Motorcycle Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
I was a motorcycle shop owner in the 1970s and I think it was Cycle News which included a poster with Evel Knievel's Snake River jump attempt on one side and "The Great American Motorcycle" on the other side. I am trying to find out a little more about "The Great American Motorcycle" in the picture. The thing is huge, has a big front fork with two huge spring shocks per side, and handlebars which have to be about 6 or 7 feet long. It has some sort of car motor, I can't tell or remember what it is though it does not appear to be a V8, a long driveshaft to the rear wheel, and there is some sort of rear suspension with the same sort of spring over shocks as in the front. In the picture a man is astride it with his feet on the ground, the thing is so enormous and obviously heavy that its hard to imagine him riding it; yet he may have because the picture is taken outside. I read an article about it some years ago, the article said, as I remember it, that the man who built it built two of them and one may still be around somewhere.

Does anyone know what I am talking about?
 

·
On The Road Again!
Joined
·
3,005 Posts
Gelbke actually built three Roadogs before he was murdered.
I believe he associated with the wrong kind of people.
 

·
Registered
Joined
·
515 Posts
It has some sort of car motor, I can't tell or remember what it is though it does not appear to be a V8,
It's a 4 cylinder inline Chevy II engine in the RoaDog, displacing 153 cubic inches, right around 2500 ccs. It was a pushrod overhead valve engine with an 8.5:1 comp ratio, that was basically the Chevy inline 6 with two cylinders removed, and put out in the neighborhood of 90 hp in stock form. Hardly an impressive power to weight ratio when powering a 17 foot long, 3200 lb monster like Gelbke's RoaDog.

For comparison, the Chevy II sedan only weighed 2600 lbs.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #8
My wife had a little blue Chevy II, nice little,or medium sized really, sedan; not really a speed demon though. I wonder why he didn't use something with more power? A small block V8? Wouldn't have affected the weight or size much.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #10
The Chevy motor was used in boats. The 153 was 120hp, and the 181 was 140hp.
UK
Well that's not too bad, my last bike a Dyna with 113 cu.in. had 120 tq and 110 hp and it would step out pretty nicely, so 120 is good hp; although my Dyna did not weigh 3200 pounds.
 

·
Registered
Joined
·
515 Posts
I'm no expert on Gelbke or the RoaDog. What I know was from reading, mainly online, but they say he wanted a smooth, dependable, long distance touring machine, so acceleration would have been much less important than reliable, hour after hour running. Since the ultimate top speed of a vehicle is mainly limited by it's frontal surface area and air drag coefficient, and making it longer and heavier doesn't increase either of those, and indeed longer likely reduces the drag coefficient, and Gelbke's big bike didn't have much more frontal area than a contemporary Harley tourer, which would have had something like 55 or 60 horsepower, perhaps he had plenty of go for his purposes.

There's are supposedly stories about him blowing through towns at 150 mph, and the cops stopping him but not ticketing him, because they wanted to ask about the bike. 150 seems like an exaggeration, but certainly he could have exceeded any US speed limit both then and now, by a good margin.

In the end, the RoaDog was just a prototype, and when Gelbke went into limited production of a similar concept, it was a much smaller, lighter bike. The Gelbke "Auto Four" did keep one thing the same though, it used an inline four cylinder engine. Auto Four - Wikipedia
 
1 - 12 of 12 Posts
Top