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Post by RT-chassis on Feb 27, 2014 18:51:12 GMT -5
New here so I hope that someone can guide me in the right direction. I am trying to explore possible RT chassis for a side by side RT. There are two simple chassis that I found, the first one is the blackjackzero that is basically a ladder frame by something I can weld together myself but the other chassis I found is even simpler. I saw the Can-Am chassis which is a 4.5"X1.5" rectangular backbone. The top tube in spyder is required for rider support and other auxiliary stuff attachemnt and aslo to mount the rear suspension shocks but I am wondering if the bottom beam of the spyder is good enough to be used as a backbone chassis for a 900 lbs empty weight. Is the top tube providing a great deal of added stiffness to the frame too? I would appreciate a response.  |
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Post by stretchmobileski on Feb 27, 2014 21:35:25 GMT -5
I wouldn't go with the stock frame. I definitely wouldn't remove the backbone and use just the bottom. It would be as stiff as an over cooked noodle.
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Post by RT-chassis on Feb 27, 2014 21:56:11 GMT -5
The reasons for looking into the Spyder were, 1. Off the shelf suspension geometry, reliable, proven, complete... no engineering needed 2. The weight of the component(hub+knuckles etc) is ideally suited for a 900-1000 lbs trike....again no need to engineer 3. The cost involved is very reasonable from a salvaged vehicle 4. The weight of the chassis itself is the lowest possible due to it being just a tubular structure. The tubular chassis as the backbone has been used before at a much higher weight vehicles so I was hoping that this backbone tube is good enough for the low weight of 900 lbs RT. The other option is the blackjack zero but the chassis is definitely heavier. The advantages are, 1. Based on the earlier Avon that has 80+ kits history 2. Very easy ladder frame 3. I have the flexibility to buy it all welded on a jig rather than making one myself but there are very big disadvantages, 1. The weight is a lot more than the spyder 2. The suspension geometry is also copied from Audi/VW so for a heavier car(overengineered for my RT) 3. Loose the flexibility of buying off the shelf 4. Much expensive 5. Only one example in the US The suspension geometry and chassis will determine the handling and I do not want to compromise that and do not want to invent it or even copy it. I really want as close to a plug and play that I can get. Is there a middle path? Thanks for the comments. |
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Post by Liteway on Mar 1, 2014 19:11:06 GMT -5
Were I just starting I would go with Spyder Components. It is the only thing available in the U.S. scaled right. Mustang II stuff is just too heavy. Atv stuff is underbraked and often Illegal. Vw stuff has wierd geometry and looks. Its just a little heavy though much lighter than Mustang. Designing and machining purpose built spindles and arms is too much of a stretch for many/most of us.
I have priced Spyder front end parts individually and they total around 4k. Can probably get a whole salvaged one cheaper, though you would want to be sure the parts you are interested in are not damaged.
I don't see how you could use the whole frame, but you could use the bottom, to preserve suspension geometry, as a subframe and build the rest in tubes to preserve structural stiffness. Also, the track is a bit narrow so you might want to graft in some width. But now, by the time you widen it, you might just as well build a frame from scratch and avoid some undesirable compromises. Just copy the measurements and relationships of the arms on the old frame and transfer to the new.
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Post by RT-chassis on Mar 14, 2014 9:30:37 GMT -5
Were I just starting I would go with Spyder Components. It is the only thing available in the U.S. scaled right. Mustang II stuff is just too heavy. Atv stuff is underbraked and often Illegal. Vw stuff has wierd geometry and looks. Its just a little heavy though much lighter than Mustang. Designing and machining purpose built spindles and arms is too much of a stretch for many/most of us. I have priced Spyder front end parts individually and they total around 4k. Can probably get a whole salvaged one cheaper, though you would want to be sure the parts you are interested in are not damaged. I don't see how you could use the whole frame, but you could use the bottom, to preserve suspension geometry, as a subframe and build the rest in tubes to preserve structural stiffness. Also, the track is a bit narrow so you might want to graft in some width. But now, by the time you widen it, you might just as well build a frame from scratch and avoid some undesirable compromises. Just copy the measurements and relationships of the arms on the old frame and transfer to the new. You are correct in that the price is in line with what i saw at can-am parts suppliers.Also, the VW, Mustang or others are just too heavy for this. The off the shelf spyder components with the right geometry already in place and the light weight is key. While I think about how to get the existing frame to work, I am a bit concerned about the small track. Here is what I going with: Wheelbase: 115-119" CG is going to be about 48" from main wheels and about 19" from ground... All this is based on I disagreeumptions of the component weights.BTW, do you know how much is the weight of the front sypder suspension components? The weight distribution is about 60(front) and 40(rear)... I think this is a good compromise. The empty weight will be about 950-1000 lbs. Now I also saw the golden rule of trike design and it says, 1. CG close to the two wheels 2. CG height <half than track 3. CG height< distance to front axle 4. CG in front half of vehicle Even with the smaller track of about 54" for spyder, all the above conditions are satisfied so I was wondering if I should be too concerned about the smaller track. Please advise. Thanks |
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Post by Liteway on Mar 14, 2014 12:18:17 GMT -5
It would probably work as you describe. But with that length of wheelbase, turning circle would be big and proportions with narrow track, strange. It may be a little tough to build a light frame that doesn't flex over that length and still have a reasonable step over height for entry. Overhead framing like the t-rex or mtntech's would help with that though.
I can understand why you need the length because with narrow track, to get foot space in a side by side means moving occupants behind front wheels. Then to maintain cg forward the rear wheel must be way back. This is one of those undesirable compromises I was talking about.
I wouldn't do it that way. I would widen track, put occupants farther forward, shorten wheelbase.
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Post by RT-chassis on Mar 14, 2014 13:21:02 GMT -5
It would probably work as you describe. But with that length of wheelbase, turning circle would be big and proportions with narrow track, strange. It may be a little tough to build a light frame that doesn't flex over that length and still have a reasonable step over height for entry. Overhead framing like the t-rex or mtntech's would help with that though. I can understand why you need the length because with narrow track, to get foot space in a side by side means moving occupants behind front wheels. Then to maintain cg forward the rear wheel must be way back. This is one of those undesirable compromises I was talking about. I wouldn't do it that way. I would widen track, put occupants farther forward, shorten wheelbase. Yes the narrow track is ahead of the foot space and the cg goes back so I moved the rear wheel back. The Elio is 110" wheelbase and is coming out soon so I was hoping for a 115-119" wheelbase is very big but not out of order. Ofcourse my minivan has a 119" wheelbase so I can relate to what you are talking about in terms of turn radius very well. I am more concerned about the track being 60" and would like to know facts about why it should change. Yes, it doesnt look right but if all the parameters are considered, my limited knowledge tells me that even 60" should work but you know better and hopefully can point me in the right direction before I make mistake  Again, the aim I have is to use as much off the shelf stuff to minimize head scratching and time. Thanks |
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Post by Liteway on Mar 14, 2014 14:29:46 GMT -5
Do not assume I know more than you. I am no expert. I bring my own set of prejudices along with me and probably rely too much on intuition. I have experience as a builder, but more eager to offer opinion than fact. So take salt along with my suggestions.
As a builder you will ultimately have to rely on yourself for making the big choices. Sounds like you have already done some helpful basic research elsewhere.
This forum can be useful. Some of these guys are good technicians. I'm just a tinkerer.
Hope you can get some more input from them with your questions and keep to the net for multiple sources of info.
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Post by noahkatz on Jun 6, 2014 1:13:31 GMT -5
Wider track reduces weight transfer/inside wheel lift and body roll.
My plan is also to get a salvage Can Am for the suspension.
I believe if the wheelbase is increased by the same % as the track that Ackerman steering geometry will be preserved.
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