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Gtir Motorsport club » Tech room » Help and Advice » Help!

Help!

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101 Re: Help! on 13th June 2016, 8:08 pm

Mr B

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gtir technician
gtir technician
Put a clamshell type separator clamp under gears and mount it in press bed much like manual, press will load far more evenly than 3 leg puller and you should hopefully have gauge to see hydraulic load . The clamshell type clamp if fits nice takes load to inner gear making less chance of an issue. 3 leg puller foot is right on gear tooth and right at edge of gear so more likely load less evenly plus leverage of contact points is working against you thus making damage to gear more likely if overly forceful.
Trouble with those leg pullers mixed with hydraulic ram is you can be putting likes of 10tonne load on small contact foot area .

102 Re: Help! on 13th June 2016, 8:30 pm

Cosmic73

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I was planning on doing that tomorrow MrB, this afternoon i already had the puller set up so i tried it with only gentle persuasion.
In any case it was too bastard tight so i backed off because its Pete's call.
The bottom line is 1st synchro ring us stuffed, needs replacing and 2nd/3rd gears must be removed to access it.
Pete's given me the green light to carry on so thats what ill do.
One thing thats standing out is a comment Pete made. He said the fitter had to use considerable force to press these gears as they were really tight.
A potential theory of mine is that if the press tonnage is massively high, how do you know if its come to the shoulder? Maybe its gone beyond it and deformed it?
Soon find out tomorrow, im taking a video of it which ill post.

103 Re: Help! on 14th June 2016, 3:06 pm

Cosmic73

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Pete's gearbox failed in 3rd gear and it's 3rd gear that can not pressed off.
I'm fast coming to the conclusion that the 3rd gear splines have twisted which is why the gear cant be removed. But this will be confirmed once its all apart.

Clamshell could not be used due to interference from the synchro underneath 3rd gear;



Hydraulic puller was used instead with 3x wide jaw pullers offering good support across at least 2 teeth per jaw,


Below are the video clips showing the 3rd gear non-removal!





So, the shaft must be cut in half then precision bored to free 3rd gear.

104 Re: Help! on 14th June 2016, 5:57 pm

PartyPete

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the one star club
the one star club
I'll have a go at removing the shaft out of my other box Thursday night Neil, either way I'll get it to you this weekend

105 Re: Help! on 14th June 2016, 6:56 pm

nomad

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Admin
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So what would cause it to twist on the shaft .... worn splines ?


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106 Re: Help! on 14th June 2016, 7:23 pm

burrows1980

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I think you need to have some Weetabix Neil and have another go Laughing fair play though that's pretty much stuck!! Gearbox I s the only thing I've never stripped down and played with, I'm finding this really interesting stuff.. Sorry Pete Shocked

107 Re: Help! on 14th June 2016, 7:25 pm

johnny gtir

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Sounds like one of the previous fails has twisted them and the builder has forced the par ones on and it's got worse but I could be wrong

108 Re: Help! on 14th June 2016, 7:33 pm

Stu

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I have a set of shafts here if you get stuck.
Just bung me a drink and the postage Wink


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109 Re: Help! on 14th June 2016, 8:03 pm

Cosmic73

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@johnny gtir wrote:Sounds like one of the previous fails has twisted them and the builder has forced the par ones on and it's got worse but I could be wrong

If the splines are twisted then its more likely to have happened after the last rebuild otherwise the builder would've/should've flagged it up.

Im also trying to confirm if a failure of 3rd gear spline could cause the 1st gear baulk ring to fail?
Soon find out this Friday....

110 Re: Help! on 14th June 2016, 8:03 pm

PartyPete

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the one star club
the one star club
I believe he has put around 2 tons of force on to try pulling them off, previous fails were just broken gears Johnny so I can't see it being that, I'm finding it interesting in a strange expensive irritating way. I've never known so much about gear boxes, stu that's a very kind offer, I'll bare it in mind, I do have a spare shaft so I'll check it's all a1 before I take it,if not I'll deffo give you a shout! thumbsup

111 Re: Help! on 14th June 2016, 8:13 pm

Cosmic73

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@nomad wrote:So what would cause it to twist  on the shaft .... worn splines ?

If confirmed, just pure simple overload, Pete's engine must have been chucking out some serious power to do it. Shocked Shocked

112 Re: Help! on 14th June 2016, 9:14 pm

Mr B

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gtir technician
gtir technician
Possible with 1st syncing engagement caused massive load to 3rd at time until synchro got ripped up.
It possibly would press off in bench press if can get or make good fitting plates to go under the gear so can put some decent press load on it. If can't then doing what can to get gears off undamaged is best way forward .

113 Re: Help! on 15th June 2016, 10:03 am

Cosmic73

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OK, I'm pretty sure I'm getting closer to solving Pete's problem and I've uncovered a systems flaw with all straight cut gears. I will be sending an email to PAR notifying them of this.
It's all to to with straight cut gears generating no axial load, which is good thing right?
This is can be wrong because the axial loads cancel out the even bigger and truly massive axial loads generated by the Final drive gear which is still helical.

I've modeled a stock and PAR gearbox in the design software i use.
(Please excuse the crudity of the models, i didn't have too much time to work on these)

As i will show switching to straight cut gears generates massive loads rightwards towards the odd geared synchros!

So below is a stock gearbox, note the helix angles on the mainshaft are left handed. There is good reason for this;


Below is an animation in 3rd;


Below shows the powerflow in 3rd,
How can the 1st gear synchro and 1st gear engage while in 3rd???


Below shows the mainshaft forces while in 3rd of a stock gearbox.
This is only with an input torque of 165Nm (approx 50kw)
3rd gear is left handed helix and being driven so it generates a leftward axial load.
Final drive gear is also left handed but is Driving (not driven) and therefore generates a rightward axial load. Note the difference in the forces;



Below shows that 3rd gear generates 3.8Kn axial load, final drive generates -6.5Kn (therefore net load is only 2.72Kn rightwards)




OK, now look at the force arrows on the straightcut gear with exactly the same load;


3rd gear generates 0nm axial load, final drive is still generating -6.5Kn axial load.
Therefore net load is 6.5kn rightwards. This is almost 3x higher than a stock box!!!
Also note the larger movement of 0.25mm rightwards,


But this is only with 50kw.
Now multiply this by the 300kw (400bhp) that Pete was no doubt pushing out??



Last edited by Cosmic73 on 15th June 2016, 3:47 pm; edited 4 times in total

114 Re: Help! on 15th June 2016, 10:38 am

ducie54

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How do PAR fix that? I reckon they would just say to buy the straight cut final drive set.

115 Re: Help! on 15th June 2016, 10:55 am

Cosmic73

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Yes, If you fit PAR gears, you should also fit straight cut final drive gears, brace the case and have zero slop in the manshaft
I think this explains why so many straight cut gear boxes are being wrecked.
PAR gears are undoubtedly stronger, but it migt unbalances the gearbox as a system which wasn't design for straight cut gears.



Last edited by Cosmic73 on 15th June 2016, 3:50 pm; edited 1 time in total

116 Re: Help! on 15th June 2016, 12:12 pm

shroom

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Interesting stuff here thanks for sharing this Mr Cosmic.

117 Re: Help! on 15th June 2016, 12:15 pm

PartyPete

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the one star club
the one star club
I don't even know they if they do them?

118 Re: Help! on 15th June 2016, 12:29 pm

Mr B

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gtir technician
gtir technician
I have straight set with standard final & no issues so far in over 2 years & 2 boxes I done with the par kit, straightcut final is recommended & they advised that to me for drag and high torque . they do a lot of gearkits wiith straightcut & helical final retained so would of thought they done plenty modeling & testing on it .
PPG do same on their straightcut syncro & straightcut dog drag box which retains standard final drive unless order it as an addition .
The final drive gear is part of the mainshaft so axial load goes direct to the rear shaft bearing & if shaft been setup with correct preload it will not have any shaft shuttling & deflection is down to box rigidity.
I use resin & plate end casing brace as still retain the helical drive which loading bearing area heavily .
I would be more inclined think mainshaft preload set well off or not even checked when built & float caused alignment issue with hubs & the failure. Hard to be conclusive without seeing it fully stripped & not knowing what floats & preloads seemed like prior to strip down .
If he needs new shaft it would be good to go for new par final drive to be more bullet proof .
Hopefully the gear splines are not damaged, shaft is softer so favorable chance they reusable .
Part of reason why you don't want reduce preloads to much in track use is because force and deflection has more end result in shaft axial bearing setup than what additional heat & expansion does unless on full straightcut kit .

119 Re: Help! on 15th June 2016, 12:39 pm

Cosmic73

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I've emailed PAR pointing this out and requesting a response.
So lets see what they come back with.....

120 Re: Help! on 15th June 2016, 1:04 pm

Cosmic73

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@Mr B wrote:I have straight set with standard final & no issues so far in over 2 years & 2 boxes I done with the par kit, straightcut final is recommended & they advised that to me for drag and high torque . they do a lot of gearkits wiith straightcut & helical final retained so would of thought they done plenty modeling & testing on it .
PPG do same on their straightcut syncro & straightcut dog drag box which retains standard final drive unless order it as an addition .
The final drive gear is part of the mainshaft so axial load goes direct to the rear shaft bearing & if shaft been setup with correct preload it will not have any shaft shuttling & deflection is down to box rigidity.
I use resin & plate end casing brace as still retain the helical drive which loading bearing area heavily .
I would be more inclined think mainshaft preload set well off or not even checked when built & float caused alignment issue with hubs & the failure. Hard to be conclusive without seeing it fully stripped & not knowing what floats & preloads seemed like prior to strip down .
If he needs new shaft it would be good to go for new par final drive to be more bullet proof .
Hopefully the gear splines are not damaged, shaft is softer so favorable chance they reusable .
Part of reason why you don't want reduce preloads to much in track use is because force and deflection has more end result in shaft axial bearing setup than what additional heat & expansion does unless on full straightcut kit .

Those deflections were at zero pre-load at the bearings, eg zero clearance so it's system deflection only that i considered. If i had've included any bearing clearance issues the displacements would be worse again..
Yes FD axial load is transferred directly to the rear bearing then it goes to the case which deflects, so the entire mainshaft moves rearwards.
But now it's got 3x more force behind it.

You make a good point about bracing, and yes this could be a solution.

So Pete's choices;
Rebuild 'again' with PAR gears, stock FD and cross fingers,
Rebuild with PAR gears and brace the mainshaft bearing surfaces of his case,
Rebuild with PAR gears and straight cut final drive,
Fuck the whole thing off and buy an EVO,  Very Happy  Very Happy



Last edited by Cosmic73 on 17th June 2016, 8:35 pm; edited 4 times in total

121 Re: Help! on 15th June 2016, 1:06 pm

burrows1980

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Jesus Christ Neil, that's some clever stuff! So is your place opening a GTi-R gearbox diagnostic section now? Laughing

122 Re: Help! on 15th June 2016, 1:23 pm

PartyPete

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the one star club
the one star club
I did have the stratcher motor sport end brace fitted Neil, mr b what sort of power were you running through those boxes?

123 Re: Help! on 15th June 2016, 1:24 pm

PartyPete

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the one star club
the one star club
Oh....and I'd rather shit in my hands and clap than buy another Evo Shocked

124 Re: Help! on 15th June 2016, 1:42 pm

Cosmic73

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@PartyPete wrote:I did have the stratcher motor sport end brace fitted Neil, mr b what sort of power were you running through those boxes?

Does this clamp against and lock the 2 surfaces on the case where the mainshaft bearings are located?

125 Re: Help! on 15th June 2016, 1:46 pm

Cosmic73

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@burrows1980 wrote:Jesus Christ Neil, that's some clever stuff! So is your place opening a GTi-R gearbox diagnostic section now? Laughing

nah, just had a few moments free while i was at my desk drink

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