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Author Topic: Stumped On Front Fender  (Read 2393 times)
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Scottie J
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« on: January 01, 2015, 10:18:12 PM »

Hi Everyone,

I am building my 1958 Enfield Indian for MPS-750-PF.  I am at a loss on what to do for a front fender.  I chopped my original front fender, but am getting mixed opinions on it.  Not that opinions are of any real scientific use, but valid none the less.  But, I also like the look of a naked front wheel too.  I'm at a cross roads because I am building my bike for multi-purpose.  It would be sweet to earn a record, but I am more after the adventure and thrill of land speed racing and don't want my bike limited to only land speed racing.  I also want to take it to local road tracks, play at the drag strip from time to time, and still cruise the streets on the weekends.  Eventually some day I'd like to install a full Charlie Toy fairing, but at this time I'm just not interested in going that route.  I am however going to install a vintage Viper fairing for now, there's a local shop that has a NOS one for $60, and I always liked the look.

So, the real question here is this:  How does a front fender ultimately effect aeros?  Is there any harm in not running a front fender at all?

Here is a pic of how I currently have the front end set up.  I recently fabricated the fork brace, and since have been unsure what to do with the fender.  Thanks!





« Last Edit: January 01, 2015, 10:20:31 PM by Scottie J » Logged
tallguy
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« Reply #1 on: January 01, 2015, 10:54:16 PM »

Here are my opinions:

If you want the appearance of a fender, it should be large enough to be seen.
I think what you have is way too short -- you should have some of it above the
top of the tire.

Your fork brace appears to be too flimsy to do much good.  the "horizontal" tube
should have a lot of torsional stiffness (suggest a round tube for this), and should
be more securely attached to the other tubes, compared to what you now have.

tallguy
mechanical engineer, and motorcyclist (for decades and decades)
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sofadriver
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« Reply #2 on: January 01, 2015, 11:02:47 PM »

Man, if that were my bike I'd slap some old pillow on the tail with a bungee and ride it just the way it is.
It looks awesome!
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Mike in Tacoma

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tauruck
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« Reply #3 on: January 02, 2015, 04:18:51 AM »

Why do you need a fork brace?

I don't think you need one.
Just my opinion.
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Scottie J
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« Reply #4 on: January 02, 2015, 06:49:14 AM »

Why do you need a fork brace?

I don't think you need one.
Just my opinion.
 


Because I start getting speed wobbles over 75mph on asphalt.
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wfojohn
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« Reply #5 on: January 02, 2015, 08:00:35 AM »

Scottie,

Right or wrong I don't know "BUT" I was told by a roadrace guy that an air cooled motor will run hotter without a fender. Was told that the air trailing up the back side of the tire as it rotates causes a disturbance at around a third to half way up before it detaches and disturbs straight clean air from reaching the engine in a direct path to cool it. It made sense to me, I never tried to prove it so take this Free Advice as an attempt to help and worth every cent you paid for it. If you look at some of the MPS bikes they seem to favor a fender that covers about the top half of the tire.

I'd be interested in imput from some that understand a bit about air flow.
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Koncretekid
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« Reply #6 on: January 02, 2015, 08:10:02 AM »

At Bonneville you'll want a fender to keep the salt off the front of the motor and your face shield, if nothing else.  I ran 125mph with the 500cc motor and a fender at Bonneville; 130 mph with the 600cc motor at Loring (asphalt) and no fender.  Not really a valid comparison, but I don't think the front fender makes much difference on a naked bike.
Tom

P.S. The Royal Enfield uses a leading axle front fork which reduces the trail.  If you can find some other forks with the axle in line with the forks, you'll increase the trail which should reduce the tendency to get speed wobbles.  If you can swap sides, you'll really increase the trail (axle behind the forks) but you may up with clearance problems.


* Bonneville Bike at Loring Naked 600cc.jpg (288.06 KB, 2592x1728 - viewed 146 times.)

* Bonneville Bike at Salt Flats naked.jpg (80.89 KB, 1648x933 - viewed 254 times.)
« Last Edit: January 02, 2015, 08:22:06 AM by Koncretekid » Logged

We get too soon oldt, and too late schmart!
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Scottie J
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« Reply #7 on: January 02, 2015, 10:00:37 AM »

I like your thinking Tom, but I believe if I reverse the fork legs the wheel will interfere with the exhaust headers.  I wonder if the plastic fender from the GS550ESD will work.
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Seldom Seen Slim
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« Reply #8 on: January 02, 2015, 10:53:30 AM »

Consider the need for a fairly big front fender on the salt.  The front wheel will pick up salt and throw some of it off the top and front of the tire.  Most of that will go all the way down and hit the surface in front of you, but quite a bit will get flung forward enough that it'll end up rising and hitting your faceshield and the rest of your helmet, with also likely some getting on your neck and even a bit flying around inside your helmet.

With no fender at all you're likely to get plenty of salt in/on your head.
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Jon E. Wennerberg
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manta22
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« Reply #9 on: January 02, 2015, 11:05:45 AM »

As Grace Slick says in "White Rabbit", "....feed your head." I don't think she meant feed it salt, though.

Regards, Neil  Tucson, AZ
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Regards, Neil  Tucson, AZ
Koncretekid
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« Reply #10 on: January 02, 2015, 12:32:54 PM »

As Grace Slick says in "White Rabbit", "....feed your head." I don't think she meant feed it salt, though.

Regards, Neil  Tucson, AZ
How about the rest of her advice?

"One pill makes you larger
And one pill makes you small
And the ones that mother gives you
Don't do anything at all

Go ask Alice
When she's ten feet tall
And if you go chasing rabbits
And you know you're going to fall

Tell 'em a hookah smoking caterpillar
Has given you the call
Call Alice
When she was just small

When the men on the chessboard
Get up and tell you where to go
And you've just had some kind of mushroom
And your mind is moving low

Go ask Alice
I think she'll know
When logic and proportion
Have fallen sloppy dead

And the White Knight is talking backwards
And the Red Queen's off with her head
Remember what the dormouse said
"Feed your head, feed your head"

What you need is that pill that "makes you small."
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We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!
wobblywalrus
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« Reply #11 on: January 02, 2015, 12:45:34 PM »

Salt on the engine fins does not help the air cooling.  Experience showed me to run the half-moon fender to reduce the salt buildup on the front of the motor, regardless of the aero.  This is especially important if you run for records like FIM with a short turn around time between the down and back.  There is not a lot of time to clean the fins and to do everything else like fuel fill up, checking into impound, waiting for escorts, etc. 
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Scottie J
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« Reply #12 on: January 02, 2015, 01:19:48 PM »

Thanks for the advice guys.  Much appreciated.
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