So on the top issue. Nobody here is a stranger to the complexity and issues of the C70 folding hardtop, and clearly many have devoted long hours and years to learning the ins and outs of the system. So I hope no one takes umbridge as the paragraphs of sacrilege I’m about to type.
Fortunately, at this point my car’s roof actuators appear in excellent shape, no leaks, the pump is good, and the roof opens and closes as it should. When I bought the car the headliner had fallen and after some consideration I snatched out all it leaving bare roof. At some point I’ll recover the front and mid-panel cardboard inserts with inexpensive Harbor Freight drop-cloth canvas – natural canvas makes great looking and durable headliners and it’s cheap, and if you want it can be dyed to a variety of colors. I also removed both front and mid “wings” including hinges and cables. So far the rear wings are still there because they haven’t made the mistake of running into anything when opening and closing. I like being able to see the roof frame and actuators. As with all aspects of the car I’ve been researching “what to do” when that day comes that the overly complex roof decides to have a major malfunction, and along the way I’ve come up with a few dozen impressions, questions, thoughts, and ideas.
As I see it, Volvo seems to have taken particular, and possibly sadistic pride in connecting sensors to nearly every moving part on the C70. For engine, transmission, and associated powertrain systems, all those sensors are welcome and sortable. The invention of closed loop feedback, computer controlled powertrain systems is what has allowed the consumer to live the delusion that internal combustion engines – with their hundreds of interacting parts are relatively trouble free – the sensors and regulators keep everything in homeostasis – much like the human body, right up until a parameter or parameters move outside the ability of the system to compensate, and then the car get’s sick and dies – much like humans as well! Luckily cars are much easier to resuscitate and not at all time-sensitive as with humans.
So here’s the deal: WHY – and this is more a rhetorical question than one seeking knowledge, did Volvo go out of their way to integrate something like a folding hardtop INTO the overall computer management system? What exactly is it about a folding roof that demands the onboard computer light up like a Christmas tree and sound the alarm because a sensor thinks the roof isn’t locked, or because the top is stopped during movement and maybe sags one way or the other, or because a rear locking latch MIGHT not be secured? I was perusing the enormous number of sensors being used to report on everything and it’s definitely NOT a needed complexity in order to have a mechanical roof fold down and back up. I’ve spent years working with precision, computer controlled milling machines, lathes, and 3D printers, capable of extremely precise movement, control, feedback, and they are grade-school level compared to what the Volvo engineers crafted up for the folding roof! It’s like they WANTED the system to be vulnerable to malfunction so they even went so far as to incorporate a byzantine concoction of stretch-prone, breakage assured “cables” to actuate huge plastic flaps GUARANTEED to at some point slam into the tallest head rests I’ve ever seen in a car! Or maybe it’s just because the roof is so low! Either way, it’s not a question of if, only WHEN those hinged “wings” are going to snag and when they do, they twist and warp, fracture and break, and stretch those cables that are made of $1.99 material if bought by the roll, but stamp “Volvo” or “automotive use” on them and suddenly a length of cord gouges the consumer for hundreds upon hundreds of $$$! Talk about a scam! The roof has no less than SIX of these flapping wings and the front four are absolutely going to get trapped and damaged, and along with it maybe torque the roof a bit so it doesn’t close perfectly according to a dozen of the 458 sensors (yes I AM embellishing) just for the roof! And that sensor won’t just like up a special roof “issue” light, no, of course not, it’s wired right into the Throne Room and lights up in the driver’s display if for no other reason to ensure the driver must “worry” if the roof is suddenly going to blow off the car, or heave up and fly away with no warning, and all occupants sucked out by the rush of air like some sort of Hollyweird disaster movie! And then comes the use of hydraulic cylinders – WHY? Again, I’m not really asking for an expert opinion because I already know they could have gone another way but didn’t. A few eons ago I was fortunate enough to be trained as a helicopter pilot in the Army and we definitely learned all about hydraulic systems, especially as applied to flight controls where a malfunctioning hydraulic actuator could force the cyclic control “hard over”, taking the helicopter and occupants with it to their doom. Over the last few decades, electric actuators have been replacing hydraulics because they are self-contained, needing only wires to connect and be controlled, and capable of extremely precise movement – stepper motors being a prime example of that. Electrical actuators are also safer – by using a jackscrew, or ball screw, if they are stopped or fail mid-way, the weight is held the same as a car is held up by a jackscrew – jack. A scissors jack cannot simply “wind down” when you remove rotational force, but hydraulic jacks certainly can and DO collapse should they suddenly spring a leak, or if a errant bystander decides to say, “wonder what this little bolt does?” as they rotate the pressure relief valve to the left and the jack suddenly comes down faster than any human can scamper out from under it. This is why scissors jacks are the standard rather than just as inexpensive hydraulic jacks.
The newest craze is an electric motor driving the scissors jack – wow, whoda thunk it!? Essentially an electric actuator and should that motor suddenly pop a fuse, the whole thing does NOT collapse, only stops….pretty safe. Clearly this a major problem with hydraulic actuators for the C70 roof. They rely on the pressure of a fluid column, and such systems are known for leaking down when the pump is off, which is compounded by the bazillion sensors eager to fire off a malfunction alert and tell the main computer to just stop working until some special incantation has been performed.
The hydraulic system demands leak-prone cylinders, pressure lines with appropriate fittings that run too and fro, a pump, a dedicated electric motor, and worse, a hydraulic control unit to apportion signals and sauces to the right cylinders at just the right instant to avoid the top parts crashing together, or being torqued hideously off to one side! The experts on hydraulic roofs have stated that hydraulic actuators are “better” because they’re less likely to cause the roof to become misaligned due to the fluid column pressure applied simultaneously, but this of course isn’t true. Electric servos can be more precisely controlled, and when a pair are fed from the same circuit, the motors will rotate in sync, and a given voltage will result in a resultant rotational speed. This is why CNC mills and 3D printers use electric stepper motors connected to ball screws to smoothly and PRECISELY align tools and objects and they’re no more prone to go out of control than what happens when one hydraulic cylinder in a pair develops a leak that prevents the two achieving equal pressures so one cylinder pushes harder than the other.
One might be forgiven for thinking the use of 11 hydraulic cylinders along with pump and motor and all the associated wiring, connectors, and of course SENSORS was the result of lazy engineering – let’s just do it the way we did thinking, or planned failure, because Volvo forums are awash in questions about malfunctioning roofs. Of course it’s not all about the cylinders, those ridiculous cables get a fair share of questions and are equally ridiculously expensive! And the problem is NOT the basic roof panel layout, nor the twin, steel, hinged folding and extending frame complexes. As seen when the hydraulic pump pressure is relieved, the roof can be easily manipulated either to open or closed, yet EVEN THEN, those sensors are reporting to the overall system to implant error messages and alerts, and tone alarms as if the operator of the vehicle has tried to steal something from the Volvo company! It’s as if they wanted to insure that even if the end-user decided to remove all the flaps and wings, and cables, flap hinges, and hydraulic cylinders, leaving only the front and rear locks to be manually actuated, the CAR will still send out not just a visual alert, but an audible alarm to sweeten the effect and make the owner wonder if he’s just lit the fuse on catastrophic cascade of clicks, beeps, whirs, and thumps that causes the entire panel to light up and shut down the car in the middle of the 405 “in protest” of a customer having the temerity to think they can bypass Volvo’s engineered in land-mines and escape having to fork over another several thousand bucks!
Volvo also CHOSE to use hydraulic servos that are not (easily) user serviceable or rebuildable. The servos could have been versions built for ready disassembly and reassembly with the full and certain knowledge that sometime down the road they would need to be serviced, but Volvo wanted to keep the hook in deep and force the buyer to come back to buy replacement cylinders at outrageous markup! Generic hydraulic cylinders are quite inexpensive, but when you stamp “Volvo” on one, suddenly it has engineering from the Angels and is worth 20-50 times more! Now, someone who knows what they’re doing can drill out those tiny dimples and separate the end caps from the tubes and source every size and composition O-ring on Earth from the internet for cheap, but that’s not 99% of Volvo buyers until you move into the used buyer groups where invention becomes the mother of necessity. As of now there’s only one notable company that rebuilds Volvo cylinders and they charge a whopping $200 a pop which for a $60K car seems almost reasonable, but for an $8,300, 13 year old car seems ridiculous and basically, ain’t NEVER gonna happen! But hey, that company knows what VOLVO charges for new cylinders so they can certainly charge what the market will bear and of course there are many who end up with C70s and other folding roof cars who simply don’t have the knowledge or skill – or time, or physical capability to do it themselves, who will use such services or worse, go without enjoying the prime reason for buying a folding roof convertible!
The roof should have never have been integrated into the major car functions. The only thing the end-user cares about is that the roof unlocks and opens, then closes and locks. There are a dozen different ways they could have designed a headliner system that didn’t need flaps and wings powered by cables – in fact, they could have powered each of the 6, hinged flap-wings with small electric servo motors that are specific to the mounted location with no central “neural” network should one snag on a head rest, and if such a thing should happen, the damage would be “local” – a bent flap, stripped nylon gear (made to strip against heavy resistance) that can be user replaced for pennies – well, maybe just $100 in “Volvo bucks”! Instead, they chose stretchable cables, running from some unknown location, along a route that only a PhD Volvo professor can decipher, making them nearly impossible for the intrepid home-mechanic to fix – score another one for the Stdealers! (The D is silent, kind of like “Django”).
So now, back to electric actuators. They cost a fraction of what hydraulics cost, are much lighter, never have a problem with seals and leakage, and when mounted require zero collective infrastructure – no pump to die, leak, or check. No pump motor, no ganglion of pressure likes with nifty little fittings. I have machine tools that are 30 years old still going great with their manual, or electronic jack-screw and ball-screw system of inducing linear motion in two directions – and they’ve NEVER malfunctioned. Take 11 e-actuators of appropriate length, load and linear speed rating, attach the exact same fittings to each end and the only thing needed is a couple of wires to a programable power sequence controller that costs about $40. The end result is a less expensive system with easy to replace servos should the need arise using simple plug-n-play. As an aftermarket solution, such a system could be powered completely independently of the car’s power grid by a small Lithium battery that can be removed for charging, or charged off a car tether. Such batteries provide numerous high-amperage jumpstarts between charging and would easily handle the miniscule, sequential draw from an array of e-actuators which don’t even register on the scale of amps demanded for cranking over an engine. Using the original connectors the OEM rear and front locks are retained – including the alert sensors which is really all anyone needs to know the roof has functioned properly.
From observing the roof’s opening sequence, the only potential point of interference is when the front panel is stopped “up high” as the middle panel is moving back and the rear section is rising. At the last instant (probably deliberately designed so), the front panel dips down just in time to slide under the rear section, and from there they all descend in harmony into the trunk. Sequencing this is no problem, as sequencers can be programed to 0.01 second precision. An e-actuator with a linear speed of 50mm/sec can be precisely timed to 0.5mm (0.019″) movement which would result in a roof movement precision better than hydraulics. Stopping the roof in mid-stroke would pose no problem, with no need for an expensive VIDA subscription to set the roof any position you choose for service or simply to admire. Being independent of the car, there would be no alerts triggered, and the jack-screw design of e-servos means that when stopped, they don’t “leak down” or slowly move out of position of some nefarious sensor designed to cripple the system rather than correct it. Since sequence controllers come with remote capability the roof could be opened and closed by someone standing outside the car, no need to get in and crank up, hold the brake and then hold the move button until the roof completes.
The C70 roof isn’t exactly heavy, nor difficult to move, as evidenced by the fairly small, almost model-like hydraulic cylinders. The difficulty in replacing them with something from the off-the-shelf world is finding cylinders equally small, though they’re out there and I have found them, but of course, once we move from mainstream to specialty, the price goes up simply because it can. Which leads us right back to the question of why not yank it all out, replace with matched e-servos wired through a controller box with a remote power source that places no strain at all on the car’s system. The roof and trunk lock function would be unchanged. Each servo would have it’s own shielded wire routed to the trunk where the controller and power source is located with simple plug connectors. At that point the roof is completely independent of the car and it’s alert system.
I’m not ready to gear up to rebuild cylinders or convert the entire system to electric, but it’s an intriguing thought and planning exercise. The labor that goes into rebuilding just one hydraulic cylinder would be more than replacing all cylinders with e-servos – wild.