stu109 Posted March 2, 2019 Report Share Posted March 2, 2019 I have always had a desire to ride a trails outfit and, after many years of prevarication, I have finally taken the plunge and bought a chair. I am planing to attach it to my 1986 JCM 320cc. The bike has an air shock and I am hoping pumping it up to the max will make the rear stiff enough for the extra weight. There is plenty of information here about fitting but would welcome guidance on some specific points. I was going for a vertical bike/sidecar wheel. Should I be looking load the bike to allow for any sag in the suspension when in use? It is suggested that some tinkering to the mountings may me necessary to get the best ride. Do adjustable mounts work well, or is it best to weld directly to the mounts? Any other advice much appreciated. Quote Link to comment Share on other sites More sharing options...
p@ul250 Posted March 2, 2019 Report Share Posted March 2, 2019 Hi Stu, If you get the geometry correct you shouldn't need adjustable mounts. But do make the sidecar detachable. The most important dimensions are, Track of 34.5",Wheel lead (sidecar wheel spindle 9.5" > 10" ahead of rear wheel spindle) and a toe in of 1.5" over the wheel base of the bike. I set mine in a jig that I built. The bikes suspension is unloaded and fitted with the heavy duty rear spring. For a modern mono bike your looking at around a 900 lbs per inch spring (so you may find that your air shock will struggle). The tires are at working pressure and the bike set vertical in the jig. Most of the sidecars used have the sidecar wheel vertical or cambered in a little and the vast majority have a suspension geometry that increases the camber in as the sidecar suspension is compressed. These are just a few I have done in the last few years. 2 2 Quote Link to comment Share on other sites More sharing options...
stu109 Posted March 2, 2019 Author Report Share Posted March 2, 2019 Thanks for the advice. Modern sidecars appear to have very little in the way of mudguard or passenger seat. Appreciate that there is little sitting down for the passenger, but are there some other practical reasons for this? Quote Link to comment Share on other sites More sharing options...
markparrish Posted March 2, 2019 Report Share Posted March 2, 2019 What an amazing collection of frames Paul250! You must be pretty slick at bending and welding tube by now! I'm impressed! 1 Quote Link to comment Share on other sites More sharing options...
rabie Posted March 4, 2019 Report Share Posted March 4, 2019 if you look at old pre 65 chairs, it prevents the passanger moving around the outfit there is an hour long video on youtube of yesterday's Normandy MCC's sidecar trial - you can see how all the passangers are moving all over the place! (lucky you can't see me making a hash of it!) Quote Link to comment Share on other sites More sharing options...
stu109 Posted March 8, 2019 Author Report Share Posted March 8, 2019 Have managed to sort out the frame mounting points, am now looking to attach the chair. Don't have any welding capability myself so am looking to get everything set up in a jig and then get someone in to do the final welding. Less luck with the rear shock though, even at maximum pressure the JCM shock was not up to the task, so need to source an alternative. Anyone have a spare shock they are not using? Solo would do as I could get a stiffer spring, but would consider anything. The idea here was to source a used chair and attach it to a bike I was not really using to produce a cheap outfit for a bit of fun. So not looking to spend more than the whole thing is worth on a trick new shock. Have to have a look and see what is available on a well known auction site. Quote Link to comment Share on other sites More sharing options...
stu109 Posted March 13, 2019 Author Report Share Posted March 13, 2019 Spoke to Joel Corroy (who designed and manufactured JCMs) about fitting a sidecar. He advised that if I changed the shock oil to 10w and pumped it up to 15Kg/cm2 it would be suitable to take the extra weight. Will give this a go before investing in a new shock. 1 Quote Link to comment Share on other sites More sharing options...
stu109 Posted March 16, 2019 Author Report Share Posted March 16, 2019 Have refilled and pressurised the JCM shock as advised. The rear suspension is now extremely stiff, so will give it a go fitting the sidecar and see how I go. 1 Quote Link to comment Share on other sites More sharing options...
stu109 Posted April 15, 2019 Author Report Share Posted April 15, 2019 Have been doing a bit of work on the chair prior to fitting and am a bit confused by the suspension set up. The chair is supposed to be a Beamish one, and is chrome plated so may well be. The swinging arm appears to have some sort of torsion set up a bit like a trailer, but also has a shock. Is this right? All advice much appreciated. Quote Link to comment Share on other sites More sharing options...
stu109 Posted April 16, 2019 Author Report Share Posted April 16, 2019 Mystery solved. Not some fancy suspension just incredibly seized bearings. A severe beating has got the shaft out but it will have to be replaced. This simple outfit project gets lengthier by the day! 1 Quote Link to comment Share on other sites More sharing options...
stu109 Posted June 13, 2019 Author Report Share Posted June 13, 2019 (edited) After much cutting, grinding and welding I have finally managed to get the chair attached to the bike. Am quite pleased with the result. Fabricated a jig to hold it together whilst I worked on it, and set it up as per the measurements from p@ul250. The headstock mount was a little tricky. I had to utilise the bolt that acts as a steering stop as one of the mounting bolts. The lower front mount is a modified engine mounting plate. The rear is attached to the original footrest mount. Had to replace the side bar on the chair as it was cracked and the fourth mount up to the rear subframe is to try and prevent this happening again. Have fabricated a footrest attached to the rear wheel axle, and a chair brake pedal, which I have squeezed in under the bike swinging arm. Have given it a quick ride around the garden with a bag of sheep feed as the passenger. It seemed to handle well and was huge fun. Need to sort out the chair brake, for which I will use an alternative wheel with a drum brake, (in keeping with the bike), give it all a coat of paint, and attach the floor and side panels. Then I just need to find a passenger! Edited June 13, 2019 by stu109 Typo 5 Quote Link to comment Share on other sites More sharing options...
stu109 Posted July 4, 2019 Author Report Share Posted July 4, 2019 Finally finished! Fitted the wheel with a drum brake. Had to change the bearings and drill out the brake plate to take a 15mm axle. Soldered a new brake cable which routed neatly under the tank and down to my new brake peddle. Painted the chair frame and brackets. Wrapped the ally panels with vinyl wrap to get a white finish to match the bike. All in all very happy with the final result. Could this be the only JCM outfit? Have had a quick ride with my daughter as passenger and the rear shock seems hard enough. Will try and convince some of my local clubs to include sidecar sections, so I can give it a proper test. If you are looking to have your own outfit I would strongly suggest you start with one someone else has already done, would be a whole pile less work! 2 Quote Link to comment Share on other sites More sharing options...
austini Posted July 5, 2019 Report Share Posted July 5, 2019 Awesome! starting from scratch you have done a great job, now to get out there and scratch it....errr enjoy it. When your learning just getting to a section is an achievement so getting from one end to the other of a solo section should keep you busy for a season or two. Quote Link to comment Share on other sites More sharing options...
stu109 Posted July 8, 2019 Author Report Share Posted July 8, 2019 Have discovered mine is not the only JCM outfit. There is one in Joel Corroy's JCM museum. Won the 1985 French championship apparently. Gives me much reassurance that the bike generally, and the air shock in particular, will be up to the job. Quote Link to comment Share on other sites More sharing options...
Kev1z Posted November 10, 2020 Report Share Posted November 10, 2020 Hi, just came across this post, I competed on a JCM 323 trials outfit in 1986 finishing 2nd in the British Championship to Robin Luscombe, it was fitted with an Otter sidecar. On 3/2/2019 at 9:33 AM, stu109 said: 1 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.