stiffening up the frame

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subxero
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stiffening up the frame

#1 Post by subxero » Mon Oct 20, 2014 5:07 pm

So it only makes sense that if someone is going to beef up their front suspension and rear suspension & swingarm that it is not a bad idea to beef up the frame a bit.

But is it a must? Say on an 84 rz350? Is the frame that flexy?

What are some solutions?

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JonW
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Re: stiffening up the frame

#2 Post by JonW » Mon Oct 20, 2014 6:52 pm

have a look thru the builds section, about a tenth of the projects do it, most dont, but it will give you ideas. Sure the frame is more flexi than a modern bike, but its not like its about to fall apart. One problem with bracing is that it becomes hard to access the motor etc, the other is that its often not where you want it to be (ie the swingarm pivot) and its also heavy...
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

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hondaror
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Re: stiffening up the frame

#3 Post by hondaror » Mon Oct 20, 2014 7:35 pm

The RZ frame is based on the TZ frame, so it's not too bad. The RD LC frame is bad, and needs bracing if beefing either or both ends. If you are going to track the bike only...go to town with bracing, running slicks. Otherwise, not such a big deal.
Rory
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1985 RZ350
9 1986-1990 RZ350s
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mkane
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Re: stiffening up the frame

#4 Post by mkane » Mon Oct 20, 2014 7:47 pm

I have a hot rodded a/c 400 track bike that's quite quick and so far I haven't really felt the need for bracing. I running non DOT treaded tires. What does flex is the front end and it's scary looking at the results. I've had to move the rotor inboard 1.5mm to keep it from rubbing on the slider. All the rotor buttons were ruined in the process. Visions of having it explode @ 100mph kept me awake until it was fixed.

subxero
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Re: stiffening up the frame

#5 Post by subxero » Mon Oct 20, 2014 10:13 pm

Glad to hear that the frames are decent enough, i wasn't thrilled about bracing it up if it wasn't to bad. Ill probably leave it be for the time being and if i feel the need for it later have at it.

mkane
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Re: stiffening up the frame

#6 Post by mkane » Mon Oct 20, 2014 10:49 pm

Careful when bracing. You can do more harm than good if not done in the right places.

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JonW
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Re: stiffening up the frame

#7 Post by JonW » Mon Oct 20, 2014 11:31 pm

or overheat the thing an warp it :/
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

Like Watches? www.PloProf.com & www.DeskDivers.com

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heyjoe
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Re: stiffening up the frame

#8 Post by heyjoe » Tue Oct 21, 2014 12:18 am

We braced up a scooter frame by wrapping it in a layer of fiberglass cloth to electrically insulate then several layers of carbon fiber. Polyester cloth was used to shrink it down tight once wet out. Were left with a frame that was way stiffer than stock. It had about 3mm of carbon over the steel. Because of the fairing covering the frame it looked completely stock.

The bike was more stable but when you take a 25mph scooter and put enough power in it to run 60, everything becomes a compromise.
RZ350K and RD350B, original owner
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CR500R ... waking up
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JonW
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Re: stiffening up the frame

#9 Post by JonW » Tue Oct 21, 2014 1:23 am

Interesting idea Joe.
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

Like Watches? www.PloProf.com & www.DeskDivers.com

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heyjoe
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Re: stiffening up the frame

#10 Post by heyjoe » Tue Oct 21, 2014 11:43 am

Here's the details of a carbon wrap of a steel frame. This frame like most scooters is a simple U shape.
Cleaned the frame with acetone.
Image
Left the paint on.
Used super 77 spray glue to apply the composite.
Image

Started wrapping with a thin layer of fiberglass cloth.
Image

Image
Here it is at the start of wetting it out with epoxy. You can see that we added some long strands of carbon to help hold the pieces in place, we used scraps of carbon fiber left over from a previous project. There are several layers in random directions . Most of the carbon is being held in place with Super77 at this point.

Image
It is wet it out with epoxy. and we are starting to wrap the frame with the rip stop nylon fabric. The ripstop is basically a peel ply. It looks like a prickley pear at this point.

Image

Then took strips of polyester cloth and stretched over the sticky wet mess.

Image
The exposed ends of the polyester were duct taped down. Used a heat gun to shrink the polyester cloth. This causes the fiberglass and carbon fibers to be pulled down on to the steel frame, bleeding out the excess epoxy. Once cured the fabric is removed from the carbon, The peel plies don't add much strength and are very rich in epoxy. Epoxy is weak.

Image
This is pretty much done.
RZ350K and RD350B, original owner
Both running!!

CR500R ... waking up
Motors by: Roger @ WickedATV

My RD-350 rebuild page updated 6/10/12

Bare
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Re: stiffening up the frame

#11 Post by Bare » Sat Nov 08, 2014 11:05 pm

Definitely an 'interesting' exercise.
Hopefully you don't actually believe that adds ANY strength whatsoever though

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heyjoe
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Re: stiffening up the frame

#12 Post by heyjoe » Sun Nov 09, 2014 12:30 am

Sure did, it added a lot of stability to the bike. We didn't test it to destruction but the bike flexed way less.

If the steel tube is flexing less it is because much of the load is transfered to the outer skin.
RZ350K and RD350B, original owner
Both running!!

CR500R ... waking up
Motors by: Roger @ WickedATV

My RD-350 rebuild page updated 6/10/12

RuZty
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Re: stiffening up the frame

#13 Post by RuZty » Sun Nov 09, 2014 12:22 pm

Bare wrote:Definitely an 'interesting' exercise.
Hopefully you don't actually believe that adds ANY strength whatsoever though
He increased the diameter of the tube by 6mm on the OD, how does it not add rigidity? Sure the fibre length and orientation might not be optimal but it has to have an effect. If the steel tube by itself was 6mm larger with the same wall thickness it would be far stiffer.

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