Bike Lore

Well the MJ-808X cost R1300, I am not going to put pen on paper for the MJ-808E yet. I have made this mistake before.

Well I am amped to announce that I will get my hands on some valuable merchandise very soon, next week I hope. The New MJ-808X Aka Xtreme(ETA 23 March 201) and MJ-808E Aka Economy (ETA April) as soon as I have them I hand I will place an advert in the classifieds. But I have got my hands on some samples of the MJ-808X. Some Background info The magic shine MJ-808 caused a stir in the cycling community over the last few years. This light offered top end light output in a stunning beam pattern but at a faction of the cost of the high end lights. The Old magic shine used the Seoul Semiconductor P7 power LED and had an efficiency of about 70 lumen per watt. Both these new light make use of the new Cree XM-L LED that can pump out +40% more light for the same input power at a clear white light (5000K) that is 100 lumen per watt for the t6 bin. What the difference between the two new models? The difference between the two lights is manly the driver circuit and what goes with it, Thermal path etc. I also suspect that the LED is of a lower bin T5 for the MJ-808E and T6 for the MJ-808X but that is just speculation at this time. The higher the bin the more efficient but also the more expensive. not sure what bin is? follow this link in summery the LED after they are manufactured get tested and sorted in to a BIN the better ones get labeled T6 and the not so good ones get labeled T5. In most cases there is more T5 then T6 hence the price difference. In short the the MJ-808E is designed for economy. Where the MJ-808X is for brute light output. Review MJ-808X (R1300) This baby pumps out very close to 1000 lumen with its 3 Amp driver. Its runtime is 160min(2h40 min) using the standard battery. I have taken some beam shots comparing the Old MJ-808 and the New MJ-808X Speculation about the MJ-808E (T.B.A) It seems that economy what the aim for this light. The driver current has been reduced from 2.6Amp to 2.4Amps. But the result is that this unit puts out 770 lumen vs the old light that did 650 lumen but the MJ-808E runs for 210min on HIGH vs the questionable 180 min on the old MJ-808 Here is a beam shot caparison between the new MJ808X and the MJ816. Note that the road is 75meter long and then there is a turn. Is should be clear that the MJ808X has a further reach and whiter light than the MJ816. it is also smaller and light. As well as the added protection for over heating The MJ816 does have more light near but the MJ808X does not stand back much.

but really what do you do? no helmet, no shoos on a clip on bike. heading away from a race area.

oops heh, how do you edit the subject?

Right so you are cycling to Jonkershoek on a Saturday morning and a very dodgy character heads your way. He is cycling a full carbon hard tail with a race number. He is wearing a worn t-shirt, slops and pants that has not seen a wash since the previous owner gave him the pants. {Edited by a Mod - coz we's pedantic likes that. }

NO Steven69 don't do it!!! the krypton inside will disrupt your metichlorine... just believe.... and send me you money T&C apply, faith sold separately form just believe pty inc

I bought a Felt F55 in 2009 and a week before this years Argus my rear stay broke near the jockey. I called BMT in Stellenbosch that Tuesday where i bought the bike and Felt replaced my frame and BMT rebuild it before the Thursday.How you like them apples?

it kind of works on the Mj808 because the light is balanced but it wobbles when the ride get shaky. the Mj816 is to top heavy and it rotates forward and wobbles to the side on not so ruff roads aswel. I have been looking out for a better mount that is cheap but so far has not found anything. It would be a gr8 improvement if one can get a quick release clamp system similar to the prinentech lights. also the light should be in the middle of the handle bar not on the side. is tend to shine to the side the way it is. o and if anyone is looking for some high and ultra batteries go to this link Magic Shine / Light Ultra batteries

If you get a extension cable you can mount it under your seat. I have a few.

I will go for the CR. it is really hard getting rid if rub without contact adjust

it happens and i agree about he last point as well.

what is the difference between applying the force in the middle and holding the contact aria fixed or other way around? IMO it will be exactly the same except that the hub will move down where now the contact aria is moving up. chancing the reference will not effect the result. example: if you are on a boat and you pull on a rope that tied to the shore do you pull the shore closer or do you pull your self closer to the shore... it all depends on how vain you are and where you put your reference. but the result is that the distance between you and the shore shrinks. well it depends if you are strong enough the counter the huge whirlpool that is sucking you in.. MWAHAHAHA DIE DIE DIE.

This is a video of a FEA that i run showing the effect of impact on a wheel has. The hub is held fixed and the force is applied at the bottom To simulate the pretension in the wheel i placed a pressure on the inside of the rim. this is wrong and should be noted that the results may very. if i get the opportunity to us a more sophisticated FEA application that can set the pretension i the spokes i will verify this results. http://www.youtube.com/watch?v=hHUMm0-zsnc Note the increase of tension in the other spokes as the bottom spokes tension are reduced due to the deflection of the rim

thanks Topwine for summarizing. I have attempted to say the same with my pictures-post before. I think there are some wording in the counter arguments that are leading to misunderstanding . I think the word compression is used to loosely. in the previous post the word compression is used when the tension in a spoke decreases from it preset value. even though it can't go in the true compression due to its slenderness ratio (effective length / cross aria) being to high it apeare to go in to compresstion becuse the pre-stress reduces. but i think we need to give this a rest now.

I think it is time that we stop this topic. it does not seem like anyone is going to move on there views and the post are become more and more patronize. it was truly an insightful discussion and JB arguments was thought provoking and it absolutely okay to disagree. Personally i have respect for anyone that is able to put there preconceived ideas away and really attempt to understand the alternative point of view without getting personal or generalizing. and it is clear that JB had this skill not like other people on this form. I my self need to work in this skill. I would advice everyone to always treat other peoples views with respect and not to become condescend. Nor should one trough there qualifications around to quickly. thank you everyone for the energy that was put in and the advice that what given. I really hope my new tubeless wheel will be awesome.B)

wow that is gr8. I have spoken to my LBS en they will help me with some rim tape and a valve. oi I should just resist buying a front wheel....

then ask your self why/how does it loosen it tension? what is the cause... the point being; the force is transfer via the top pointing spokes to the rim which then pushes the rim in to the ground. the deformation of the rims is countered by the horizontal spokes. if the bottom spokes did not loosen it tension the hub will not be in equilibrium and it will continue to move down. yes it does move initially down due to the sum of the forces. when this happens the distance between the hub and the contact point shrinks and the tension in the bottom spokes are relieved. the bottom spokes never(i hope for my inner lining sake ) pushes against the hub and the wheel. it just pulls less. I should add that up to the point where the tension in the lower spoke has decreased from the pre-tension to zero the tension in the top spokes has not increased due the the loading of the wheel. after this the tension will start to increase. but i think we need to stop this now. it was interesting doing the calculations and discussing this with my fellow engineers and scientist at work over brake times but the problem is solved. now lets get back to the serious stuff like riding my bike. today is interval day

I hope so. can't wait for the thing!!! and it is still being ordered.... ooi!! how am i going to survive the tension....

wow thank goatman. will defiantly do that. just need to get my self a valve.

Hi JB. sorry but I am back to disagreeing with this statement. it is amazing how many problems i solve while exercising. the loaded hub definitely does not stand on anything and does hang from the spokes and i will explain why. there are 2 superimpose stress systems in the wheel. the first is caused by the riders weight pushing the hub to the ground. and the second is due to the deformation of the wheel. lets analysis the first system. we know from newtons laws that if a body is subjected to a imbalance force then it will accelerate. consider that the hub does not accelerate we can simplify the system to the following diagram. http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs267.snc4/39666_452340510559_641460559_6613154_4880622_n.jpg the downward force that is caused by the riders weight must be counter and equal to reaction force. or else the hub will start to accelerate to the bottom. therefore any spoke with an upward vector will contribute to the reaction force as illustrated by the below diagram: http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs247.snc4/39666_452340505559_641460559_6613153_3306120_n.jpg therefore it is clear that the vertical most spoke will carry the most force and the other will decrease as there vector components change. please note that only spokes in tension can contribute to the holding of the position of the hub. the second system, due to the reaction force the forces on the rim can be simplified to the following diagram: http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs247.snc4/39666_452340500559_641460559_6613152_2791038_n.jpg where yellow is the reaction force caused by the weight of the rider and the pink is the earth being very stubborn and not moving. the result is that the wheel deforms. due to the spokes in the wheel having a fixed length it will resist this deformation. if you superimpose the forces on to each other you should be able to see why the tension in your wheel stays ruffly the same. expet for the sopkes that are at the contact aria. it can also be seen that all the stress in the hub is on top and to the sides not the bottom. the 3rd Principal stress method is excellent in indicating compression. http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs187.snc4/37696_452208935559_641460559_6609133_6568016_n.jpg therefore i conclude that the hub is hanging in a web and the bottom spokes give up there tension due to the deformation of the wheel in which case the hub remains where it is because it is still a balanced system.

darn!! already ordered the wheel. thanks for the tip. will go investigate. but can one remove the velox tame and install the stans yellow tape later?

just a note. my anthem had 3.5" rear travel and i am sure if it had 4" i would have had difficulty feeling the difference between the SJ with 4.7" travel but Mecnic is correct, do you like a race horse or do you like a cruiser that eats anything and still looks good.

You are more than welcome. if you pm me your email i will send you high res ones. But if you use them please note that the one that i have posted above is of 3 principle stress which is wrong to use if you are interested in tension. I use it because of it illustrate the argument and it has artistic value. here is the 1 principle model with pre-stress in the spokes. http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs204.snc4/38554_452229310559_641460559_6609439_1995136_n.jpg note that the horizontal spokes has the highest amount of stress due to the deformation of the wheel. they are the most likely to brake. i would rather say that the load is carried/absorbed by the bottom spokes by reliving there tension. but that is just how i see it.

Well JB I no longer disagree with you regarding the stress distribution in the spokes of the wheel. It is clear from the FEA that that the wheel deforms and expands and this expanding is countered by all the spokes. therefor the force is evenly distributed between all the spokes expect the ones where the force is applied. http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs187.snc4/37696_452208935559_641460559_6609133_6568016_n.jpg There is a very small amount of higher stress in the top side spokes but this is minimal. if the elasticity of the spokes are greatly increased then this higher stress does have a role but in a normal wheel setup it is negligible I am aware that there has been several simplification done to the model but i am under the impression that it demonstrate the principal of a wheel and spokes very elegantly. B) so we learn

that is good. again i realize that love is blind. enjoy