Going to try and build a hack for my FJ like this: http://www.mobec-international.com/53276097880f0b705/53276097880fb0501/53276097881013d06/d007.html and i was wondering how those who homebuild figure out at what position to place the wheel? Is there an accepted range or... I realize that it must have a bit of a lead but how much? Why I asked is that I plan on trying to create my own sidecar drive (w/viscous coupling) and need to know how to decide where to put the wheel, and therefore be able to better understand how to set up the drive. Please, let me know what you know. If that's been done already by a homebuilder and i have not found their site please post a link or just shoot me some ideas if you have some. I live in canada and wish to have a year round ride so the driven wheel would help alot. If i can't sort that out I'll build first and mod later to add the drive when I figure it out. Thanks y'all, Formernortherner
I'd say the average is 6 -9 inches. It effects turning and general stability. OTOH, harley places the SC wheel next to the back wheel- no lead. ? ! Look up Claude here. He has a shop and also is very into HP sidecar rigs. He can explain it better than I can. Or he hangs aut at the United Sidecar Association a lot. Or, e-mail his shop here; cstanley@sunlink.net (This stupid black backgound makes it hard to see, but there IS an e-mail address after the semi-colon there.)
Old skool rule of thumb says lead in mm equals weight of bike in kgs. So your FJ weighs 280kg (guess), lead should be 280mm. I'd go a little more, say 300-400mm. Too little lead will make the hack nose heavy, too much and it will affect steerring. Paul.
Yep, you're right, old school rule. Sidecar outfits like these (heavy, wide, car type wheels) have a lead of at least 320 mm (12 to 14 inches will be OK). If you want to go on with the sidecar drive, it's very important that the trail is allmost zero. Even with the visco-coupling the handling is completely different from an one-wheel drive sidecar. LL or Hub steering is equal. Without doing that, you'll have a sidecar that steers as a very basic sidecar with a telescope fork. Very heavy. Can easily be checked. Richard-NL
One more thing: Pro sidecar-builders say a two-wheel drive sidecar doesn't need any (or nearly none) toe-in and apply some camber to the sidecar-wheel. I personally don't agree. In my opinion you should consider the possibillity to adjust the toe-in on the sidecar-wheel. Once you have the sidecarwheeldrive on, you cannot adjust it anymore over the (sub-)frame. You get to much space on the axles. Depending on how fast and with how many weight etc. you wanna ride, I think it's important to have some possibillities to adjust that to your personnal preferences. Hopefully clear what I said. Sidecardrive isn't that easy as it looks. Richard-NL
As you can see in the pic included, I will be trying to incorporate a car type front suspension as well. For doing this would a similar type of steering angle be recommended, as in caster? if so, you're saying close to o degrees of caster for better steering? steering will be done through spherical ended control rods attached to stub forks in the normal position.
If I understand you correctly, the answer is yes. You will be needing a proper steering-damper too, but you understood that allready I suppose. Richard-NL
Don't see no pic. Am I correct thinking you want a driven AND steerring 3rd wheel? Then you want to take a close look at a Mcpherson (sp?) type of arrangement as used in a fwd car. And think of a clever linkage to get the steerring angles right, more angle when steerring around the hack, and less when going the other way. Paul.
Hi to all. I was taught that the formula was 7/8th of the wheel base. This works for the width of chair also. So for instance my K1100 has a measure axel to axel of 1700mm(with leading links), 7/8s of that is 1487mm giving a lead of 213mm and a width/track of 1487mm. But if doing lots of dirt/ outback roads get it to suit the width of a general 4x4 eg. 1450mm width of wheel track. Just ideas, all up to the individual. All the best Beet.
Not exactly Paul. Not adding steered 3rd. way too much geometry! maybe next time out. I'm doing a hub steered single side front end. see the link in the first post for the type I'm doin. Cheers, Formernortherner
Hey Beet, This is going to be a year round street ride and the viscous coupled third drive will be for snow and/or general street thrashing. it may see dirt roads/ fire roads, but no trails. I'll be scooping the step-son's XL600 for that duty. So, that being said, width is a non issue, as long as it's less than the average minivan, but I've been thinking that wheel lead about even with the swingarm pivot would make it minty. Thoughts? Formernortherner
Hey all, Thanks for the replies so far. Good responses all. Thought I'd tag on a pic in case the earlier link didn't work.
The swingarm pivot is probably a little too much lead. Instead start with the sidecar wheel axel approximately even with the front of the rear wheel. Adjust from there.
As you have seen the answer related to how much wheel lead is required is all over the map. Let me throw some food for thought at you. You will have to make the decision of what you feel is best in the end as there are tons of compromoses to be dealt with. I am referring to a right hand mounted sidecar below. I can say that most HPS rigs run quite a bit of lead. Why? The more lead you have the more stability is created in turns away from the sidecar. What are the drawbacks? Everything being a compromise is factual. Too much lead will unhook the front wheel earlier in left turns (away from sidecar). Too little lead will allow nose diving of the sidecar. It is possile that a swaybar equipted rig can run less elad than one without a swaybar. We typically speak of wheel lead in inches. This is too bad as it really does not compare apples to apples. Diferent bikes have longer or shorter wheelbases so a percentage of the bike's wheel base may be the better way to descibe wheel lead right? Well maybe, but other factors come into play as well. Track width moves the front bike wheel to sidecar wheel tip over line in a way that gives more left turn stability. How does this affect lead figures? You would think that a wider stance woudl allow less lead maybe? Dunno for sure. Okay think of this: Imagine an automobile with two rear tires and the front right tire removed. Lets pretend that the car woudl sit still without the front right dropping down. That car could be turned right at speed with litle issues. That same car would dip the right front to the road easily in a left turn. Now, lets consider an automobile with two front tires and only one rear tire being on the left rear. The right front tire is fixed and does not steer. It would be hard to steer especially in left hand turns. It woudl never dip the nose though in left turns. These are examples of drastic lead but I think you get the idea. On a rig like you are describing I would probably go for 12" minimum but coudl be wrong. A driven sidecar wheel will make the rig act unlike any conventional sidear rig.Some have reported a drastic pull towards the sidecar on these type rigs. Some not. If you are going with wide tires you can possibly compensate if you have an adjustable scrub radius on the front end. If you are going to use a conventinal center hub system these adjustments may be more difficult than if you did a true center hub with adjustable pivot points for the steering axis. Another approach may be to design in a scrub radius and make it so you could add or subtract from it with Wheel spacers. Another thing to think on is that Rigs can theroectically run more lead if they have a steering sidecar wheel. This can also lead to a lot of geomtric challenges on a sidecar rig related to whether ackerman is desired or not and of so how much and all of the linkage that goes along with it especially with a non symetrical vehicle such as a sidecar. I know you said you were not planning on a steerable sidecar wheel but being able to adjust the scrub radiu smay still be a good idea. Like Richard said once you are mounted and setup with the driven sidecar wheel no, or very little, adjustments will be avaiable to you. Being able to adjust toe in at the sidecar wheel and having a means to adjust the scrub radius at the front wheel sound like good ideas to me. Pictures of completed rigs make things look pretty straight forward. The geomtry that makes one system work better than another are not that obvious sometimes and to be quite frank about it the jusry is still out on a lot of the theory behind what is done. So, think it out and if you decide to follow though with your project I am sure you will have fun while learning a lot. You may learn that much of what others mentioned was right on and that much was not 'in your case'. You may even learn some new tricks for yourself that can be shared with the rest of us wackos who are willing to get invloved with these crazy things Hey, never hurts to call Mobec. The phone bill may just be a good investement.
Uncle Ernie wrote: "OTOH, harley places the SC wheel next to the back wheel- no lead. ? !" Actually Ernie , they did in years past but since getting away from hardtails they have run lead on the sidecar wheel.
Ok Claude First of all, wow...long post, but thorough. Maybe to clarify it should be noted that I intend for the suspension to be made with parallel a-arms at all three wheels, as the front of the bike in the picture.I intend to make the hack wheel adjustable for camber and toe, the steering on the front adjustable for caster, toe and (very slight) camber. There is to be a sway bar system (if i can figure it out) to react on all three wheels. That way as one wheel squats in a corner it brings both other corners of the rig down to match. This should help with tip over from either direction, right? Also being able to put the wheel as close to the c of g as possible longitudinally, while having a width as close as possible to equal of the wheelbase (about 3/4 to 7/8) should lead to a very stable rig, given the common chassis mounting of the suspension. That positioning will also make fitting the hack drive a much simpler proposition, since it will already be coming from the other side of the bike and being able to pass it as directly behind the main frame spars as possible with a straight shot to the hack wheel. Further, there would be no interference with traditional swingarm this way as there won't be one. I'll stop here for this one. Am I making sense to everybody here? Let me know what you think so far. Also, anybody know of or have a autocad type software i could use to get the layout on paper? My art skills aren't great and i think it would help a lot. Take care all and thanks again for the preceding and ongoing input Formernortherner
FormerNorthener wrote: >>There is to be a sway bar system (if i can figure it out) to react on all three wheels. That way as one wheel squats in a corner it brings both other corners of the rig down to match.<< I hope you do that! I have been thinking about trying a swaybar connection beteen the front and rear wheels for a long time but have never gotten around to it. Need a center hub or that type of front end to make it work and your Mobec type a-frame deal should do it. I think with a system like this when you brake hard the whole rig should just squat and stay pretty level in all planes. The opposite will occur when you gas it. The rig should lift which is planting all three tires to the pavement. No doubt there will be some playing around to get it right but I am excited about the idea. Please keep us posted, you have intentions of a pretty wild project there.
Hey again Claude co., I figured out last night how to do the swaybar linkages pretty easily and would love to share it, but I have no way to illustrate it (drawing software, autocad etc.). I would really like to be able to create a blueprint quality drawing of all of this. Who knows, if I can get this built to a good standard, I may have a marketable design for a marketable hp sidecar combo. If it even works half as well as it should, I will have a wicked good year round hack combo. Thanks for all the encouragement guys. It means a lot. Formernortherner