My 131 abarth (never ending) story - 2017 season updates

[miro-1980]

Hi Gents

Here is the draft design of the new livery .

ALL SANREMA 77 DESIGN v small .jpg (112.12 KiB) Viewed 10998 times

What do you think ?

The front is absolutely accurate m based on picture from the start. Side and rear is accurate but placement may be a bit off. If anybody knows better, I hope he will tell me.

Note this is a replica of the livery from 19th San Remo Rally 1977 car driven by Jean-Claude Andruet / Christian Delferrier (Fiat France) who won it . Not any later rallies of his.

This was his car at Fiat France and no one else used it ( AT LEAST WITH THE SAME NUMBER PLATES !) :
R 19729 TO
Andruet/Delferrier - FiatFrance - Rally San Remo - 1977
Andruet/Delferrier - FiatFrance - Tour de Corse - 1977
Andruet/ - FiatFrance - Rally Monte Carlo - 1978
Andruet/Biche - FiatFrance - Tour de Corse - 1978
Andruet/ - FiatFrance - Rally Monte Carlo - 1979
Andruet/Biche - FiatFrance - Rally Monte Carlo - 1980


There are very few pictures of this car from this very rally , though there is quite a lot for other rallies in 1977 and 1978 including Monte Carlo. In all later rallies the car looked different in small but important details (i.e. lights, livery details, etc.) Note that often the pictures are incorrectly signed ( i.e. San Remo Rally 1977 , while you can see the RMC starting number and rally label.)

II will really appreciate any help with the livery.

Miro

[miro-1980]

Gr 4 gearbox to shaft connection question.

I am trying t understand how this was actually constructed, based on very few pictures and drawings.
However, the gr 4 connection sequence is not clear to me. Trying to understand it hit a hard wall.

From the gearbox side: The drum steel plate (from the gearbox side) is in fact a flange. It has 8 holes : 4 small holes for bolts ( what are they attached to ? ) and 4 large access holes holes to access additional 4 bolts.( what are these bolts attached to?)

gr.4 drum gearbox side .jpg (42.39 KiB) Viewed 10945 times

From the shaft side the drum cylinder has 4 prongs which are attached to the 8 holes donut

gr.4 drum shaft side .jpg (24.45 KiB) Viewed 10945 times

D and F 3.JPG (83.4 KiB) Viewed 10945 times

Four bolts fasten the donut to the drum cylinder.

What are the other four bolts for ?


Are there two donuts with a flange between them ???
In this case :

On donut is the gearbox side.

This donut is attached by 4 bolts to the steel back plate and by 4 bolts to the the shaft flange.

On the shaft side.

This donut is attached to the drum cylinder by 4 bolts , and by other 4 bolts to the shaft side flange beneath the donut.

This would make the flange between the two donuts an 8 bolt flange (not 4 bolt flange). 4 holes attach it to gearbox donut and 4 to shaft side donut.

So what the flange looks like?

I have never seen it ? Did anybody see it or has pictures?

Can anybody explain the actual construction of the connection between the gearbox and the shaft ?

Help would be appreciated.


Miro

[badlyworntoy]

Miro

Tell me to bogg off if you like but..........

Its 2013 and these days they is much better solutions. This drum is there as a fail safe for when that horrible" Donut" decides to fail. So why dot delete it completely. Have a look at my propahaft. The company Bailey Morris can make. you a high quality bespoke propshaft

[badlyworntoy]

viewtopic.php?f=4&t=2921

This is the thread for it

Nix

[miro-1980]

Miro

Tell me to bogg off if you like but..........

Its 2013 and these days they is much better solutions. This drum is there as a fail safe for when that horrible" Donut" decides to fail. So why dot delete it completely. Have a look at my propshaft. The company Bailey Morris can make. you a high quality bespoke propshaft

I understand your point and agree this is an old and not very good solution , but the issue is not what is best and what to use but :

How was it on the original gr 4 ?

Miro

[Guy Croft]

My take on this is that it is no more than simply a protector for the donut.. (?)

The transmission is still the same as the non Gp4 version - via the bolts in the donut..

G

[TomLouwrier]

hi Miro,

Where did you get the bottom picture, that shows the assembled unit? From your own car or from an original Gp4?
It seems to contain 2 donuts. These may be in parallel or in series, depending if they wanted to stiffen the joint up (resulting in higher tensions but better location), or make it softer (resulting in lower tension and more movement between parts).

I feel the flange and drum are not assembled correctly but 45 degrees off: the big holes in the flange could/should be over the lugs. That way there is an assembly sequence for both possible setups.

Please tell us more.

regards
Tom

[miro-1980]

UPDATED:

Hi Tom,

I have personally taken this picture under a genuine gr 4.

Re proper assembly :

It seems OK to me.

bolts # 1 , 3 5 ,7 go through ( starting from the bottom )
- the gearbox flange
- the first donut
- large opening in the shaft flange
- the second donut

bolts 2,4,6,8 go through (starting from the top)

- top donut
- one of the four prongs inside the drum
- shaft flange
- bottom donut
and large holes on the gearbox flange

bolting .jpg (26.55 KiB) Viewed 10773 times

This way *because of the 4 large openings in the gearbox flange and large openings in the shaft flange the two flanges are connected only through the donuts which makes this connection both strong and flexible.

To achieve this flexibility the shaft flange must have similar large openings as in the gearbox flange.

gr 4 flange 1b.jpg (58.13 KiB) Viewed 10773 times

But this would be impossible to assemble , as the shaft flange could not be inserted below the 4 prongs on the inside of the drum.

Thus, this flange may actually be constructed pretty much as the standard 3 bolt (3 prong) flange , but have 4 holes on four prongs 4.

gr 4 flange 2 b.jpg (49.61 KiB) Viewed 10773 times

This would allow assembly of the whole element in the following sequence

1/ drum with the first (bottom ) donut bolted on 4 bolts (1,3,5,7)
2/ shaft flange inserted
3/ top donut inserted
4. holes for 2,4,6,8, bolts aligned
5. bolts put in place and tightened

So the way it seems to be constructed and assembled.

Is my thinking accurate ?

Miro

UPDATE :

Here is a picture of the original assembly. Looks like my thinking was correct after all !

original drum assembly .jpg (27.66 KiB) Viewed 10555 times

Miro

[miro-1980]

Here is a work around as built by a friend Mike from Holland.

This allows to make a drum and make it fit in a standard gearbox setup:

workaround 1.jpg (26.86 KiB) Viewed 10772 times

The actual standard drum looks like this, and uses all standard 131 parts ( donut and 3 prong flanges) :

standard gearbox flange .jpg (23.32 KiB) Viewed 10772 times

drum.jpg (42.85 KiB) Viewed 10772 times

Here are the detailed dimensions to build it:

002 (480x640).jpg (215.26 KiB) Viewed 10772 times

019 (480x640).jpg (213.82 KiB) Viewed 10772 times

Attention : there is a trick to it. The standard Abarth gearchange extension is too low to fit the drn under it. . The gearchange extension must be lifted by a 9 mm aluminum spacer. It works and makes n difference in shifting at all.

9 mm spacer here .jpg (31.41 KiB) Viewed 10772 times

I intend to build one ...

Miro

[TomLouwrier]

hi Miro,

Good, your picture from the original proves the drum is in fact meant to house 2 donuts.
I've been thinking and come to the conclusion that this drum has 2 functions:
1- continuity: 2 donuts mean less chance of losing the connection between box and shaft. You may finish your race.
2- safety: if both donuts fail, the driveshaft is prevented from flying around at speed, entering the car or jamming in the road surface. You live to tell the tale.

Your friend's replica-like drum (3-arm flange) offers only function 2, but no extra guarantee if the one donut inside fails.
If he fits 2 donuts on top of each other he will still have the second one, but there is chance that the asymmetrical stresses from one donut failing will take out the other donut quickly anyway. Your drum offers the correct solution, locating both donuts in the flange/drum properly.

You are right about the 4-pronged shaft flange. The prongs will have the same thickness as the lugs inside the drum, so that both donuts lie flat on either side of them. This flange will be bolted onto the shaft, so that you can fit the outer donut over the shaft first.
I expect the distance between the box-side flange and the lug to be identical to the donut's height, or you fill it up with shims.

The bolt arrangement as you describe cannot work. Since the box flange and the drum are bolted together, they are one object. Thus the bolts going through the smaller holes in the flange must also go through the ones in the lugs. The bolts going through the shaft's flange can not connect to the lugs.
So in order to assemble this you must fit the odd bolts 1,3,5,7 through flange (box), donuts and lugs (drum). The even bolts 2,4,6,8 must go through donuts and flange (shaft). That is what the larger holes are for: doing up the bolts in the shaft flange (the even ones).
Hook it up as you describe and you will have a stiff connection: flange (box) - drum, drum - flange (shaft) all acting as one hard bolted assembly. The donuts will then have no function.

If you want I'll try to make some sketches for you.

regards
Tom

[miro-1980]

Tom,

you are right, the way I suggested would make it a stiff connection. Looks simple until you try to figure out the details.

Correct connection sequence is as follows
The odd bolts 1,3,5,7 through flange (box), donuts and lugs (drum).
The even bolts 2,4,6,8 through donuts and flange (shaft).

CORRECT odd - even SCHEME.jpg (22.84 KiB) Viewed 10811 times

The above drawing shows on one side - the odd numbers and on the other -the even number bolts

Based on this , the same is possible for a three prong flange with two standard donuts. This would effectively provide two functions you mention:
1- continuity: 2 donuts mean less chance of losing the connection between box and shaft. You may finish your race.
2- safety: if both donuts fail, the drive shaft is prevented from flying around at speed, entering the car or jamming in the road surface. You live to tell the tale.
Do you agree ?

3 bolt flange connction .jpg (22.21 KiB) Viewed 10814 times

The only difficulty will be machining the inside drum lugs. Difficult , but not impossible.

The tree prong standard flange connection, given the car has somewhat less HP and torque than top power ex-works this should be sufficiently strong to actually increase both safety as well as connectivity (chance of failure).

What do you think ?

Miro

By the way , doing it this way will require significant corrections to the dimension sheets and drawings published few messages above ...

[TomLouwrier]

hi Miro,

Ah, I see you already made the sketches yourself. (You left a piece of donut white though, under the word 'odd'. Shame on you.)

Sure, no reason why you could not fabricate one such joint based on the standard 3-prong flanges and 6-point donuts. Your design does exactly that.
We don't really know why Abarth chose the 4-prong flange / 8 hole donuts. Maybe they are stronger to start with, but certainly stiffer and in theory a tripod has a much better behaviour than a 2 or 4 leg cardan joint. CV's are always tripods, it's Constant Velocity.

Making the lugs inside the drum is not that hard, it's just a lot of work and 'waste' of material starting with a massive piece of aluminium billet.
You may have to machine the back of the original flange (box side) so that it lies flat on the drum 'cover'. The other flange (shaft side) must have the same thickness as the lugs in the drum. This logically follows from your drawing. You can adjust the lug (design), the prong (adapt) or both.
Also make sure that the stack of cover-prong-donut-lug on bolts 1,3,5 has very little or no play in it, you'll be doing up those bolts 1,3,5 tightly and the inner donut must be clamped well.
The cover will lie on top of the drum like the original, as the small bolts go in parallel to the shaft, but I suppose it will get a nose to center it nicely in the drum.

Another fine piece of functional and correct detailing on your car. Hats off!

regards
Tom

[miro-1980]

Tom,

Please find this major inadequacy corrected. LOL

The 4 prong flange use by Abarth - in light of the tripod better spinning performance is a very good question.

I do not believe they made this decision without due technical/performance consideration. Maybe the rough habits of the rally drivers ( very very short clutch engagement and very quick release) decided on the the final determination.

Constant quick 0-1 clutch engagement at high RPM does make the connection wear of quickly. Using 4 bolts and a using a full disk box flange makes this very much panzer like!

Thank, Tom, I try and try ... and try again.

incidentally, the fine detail of Abarth design still keep some secrets to discover.

Miro

[Guy Croft]

MODEL POST!

I never fail to be impressed here, well done indeed Tom & Miro

GC

[miro-1980]

Gents

Here are some pictures of the bias adjustment of the rear front brakes on two pedal boxes we have. Note the original gr.4 did not have an adjustment knob and was a bit more primitive.

gr 4 original design .jpg (63.1 KiB) Viewed 10766 times

gr 4 upgraded with dash mounted knob .jpg (84.37 KiB) Viewed 10766 times

knob with cable .jpg (33.82 KiB) Viewed 10766 times

knob .jpg (55.73 KiB) Viewed 10766 times

Please notice how the rods are prepared for welding. This way the connection will be much stronger.

3 sets of gr 4 replica streerig rods.jpg (53.37 KiB) Viewed 10766 times

steetring rod prepared for welding .jpg (58.4 KiB) Viewed 10766 times

Miro