aren't facing infinite resistance from the driveline like they would be in both my test and the test Dave took part in. However, I would still expect to see at least few thousand ft-lbs of torque finding its way through your gears for a split second during a really violent launch, and that's not even including the torque that your engine is also applying to the driveline along with the inertia in all of the engine's moving parts (crank, pulley, rods, etc.).

This sounds like a lot, but think about it... Even a small hand-held pneumatic impact gun can be rated at 250-300 ft-lbs with the tiny weight it has spinning inside, so it's not so hard to believe that a big 21 pound flywheel can generate so much gear carnage.

When all is said and done, it's the gears that have to take the abuse, so they're still going to be a point of focus. Dave's test seems to prove that the gears themselves are moving around in there, and the shafts on which they spin are flexing beyond what the gear teeth are engineered to handle. No surprize to me really, you'd really have to have been there to see just how much that input shaft twists at 300+ ft-lbs, it was quite amazing to me. I do agree with Dave that the failure rate we see is due to gear seperation caused by shaft flex, with lots of other little contirbuting factors. So when it comes down to it, to build a really strong box, it's going to take really strong gears. Again, the way I see it is that better hardware and some reinforcement to the case can keep those bearings just a little more stable, and that at least is a starting point. It doesn't solve the root cause of many 5mt failures, but it does address one of the many contributing factors.

Last edited by jhargis; 01-21-2009 at 03:12 PM.
jhargis is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Feeler: Developing a reinforcement for the 5mt case jhargis Transmission (AT/MT) & Driveline 36 09-24-2008 09:18 PM
The power switch is going out in my case. bomber991 Off-Topic 9 02-05-2008 05:54 PM
What is going on with my '99 legacy GT LTD 5MT jw5216 Electrical & Lighting 1 11-24-2007 11:54 AM
WTB: 5MT case Starkiller New England Impreza Club Forum -- NESIC 6 09-21-2005 01:04 PM
v6 STi RA gearset in 5MT case, motor, and VF22 BoostdScubaru Private 'For Sale' Classifieds 42 10-22-2004 07:15 PM

All times are GMT -4. The time now is 06:12 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2017 Axivo Inc.
Copyright ©1999 - 2017, North American Subaru Impreza Owners Club, Inc.