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Old 10-20-2011, 07:01 PM   #16
CosentinoEngineering OP
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V-max questions

The Vmax is definitely a beastly bike. The early years suffered from Japanitis in that it had a frame that was woefully inadequate to the engine. With a hacksaw and welder this can be fixed!

1. Fork brace - will filling the standard die-cast Ally mudguard piece with hard-setting resin work as well as a 1/2" thick billet piece? The resin is really light.....

The resin will work but likely not as well as a billet piece. For a piece of a given size the heavier material will usually be the stronger part. Resin may seem strong but it is not when compared to metal and you also have possible bonding/separation issues. Making or purchasing a fork brace would be the strongest solution. Whichever route you go you need to ensure that the fork brace does not pinch the forks at all. That would lead to binding in the forks and very poor suspension performance.

2. Frame brace - Would using hi-strength/lo-elastomer Polyurethane engine mount bushings strengthen the frame without having to resort to big chunks of railway track across my bloody lovely V4? Bushes are light......

Same as above. The stiffer bushings will deflect less but installing solid metal bushings would be even better. Vibrations may be an issue with solid mounting the engine but it can't hurt too much for a quick test. Even if the vibrations are low enough to accept from a rider's perspective the increased vibration will likely cause more long term cracking of various frame and bracketry. Not too bad for a racer as frames are always being checked and repaired but not so nice for a street bike that is not constantly being disassembled. Adding frame braces will definitely stiffen things up but there is still some danger that the stiffer frame can cause long term fatigue cracking. The bracing does not need to be too large. This article on Tony Foale's website shows a real world example of stiffening a mid-80s tube frame with lots of details. He does highlight one of the dangers of DIY frame stiffening:

Frame stiffening as discussed will in most cases significantly reduce the stress levels in frame members as well as stiffening the whole structure, but there are occasions where the stiffening of one part of the frame may lead to increased risk of failure in another unstiffened area.

So be careful. I was helping a vintage racer friend get his bike to go faster and as the frame started cracking I'd weld in a brace. Then the next week he's come back with the next weakest area showing a crack. I'd repeat until he was finally able to spring for a true roadrace frame which has not given him any trouble. At that point the original frmae had additions all over the place!

3. Swingarm brace

Triangulation is the most efficient way to stiffen a structure. Doubling up with a tube and stitching them together as you say will work but making a triangular brace will work even better. You can triangulate below the swingarm if you need to, it doesn't need to be above it. However, if you don't like how a triangular brace looks a stitched second tube will work and may work well enough for your needs. More than doubling the engine output will make some modifications necessary!

One thing to check is your swingarm pivot bearings. Any slop in this area will definitely introduce a low frequency oscillation to the bike when it is on the gas.

Also, maybe install a quality steering damper.

Let us know how the mods go.


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Old 10-21-2011, 01:54 PM   #17
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Thanks Chris.
Nice to have my own thoughts confirmed, even if I'd prefer the easy way suggested!
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Old 10-21-2011, 11:00 PM   #18
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Chris!!!

I have a question.


This may seem out of place here, but I was directed to you and this thread from a distant place on the internet, (thumpertalk) that you are the knowledgeable guy willing to give advice. so here it is.


Cooling systems. What's the deal with running dual rads parallel vs series?


If you'd like to read my whole build thread, it's right here: I'm an amateur, first real bike build, lots of experience working on stock bikes.

http://www.thumpertalk.com/forum/sho...969189&page=12

Short version is this: 1996 KTM 300 2t engine in a 2004 kx250f motocrosser. It's going to be an full time woods bike, no motocross. I do pretty long rides, usually 50-80miles a day. I ride in all weather conditions from blazing hot to snow. alot of the riding is fast, but in stock form with the ktm300 I overheated a couple times because I do ride some stuff that's just brutal challenging and good material for overheating. So....I need to cooling system to be above par.

The stock KTM radiators are a little bigger than the kxf radiators, but the kxf ones I'll be using are the heavy duty alum fluidyne copies so they're thicker. The OE ktm setup is plumbed in parallel, the kxf stuff is plumbed in parallel also, albeit in a little different fashion. In either case I will probably end up having to reweld all or most of the cooland line ports on the rads, so that's not the issue, BUT in order to run them in parallel I'll have to do another frame mod, and maybe run a cooland line behind the engine. It can be done, but it's alot easier to set them up in series. Also, I was planning on running a single 12v computer fan to improve my low speed cooling, and running rads in series lends itself very well to this because I can put the fan at the hottest spot and have the greatest efficiency. BUT, what's the deal with parallel vs series. I'm getting all kinds of conflicting advice on thumpertalk and doing research, but it seems to me that the main issues are increasing fluid flow velocity with series, which could in turn raise the pressure in the rads, in turn lowering the pressure in the head. It's my understanding that would be bad.


I'm pretty much in the dark here though, so should I run the rads in series and see what happens, or spend another week doing frame mods to run them in parallel.


If I do run them in parallel, where should I put the fan? Will i need to then run 2 fans to get any benefit?




thanks so much for any advice anyone can give,

Thanks,

Joe
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Old 10-23-2011, 08:23 PM   #19
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radiator arrangement

Ah, I remember the thumpertalk days. There may still be some pics of my original bikes floating around that site.

I think a parallel radiator arrangement would work best for 2 reasons: mainly flow resistance and secondarily heat transfer.

Flow resistance relates to how much power the water pump consumes to push the water through the rads. Series and parallel flow resistance is treated the same as basic electricity flow, series resistance adds, parallel resistance adds in reciprocal. If you had 2 radiators that each had a flow resistance of '2', in series the total flow resistance would be '4' (2+2) and the parallel flow resistance would be '1' (1/2 + 1/2), or 1/4 of the series version while having the same radiator area, a pretty good decrease in flow losses. In this way the mfgrs are making the engine see the 2 rads in parallel as the same as one wide radiator like most street bikes have. Dirt bike mfgrs seem to have an allergy to designing the bike with one wide rad (maybe because of the large front suspension travel they need) so this how they have enough radiator area for cooling without having excessive flow resistance.

The heat transfer issues is a related to efficient use of radiator area. When we talk about heat transfer we have to think about what is going on. Heat and temperature are not the same thing. Heat is energy and can accomplish work. Temperature is just a gauge of how much the moleclues in a material are vibrating. Heat (energy) can only be transferred across a temperature difference. This makes sense as you can't transfer energy in the form of heat between two bodies of the same temperature. There is no driving force, similar to two bodies of water at the same altitude, water won't flow from one to another on its own. If you move one body of water down (or cool down one body) then water (heat) will flow from one to another until a new equilibrium is reached. The bigger the difference in height or temperature the greater the flow. What this is getting to is a description of how a radiator transfers heat from the coolant to the atmosphere.

If we imagine ourselves floating in the coolant stream as we enter the top of the radiator we can see that we are very hot, just coming from the engine. We can assume the outside atmosphere does not vary in temperature from the top to the bottom of the rad, a good assumption. As a result, at the top of the radiator there is a big tempature difference between the water and the atmosphere and therefore a lot of heat flow from the water to the air. As the water moves to the bottom of the radiator it cools. This cooling results in less heat being transferred from the water as it travels down the rad. You can imagine that if you had a really long radiator that the water would be at the same temp as the air well before it reaches the end of the rad. Any radiator after that point is a waste of space and flow resistance.

So the combination of a wide and short radiator (or 2 skinny radiators in parallel) allows for both low flow resistance and an efficient heat transfer profile.

KTM has a good fan kit that I use in some race applications. A computer 12V fan may not have enough oomph to make a noticeable difference. I think the most efficient place for it is where the coolant is the hottest which would be at the rad inlet but you need to be sure the fan is blowing on a part of the core that is always full of water.

All this is not to say that a series arrangement will not work it is just saying that a parallel arrangement will work better.


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Old 10-24-2011, 05:34 AM   #20
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First up, great idea for a thread. Love this thread and your other build thread.

I am not an engineer or anything, just a mechanic who works at a fab shop and who loves researching different designs.

Re the cooling system.
I remember reading somewhere on the web (can't find it right now) about a guy who did some testing on his cooling system (Subaru SVX IIRC) because he couldn't get straight answers from anybody why his car kept overheating. He set up clear rad hoses so he could see the coolant flow, he had pressure gauges set up at various points in the system as well as temp gauges everywhere, etc. Anyway his conclusions were that the flow restrictions in his cooling system (rad hose size) were creating pressure drops (think carby venturi) and it was these pressure drops that were reducing the boiling point of the coolant even though he had upgraded rad caps, etc.

What you said Chris about the radiators being in parallel rather than series corresponds to these theories. I agree with everything you said there and I just thought I'd add this as it may help somebody doing a cooling system upgrade if they have problems with overheating still, even with bigger radiators, etc. They may have to look at other areas like rad hose size, elbows, tee pieces, coolant passage size instead.
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Old 10-24-2011, 08:45 AM   #21
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Thanks so much for the advice guys,

It sounds like I really need to go the extra mile and run these in parallel. The problem now is going to be with routing. I'm not sure if it matters which way it's done.

I may have to draw a diagram, but here's how they're layed out:

KTM: The cylinder pumps into a T right out of the cylinder, and feeds into the top of each radiator separately. This part I can accomplish with no problem. Then the coolant flows the the bottom of each and the pump pull from the bottom of the right rad only, but there's a connecting line linking the bottom of the left and right rads. THIS is where I have a problem. I have no idea how I'll get a connecting line across the bottom. I can post a pic, but I'd have to either run a line in front of the frame, and somehow make a strong steel shield for it, or I can directly pull from both rads, but I'd have to run a line behind the cylinder, which is a fairly long line.


KXF: This one in stock form feeds to the top of the right rad, then has a connecting line going to each one at the top, and then the coolant falls and the pump pulls equally from the bottom of both rads. This basically presents me the same problem because I still need to run a line from the bottom of the left rad to the right side somehow.


Is there any fundamental difference between the way these are plumbed? Can I feed equally into the top of both like the KTM and also have a connecting line at the top, and then pull separately from the bottom of both without a lower connecter? Can the spillover point at the top take care of things?

If this is too rambling, let me know I'll diagram each method.


With respect to the fan: your typical 80mm computer fans are pretty thick and only move about 20-45cfm, however, with a little searching I've found some nice 92x92x25mm fans that would cover half my rad perfectly, and pull 100+cfm. I've heard some other people run similar with great success, so I think I'll give it a try. The fans are about $9 each, whereas the KTM kits are like $90. Plus the KTM was an EXC model, so I was going to run the fan right off the headlight power, and put the switch on the bars, since my bike will have no headlight.


Thanks so much for the advice guys, any other thoughts?
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Old 10-24-2011, 10:40 AM   #22
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Quote:
Originally Posted by up2L8 View Post
......
With respect to the fan: your typical 80mm computer fans are pretty thick and only move about 20-45cfm, however, with a little searching I've found some nice 92x92x25mm fans that would cover half my rad perfectly, and pull 100+cfm. I've heard some other people run similar with great success, so I think I'll give it a try. The fans are about $9 each, whereas the KTM kits are like $90. Plus the KTM was an EXC model, so I was going to run the fan right off the headlight power, and put the switch on the bars, since my bike will have no headlight.


Thanks so much for the advice guys, any other thoughts?

The KTM has a split AC/DC electrical system. It drives the headlight with AC power. The fan will need DC. You can run the fan off the DC side of the regulator output or convert the whole system to DC. If you use the stock system, note that the DC side can supply a hair under 2 amps. The KTM fan draws 2.5 amps so there's a bit of a juggling act going on with regard to the fan, the e-start, and the battery.
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Old 10-24-2011, 11:27 AM   #23
CosentinoEngineering OP
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>>You can't be a degreed engineer. Your explainations are too concise and too coherent and
>>too understandable by a layman, and lack any mind-numbing polynomial equations to prove your point.

That's funny. It's because I started my engineering career at age 5 in my father's 2 bay auto service station. Practical applications of knowledge has always been my forte, although how practical a boutique road-race motorcycle is can be debated.


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Old 10-24-2011, 11:39 AM   #24
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more rad routing

The KTM or KXF routing would work fine. The KXF version may be more thermally efficient (likely not noticeable) at lower speeds because the inlet tube feeds one rad directly and the 2nd rad is only fed when the first is flowing at capacity. Since water speed is proportional to engine speed at low speeds water is being circulated through one rad and as engine and water speed increase the overflow from the first rad beings the second one into the circuit.

I'm not sure about the electrical capacities of the KTM setup so will defer to Luke here. Practical experience trumps book knowledge 9 times out of 10.

As for the fittings and flow restrictions the posted comments are right on the money. Lots of people concentrate on hop-up parts to have their engine make the most power possible (high IMEP- Indicated Mean Effective Pressure or an engine's gross power production) without thinking about the losses the engine makes (PMEP- pumping mean effective pressure which is a power loss, and FMEP- frictional mean effective pressure, another power loss). Restrictive water lines, oil hoses, and crankcase breather lines are all areas where the engine wastes power it's already made to overcome losses that can and should be minimized.


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Old 10-24-2011, 03:30 PM   #25
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I havn't looked into the electrical system yet, but I'm surprised to hear they might have split AC/DC. Is that with all their bikes? It's a 96 engine and no electric start. It's not a street headlight either, it was just a cheezy trail light. I'd be surprised they would go to that trouble for a tiny light.
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Old 10-24-2011, 06:39 PM   #26
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Quote:
Originally Posted by up2L8 View Post
I havn't looked into the electrical system yet, but I'm surprised to hear they might have split AC/DC. Is that with all their bikes? It's a 96 engine and no electric start. It's not a street headlight either, it was just a cheezy trail light. I'd be surprised they would go to that trouble for a tiny light.

My mistake. I read EXC and was thinking of the newer 4 strokes. But according to the microfiche, your bike has a SEM K11 system which is probably set up AC only.
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Old 10-29-2011, 09:27 PM   #27
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Thumper motor into Gasgas EC300

I've been searching for the perfect dualsport - you know, one that weighs under 250 lb, does trails like a trials bike, will run 60 mph down the road, is quiet as a field mouse, and has Honda reliability.

I happen to have a Gasgas EC300 which pretty much fills the trials handling and reliability, but the motor is loud and has a real narrow range transmission.

I've been thinking about getting a small engine with a wide ratio transmission, like an XR250L, CRF230L, or maybe DR350, and transplanting it in. The first dimensional problem I can see is that these motors are a little taller than the space available.

The Gasgas has a steel tubing frame, is it reasonable to consider cutting and welding on it to make room for the bigger motor? I realize that there are probably many other issues to consider, but this one seems pretty basic. I can do some of the cutting and tube fitting myself, and I can get professional friends to do the actual welding.
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Old 10-30-2011, 05:55 AM   #28
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I had a similar project putting a CR500 motor in a YZ450 chassis. You're correct getting the bigger motors to fit, especially an older air cooled motor is tough. Height above the head and also sprocket alignment are two things I look for in every project I do. For the YZ I remade the engine cradle to accommodate the new motor. Also you'll want to check where the exhaust exits, hopefully its close or you'll need to modify the down tube as well.

Not to talk you out of it, but I'd seriously consider if you can get it done and what you'd do to a running bike. My YZ was a basket case without a motor anyways so I didn't care.

I'd get your hands on a real live motor and hold it up next to the frame to visualize where the problems are going to be and decide how much of your gas gas frame you want to modify.

If it will fit in the envelope you're set. Just get some prefab motor mounts from AA and go to town, just make sure that your alignment is cool with the rear sprocket and that the countershaft sprocket is in the same general area to minimize chain whip.

I've got an XL500 motor if you want it
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Old 10-30-2011, 06:06 AM   #29
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This should give you some ideas as to what I had to modify:









Oh and if your swingarm goes through the motor that would be the biggest show stopper. You basically need the width of the motor to be equal or smaller than the GG motor. I got lucky and the CR was slightly narrower than the YZ so the swingarm fit however I had to drill out the CR cases 1mm I think from 17 to 18 or something to get the pivot bolt to go through the motor. Check this first, its probably going to be the most difficult part of the build, everything else is fairly straightforward.
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Old 11-01-2011, 06:48 PM   #30
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Steel Tube Question

What do you guys like to use for steel tubing for frame work. 1018 CR? 4130? DOM? CREW? Diameter and wall thickness favorites? Assume the tubing will be TIG'd

Thanks,
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