I'm not an electronics expert, but I think that you might struggle to get the exactly linear speed response you'd need from a DC motor as the voltage increases. You'd need this to get an accurate speedo reading throughout the range rather than at just one point.
If you can't adapt the T5 you have to a gear driven speedo setup, it should be possible to rig up a lightweight belt drive for the speedo using the the transmission slip yoke as a driving pulley. Lots of early European cars used this type of setup to drive a speedo cable via a driven pulley mounted alongside the transmission. A lightweight round section belt is all you'd need, it's not really transmitting any power.
Stuart.
Last edited by Stuart_Giles; 12/09/2008 2:31 PM. Reason: spelling
