Archive for September, 2009

Pedal hydraulic power system – Working!

September 29, 2009

I pushed through and got the bike hydraulic power system working this evening – it’s pretty sweet.  Here’s the overview:

bike hydraulic system

I borrowed a bike exercise stand from my friend Emily and mounted a Haldex-Barnes 11gpm two stage hydraulic pump to it using T-slot extrusion.  My friend Keith got a wheel on Ebay and machined a BMX chainring to mate to the left side of it, and I put it on the rear end of my old Bontrager.  A short loop of bike chain connects the wheel to a 12T 45 pitch sprocket.  The pump draws from a reservoir consisting of a 2 gallon plastic bucket; there’s a plastic mesh strainer clamped over the inlet tube.  The pump feeds oil to a 2-position motoring valve.  The valve operates a 4″ bore, 20″ stroke hydraulic cylinder.    Here’s a detail of the pump and drive:

bike hydraulic PTO pump detail

Here’s the valve and cylinder.  The system works as slick as can be.  In highest gear it takes about 40 easy turns of the pedals to drive the ram all the way from one end to the other.  In low gear it’s not too hard to achieve 1500 psi, which is probably a good operating pressure for what we want to do.  By the feel of it it wouldn’t be that hard to do 3000psi either, but either the pump or the valve has a relief that’s kicking in at about 1600.  Before it was kicking in at 1000psi, and I turned the adjuster screw on the valve most of the way in to get the 1600, so I suspect the pump (both are rated for 3ksi).

Brandon did a nice job on the assembly and it’s mostly dry though a few fittings on the valve assembly leak a bit at pressure – gotta torque some of them down further.  I’ll wait until the whole system is assembled in the yard so I can make any layout modifications at the same time.


bike hydraulic valve and ram detail


Bike-Hydraulic Cider press – dry fit, ram in place

September 27, 2009

A quick update – Holly, Brandon, and I did the final dry fit assembly of the new cider press, including the hydraulic cylinder.  It is massive – check it out, with my old MTB for scale:

bike hydraulic press dry fit

We did the last bits of woodworking – mortised and bored the feet, hit the hard edges with a roundover router bit, and tensioned the tie bars for the first time.  I also machined a substantial slab of aluminum – 2″thick, 8″ wide, and 15″ long – to interface the hydraulic cylinder to the wooden crosstimbers.  The resulting structure is quite imposing.  Brandon put together the hydraulic valve assembly with sealant.   Everything got finish planed and sanded by around sunset on Saturday.  It was raining Sunday morning so I put the first coat of poly on the timbers in the basement, and then I machined a couple of simple parts to adapt the hydraulic pump to the bike stand which I borrowed from my friend Emily.  I’m still short a couple hardware bits, but no more than an hour or two away from assembling the hydraulic system complete.

Pedal Hydraulic Cider Press – timbers rough fitted

September 13, 2009

Holly, Brandon, and I put in a good effort on the new press this weekend.  We drilled holes in the oak caps and pine cores of the cross timbers – starting with drill press and Forstner bit, finishing with bit brace and auger.  We then assembled the caps to the cores with wood glue (around a quart total) and clamped, using both the 1″ threaded rods that will become the tie bars and also K-body clamps borrowed from Holly.  I had to run over to Holly’s where we got out some more oak caps since I had only made 4 in Maine instead of the necessary 8 due to a temporary brain malfunction.  Sunday morning I bonded the second pair of cross timbers, and started work on the verticals.  I then took a break to go walk the dogs around Fresh Pond, and Brandon came over later in the afternoon.  We cleaned up the joinery with rabbet plane, chisels, low angle block plane, and (new addition) carbide-tipped 3″ Bosch power planer, then belt sanded everything and dry fit it.  The result is seen in the photo below – next steps are to bore the cross timbers for the threaded rods that will bind them to the verticals, do a final dry fit to soften the edges with a roundover bit, and then assemble and finish.  It’s going to be BIG!


Hydraulic press progress

September 11, 2009

All the parts are on hand, and construction begins in earnest this weekend on the bike-hydraulic cider press.  The pine cores and oak caps for the main crosstimbers are planed and jointed for lamination, and the side posts and post feet are rough to length.  The next step is to get a jug of wood glue and bond up the timbers.  Meanwhile I can cut the mortises and tenons on the posts and feet, and drill some of the holes.  Should have something to look at by the end of Sunday…