Front fender airflow

[JPark]

Is there a significant advantage in cooling airflow using the 100B low mount fender instead of the 100B+ high mount style? Much as I nostalgically relate to the Rat style MX high mount, I'm also fine with the trials look low mount.

Hodaka Parts lists the weight of the bracket assembly as 8 lbs which seems rather porky and unsprung to boot, though it should have some utility as a fork brace. I do some prolonged high speed [such as it is on these things] now and then and probably there is enough swirl around the high mount to cool things, but the fender does live awfully close the the fins.

A low mount should have less aero drag as well. The top of a knobby tire is a windmill going twice as fast as the bike [4X the drag] while the bottom has no drag at all.

[thrownchain]

Woah, way too much thought on that one, been stuck inside tooooo long.

[Dale]

Yeah, I have zero scientific data however I do have some history with the high mount front fender. Back in 1971, I wrung out a B+ daily and it never over heated. Never an issue with that bike of any kind. So I vote for the high fender.

[Darrell]

In the late '70s Yamaha, for one, started louvering the rear half of the front high mount fenders for cooling air to pass through to the engine. It looks pretty trick, at any rate.

[JPark]

I have a rather 'experienced' fender that I could practice louvering on. It would be a lot easier in aluminum. I'd think that the result would probably end up pretty floppy because, as it is, it's only real stiffness results from form stiffness and much of that would be gone. I could just perforate it, but drilling stainless is a 'bit' tedious; you have to go slow or it hardens on you. Plus, I'd need to choose between a lot of small holes and a few big ones.

It's not as bad as it looks because there's bound to be turbulence behind the fender which at least exchanges the air. It's just not as linear with speed as being out in the breeze, like a BMW cylinder.

The effect of air speed on cooling maxes out at about 45 mph; faster airflow doesn't remove heat faster. This explains military convoy speed, and why tires get hotter the faster you go.

I thought of making an aluminum low fender mount, but without the long stays the fender would probably crack apart. It's a lot more isolated up high and above the suspension.

As Thrown says, way too much thought.

[Bullfrog]

The weight quoted for the low front fender mount (8 pounds) is surely the all-up weight of strong box, part and packing to ship a relatively bulky part. I don't have a loose fender mount to weigh . . . but I'm purty dang shure the part weight is more on the order of 1 pound. And I used the low mount system on my trials bike - and I simply wouldn't tolerate a fender mount system which weighed that much on the front end of a trialer.

When I was in my twenties, I worried about improving air flow over the cylinder - especially after installing a Tony D Preston Petty front fender. But I never got around to actually doing something about it . . . and never had an engine cooling problem either (well, except in mud . . . which is why I wanted the Tony D fender ).

Ed

[JPark]

Yes, eight pounds seemed way too high. Maybe he ships them between two fir 2X4s. I like the look of the low mount so maybe I'll scavenge around for a mount. Then I'll have both options.

It would be nice to know what the actual weight is. Anyone?

[taber hodaka]

Sissy,s ride it standing up and keep it in a wheelie you will have less friction from the front tire turning and full air flow available to the engine. Boy eight pounds over weight is better than the extra 30 pounds ive added now --------------------------- Clarence

[matt glascock]

I like that idea Clarence. Saves a fortune in front tire replacement.

[Darrell]

What about lowering the front tire pressure about 8 pounds to offset the extra weight of the fender? No-brainer.

[MTrat]

A 100B low mount front fender weighs 2.25 pounds with the mounting hardware but without the rubber mud flap.

[bobwhitman]

Watch out Ed, Darrell’s a serious candidate for Tech Editor with the 8# recommendation!
Bob

[Bullfrog]

Oh my! The math works! Why didn't I think of that???

Ed

[matt glascock]

Hey, that has me thinking. If I attach the valve stem of the front tire to a vacuum source and back it down to, say, -4 PSI, would the front end loft itself - maybe get me into the single digit dab count on the C-line?

[viclioce]

Hey, that has me thinking. If I attach the valve stem of the front tire to a vacuum source and back it down to, say, -4 PSI, would the front end loft itself - maybe get me into the single digit dab count on the C-line?

Victor

[MTrat]

Victor, I had to quit using helium in the tires and sealed frame after I lost the bike to the clouds. =)