DRLY FILM LUBE COATING APPLIED TO STEEL TRANSMISSION PARTS 4

[bob8907]

We have a transmission that simply will not shift under load. We increase the engine output by 300% and this creates binding in the sequential transmission. The thought came to mind to try and reduce friction on all the sliding components in the trans to help shift quality.

I am looking for real (not theoretical) feedback on DFL coatings to see if they are more of a fluke than actually helpful. I have a hard time believing that a moly coating will be much different than oil with moly in it...

I also posted in the automotive area but thought a metallurgist might have a good explanation if DFL is truly worth using. They say that once the metal has been treated, it soaks well into the metal regardless of appearance. If this is such a great coating, why is it not main stream?

 

[unclesyd]

The is no magical DFL, there one different ones for different application. In a dynamic situation a DFL is usually removed quite rapidly and you then have to depend on your lubricating oil. Your problem sounds more mechanical than a lubrication problem.

What type transmission is this?

Is this one that requires straight mineral oil?

What the loads on the transmission?

Does it shift when not engaged?

How does the rotation feel?

Before I would go with putting on DFL or polishing gears I would give Lubrication Engineers a call. If you you spin the transmission in neutral for 10 or so minutes with LE oil
and it doesn't shift you have mechanical problems.

http://www.le-inc.com/products.jsp?productID=310

PS:
Don't do like I did a 32 Ford, put the cluster gear in backwards.

 

[bob8907]

Thanks. This is a sequential transmission. 6 speed. They must be rotating to shift properly. Trans will shift just fine with lighter torque inputs. IE, let of the gas, the trans shifts just fine. In it to win it, it will not take gears very well. The transmissions certainly are not bad and we have tested countless assemblies with the same problem.

Who do you recommend to call? Certain office and such? I had a feeling the DFL would wear off quickly and probably just used for race applications where components do not last long anyway. Just seems too good to be true....

 

[unclesyd]

i would call the head office and they will give you rep in your area. Most reps are quite knowledgeable about their products. As posted this will cut to the chase where hopefully want be chasing several gremlins.

It sure sounds like something is moving out of alignment under load, which could be anything in the box or the box itself.

I've only seen a few transmissions of this type but worked with what we called a preselector, 5 speed gearbox that had to use straight mineral oil, this was the reason for the question.

 

[bob8907]

These transmissions are used in racing and lubed with everything from 10w-40 to ATF. I will agree that there is certainly something hanging up and we are trying to pinpoint it. I would add though that this is pretty typical of sequentials. Add too much power and they become harder to shift. F1 does not seem to have any problem though...

I would be real interested in building a test to find the flaws or even talk to a prominent sequential engineering company to discuss the issues at hand. My concern is deflection of the shift forks causing uneven stresses on the sliding gears.

 

[mfgenggear]

sure seems like the extra torque is twisting, there fore binding the gear train. I am not familiar with the inside of this type of transmision, but basic mechanical assembly
would seem to apply.

is the housing made of aluminum? are there cut or ground gears. through harden or case harden?

MfgEngGear.

 

[bob8907]

Box is cast Al, gears are all case hardened. All gears are machined. The box has been in use for 30 yrs in assemblies. All gears follow on spline shafts. Guys are getting around the problem by grinding the dogs off or at an angle but this sacrifices life of the trans and will commonly ruin the shift forks because of all the extra force on them to hold in gear.

 

[unclesyd]

The only way you can stiffen up the forks is to make a thicker section or move the pivot point closer.

Does the fork ends fit in a defined groove\slot that would limit the cross section of the fork?

 

[bob8907]

Yes, the forks will be difficult to reproduce. If I knew for certain that they would fix the problem, I would get it done as we are a machine shop as well. Problems with the forks are all the mfg processes.

Right now I am looking for some sharp engineers to collaborate with to see if we are on the right track. Sequential just are not that main stream in the US.

 

[Tmoose]

Are the shift forks steel or bronze?
Are you allowed to rig an ignition/fuel interrupter to kill power just during the actual shift, like the air shifter guys sometimes did?

 

[CoryPad]

You should contact Ricardo. They have expertise in motorsports transmissions.

http://www.ricardo.com/

 

[EdStainless]

F1 manages because they use fully electronically controlled double clutching to shift. The drive just taps the buttons.

I would look to reduce tolerances and improve surface finishes before DFL.
An oil with the right EP additives might help, but if overall distortion of alignment is causing the issue then you either need to stiffen the structure or reduce torque.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[tbuelna]

bob8907,

If your gearbox uses dog rings and it's difficult to disengage the dog ring from the gear, then what you likely need to do is regrind the dog faces with slightly less undercut, and increase the shifter dentent spring forces some.

It's the undercut that keeps the dog ring and gear engaged while they're under load. When they're not under load, they can separate since there is generous backlash between the mating dog ring and gear teeth. But the shifter detents keep the dog rings in place when this occurs.

I'd guess that most dog rings have an undercut around 3 to 5 deg. You can probably reduce this to 2 deg without having your transmission jump out of gear, as long as your shifter mechanism is not sloppy.

As for DFL coatings, they can be effective but they only really help when there are marginal lubrication conditions. Your dog rings have three points of contact that produce friction: the dog tooth faces, the spline teeth faces, and the shift fork groove faces. The dog tooth and spline tooth faces are boundary contacts with high contact pressures, so a typical DFL would not likely last long in these areas. The shift fork grooves have constant relative sliding with oil present, so this contact is likely hydrodynamic in nature and would not benefit from a DFL.

Hope that helps.
Terry

 

[unclesyd]

As posted by EdStainless one option is to improve the surface finish on the gears to lower the COF. Here is the address for Rem who's work I've seen and it was impressive.

http://www.remchem.com/

 

[unclesyd]

Was just watching a piece about the design problems with the Bugatti Veyron.
Most of the gears in their transmission where super finished.

Addenda:
The transmission was design with a double clutch arrangement. There are two main drive shafts in the transmission one for the even gears and one for odd gears, each with it's own clutch. This allows the transmission to preselect the next gear so they achieve a 150 microsecond shift.

 

[Tmoose]

"......... You can probably reduce this to 2 deg without having your transmission jump out of gear........."

I got into a discussion with a burley Harley owner one time, who stated that he had used some oil additive that was so slippery that the tapered valve spring retainers kept popping out.

http://www.kmotion.biz/images/Installed.jpg

I did not dispute the statement, at least out loud.

 

[mfgenggear]

bob

Very good engineers on this site & good advice.

I wouls start with the easiest advice and start from there.

Better type of lubrication.
Check for worn parts "shift forks, dogs & gears".
geometry of the dogs " polish & super finish"
less friction.

also verify the edge breaks. make sure there are no sharp edges unless it is critical to have one.
gear teeth .005"-.020" edge break except gear teeth tips .005 max edge break, the tips of the dogs .005"-.015" EB if gear teeath are Case Harden take temper etch & post bake precautions. do not burn or crack.

definetly double clutching "added electronic control"
not my speciality "but a very good suggestion".

stiffen up the structures that hold the transmission
aluminum housing is not helping "just my opinion" twist

are these straight cut gears or helical?

Good luck

MfgEnggear

 

[tbuelna]

This might be a little off-topic, but bob8907 did mention his xmsn is a sequential racing unit so maybe this might help.

Back 20 years ago I was doing engine/transmission design work on an IMSA GTP car. It was mid-engined and used Hewland VG transaxle internals in a custom case. The single push/pull rod shift linkage ran down the right side of the chassis tub, passed along the engine block just under the red-hot turbo header primaries, and then all the way to the aft end of the transxale housing where the selector rods were. After hard running, the steel push/pull shift linkage rod would get very hot from the headers and would actually grow in length enough so that the transmission could not be shifted properly.

Until we redesigned the linkage, the quick remedy was to bring the car into the pits and douse the linkage with water.

Here's a nifty website with detailed drawings and manuals of racing transmissions:

http://www.hewland.com/svga/down loads.htm

Regards,
Terry