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It’s a drag…

October 16th, 2008

Sorry to give you a heart attack, Willem and hdegroot.

I’m concerned about the extra drag that the high cap will introduce.   Trog is already underpowered, with the B30A engine only producing 125HP or so.   So, I did some modeling of the drag calculations.

Google spreadsheet here.

I had to make a number of assumptions, some of which I think are a bit suspicious.   However, I believe the general shape of the curves are accurate.    See the spreadsheet for values and some notes on uncertainties.

Speed vs HP

I added 500lbs to the high-cap version to account for the new walls and windows.    At 60mph, the practical top speed of Trog due to engine RPMs, there’s an additional 16HP required to push that cap thru the air.   When laden with an upper limit of 1500 other camper conversion junk, it’s pushing 100HP.   I’m not comfortable running Trog that hard.

On a 6pct grade, Trog already bogged pretty severely, with top speed being around 30mph.   With the extra weight it’s much worse.   Since speed is reduced, the extra windage caused by the cap doesn’t matter as much.

I encourage readers to check my spreadsheet and look for anything that seems out of whack or missing.   (the 30% mechanical losses seem way high to me).

So, it’s back to popup designs.

  1. October 23rd, 2008 at 03:42 | #1

    well , good to hear you aint destroying the looks all that much 😉 Maybe a turbodiesel Mercedes 300D engine something for you?

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