Originally Posted by Toobuilder
...Engineering practices specifically caution that hose assemblies need to have some slack in them so they don't become a "structural element" between two assemblies - In this case the hose is certainly a tension element, and thanks to the adel, it's a fairly effective compression element as well. When the heads move apart due to thermal or operating stresses, the hose is not going to stretch. The reaction is going to be bending through the 1/8NPT nipple.
Originally Posted by rcpaisley
The teflon hoses linking cylinders are not stiff hoses. Hard line is a "stiff hose".
We have had no issues what-so-ever with properly supported installs. The referenced injector failure was after many years of operation with an inadequately supported install.
"Support your fuel rails and anything else bolted to your engine -properly" is the lesson here. Robert
Both arguments have merit, although the parties are not talking about the same loads. Mike is discussing tension/compression due to fore and aft
movement of the heads. Robert's adel clamp addition is an attempt to provide support in response to a vertical
movement of the heads, the effect of torque reaction (block shake counter to prop rotation), or piston side loads within the cylinders.
The modulus of elasticity for teflon is only 0.5 Gpa, roughly 140x less stiff than alumimum, and fore/aft cylinder displacement would be very small. Given those factors I would tend to ignore the tension/compression concern.
However, Robert can't have to both ways. If we buy into the argument that the teflon hose is not
stiff (and the above modulus says it's not), then the adel clamp cannot support the injector bodies. At best, the adel can only support some percentage of the hose mass. It's an improvement, but the feed fittings are still free to vibrate in the threads of the aluminum tube injector mount, and the injector mount itself is still cantilevered from an 1/8" NPT aluminum nipple.
Previously I asked Robert to confirm where
the injector mounts had broken, and here's why. Although the cut-thread NPT nipple is being fingered as a potential failure point, I suspect the broken mounts pre-dated those nipples, and being installed on welded steel bungs, had to have been failures of the aluminum tube body.