I bought a Shrinker Stretcher machine. I have seen them used on some Youtube channels and they looked pretty handy. They seem to help a lot in making tighter curves and radiuses. The English Wheel is handy also, but the Shrinker Stretcher seems to speed up some operations a lot. Also – at my skill level – shrinking edges with just a hammer and a dolly (or stump) is challenging. Making an even shrink along an edge is especially difficult. So, I decided to try it out.
How a Shrinker Stretcher works
The device comes with two sets of jaws. One set for shrinking and another for stretching. The jaws clamp on the piece of sheet metal and pull the metal in towards the center (or push out if stretching) when you pull on the handle. This forces the metal to curve.
The jaws can shrink and stretch steel about two inches or 5 cm deep, and around 1 mm thick.
Above you can see the teeth marks the jaws make on the metal. These need some smoothing out after the desired shape has been attained. An English Wheel is a great help.
Foot operation stand
Already after my limited experience I would say that a foot operation stand is a must. A stand would have cost almost as much as the device, so we decided to make one of scrap metal. The pedal is a Saab 96 brake pedal.
The foot stand gives you a lot more power but it also frees up both hands to hold and guide the piece you are working with.
Repairing a Saab 99 Turbo rear brake dust shield
So here’s the first real test repair where I used the shrinker stretcher.
All in all I have to say that using the shrinker was a lot easier than I thought. Ofcourse making complex panels is a completely different thing, but for small parts like this it seems a real helper.
I’m putting the Saab 96 Rallycar up for sale (not for sale anymore) since I have a new project coming (more on that later) and I simply do not have the room to keep them all. If you have followed the blog you pretty much know what I’m selling – check out http://www.saabisti.fi/1969-saab-96-rally/
The car has competition history from the seventies, but was later returned to civilian use. It has been restored to original competition colours.
No rust. Great car for Pro Regularity racing. Historic racing would require new rollcage, new seats, belts and safety gear.
Around 2000 km since rebuild. Very nice engine, healthy Hp. Could use a proper tune-up of the Webers and the distributor for maximum power.
1.8 Liter engine
– New+1mm OHC/Pinto pistons, Mahle
– Inspected for cracks 1.7 crankshaft
– 7.6 camshaft (Finnish specialist GT Motor)
– Lightweight valve plates, lifters, pushrods and stronger springs by ClassicSaabRacing
– Stock heads with opened up exhaust ports
– All bearings New
– Light weight flywheel
– CT cross-flow manifold, 2x Weber DCOE 40
– Electric fuel pump (Mitsubishi)
– High flow oil pump, New
– 99 radiator, electric fan
– longer 1st and 2nd (Not Special)
– opened, inspected, adjusted, works great
– freewheel disabled
Body and chassis
– strenghtening plates
– no rust / welded
– sump guard with Sport&Rally fittings
– Mexico brackets
– Saab 95 rear axle (stronger)
– Strengthened suspension parts front and rear (as per Sport&Rally)
– strengthened 2.5″ exhaust system, exits next to gear box (S&R style)
– rollcage (needs to be replaced if raced)
– sport seats (needs to be replaced if raced)
– 4 point security harness (needs to be replaced if raced)
– New brake disk, refurbished calipers, Saab 95 pistons rear, new pads and shoes
– Extra lights (quickrelease)
– main power switch
– Some signs of use (dents etc)
– oil pressure cage, oil temp cage, rev counter
Also available spare parts, negotiable:
– Some new parts, gaskets, bearings etc
– Front fenders – Longnose grille complete
– Sport&Rally grille complete
– Block, heads, other engine parts
– 1.5 cranks
– 1.5 engine in running condition (77)
– V4 stock gearboxes
– miscellaneous stuff
Saab 96 T5 – sounds interesting enough. But at the Back? Now that looks like an interesting project. Unfortunately I don’t know a lot about it. But this guy is fitting a Saab NG900 engine and suspension in an old Saab 96 sprint car and making it mid engine.
There’s some photos at this Google gallery, but other than that I don’t really know much more, other than it is work in progress. Looks like it’s coming along nicely.
This is pretty much exactly what i was thinking of doing at one point. Although I would have done it in a bullnose 96 or 93…
It is becoming increasingly difficult to find new directional light lenses for the two-stroke bullnose Saabs. Or actually it seems almost impossible. And I need four of them for the Saab Sport – and a few spares wouldn’t hurt.
I have a few lenses that are in more or less decent shape, so I figured I could try and make copies of them. I read about polyester resin casting using a silicone mold, and decided to give it a try. This is a pretty popular way to make hobbyist plastic parts for model railways or scratch built scale models, so i figured it can’t be too difficult.
I was actually somewhat surprised, but making a polyester resin casting worked out very well as you can see above. Basically what you do, is make a two-part mold (it needs to open up to remove the finished piece) out of silicone mold rubber. The mold rubbers available come in many flavors – soft, hard, heat resistant, not heat resistant, etc. Then you pour in polyester casting resin and wait for it to cure and harden. After it has cured you open up the mold, take out the part and remove any overflow or excess resin. You can buy suitable materials in most hobbyist stores or online.
As I have not done any of this before I used what the local hobby store had (Harraste, Tampere). Efco Silicone mold rubber and Efco Polyester casting resin. Efco Polyester resin is water clear and should make very nice clear plastic parts. There are a few drawbacks – polyester resin is hazardous to your health when casting and it does shrink a bit when curing ( 6 to 8 %). So you will end up with a slightly smaller part than the original.
UPDATE: I have been recommended UV protected polyurethane instead of polyester. It is more impact resistant and should not yellow over time. I tested the polyester lens and it does break quite easily. I will try out polyurethane and report on the results.
Both – the silicone rubber and the casting resin – are two component chemicals, so they are mixed in a very specific ratios with the accelerator. There is no hurry in the mixing as the working time is usually at least 15 minutes before they start hardening. Read the instructions.
Making a silicone rubber mold
First I cast one half of the mold. The inner part of the light lens. You need to make a little tub for the part and design it so that the silicone rubber doesn’t get too much under the part. Otherwise it is hard to remove the original from inside the silicone.
As you can see from the photo above the silicone reproduces all the surface detail of the original piece. Including all the scratches and other imperfections.
When the first half was done I applied some mold release (Vaseline grease) on the edges of the first half. I then put the original light lens back in the mold and made a new tub for it, proceeding to cast a new layer of silicone rubber on top.
Polyester resin casting
Next I cut a few holes at the highest point of both ends of the “lid”, so I can pour in the polyester resin. The second hole is for the air to escape as the resin displaces it. You know that the mold is full when the resin comes out of the second hole.
Above you can see the cast part still attached to the mold half. On the left you can see the small square hole where the resin was poured in. There is a similar hole on the other end. The holes need to be at the highest point so you will not end up with a partially filled mold.
As the silicone is quite stiff and the polyester resin shrinks a little when curing it can be quite tricky to remove it from the mold. Despite being careful I tore the mold a little. Nothing to prevent using it, but I need to be more careful with it.
Above you can see both the mold halves and resin part just removed from the mold. Some cleanup required.
New polyester resin light lens for the Saab Sport on the left and a Saab original on the right. So far looking great.
There is one more downside to polyester resin. Most of them yellow over time if not UV protected. You can coat the piece with UV protecting agent though. Some of the resins also contain UV protection chemicals.
I don’t know how good the Efco resin is in this respect so I’m going to test the part in my two stroke. I’ll install one polyester lens on the car and store another in dark cool place for the same period and see if there is a difference.
Also I don’t know if the resin can withstand all the weather – rain, sun, stones etc. as well as the original. But I think after the summer I will pretty much know if polyester lenses are a go for the Saab Sport.
Please let me know if you have experience in polyester resin casting parts and know suitable resins with good UV properties.
The International Saab Meeting 2016 will be held in Sweden. I will be there and have already registered. IntSaab seems as popular as ever as the registration remained open for a very short time – only a day or two – before the places filling up.
Most of the action seems to be around Vadstena and Linköping. At the moment I think I’ll be staying at the Camping site in a tent. Unfortunately I don’t have the time to attend any of the Pre-Tours. The main event for me will be the track day in Linköping but I also hope to find a bunch of Saab parts to take back home.
See you there! Let’s hope the weather will be better than last years Saab Festival…
I’m taking a break from the Saab 99 turbo metal work. Just to do something else for a while I decided to inspect and repair some two stroke gearboxes. Also a friend asked me to fix his shortnose 95 noisy gearbox.
Finding the necessary bearings was not exactly easy. I did have some new bearings and components that I used on the Saab Sport rally car gearbox. Some are simply not availlabe, like the 25x29x28 mm 2nd gear needle bearings. I needed to find a suitable replacement.
I also did a spare box for the Sport. I got offered a V4 Special 1 drive gears. Fitting them in a two stroke gearbox required using some bearings and the side axle from a V4 box.