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Author Topic: Should I enclose my rear wheel?  (Read 6472 times)
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sofadriver
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« on: January 01, 2015, 10:48:39 PM »

Wheel discs (similar to Moon hub caps) on a motorcycle rear wheel. Is it worth it? Any pros or cons?
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Mike in Tacoma

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Stainless1
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Robert W. P. "Stainless" Steele Wichita, Kansas



« Reply #1 on: January 02, 2015, 12:30:10 AM »

Wheel discs... no
tail Fairing as described in special construction... 10 inches behind tire, 4 inches off the ground... yes, major reduction in drag as compared to the tail in your avatar
 cheers
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Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
sofadriver
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« Reply #2 on: January 02, 2015, 01:01:49 AM »

Wheel discs... no

Fair enough. I really didn't want to jump thru all the hoops to do 'em anyhow.

The avatar pic shows my A/G tail with the APS fairing. I was planning to run both classes. Didn't want to change it just for a pic in front of the sign.
Here's a (bad) pic of the APS tail.


* rsz_2014-07-26_182541.jpg (176.57 KB, 800x600 - viewed 174 times.)
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Mike in Tacoma

"aww, what the hell - let's just do it".............

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tauruck
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« Reply #3 on: January 02, 2015, 04:15:25 AM »

I'm a simple lad and rocking the boat isn't my thing but how will you
know if you don't try?.

R&D is a big part of racing so I'd say do a back to back and get your answer that way.

How many bikes do you know of that run wheel discs?.
Someone came up with the wheel disc idea and they are still around.

Try them and see what you get. wink
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Koncretekid
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« Reply #4 on: January 02, 2015, 08:34:01 AM »

In 2012 I ran the 500 APS PG record at 134 mph.  For 2013 I added rear wheel discs, a modern 3 spoke front wheel, a few changes to the motor (length of intake and exhaust), and ran the same record to 143 mph.  This was at AMA/BUB before the fully enclosed tail was permitted.  I almost think the wheel discs were part of the 9 mph increase in speed, but you know, change 4 or 5 things and then try to decide which change made the real difference.


* Bonneville Bike at Salt Flats APS 500cc.jpg (46.22 KB, 1438x953 - viewed 171 times.)
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Seldom Seen Slim
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« Reply #5 on: January 02, 2015, 10:37:36 AM »

Here's a quick tangent/hijack:

I was looking through the rules to find what they say about discs covering the wheels -- and found the page where we're told that fronts must be "cross ventilated" but rears are okay for discs.  At the end of that rule (7.B.10) is a comment that the installation of the disc must be of "...a workmanship like manner".  The word workmanship has baffled me for a while since workmanship (the word) is a noun.  It means something like "the degree of skill with which the job is done".  It isn't an adjective - so the use here (7.B.10, for instance) could easily be interpreted as "...a crappy manner" or a "...a super-duper manner" or anything -- and still be correct to the letter of the rule.

Next -- look one word above workmanship in the dictionary to find the adjective "workmanLIKE" (emphasis mine).  This one means "showing efficient competence", and that's probably what the rule-writer had in mind.

Being pedantic sometimes is a good thing*.  I wonder what it'll take to get the word changed throughout the rulebook? smiley

*Ask me how I know, but be ready for a story.
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Jon E. Wennerberg
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Stainless1
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Robert W. P. "Stainless" Steele Wichita, Kansas



« Reply #6 on: January 02, 2015, 11:10:03 AM »

Jon, submit a rule change request...

back to subject...
Maybe that is a bad pic, it looks a little like a closed scoop... is there an opening in the back for trapped air to get out?
does it end up 4 inches from the ground with the rider mounted?
Does your fairing bellypan go back close to the rear tire?

Hey, not being critical, I am not a bike aero guy, I know what worked for us before the long tail was allowed, we met our goal and decided not to build a long tail and stay in the fight.  Building to the limits of the long tail put 10 to 25 MPH on bikes at Bonneville
It is a discussion... look at the A fairing pictures that have been posted.
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Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
wobblywalrus
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« Reply #7 on: January 02, 2015, 12:31:00 PM »

A few changes were made last year including rear wheel covers.  A 7 mph gain was made and all of this cannot be attributed to the 5 hp power increase.  There were a few aero changes and it is hard to attribute the increase to the wheel covers.

Last year was a wetter one and salt accumulation was an issue on some days.  The covers kept salt from accumulating on the rear wheel rim and the wheel stayed in balance.  The covers stay on the Triumph for this reason.   
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sofadriver
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« Reply #8 on: January 02, 2015, 09:46:21 PM »

back to subject...
Maybe that is a bad pic, it looks a little like a closed scoop... is there an opening in the back for trapped air to get out?   (YEP - cellphone pic at a bad angle)
does it end up 4 inches from the ground with the rider mounted?   (Nope - poor execution of a mediocre design   embarassed
Does your fairing bellypan go back close to the rear tire?   (YEP - but not nearly as close as the new design will)  evil

The new version will use only the wheels, fork and transmission from the first bike. It's a whole new build. Much was learned.
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Mike in Tacoma

"aww, what the hell - let's just do it".............

Bike #833
100cc A/G, A/F and APS/G (in 2019)
Stainless1
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Robert W. P. "Stainless" Steele Wichita, Kansas



« Reply #9 on: January 02, 2015, 11:41:32 PM »


The new version will use only the wheels, fork and transmission from the first bike. It's a whole new build. Much was learned.

That is the important part... Experiment, change, try to go faster.... it is what we do  cheers
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Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
wobblywalrus
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« Reply #10 on: January 02, 2015, 11:49:59 PM »

"How did you make the wheel covers?"  I was asked this today.  This looks like a good place to put the photos.

Several bikes go real fast without much horsepower and they use wheel covers.  Rocket scientist logic told me that wheel covers couldn't hurt.  They might help aero a little bit.  They keep salt from accumulating on the rim and they look cool.  These are enough reasons to use them every year.

The covers were made using what I had on hand.  The wheel rims are covered with tape so they will not be scratched by the covers.  Blue duct tape was used in the photos.  It peeled up from the rim after sitting in place for a few weeks.  Now I use two layers of contractor's grade very sticky masking tape.  The good quality American made stuff.  It stays where I stick it.

The pix shows the first cover.  The inner circumference fits between the spokes and the spoke flange.  The cover is made from two halves that are pop riveted together.  Three aluminum spools attach one cover to the other using flat head stainless steel screws.


* Wheel cover 1.jpg (361.61 KB, 1024x654 - viewed 182 times.)
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wobblywalrus
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« Reply #11 on: January 02, 2015, 11:53:10 PM »

The wheel cover shown in the previous post is shown on the bike.  The edges are taped to the rims.  There is a little hatch to provide access to the valve stem.


* Wheel cover 3.JPG (300.55 KB, 768x873 - viewed 190 times.)
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wobblywalrus
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« Reply #12 on: January 02, 2015, 11:56:18 PM »

The second wheel cover is shown.  It is all one piece.  It is taped to the rim.  The paint marks near the screws tell me they have been tightened and I do not need to recheck them.


* Wheel cover 2.JPG (269.56 KB, 795x768 - viewed 180 times.)
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sofadriver
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« Reply #13 on: January 03, 2015, 01:41:56 AM »

Pretty cool Wobbly, but let me make sure I'm gettin the concept here.

You cut the discs then you cut a hole for the hubs. The three screws simply hold the two discs together but do not act as locators, is that right? (locating is done by a VERY close fit of the disc over the hub, correct?)
What keeps the discs from rotating around the hub? I can see that they couldn't rotate very far before being stopped by the spokes but is that the job of the tape? And being taped in place is OK with tech?

Did you have those discs water cut/ laser cut?
How do you apply wheel weights?
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Mike in Tacoma

"aww, what the hell - let's just do it".............

Bike #833
100cc A/G, A/F and APS/G (in 2019)
wobblywalrus
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« Reply #14 on: January 03, 2015, 06:31:19 PM »

That first cover is two pieces riveted together so the inner circumference will fit inside the gap between the spokes and the spoke flange.  The Triumph is sorta weird in this way.  The spokes on the back wheel on that side are all "inside" style spokes.

The three spools stick through the spokes and they are located so the cover is positioned exactly right.  The spokes keep the spools fixed so the covers will not turn.

The wheel is balanced without the edges being taped to the rim.  There is enough room for me to squirrel the weights inside and to stick them to the rim where needed.  The edges are taped after the wheel is balanced.

Tech would be a problem if the tape held the covers on.  They are securely locked in place without the tape.  It is simply there to keep the salt out of the space inside the covers.

I do not know anything about water or laser cutting.  The covers are cut using tin snips and pounded flat on an anvil with a rubber hammer.  Do not use a metal hammer.  It will spread the aluminum out when hit and the dang covers will never fit. 
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