Jump to content

gearbox & overdrive angle


Recommended Posts

Morning all,

I’m trying to determine the angle of the original gearbox and overdrive unit to set the correct propshaft height & pinion angle - unfortunately this was the one thing I forgot to measure when taking everything apart! 

I’m now fabricating some different engine mounts and it would be handy if anyone can measure any features of the overdrive unit relative to the floor pan or  the chassis in terms of height. The back of the overdrive unit is set by the height of the rear mount,  so maybe the flat base of the overdrive housing relative to the bottom of the chassis would be a good dimension to have. Easy to measure if someone is part way through a body off restoration :-) 

It’s a j-type overdrive in a CR chassis.


Thanks,

 

Dan 

Link to post
Share on other sites
27 minutes ago, stuart said:

Dont know if this helps. I was converting an "A" type chassis to "J" type

Stuart.

 

CR 526 O 030.jpg

CR 526 O 031.jpg

CR 526 O 032.jpg

Thanks Stuart, how are you setting the height of the Overdrive mount, from the looks of the picture its not yet in the frame? It does confirm what i remember that the engine sits nose up slightly

The dimensions im after ive put on the pictures, not sure how useful they would be if the rear mount hasn't been set yet. 

638446020_CR526O031.thumb.jpg.2ee44f738e6d29cc45f7b63443379665.jpg

601962571_CR526O032.thumb.jpg.2fa715253b686f27d0812c61298aef9e.jpg

Link to post
Share on other sites

Unfortunately those pictures are library ones from 13 yrs ago so cant help with measurements Im afraid.

Stuart.

Link to post
Share on other sites

I can measure the rocker cover angle if you want. That should do it.

The center line of the GB should be in the CL of the chassis, I think, regardless which type OD you have.

Link to post
Share on other sites
4 minutes ago, Waldi said:

I can measure the rocker cover angle if you want. That should do it.

The center line of the GB should be in the CL of the chassis, I think, regardless which type OD you have.

thanks,  I would expect you would need to know the rake of the chassis to know what angle the rocker cover sat in relation to the chassis, the overdrive is the only original part that's going back in so a direct measurement off that to the chassis would be better, plus not much of a flat surface on the top of it for a bubble gauge. 

The diff input is offset which made me think the prop itself is offset and everything isn't necessary central to the chassis - might be wrong though

Link to post
Share on other sites

Similar question on FB.  Same OP maybe?

The engine/gearbox axis is centered in the chassis, but the differential axis is offset to one side. This offers a small angle to each U - joint in the horizontal plane, but since the axes are parallel, the angles are the same for each joint. This is important for vibration cancellation.

Same situation for the vertical plane. There can be an offset of the axes, but they should be parallel.

Ed

Edited by ed_h
Link to post
Share on other sites

Ed makes an important point. If both axes are not parallel, the dif end will be accelerated/decelerated every turn, this will damage something.

This provides what you need I think. 
Axes parallel and engine/GB in CL of car.

Waldi

Edited by Waldi
Link to post
Share on other sites
4 hours ago, ed_h said:

Similar question on FB.  Same OP maybe?

The engine/gearbox axis is centered in the chassis, but the differential axis is offset to one side. This offers a small angle to each U - joint in the horizontal plane, but since the axes are parallel, the angles are the same for each joint. This is important for vibration cancellation.

Same situation for the vertical plane. There can be an offset of the axes, but they should be parallel.

Ed

thanks Ed, yes its the same one on facebook, just trying to ask in a few areas in the hope I can measure one.  I will look tomorrow but from memory its going to be difficult to measure the angle of the propshaft to check that the Overdrive is at the same angle and on a parallel axis.

If I have a similar car to measure there is no guesswork/measurement error on the angle of the prop to make sure the OD matches. 

Link to post
Share on other sites

Dan, 

you can use a water level for this, clamped to the flange. Or 2 straight edges, one on each flange face and then measure the distance top and bottom.

Waldi

Link to post
Share on other sites
1 hour ago, DanTR6 said:

thanks Ed, yes its the same one on facebook, just trying to ask in a few areas in the hope I can measure one.  I will look tomorrow but from memory its going to be difficult to measure the angle of the propshaft to check that the Overdrive is at the same angle and on a parallel axis.

If I have a similar car to measure there is no guesswork/measurement error on the angle of the prop to make sure the OD matches. 

 

Yes, measuring the angles can be tricky.  I found it easier to measure the angles of the flange faces, which should be at right angles to the axes.  Some details here:

http://bullfire.net/TR6/TR6-91/TR6-91.html

Ed

Link to post
Share on other sites

Dan,

I respectfully wonder if you're concerned about something that really isn't that critical. ?  

My own thoughts on the subject are that despite the haphazard alignment of gearbox and diff in live-axle cars, they have for the past 100 years have survived well enough ..and have been smooth driving without overdue concern for the fine degree of engineering otherwise here being proposed.  Many of those car didn't even have a Panhard rod or other kind of axle location, and their cart-leaf springs bend and twist quite amusingly ..often to the point of tyres wearing away in the wheel arches and that wonderful phenomenon known as axle tramp.  

The following images I've downloaded off the internet a couple of years ago, although they may well be from ed_h's most excellent bullfire.net/TR6 pages.  (My apologies to ed if they not his, and equally to the photographer of this chassis)

IMG_0045b.thumb.jpg.c24177477749679cdcf24909483fab01.jpg 

IMG_0044b.jpg.2ea4a51bc5b0c52debc52e6cffd46dd6.jpg

Surely with the renown twist and bounce and bending of the TR IRS chassis,  and then the twist and bounce and bending of the engine, gearbox and diff rubber mounts - things can never be beautifully aligned any more than a non-working watch is accurate more than twice a day.  

Just a thought,

Pete.

Link to post
Share on other sites

Absolutely true that flex in the frame and movement of parts will affect the relationship between the diff and gearbox axes.  It would still seem prudent to design for the variation to center on the optimum alignment. This would minimize the deviations from optimum.

Ed

Link to post
Share on other sites

I cannot disagree with your reasoning Ed.  

Even so.,  I do get the impression that bulkhead clearance over the gearbox,  and that of the brake and fuel pipes, wiring loom, exhaust and drive-shaft in the tunnel ..are in fact more critical issues in this particular case. 

Surely, if it were necessary to 'get it right' in terms of shaft alignment then Triumph would have specified a 'critical' vertical dimension for the gearbox mount in their workshop manual.?  And of course, the relatively "fixed" position of the IRS diff is already a thousand times better aligned than any live axle design anyway.

If it were me I'd just tack the mounting brackets in ..about 1/4" (6mm) above the chassis rail's mid-height level (based on those photos), and then check the aforementioned body-tub clearances from that.

Pete

.

Edited by Bfg
Link to post
Share on other sites

Pete--

It's fairly easy to determine how much rotation distortion a given variation from parallel axes would cause.  The unknown part (for me, at least) is how much it would take to be detectable, even subliminally, or how much would significantly affect component wear.  I think you are correct: getting pretty close is probably good enough for practical purposes.

When I measured the variation from parallel on my car, it was almost 2 degrees, probably mostly due to frame sag.  I was able to pretty easily get it to under half a degree, and I called it good enough.  I don't have anything concrete that shows that the 2 degrees is not good enough, or that half a degree is, but I don't see a downside to doing it, and probably would do it again (though it would be a lot easier before the body was on).

Ed

 

Link to post
Share on other sites
On 2/18/2020 at 10:33 PM, ed_h said:

 

Yes, measuring the angles can be tricky.  I found it easier to measure the angles of the flange faces, which should be at right angles to the axes.  Some details here:

http://bullfire.net/TR6/TR6-91/TR6-91.html

Ed

Thanks Ed, the diff is away for repair at the moment so hopefully when its back I can measure the flange angles. For the moment im going to build in some adjustability into the motor mount so it can be adjusted in situ, I've not got the weight of an engine and gearbox, just a 55kg AC motor onto the end of the overdrive so it may well compress the rubber bobbins less on the overdrive mount and change the angle.

Link to post
Share on other sites
14 hours ago, Bfg said:

I cannot disagree with your reasoning Ed.  

Even so.,  I do get the impression that bulkhead clearance over the gearbox,  and that of the brake and fuel pipes, wiring loom, exhaust and drive-shaft in the tunnel ..are in fact more critical issues in this particular case. 

Surely, if it were necessary to 'get it right' in terms of shaft alignment then Triumph would have specified a 'critical' vertical dimension for the gearbox mount in their workshop manual.?  And of course, the relatively "fixed" position of the IRS diff is already a thousand times better aligned than any live axle design anyway.

If it were me I'd just tack the mounting brackets in ..about 1/4" (6mm) above the chassis rail's mid-height level (based on those photos), and then check the aforementioned body-tub clearances from that.

Pete

.

Pete,

my reason for wanting to do it is that I've lost a lot of the datums as there isn't a engine and gearbox anymore, just a large AC motor bolted to the back of the overdrive. its got a lot less weight so the nose of the overdrive probably sits a bit higher which is why I was trying to get some datums around the overdrive unit to set the height of the motor mounts.  

As you have said, does it make a difference, which is dififcult to know but im putting a lot more torque than standard through the relative drivetrain joints so wanted to start with the best chance possible.

Link to post
Share on other sites
1 hour ago, DanTR6 said:

Pete,

my reason for wanting to do it is that I've lost a lot of the datums as there isn't a engine and gearbox anymore, just a large AC motor bolted to the back of the overdrive. its got a lot less weight so the nose of the overdrive probably sits a bit higher which is why I was trying to get some datums around the overdrive unit to set the height of the motor mounts.  

As you have said, does it make a difference, which is dififcult to know but im putting a lot more torque than standard through the relative drivetrain joints so wanted to start with the best chance possible.

Presumably your building an electric TR6 then?

Stuart.

Link to post
Share on other sites
Just now, DanTR6 said:

Thats right, electric motor with the overdrive and a lower rear diff ratio

Good luck with that, there are a number of companies doing that already, might be an idea to go and have a nose round one.

Stuart.

Link to post
Share on other sites
4 minutes ago, stuart said:

Good luck with that, there are a number of companies doing that already, might be an idea to go and have a nose round one.

Stuart.

Thanks Stuart, not seen another TR6 yet apart from one in Germany but i've been to a few of the UK converters as they are the distributors for things like the motor, batteries etc

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.