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Sidecar sags down

I attached my spirit eagle sidecar to my burgman 400. This is 4th bike I have had this sidecar attached to.  

The problem is that when I ride it, the sidecar starts quickly sagging downward, causing the bike to LEAN into the chair significantly. 

I never had this problem before with other bikes. 

Any ideas what I am doing wrong?

I Suspect the Z bar is the culprit.  Can I replace it with a strut?

Thanks! John 

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That mount system looks pretty flimsy to me and all the brackets seem to be angled in the same direction with nothing to oppose them rotating backwards apart from the Z bar. I believe that when mounted the side car and tug frames should be like a single entity. With more photos it would be easier to study the problem and suggest a solution       Chuck

John Holbrook has reacted to this post.
John Holbrook

Really poor triangulation, with "universal" type frame clamps that can loosen. It is no wonder that you have sagging. You have in essence built a parallelogram which can collapse. You want to be making a trapezoid which will not collapse. In general we try and avoid "universal" type clamps, when we do use them we try and use them in a manor where the forces being applied are trying to slide the clamp on the tube, not rotate the clamp.  The Z bar is in general a stupid way to do a lower front mount for the same reasons that it is stupid on other sidecars that have a more or less fixed lower front mount as it does not allow for the proper setting of wheel lead any other way then by having the front lower mount in the exact right position.  In the case of the "Z" bar the issues are compounded in that you are hoping that the jam nut will keep the bar from rotating on its threads. At this link you can see how we deal with this on Velorex sidecars which are fairly similar Sidecar Mounting | DMC Sidecars While we do not have mounts for the 400 Bergman, I have attached information as to how we do the 650 Burgman where you will see we use no "universal" type clamps.

Jay G
DMC sidecars

http://www.dmcsidecars.com

866-638-1793

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  • Burgman-650-mount-assy.JPG
1bmwmc and John Holbrook have reacted to this post.
1bmwmcJohn Holbrook
Jay G DMC sidecars www.dmcsidecars.com 15616 Carbonado South Prairie RD Buckley WA 98321 866-638-1793 Hours Monday - Thursday 6-4:30

Jay, and Chuck, thanks for the advice. I have a welder friend who is going to try and fabricate some similar mounts.

The 400 and 650 are completely different machines, so it may be a difficult process.  The 400 is a true scooter with the engine and drivetrain mounted on the swingarm.  The 650 is more like a regular motorcycle. 

I appreciate the help 

When you design your improvements keep a few rules in mind. Never ever terminate anything to have to deal with a rotating force ever"" it will move"" Always anchor anything in 2 opposing directions or it will find a way to pivot around a fulcrum. Like Jay said if you have to clamp make sure it is a sliding situation. If you do try to be able to anchor it to a bolt that will resist the sliding action. Look for hardpoints on the bike frame and use them they are usually stronger than unsupported frame sections which will either flex or yield when you apply forces to them that they are not really designed to resist. look at the frame of the bike around the engine mounts as that is usually the strongest part of the frame that is why the rear suspension is anchored there too do not make brackets etc that have any sharp turns and if necessary try to use the slowest curves you can get by with.

Lastly make sure that your welder is capable of making the welds and try to stay with fillet welds. How do you know the welds are good.  Weld 2  pieces of similar material together and do a fillet weld break  and that will show you how good the workmanship is. Its your butt on that bike                                                   Later Chuck

 

 

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John Holbrook

Finally got the sidecar remounted. I added two more struts for strength and stability.  Bike and sidecar are doing fine. The little 400  Burgman does well with the sidecar. 

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"Sweet" glad you like it. My tug is like on steriods  and I have a heavy car and a little leggy geared I have to be very conservative in my thinking and design work or it probably will come apart or do other horrible things. How does that little bike run up hills and into headwinds, or with a passenger  Ride safe   Chuck

Spoiler
The bike runs 65 mph just fine. Have not been on interstate yet. I need to get more acclimated to the bike before I do that.  I have not had a passenger in the sidecar yet. My wife is unable to ride at all due to health issues. Grandson said he will ride after  I get a few miles of practice. We got it stuck in the mud behind the barn! It is fun to ride. 

All in all, it was difficult to mount to the scooter. 

Here is a pic of us in 1984, in the Smokies.  Wife took the pic. Same sidecar mounted to a Suzuki gs550.  Rode it on interstate 330 miles to get to smokies, then rode the twisties. Of course, the speed limit was 55 back then

 

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Nice rig. I find the super slab the easiest riding. My wife also has issues getting in and out of the car I am going to put a little rack on the car fender she can use like a seat to help getting out. Getting in is not so bad. It helps to have a nice big car and she is comfy once she is in. 65 is not a bad cruising speed on the slab in the right lane. It can be a little bumpy but generally not too bad If you get behind a empty or lightly loaded truck. Like a Frito Lay  or a  flat bed carrying a smaller load. they keep a more consistent speed going up hill. I try to watch my speed on twisty corners and also to avoid power until I am coming out. Sorta in like a lamb and out like a geriatric lion. Dunno but it seems to make my rig more manageable at this time.     later Chuck