How much weight comes off with weld-on hardtail kits?

[kitabel]

The weight loss affects performance not compared to the weight of the frame, but based on the weight of the entire bike including rider. It's not much.
450 lb. bike + 150 lb. rider vs. 415 bike + 150 rider = 6%
Depending on the design, it may affect the wheelbase by moving the axle back, which changes the center of gravity, turning circle, front vs. rear brake action, etc.

[MODO SIKLER]

Originally Posted by kitabel

The weight loss affects performance not compared to the weight of the frame, but based on the weight of the entire bike including rider. It's not much.
450 lb. bike + 150 lb. rider vs. 415 bike + 150 rider = 6%
Depending on the design, it may affect the wheelbase by moving the axle back, which changes the center of gravity, turning circle, front vs. rear brake action, etc.

Exactly ... 6% or there abouts. But that's not THE only effort. Wheels (lighter ones) actually help improve performance as well. These percentages add up ... cumulative effect.

My questions about weight are only a very small part of research I am doing pre-build. I have built flat track racebikes, road race bikes, etc. (62 years old, owned/operated shops for over 25 years). While I am quite experienced, I have very little Harley knowledge. I can understand how my questions may seem novice-like.

You're going to see more of these ~silly~ questions out of me. They all have their place in my design and engineering methods. I'm learning a new brand here, so again, many shadetree mechanic sounding questions.

I've already planned on buying a road worthy bike, using struts to test the idea, and either moving (or not) forward. First I must sell my Ducati 900SS as well as four other project conversions I've done with other brands. Can't buy a Sportster until I raise money.

My 700 ft/sq home shop is equipped with a 24" 2hp lathe, a 22"x19" 2hp mill, Oxy/Acet rig, 300amp Miller TIG, 200amp Lincoln MIG. For 25 years my wife and I owned and operated a warranty and authorized service center for Victor Equipment, Smith Equipment, Miller Electric, Lincoln Electric, Hobart, probably every power tool manufacturer you've ever heard of, five emergency power generator manufacturers (Onan, Generac, etc), a number of hydraulic manufacturers well. I've raced since 1972 (including Perris, Ascot, and pretty much the whole SoCal motorcycle racing scene all through the 70s/80s including District 38 SCORE Desert Racing. I've designed and built my own frames/bikes for at least forty five years.

I'm not bragging, I'm letting folks know me a little better. It will help you, to help me.

[MODO SIKLER]

Originally Posted by kitabel

The weight loss affects performance not compared to the weight of the frame, but based on the weight of the entire bike including rider. It's not much.
450 lb. bike + 150 lb. rider vs. 415 bike + 150 rider = 6%
Depending on the design, it may affect the wheelbase by moving the axle back, which changes the center of gravity, turning circle, front vs. rear brake action, etc.

I'd also point out that adding the variable of the rider's weight to the power/weight figures makes for corrupted conclusions. There are no P:W figures by manufacturers when they publish their specs. That said, for MY purposes adding an unneeded variable into the equation does nothing in the manner of comparisons with other motorcycles I've owned and built. I only need to add the rider's weight if I am comparing another set of datum that also includes the rider's weight, which is extremely rare.

More plainly said, I do not need the rider's weight included in my calcs. Perhaps in a different situation, yes .... but not this time.

[kitabel]

What performance analysis can be made based entirely on the bike's weight?
Sprung vs. unsprung? Read my article: http://victorylibrary.com/brit/M-sprung.htm

[MODO SIKLER]

Originally Posted by kitabel

What performance analysis can be made based entirely on the bike's weight?
Sprung vs. unsprung? Read my article: http://victorylibrary.com/brit/M-sprung.htm

The rider is an unnecessary variable in the numbers I am looking for.

For example, often times engines' power/weight ratios are compared. Often times entire motorcycles' power/weight ratios are the topic of discussion or research. Then again other times motorcycles with rider power/weight ratios are needed for (everwhat) reasons.

In my situation I do not need to add the rider's weight since that number would effect every single motorcycle/mods exactly the same way. In each situation I would be adding the exact same ~rider's weight~ to each motorcycle which would have no effect on "which bike won".

If 3 bikes were compared p/w ratio with rider and (let's say) Bike #2 came out with the best figures .... the outcome would be exactly the same if the rider's weight were eliminated from all three bikes being compared ... #2 would still win. Why? The rider's weight never changes in those equations, adding them making it unnecessary complex.

You're talking about comparing performance modifications measured on one single motorcycle. I'm talking about comparing what I already know to be what I want with learning about how to get there within this brand and it's vast aftermarket. For instance, I already know what a motorcycle that works out to be about 5:1 without the rider feels like, and I like that number. So to obtain a proper perspective on what is needed to arrive at those riderless numbers, I need to stay ~riderless~ in all of the further comparisons.

There is no single "right" way to go about this. It all about how one wishes to apply the maths. Engine's p/w? Wet bike p/w? Fully laden wet bike p/w?

See there? ... it's how one wishes to use the maths to compare things ..... any .. things.

EDIT: To reply to unsprung vs sprung weight ... I am well versed in that area of mechanical engineering. (I am not an engineer).

Not a young'n that saw a hardtail chopper in a magazine and now wants one cuz it loox kewl. I fully understand the limits that a hardtail frame has. I want a hardtail because I want a hardtail this time. I'm not klinging to rationale or starry eyed desires. I want those limits. I want the reduced capability. I am purposely and fully minded going straight at the hardtail design without any attempt to offer excuses or apologies. I am aware of what moving the rear wheel back several inches (seems any added length those weld-on kits have is aft of the CG). I am aware that pretty much the entire motorcycle becomes unsprung weight once the rear suspension is removed (except for the parts on the front end that move up and down). I get that. And it's what I want this time around.

[kitabel]

If 3 bikes were compared p/w ratio with rider and (let's say) Bike #2 came out with the best figures .... the outcome would be exactly the same if the rider's weight were eliminated from all three bikes being compared ... #2 would still win

Only if all 3 bikes weighed the same.

[MODO SIKLER]

Originally Posted by kitabel

If 3 bikes were compared p/w ratio with rider and (let's say) Bike #2 came out with the best figures .... the outcome would be exactly the same if the rider's weight were eliminated from all three bikes being compared ... #2 would still win

Only if all 3 bikes weighed the same.

Yessir. You've won!





So, I've learned that the difference in dead weight between a stock/suspended 95/03-ish Sportster frame w/shocks and swingarm compared with the same frame converted to a hardtail by using one of the weld-on kits is ~roughly~ 30 to 35 pounds, the hardtail being lighter.

Precisely what I was trying to find out about. I'll add that to the other things gathered for where I want to go with this. Comparing weld-on kits with one another with more scrutiny is next. I have a design for the rear axle hole and chain adjuster system that's more sportbike-ish that I'm working on. More of an aggressive slot-and-block system used on sportbikes. The design also will need to fit within the capabilities of the machine tools in my shop (I don't believe that will be a problem however). Once I get the design worked out the engineering of the design comes next.

Steel block welded to the axle plate.. one way or another (and the shape and fitment of this "block" would depend on what the ass end of the weld-on kit I've yet selected looks like) and this block will have a deeply cut "slot" that goes for and aft ...while larger adjuster blocks will ride nicely within the slot (channel?). Maybe not really needed but it's something that kinda screams "DO THIS TO THE BACK" to me.

I've seen a few of them by now ... Low Brow, TC Bros, Twisted, maybe another one. I figure there are others as well.

Just to get it said, I cannot afford an entire hardtail frame .. those that I've seen are around $1,500 munnies.

Basic plan is to buy a 94 to 98 883 that runs and is roadworthy. Add a set of struts to test out the hardtail to settle any doubts (or confirm any beliefs). I may either locate a frame with title and no swingarm/shocks then weld on that one. Or just do the conversion to the rider if locating a donor frame with clean/clear title is too difficult to locate.

All depends on opportunity and availability (or lack of) munnycheck.

Any more information and I'll have to fetch it out of the garage ... it's right next to my Corvette. Been there for years. But I was unaware of it.

[rejeanprimeau]

Just hardtailing a motorcycle is half the job. You'll have to lift the front, change the raking and get yourself a nice fork. Look at SugarBear springer fork. It will give you great idea of how a hard tail bike should be done.

[MODO SIKLER]

Originally Posted by rejeanprimeau

Just hardtailing a motorcycle is half the job. You'll have to lift the front, change the raking and get yourself a nice fork. Look at SugarBear springer fork. It will give you great idea of how a hard tail bike should be done.

Thank you. I'm aware of that. It may help to know that I'm not building a "chopper" so to speak. I may (heavy emphasis on the word "may" so don't go too far off the cliff about that) even take on building my own girder later on ... a rather more modern-tech girder .. but that's dreamin' for now. For the time being telescopic hydraulic forks (y'know ... "forks" .. haahaa) with 49mm stanchions are on the ~for now~ list. Wide or perhaps mid glide. No extra rake. Perhaps two inches over ... or so. I'm still working on some of the engineering.

I've seen SugarBear's work. Wonderful stuff, without a doubt. But that's not the kind of motorcycle I am putting together. In fact it couldn't be any farther, design wise. A springer is not well suited for this project.

If y'all haven't put it together yet, I'll be more blunt. I'm building a motorcycle that is something most Sportster folks wouldn't think of building. Think early 1980s AMA Production road racing (Jap bikes). Think 1950s at Ascot in the expert division. Think salt flats bikes. Think hooligan/asshole bikes of the 1950s/60s. Mix it together, and stick with as many HD chassis components as practical.

If I provide any more detail there will be a tsunami of posts telling me why it's wrong to go this way, and that's a fight not worth engaging in.

[MODO SIKLER]

...... (continued from last post) ...

Think much more like this ....



BUT!!! ... street legal, with a mid-90s Evolution sportster engine and a completely different front end arrangement. This is important to keep in mind, ok? This is just a design protocol (call it "course and heading" if you will) I'm not making some sort of copy of that motorcycle.

Remember, this picture is NOT an exact representation of every detail I plan on adopting. It's just used to provide you fellas some idea of a little bit of what I will be doing. Totally different front end though. Not looooongerr. Just unexpected (and ~no~ not a USD system ... that's overdone in my opinion).

Oh right ... one more color to add to the mix that I failed to include in the posting above ... so add ~heavy bagger~ to that mixture I listed in that post.