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| Home Made Boards (6188 Posts)
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Home Made Boards |
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On 10/1/2004
Svarteld
wrote in from
Sweden
(213.64.nnn.nnn)
Brad and herbn,
Thanks for the info about maple and birch. V-lam seems interresting, I have one (bought) board that uses it, and it's very lively and springy - a Loaded Vanguard.
The previous 9 mm board is more of an experiment than something working, I use it mostly to practise slides. Maybe I'll try to add diagonal carbon fibre to help, I have some waiting to be used.
Think you're right about the need for more torsional rigidity. The board I've ridden the most so far sure got some of that... weight also, heavy as hell. Guess I over-done it somewhat here... It's absolutely stiff, regardless whatever. I'ts one of the boards that require a wet press stage when using 3-4 mm plys. I'll make an updated, lighter version of it this winter, with other truck angles - will aim for 45 front, 25 rear with DH bases.
Thinking of trying to use the old one for an experiment of hollowing that thick wood out with lots of holes - more of them where strength is not so important, and keeping the edges and truck mount areas intact. Then lay some carbon fibre on both sides of this cheese-looking thing, and figuring out a way to not let the epoxi fill the holes. Maybe this got some similarities with your project, herbn?
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On 10/1/2004 herbn
wrote in from
United States
(64.12.nnn.nnn)
one more thing,there's a reason for the word aircraft in "aircraft birch" i don't think i've ever heard of "aircraft maple", it follows my theory to the general superiority of aircraft epoxy too marine epoxy. Birch must have a bit higher strength to weight ratio,spruce is up there too,balsa is way up there, strengthwise.
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On 10/1/2004 herbn
wrote in from
United States
(64.12.nnn.nnn)
birch vs maple;major difference 1) toughness, maple takes a beating birch can be kind of crumbly. Maple feels springier, birch feels a bit more dampened,warmer perhaps. Birch does feel much springier(than ply birch) in none ply construction (v lam). I believe in thickening the core ,but then i thin the rails, add rail grabs, big blended bulldog style wheel wells. Pretty soon i'm gonna route out big sections of wood out of the top of a ply board and inlay sections of foam with carbon or glass wrap,inlayed beams with carbon tucked under.I'm gonna try to make some really light boards. I've been itch'n to try vertical grain balsa for some time now, maybe since duane talked about them.
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On 9/30/2004
Brad
wrote in from
United States
(64.136.nnn.nnn)
Svarteld,
Maple is more rigid than birch, but Birch does have a nice "warm" feel to the ride...very comfortable.
Tortional rigidity is a must for carving...I realize your decks aren't
carving decks....also for slalom...also for downhill. If your decks are somewhat twisty, then yes, that could be a problem in downhill, as you stated. Vibrations from the road/rider/etc, would be transferred to the trucks and once high speed wobble starts, the tortion of the deck would exasperate the resonant frequency, which basically is what high speed wobble is anyway...a vicious cycle.
Hmmm 9mm.
would adding one more ply affect your deck weight so much? You'de be close to 1/2" (.468") and the added stability would probably outweigh the modest weight gain. I would probably even go for .585" (5 ply) and really make a killer deck
for speed. Don't worry about weight..when it comes to downhill,press up a beast and go for substance! Just my .02 :)
oh, thanks for the compliments on my decks!
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On 9/28/2004
Svarteld
wrote in from
Sweden
(213.64.nnn.nnn)
Brad,
Thanks for the tips. Your boards look like good craftmanship! Iv'e seen Hugh R likes them too.
The finished pictured one is made of 3 x 3 mm plys = 9 mm thick, light and stiff, no noticable flex when standing in the middle. It's probably the high concave that helps here, and that aircraft epoxi (stopped using it though, it's cancerogenous and very naughty in every imaginable sense). But the torsional rigidity is not so high, each foot can steer each truck pretty individual... guess it's a bad thing for speed. The thicker decks got a lot more torsional rigidity, but they're also heavier. It's dropped about 20 mm further than a normal drop-through, with epoxied wood blocks serving as drop support. They also serve as rigidity help for those thin noses, as the blocks extend into the wider area while getting thinner.
I'll try to find hard rock maple veeners to see if they can be formed without wetting, but I know they're hard to find here. I use the thinnest birch plys I can get hold of now. I've heard maple would be stronger? Would mean less weight.
Anyone tried some kind of steam pressing?
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On 9/27/2004
Brad
wrote in from
United States
(64.136.nnn.nnn)
Svarteld,
hmmmm...that would explain the wetting of the wood. I see how extreme the bends are, and why the wood would crack.Because of my lousy internet server, I can't see your pictures very clearly, but the boards look pretty cool. is that 3 pieces of wood or one on the complete with the drops? Again, bad res here.
Ok the math: At 3mm, your plies are .117 inches thick. Mine , at 1/16" are .0625" (1.5875mm)thick. I can easily bend the wood (12" wide, 304mm)to a 90 degree curved angle with no breakage, so there lies the problem.My decks tend to be 8 and 9 ply thick, so it DOES result in more gluing, but I think you would still be ahead. I realize the problem is probably not easily fixed, as wood suppliers are hard to find anywhere. Can you get your supplier to get your plies closer to < 2mm? It would save you killer time, and you could bend almost any way you'd like.
My press is a 50 ton "Dake" "H" frame press with 3 pyramid shaped 1" thick steel plates welded together which sit on the mold to distribute the pressure of the 3" ram.
By the way, we are talking about Hard rock maple here. Is that what you are using? Oh, go to www.noreasterlongboards.com to see the decks.
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On 9/26/2004
Svarteld
wrote in from
Sweden
(213.64.nnn.nnn)
Brad,
Wow, 40 tons... I press 3-4 plys of each 3-4 mm at the same time, first wet, and leaving them in the press for some time just to let them dry some. That time could probably be a lot less than one week, as you say. I let them dry out of the press also. Then, they go back with industrial epoxi - same press. The epoxi we use takes one week for full strenth, so I let them stay for a couple of days. The press uses no huydralics, just some solid wood to spread the load from twelve large clamps. The previous plys been through this (plus concave):
The small radius and three-dimensional curvature that some bends have in my boards, makes even 3 mm plys crack long before the press reaches the end position. That's why I wet them in the first stage. But if I could avoid it I'll be glad - any suggestions?
Some boards I've built with just mellow two-dimensional curvatures uses only the last dry stage, with epoxi, like this one (built with the same epoxi as the Swedish jet-fighter Gripen :-)):
I've just started working with wood, so I'm very grateful for suggestions and help. Would be nice to hear more of how your press works, and some pictures of your boards.
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On 9/26/2004
Brad
wrote in from
United States
(64.136.nnn.nnn)
Svarteld,
A week? in a press? what kind of press is this? my decks stay in the press for an hour, then sit for 5 days, clamped to the form to prevent warping...of course, this is with 40 tons of pressure. I'm a little confused as to why your pressing for so long. I'll assume this isn't a hydraulic press, and you're keeping the wood wet to incur a permanent bend...you can clamp your decks together for the bends you need(with your mold of course) with the epoxy for much shorter time periods if you don't have a hydraulic press...all you need is 2 sheets or more and the bend will be permanent...this will eliminate the molding...From the pics you posted, those decks look very thin....thin enough to bend against your mold with clamps.Use the clamps with wood boards which cross the deck at several spots to distribute the pressure of the clamps (important!) Forget wetting the wood...it's bad news, and may have an effect on the quality of the bond.
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On 9/26/2004
Tyler
wrote in from
United States
(67.83.nnn.nnn)
Thanks, svarteld. That will keep herb and I busy for a little while.
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On 9/26/2004
Svarteld
wrote in from
Sweden
(213.64.nnn.nnn)
Tyler,
We don't build things with imperial units in Sweden, so I ordered them from the US. I've got them at McMaster Carr:
http://www.mcmaster.com/
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On 9/25/2004
Yan0
wrote in from
United States
(140.233.nnn.nnn)
DaveWave,
Find your local cabinet maker or hardwood dealer.
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On 9/25/2004
DaveWave
wrote in from
United States
(198.81.nnn.nnn)
We are a class of renegade potential dropouts and we are making decks but don't know where to get a good supply of hardrock maple. Any sources?
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On 9/25/2004
tyler
wrote in from
United States
(24.62.nnn.nnn)
For Svarteld and Duane who are doing the mods on randals, where do you get your spherical bearings from. I am having a hard time getting a hold of some.
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On 9/24/2004 PSR
wrote in from
United States
(24.53.nnn.nnn)
RJ, if all you need is metal for framing your wooden mold-up, look up Mc Master-Carr Tool Supply. I'm fairly sure they've got metal beams or box tubes that'll suit your needs. BTW, have considered Vacumn Kits for making laminates? Just a thought...
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On 9/24/2004 PSR
wrote in from
United States
(24.53.nnn.nnn)
Svarteld, you should consider adding an anti-fungal agent in small quantities to your water source, or in the press itself. The thing is,you need to be fairly sure it won't create bonding issues once you lay the plies up. I'd suggest either Triclosan or Alkyl ,which are commonly found in household cleansers. Use these in diluted amounts. However,It may be prudent to do a test on similar wood run through the Wet Press, and then glued to see if any discoloration or insolvency of the gluing occurs. Natrual Salts may also do the trick here, but again the effect on the gluing or color of the wood may suffer.
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On 9/24/2004
Svarteld
wrote in from
Sweden
(213.64.nnn.nnn)
The plys for the zero-rear-steer-deck came out of the press today - first stage, wet press. In a couple of days they go back, this time with epoxi. Problem is they show green fungus rash, smell too. I've had them in the press for one week, done about the same thing before without this green decoration. Any tip on how to avoid it, except shorter wet time?
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On 9/23/2004
RJ
wrote in from
United States
(63.173.nnn.nnn)
What i need is a jig that is able to concave and press a skateboard evenly. All i need are 2 metal beams running parrallel that are 50" long, level and 12" apart. I actually make my jig out of wood but am having warping issues as the jig ages the boards develop unwanted camber as well as concave. It might be easier if i sent you a picture of it and what i am trying to acomplish.
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On 9/23/2004
FL
wrote in from
United States
(65.249.nnn.nnn)
What kind of metal ? What size ? What kind of bends ? Some fixtures can be real simple , others extremely complicated [and pricey] .FL [metal fabricator guy]
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On 9/23/2004
rj
wrote in from
United States
(63.173.nnn.nnn)
Anyone know of a fabricator who can make a metal bending jig??
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On 9/20/2004
silversurfer
wrote in from
United States
(24.62.nnn.nnn)
Duane or PSR, did one of you post pics of lathed or shaped
Flashbacks here awile ago?
I'm interested in those but I've looked and I couldn't
find the photo anymore?
Who had lathed flashbacks?
Can you post that picture again?
Thank you!
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On 9/20/2004
Svarteld
wrote in from
Sweden
(213.64.nnn.nnn)
Oversized bushings, ball bearings
Would be interesting to see some details of the JimZ trucks, regarding construction, around the bushing/ball joint areas - nice to see similar constructions grow on their own :-) I'll post details of mine as soon as I can. I've taken a slightly different approach on the bushings - I machine the bushings instead of the hanger. Here's some rough drawings on 1,5" polyurethane bushings for RII hangers - these have very little meat to remove anyway, but it seems to be a good idea on the DH hangers. I've made them from 75A rubber, plus 80A and 90A polyurethane. I actually did the downhill race on 80A front, 90A rear 1,5" bushings. Very stable, but probably too stiff for carving. As you did write, softer duros seem to be a good thing to try.
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On 9/20/2004 PSR
wrote in from
United States
(24.53.nnn.nnn)
Svarteld,that looks like it'll hold together just fine! It should be pretty sweet as a No-Steer,and as a steerable truck,it'll likely be very accurate and hopefully wobble resistant. Nice Stuff!
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On 9/20/2004 Duane
wrote in from
United States
(68.15.nnn.nnn)
Svarteld, JimZ speed hangers have the ball pivot at the kingpin. it seems to work very well. The early versions I saw in person needed larger bushings as you suggest, which is why I'm in posession of some 1.5" diameter rubber stock. It is soft since I figure it will have 1.5x the leverage of 1" bushings. The DH hanger has plenty of meat to hog out to make seats for both bearing and bushings. A very versatile hanger for modifications, I'm running them from 90mm to 200mm.
With ball pivots at both locations, you have to be careful as the hanger, when the bushings are compressed, can wedge down and get jammed in place due to the distance between pivots trying to change (it can't) That can happen, too with Radikal trucks for the same reason, which is why it is important to keep the angle correct at all times.
I've drawn up a solution whereby the bearing that engages the kingpin is installed in a oval-shaped hole, or track. It need not move much to allow quite a few degrees of hanger travel. Large bushings would be contoured to fit and keep the bearing from moving too freely. This type of design would work best with a Jim-Z like two-piece hanger, as the oval hole could be easily milled in each half.
I can envision trucks like this with very large, soft bushings offering a superior cushy ride with lots of suspension travel, yet being precise since the bearings would disallow unstable movements. In fact the bushings might be best made from foamed polyurethane, as even very soft solid urethane might be too hard.
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On 9/20/2004
Svarteld
wrote in from
Sweden
(213.64.nnn.nnn)
No rear steer
Folks, thanks for the feedback about rear steering and the pivot point. I've done som modifications to Randal DH lately, like a metal ball joint bearing at the pivot point, see crappy picture. It's Duanes idea - thanks! Hopefully this will let the pivot work without loading it into the cup. Only DH hangers can be modified in this way, not RII, because of lack of aluminium to drill in. I've used 8 mm axle steel, sanded down to a really snug fit in the 5/16" ball joint, and fixed everything with expoxi, both inside and at the edges.
The more I modify trucks, the more I realize the original construction is really well thought out... That rubber pivot also acts like a vibration damper, and also seems to damp the turning somewhat - like a tiny steering damper. The new pivots are faster-steering than standard with the same bushings, probably because of less fricion under load, but they also rides harsher on rough roads. No speed tests so far.
Iv'e just finished some hangers wich also have a similar ball joint bearing between the bushings, at the kingpin, to avoid movement here too. It requires over-sized bushings (I've made them from 1,5" polyurethane rods), gripping the hanger in a wider manner than normal, but more of this later...
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On 9/20/2004 SFKasJ
wrote in from
United States
(68.7.nnn.nnn)
psYch0Lloyd,
Have you tried the Roe version of the S-Camber? I am curious how it compares to the Airflow version. The big advantage that I see in the Roe is that it retails for $115 instead of $130 for the Airflow and that it is available to order in the USA saving on overseas shipping. The potential disavantage I see in the Roe is that it is lacking the spoon-nose concave of the Airflow.
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