Featured image: a modified Heusinkveld Sprint brake pedal
A Facebook post caught my eye a few weeks ago. It was a mod kit to add a hydraulic damper to the excellent Heusinkveld Sprints.
As much as I’m kind of keen to own a set of Ultimates, I can’t justify the extra expense. I think that same applies to most of us! But still, I do like Hydraulic pedals.
What does a hydraulic sim brake pedal feel like?
A Hydraulic damper on a brake pedal adds a sense of realism to the compression (pressing the brakes) and rebound (lifting off the brakes). Sit in your road car and compress the brake pedal and you’ll know what I mean, a smooth feeling of compression that won’t move any faster by pushing harder; it’s set (or “tuned”) to compress (“bump”) in a certain way. Same when you lift off the brakes, the pedal won’t immediately spring back. They return according to the way the damper is tuned.
The best hydraulic sim pedals do this so well, they feel like real brakes. The reason why hydraulic pedals cost more, is that a good damper is expensive. Companies like Heusinkveld custom tune their own dampers for the application, which again takes time and costs R&D money. The engineering required to get a smooth mechanical input to produce a linear, predictable output from a load cell is also much harder than you might expect.
Can you modify Sprints to feel like Ultimates?
The tl;dr, I’m disapointed to say, is not with an inexpensive 3d printed kit. Although it’s a little more complicated than that. Read on, and I’ll explain.
I’m not going to name the manufacturer of the kit I’m using. I feel it’s unfair to call a hobbyist out when there are cheaper pedals on the market that would benefit from a hydraulic modification. So, if you’re a Logitech or Thrustmaster owner, or with any less sensitive potentiometer based brake pedals, I think you’d be very happy with a well-reviewed hydraulic brake mod.
But Sprints are a different animal to a set of Thrustmaster T-CLMs. Sprints have load cells, which are in orders of magnitude more sensitive than potentiometers. You can stroke a brake pedal on a Heusinkveld set with your finger and see the input in Diview! Sprints also deal with significantly higher brake forces; I often have mine set to around 50kg of load – I’m reasonably sure 50kg would snap G29 pedals in half.
So when you’re looking at modifying high-end pedals, this is what you need to take into account. Nevertheless, I thought it’d be fun to test this in practice and install a hydraulic kit for my Sprint pedal.
The kit comprises of a set of 3d printed components, a damper and a medium sized elastomer stack:
Compressing and releasing the damper in my hand immediately gives the game away: there’s no rebound on this damper, only compression damping. That’s weird; hydraulic dampers control both as we already know. But other than this, the kit is manufactured to good quality.
It’s quite easy to install, once you’ve seen a picture of a pre-built version. My only feedback is the tolerances – the elastomer fits so tightly it needs a fair bit of patience, and grease, to fit. Here it all is:
Once installed, I found that the new elastomer was much too soft. With a bit of a reconfiguration, I decided upon the original HE rubbers and spacers with a stiffer setting on the damper.
Here it is in use with my Porsche RSR (I’m getting ready for the Sebring 12 hours).
I mentioned earlier, I don’t think this design is right for a Sprint pedal. If you have a budget pedal, like the Logitechs, Fanatecs and Thrustmasters of this world, I think the additional stiffness added by the damper will improve the feel of compressing the brake pedal, with a small amount of benefit to the rebound.
With Sprints it’s a different matter. In my opinion, there are two problems.
Firstly the damper is poor; it’s only 1 way – lots of damping on the compression but no rebound – it springs back very quickly. This is quite unlike the approach you will experience on professional hydraulic dampers, like Sim Trecs, Ultimates and so on. The dampers on my RC Tamiya model cars were better than these!
In the image, you can see the damper is mounted along an axis that looks like a parallel to the elastomers. But I think the second problem is that they’re only parallel at one point under load, the slope surely can’t be perfectly constant as the brake pedal compresses. As the bottom end of the damper has limited pivot potential (i.e no cam based movement) it is constrained to be parallel to the load cell axis, so it can never work properly.
Hobbyist mods cause more problems than they solve for high-end sim gear
The outcome is that this mod stiffens the compression as you’d expect, but the almost negative amount of rebound damping they’re adding (the dampers spring outwards quickly) makes the brakes harder to control when you’re trailing off.
As you lift off the brakes, I think there’s a tiny amount of snagging as the slope changes which the load cell detects as an input. It makes trailing off the brakes a bit of an art form. The bottom of the damper mount needs to be able to flex up and down to avoid this problem.
In summary, this mod kit adds nothing and creates new problems on an otherwise really good set of pedals. It’s sad but true that unless you cough up the extra cash, or do a far, far better job than this with the design of a modification, you’re going to cause yourself more problems than you solve.