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Frame geometry, What are you thinking about this one? 700, slopey 54x54

Frame geometry, What are you thinking about this one? 700, slopey 54x54

Here is my idea.
My actual kona is way to big for me (56).
I need something shorter and with an harder angle on the head tube (my kona is more than 72 right now).
but i don't want toe overlap and keep 700's, so i can't make it shorter i think.

here are my questions to people who knows a lil' bit about frame building:

-Is slope top tube an advantage for rigidity?
-What's the minimal distance with a 170 classical sughino crankset to the front tire to avoid toe overlap?
-How a bike like this one would react to a lot of hop' play?

I would add:
I made this geometry sloppy as that also to get a 90° angle between seat tube and top tube, and head tube.
This would help the friend who gonna make the frame, and i was thinking 90° is a good angle, any opinions about it?
is that bad to have a long seatpost?

There's little real world difference between compact and traditional geometry (some stiffness and weight changes).

The main reason compact became HUGE is because it enabled manufacturers to produce less sizes of frame for a wider customer base. It also enabled the use of less material (materials became stronger) and brought the centre of gravity down whilst reducing weight.

Why are you amending an existing frame Clem? Tubesets aren't too expensive nowadays and you're possibly making extra work for someone by adapting an existing frame (not to mention your frame will have been stressed twice in it's construction and will have a shorter lifespan)?

Clem,

I don't claim to be an expert on any of this but your geo looks good to me. A sloped top tube is rad - perhaps is will result in a small structural advantage and make the bike more rigid, but I think the result would be negligible. There are other things that probably affect rigidity much more, like tube size and proper support gussets or support members.

As for your toe-overlap question, I would just clip a shoe into the crank and measure the distance to your toe from the center of where the crank links to the bottom bracket.

Personally, I see no trouble with a long seat post. Your measurements are a bit hard to read but are you showing 73 degrees for the seat tube and head tube? I think some might consider bumping that up a degree but that measurement is totally reasonable. 390 for the chainstays is nice and short. The bike looks dope to me.

As a side note, I think you're trying to say "slopey" instead of "sloppy". But the bike looks awesome, sloped top tubes rule. Build that sucker!

---------------------------------------------------------------------------------
fixcraft.net

Thanks man!

If you enlarge the image size you can read the dimensions better.

Yes angles are 73°.

The geometry looks good to me.

I assume the light grey lines are the center lines of the ending joints.

A smaller frame design with the same angles as one with a flat top tube are inhearantly stronger as the distance between the points you are flexing have now gotten closer. This introduces different construction techniques as you want this frame to go to hell and come back with all your hopping around. I would make it of steel, with heavy wall thickness on all tubes and stays. If you want a joint that resists breaking using the high end air hardened tubing or even just 4130 have your frame builder tig weld it then have it professionally heat treated to neutralize the heat affected zone of the welds then flow brass or silicon bronze over ther welds as a reinforcement.

Also get a Thomson 410mm seat post as you will need a serious seat post.

My two cents.

Keep your standards low, and morale high.

The geometry should work well for polo.

Toe-Overlap depends on shoe-size and cleat position. I would measure it, like Booze suggested.

For my personal taste trail is way to less for polo.
56mm is a typical street-bike value. Your point of zero trail (this is when the handlebar flips over) is at 63.5 degreee for the given frame.
I tried trail from 60mm up to 78mm. I like the range of 68-75mm. Needs a little more force to turn the handlebars, but it feels a lot more stable and the handlebar nearly never flips over.

Going for 74° headtube and/or seattube angle could be an option.
- Chainstays could be a little shorter / more clearance tire to seattube for steeper seattube.
- Depending on the length of your upper body (I don´t know how tall you are), steeper headtube is an option to hold wheelbase and get a longer toptube. Good for people who like extremly short stems also.
- 74° headtube feels a little more agile imho.

I agree with the trail. I would go a little steeper on the head tube. But hey, that me.

Keep your standards low, and morale high.

Going to 74° headtube with the same offset fork will give me less trial. If y want something more than 60mm i have to go to 72° headtube angle, as on my actual kona paddy wagon frame, wich is very confortable and stable.

Ah, so this is an existing fork you want to use and the offset is given ?
45mm offset is to much for polo for my personal taste.
I would not build a custom frame around a fork which is less than optimal.

Is it a steel fork ? Should be easy to weld new dropouts to it and change offset to less than 30mm.
Otherwise I would build a suitable fork or buy one.

I made new measurement, the fork is actually 43mm offset.

As that's a kona retro road, it's hard to change the offset i think.

PreviewAttachmentSize
Sloppey.pdf171.02 KB

So this could be something with a better trail, with a 35mm offset fork:

  • sloppey 54 54 . 35mm offset fork.jpg
  • sloppey 54 54 . 35mm offset fork preview.jpg

Why so little BB drop?

What program do you use to make the designs?

Rattle cad. Free and nice to use.

@ Matt:
Don't know, i thought i would love to get a high BB to avoid pedal strike. But it's too high.

Here is the fork i have, the 43mm offset retro road from kona:
http://direct.coresites.mporatrons.com/rcuk/wp-content/uploads/old_image...
I don't know if a frame builder can change the drop out from 7mm.

one last question, if i can't find or customize the fork, should i go to and angle of 72° on the headtube (like on the kona paddy wagon i ride) to get a better trail? I found the paddy wagon original set up pretty nice to ride by the way.

I can´t see if the frok-dropouts are brazed or welded.
A pro-framebuilder will most likely not do any changes to such a fork.
It would be possible to cut away the old dropouts and braze on something like this,but behind the fork.
http://www.maxpowercycles.de/wp-content/gallery/frames/max6_web.jpg (2-offset positions for personal taste)

But: This will look quite strange / ugly and most framebuilders won´t do such a frankenstein job. Probably it is even more expensive than buying a suitable fork.

I can´t say anything to the question if you should go for less headtube angle with the 43mm offset fork.
This setup differs to much from my personal taste, I don´t like riding polobikes with small headtube angles and big forkoffset.

If you like how the kona paddy wagon rides, maybe try 72°.

Thanks for your advices.

Another question, is a shorter headtub better for rigidity or not?

how important do you find rigidity to a polo bike?

I don't know. I feel that my kona is a bit too flexible when im pedaling strong on him, and i don't really like this feeling. The headtube is pretty long on him, so i was thinking maybe a shorter one can be better.
Also im not using vocabulary as i should, i also want to say "resistant" or "solid", is a shorter headtube less stressed so more resistant or not?

are you noticing the flexing in the head tube/ handle bar area? or just in the bottom bracket?

I noticed on my home-built polo-frames that I really appreciate a stiff frame for polo. So I think it is a factor to consider, yes.

But, frame stiffness is influenced by a lot of things and headtube length is quite a small influence.
Speaking of flex / twist between Seattube and Headtube (this is mostly what you feel when pedaling strong), the stiffness of the DT (first) and TT (second, less influence) is important. Also, how they intersect / connect to the headtube.

In general: Shorter tubes (small frames) are stiffer. And tubes with bigger diameter and/or with "thick" walls are stiffer.
Don´t go for an ultra expensive ultra leight tubeset like 0.6/0.4/0.6mm. Cheap double butted like Columbus thron will do a good job on a polo bike. Go for big diameter.

On my polobike I used Columbus Gara straight gauge 35mm*0.9mm for the downtube. This makes a stiff connection HT / BBS.
(I don´t care about the extra wheight of less than 100gr. compared to an double butted 0.9/0.6/0.9)

A stiff back (rigid chainstays + seatstays) also is noticeable when riding. Consider not using road-racing tubes. Go for MTB tubing or use straight gauge 18*1.0 (Columbus gara, which is what I use for the rear triangles of my bikes) or something like that.

My only bike is a polo bike, so even though i no shit about bikes, my, joust custom built by Awesome is phenomenal.Ride2Believe2Believe2Ride2Believe..............again and again,

"So this is how it ends"MACHINE

590mm is the minimum front and center distance to avoid toe overlap with 170mm cranks and that depends on your pedals and possibly big ass feet or goofy way you put your feet on the pedals. 600mm would be safer. A lot of polo players and i don't think they realize it but use the top tube with their thighs (a lot) to control the bike. If you don't have a straight top tube now then you won't miss it but if you do you might really not like this frame for a few weeks.

Really good points.
My frame builder put me the idea of a sloppey frame in head because one of his point was the fact that a sloppey frame gonna be less "into your legs" when move it for differents reasons. But your point is really true, sometime we use the top tube with our legs to keep balance. My actual kona is sloppey, the the frame is to big for me, and the top tube is pretty high, and i think im using it.

Here is my project now:
http://static.lfgss.com/attachments/59354d1349444199-54x55.jpg

Here it is:
http://uppix.fr/?di=6KBH
made by sammy from Mother fucker.

Sloppey feel really nice, really rigid when im "en danseuse" to get speed. The whole bike feel more rigid than my old kona. he's pretty light, around 10.5 kilos with this set up (i lost a good 500 gr witn my Trial set up instead of the old MKE guard).

Finally i can't put my kona fork on him, so i took manu's pompino one. No v-brake on the original project fork, and less offset. The on one put my BB 1.5 cm higher than on the plan.(31.5 cm)

The wheel base is short and the bike nice to handle, I found it pretty responsive. Way easier to play in front of the the wheel.

The issue is toe overlap, i get some, around 1,5 cm i think, with 170 cranks. Nothing really unplayable, but just enough to get small trouble with endos if im not used to. I think im gonna go throught that pretty quickly, but i would have a make it 1 or 2 cm top tube longer to avoid that.

Saddle position: no offset on the one i found first, i will put something with 2.5 cm (less or more) to be more on the back soon.

http://uppix.fr/?di=6KBH

Awesome! I like the trials crank setup and the 45 integrated headtube.

"rubber side down boys"

Trial cranks are the way to go. Lighter, easier to switch ratio, bette weight distribution, shorter drive chain.

Is the rear fixed like other trials setups? If so, does that mean while coasting the chain keeps spinning while the cranks aren't being pedaled? Idle curiosity.

yes it is.

This trend come from Toulouse in France.
I find it cheaper and lighter than a good bmx crankset. Without buying a new freewheel you can get rid of your heavy MKE polo guard and goes to a similar ratio for cheap. i like it.

MKE polo guard: 217g

White Industries 21t F/W: 203g

A constantly spinning drive train doesn't seem ideal for polo to me and could eventually lead to an unfortunate crash with bike parts, limbs and mallets getting stuck into a spinning drive train.

http://www.tribalzine.com/IMG/jpg/CONTROLBIKE-SILVER-CRANK.jpg

looks great clem. was thinking of doing the same thing, as my profile bmx cranks are pretty heavy. what crank/bb combo are you using? my trials knowledge is pretty limited.

Echo crankset, 170mm
White industrie ENO (the classical red and blue one), 22 teeth.
Echo cog, with 5 mm offset on the right (to get a good chainline)
Reset ISIS bb, 128 mm (the only one who works with the White industre + echo crank combo, otherwise the freewheel can touch the bb).

Only thing to look at is the chain line, if you get a classical cog on a 120mm rear wheel, with a 128mm bb length, you can get trouble (as a 1 cm offset chainline). special cog is the way.
Cranks
http://www.biketrial.ch/shop/shop/pop_up.php?bild_gross=769_gr.jpg
Freewheel
http://www.biketrial.ch/shop/shop/pop_up.php?bild_gross=134_gr.jpg
Cog
http://www.biketrial.ch/shop/shop/pop_up.php?bild_gross=353_gr.jpg
BB
http://www.biketrial.ch/shop/shop/pop_up.php?bild_gross=1117_gr.jpg

Shop in switzerland:
http://www.biketrial.ch/shop/index.php

that's great. thanks for all the info. i'm stuck between going for the external bb/howitzer combo and the trials set-up. both look good, and both look lighter.

It's really too bad you can only run ISIS, because that poorly designed interface is crap! I would stay away from it at all costs, because you will ultimately end up replacing multiply bb's over time.

Just trying to give you some sound advice Clement:)

That's a good point, i would let you know when i will switch my bearing (wich by the way you can buy any piece separtly). It's gonna be a problem with my kind of play for sure.

Constant driving chain isn't a problem in my opinion, as the chain is really short, you get a small surface to get trouble. And if you think about the uncovered wheels, the fixed gear, pedaling, you have a lot of reason to be affraid of spining objects on your bike. If you begin to think about that when you play, you better stop playing.

Otherwise, the set up is really light, and i like it for now.

. double post

http://uppix.com/s-proto_fourche_ko5086839c00112a9a-jpg.htm

Nice set up clement,

Just another idea for you, I have basically the same set up but I have also decided to run two fixed gear cogs on the rear wheel on the freewheel thread and a spring loaded chain tensioner mounted on the bb this way the polo gear has a better chain line as it is the one that will get the most use but it also means I can have a reasonable commuter gear for when traveling to polo tourneys. 22-14 for polo and 22-12 for getting around (not a great improvement for commuting but makes a difference) The chain tensioner allows me the ability to move the chain across with no tools and it is hidden safely behind the cranks/freewheel.

Just a thought

biliken3

Any picture of the chain tensionner?

Any picture of the chain tensionner?

one of our new players here in Seattle just bought this frame, very interesting. and if the price is the point, 159 dollars cannot disappoint (that was a rhyme)

clement. your bike looks dope. I had never seen a trials front freewheel cranks setup. do people have problems with the isis bottom bracket bearings? I have read that since the axle is bigger than say a square taper it puts more stress on the bearings and wears them out.

I have a shimano external setup that is supposed to solve that problem by moving the bearings outside the bottom bracket-allowing larger bearings and a larger axle. However, I have had my share of problems with these. I even replaced the bearings with Enduro which are supposed to be better sealed , and they are still very susceptible to water and grime getting in them due to being outside the frame. My replacements are starting to fail on the non drive side due to water getting in. I have never had problems with my cheap truvativ square taper bottom bracket. Have had it for 3 years through every season including salt and snow and it works like a champ. I'm not a heavy guy so I dont have problems with the arms rounding off that some do.

Max-

That frame looks like a sick deal if you ride 700s. Curved ST and Triple Triangle. Although the scrambler is still cheaper and been tested. Nice to have options though. Swap in a V brake or Disc brake front fork and you're set. Should post a thread about it if you haven't already. Curious to see how it works for polo. Also curious about the tire clearances and geometry. Looks like it should have relatively short chain stays with that curve.

I'm gonna let it float and maybe the frame will pick up... but the player with this bike has welded on v brake mounts and it has definitely helped his game. For a cheap frame it's a lot more stylish than the scrambler.

drewthomas06 wrote:

I have read that since the axle is bigger than say a square taper it puts more stress on the bearings and wears them out.

Exactly.

When discussing inboard bearing bb's:
Larger axle = smaller bearings
smaller bearings = premature failure

Quote:

I have a shimano external setup that is supposed to solve that problem by moving the bearings outside the bottom bracket-allowing larger bearings and a larger axle.

nailed it.
Whenever you have a bearing exposed to water/grime over time, it's going to go. That's why you run full fenders so the splatter is reduced in the bb area!

Matt-Hewitt wrote:
drewthomas06 wrote:

I have read that since the axle is bigger than say a square taper it puts more stress on the bearings and wears them out.

Exactly.

When discussing inboard bearing bb's:
Larger axle = smaller bearings
smaller bearings = premature failure

Quote:

I have a shimano external setup that is supposed to solve that problem by moving the bearings outside the bottom bracket-allowing larger bearings and a larger axle.

nailed it.
Whenever you have a bearing exposed to water/grime over time, it's going to go. That's why you run full fenders so the splatter is reduced in the bb area!

I would run full fenders if it wasn't my polo bike. Only got the external crank because it was cheaper than a square taper at the time for a used one on Ebay. I'm going to replace it with a square taper once the bearings die.

it seems that some external bearing
http://www.biketrial.ch/shop/shop/pop_up.php?bild_gross=332_gr.jpg
exist for isis axle.

There's one solution!

Hey Clem, how tall are you?

#Polofad

around 1m70

the top tube angle its to much MTB.
I try many frames, and I think when the top tube angle is 90º if the head and the seat tube, its better to get in and out for the bike