Grease Gun Hydroforms Custom Motorcycle Parts

Never underestimate the power of an incompressible fluid at high pressure. Properly constrained and with a full understanding of the forces involved, hydraulic pressure can be harnessed to do some interesting things in the home shop, like hydroforming stainless steel into custom motorcycle parts.

From the look of [Clarence Elias]’s video below, it seems like he has a 100% custom motorcycle build going on in his shop. That means making every part, including the reflectors for the lights. While he certainly could have used a traditional approach, like beating sheet stainless with a planishing hammer or subjecting it to the dreaded English wheel, [Clarence] built a simple yet sturdy hydroforming die for the job. A thick steel ring clamps the sheet stainless to a basal platen with an inlet from the forming fluid, which is ordinary grease. [Clarence] goes through the math and the numbers are impressive — a 1,500-psi grease gun can be mighty persuasive under such circumstances. The result is a perfectly formed dish with no tool marks, in need of only a little polishing to be put into service.

Whether by a pressure washer, a puff of air, or 20-tons of pressure on a rubber pad, hydroforming is a great method to master for making custom parts.

Thanks to [Michael Hogan] for the tip.

28 thoughts on “Grease Gun Hydroforms Custom Motorcycle Parts

  1. This would’ve been even cooler if a simple grid had been traced onto the back of the piece. It’s not the optical surface anyway, and the scalloping effect would’ve been even more dramatic.

    Nice work! The final piece is beautiful and looks super light weight.

    1. Not really much of a “bomb”, there isn’t enough kinetic energy stored. Grease would be pretty uncompressable, if the air is purged out before being pressurized the only energy stored would be in the hoses from expansion. If a leak occurs you only get a little pop and some ooze; if air (any gas) is compressed and a leak occurs you have potential for an explosion. This is why hydraulic cylinders are used in presses instead of air cylinders.

      1. I think this is why he uses grease .. it is probably viscous enough to keep contained easily even if there are tiny spaces at edges of the jig, whereas any stray air will get pushed out through those spaces before it is compressed enough to be dangerous.

        Kind of like how injection molding works ..

      1. Why not. but a 200bar hand-pump is cheaper and you dont have to cut it up and weld/braze fittings to connect a hose to it.
        A cheap way to obtain manually operated high-pressure hydraulic pumps is the cabin-tilter of an old trashed cabover truck. Just three or four screws and you got the Pump, tank, fittings, hoses. All set.

        1. My 20 ton hydraulic press gauge goes up to about 6500 psi. It has a large hand lever pump. You can determine the pressure of a jack pump by a bit of arithmetic using the piston diameters and the jact load rating.

          For a powered version, use the power steering pump from a scrap car. Also considerably easier cleanup than using grease. IIRC, steel boat builders use them with water instead of hydraulic fluid to form compound curves in plates for the hull.

          For the deluxe version buy a hydraulic pump and valve. For higher pressure use a big piston driving a smaller piston.

          Don’t know why anyone thinks using a pressure washer pump is more dangerous. A pin hole leak makes any pressurized liquid dangerous. A large leak is harmless. The only energy stored is the compression of the liquid which is quite small and the expansion of the apparatus which can be large depending upon design. A thin sheet metal shield is all you need to contain leaks safely.

    1. Using hydraulic fluid introduces a significant hazard: high-pressure injection injury. If the work piece fails catastrophically, not a big deal because the energy is quickly dissipated. But if there’s a pinhole in it, a nearly-invisible high-velocity jet can be produced.

  2. Interesting to watch the process. But my hands nearly started bleeding spontaneously when he was using the tin snips. I can never seem to avoid a bloodletting when I cut sheet metal unless I dig out the gloves.

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