Suspension type for high unsprung mass

[Mar-1]

We are designing a new type of in wheel motor for our car. The problem is the tire,rim and wheel all weigh about 45 Kg. Im not sure about which type of rear suspension to use in case the type of suspension matters. Any help !

thanks in advance for your time and aid.

[Mar-1]

We are designing a new type of in wheel motor for our car. The problem is the tire,rim and wheel all weigh about 45 Kg. Im not sure about which type of rear suspension to use in case the type of suspension matters. Any help !

thanks in advance for your time and aid.

[Drew Price]

I am pretty sure I don't have anything nice to say to that request, but I will say that Google, or any of the books listed in the BOOK LIST to reference for car design (http://fsae.com/eve/forums/a/tpc/f/125607348/m/1956095883) thread should help.


What makes you think the suspension layout decision has anything to do with if you have high vs. low unsprung mass?

[Mar-1]

I have made lots of research, the thing is all books and resources always assume that the unsprung mass is low/very low and i was just curious if the unsprung mass is increased to higher values like in our case, would that have any effect on the suspension layout?

[acedeuce802]

That's something that you, as the Engineer, have to analize.

[Dash]

I think the main thing is determining how you are going to manage the inertial forces from the wheel mass moving up and down. ( Probably going to be a lot of damping )

[Drew Price]

Which competition are you entering?

[Spetsnazos]

I think you should go with either the Swing Axle or leaf spring.

both seem pretty awesome to me and I think they just got a bad rap from people who don't know how to tune them properly.

http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Mar-1]

Thanks alot dash, Inertial forces are my biggest concern at the moment and we are working on it. I have already designed the layout (pushrod). And it was really tricky since the upright is the stator itself and there is the half shaft problem too since the brakes are inboard.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Dash:
I think the main thing is determining how you are going to manage the inertial forces from the wheel mass moving up and down. ( Probably going to be a lot of damping ) </div></BLOCKQUOTE>

[Mar-1]

Class 2 at Silverstone, England.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Drew Price:
Which competition are you entering? </div></BLOCKQUOTE>

[Mar-1]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by acedeuce802:
That's something that you, as the Engineer, have to analize. </div></BLOCKQUOTE>http://media.tumblr.com/tumblr_m2dy5iUEl61qcsjbg.jpg

[Warpspeed]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Mar-1:
Thanks alot dash, Inertial forces are my biggest concern at the moment and we are working on it. I have already designed the layout (pushrod). And it was really tricky since the upright is the stator itself and there is the half shaft problem too since the brakes are inboard.

</div></BLOCKQUOTE>
So if the brakes are inboard, and you already have the drive shafts, why are you placing the motors inside the wheels ???

[Mar-1]

well its an electric outer rotor motor. Variable Reluctance and Permanent magnet brushless Dc motor fused together. Its something a friend and me designed by ourselves and thought we should try it. Of course its still a crude idea and there way too many refinements to be done but it will do for now. And if it works, the application could be anything and not necessarily automotive.

[/QUOTE]
So if the brakes are inboard, and you already have the drive shafts, why are you placing the motors inside the wheels ???[/QUOTE]

[Mar-1]

there is no space inside the wheel since the stator has taken most of it. So we used a half shaft to connect the hub to the inboard brakes


[/QUOTE]
So if the brakes are inboard, and you already have the drive shafts, why are you placing the motors inside the wheels ???[/QUOTE]

[Mar-1]

why go through the trouble and place the motor inside the wheel. Well for one the efficiency is much higher than transmitting power through a drive shaft, differential etc. coz of the losses, although they might be minimal. How much has the efficieny increased, i dont have exact numbers yet, lots of testing needs to be done to find out and its not our main concern now since we want to finish the design.

[/QUOTE]
So if the brakes are inboard, and you already have the drive shafts, why are you placing the motors inside the wheels ???[/QUOTE]

[Gruntguru]

So you decided the transmission efficiency gain would be sufficient to make 45kg unsprung weight a tolerable compromise. On the other hand you don't know what the transmission efficiency gain is and you haven't got time to find out (perhaps just ask or Google "universal joint losses") because you need to get on with finishing your design?

[Mar-1]

According to our calculations and 4 Proffessors it is more than a tolerable compromise upto this point. And hey if we dont experiment and try something new then we will never know if it is possible or not.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Gruntguru:
So you decided the transmission efficiency gain would be sufficient to make 45kg unsprung weight a tolerable compromise. On the other hand you don't know what the transmission efficiency gain is and you haven't got time to find out (perhaps just ask or Google "universal joint losses") because you need to get on with finishing your design? </div></BLOCKQUOTE>

[Zac]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Mar-1:
According to our calculations and 4 Proffessors it is more than a tolerable compromise upto this point. And hey if we dont experiment and try something new then we will never know if it is possible or not.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Gruntguru:
So you decided the transmission efficiency gain would be sufficient to make 45kg unsprung weight a tolerable compromise. On the other hand you don't know what the transmission efficiency gain is and you haven't got time to find out (perhaps just ask or Google "universal joint losses") because you need to get on with finishing your design? </div></BLOCKQUOTE> </div></BLOCKQUOTE>

While this is true to an extent, before committing to a fairly non-conventional solution you might want to look at running some vehicle sims.

[Mar-1]

Since we are entering a Class 2 competition, everything is simulated and so far it looks good. Possibly we will manufacture the motor that we designed as a prototype.

While this is true to an extent, before committing to a fairly non-conventional solution you might want to look at running some vehicle sims.[/QUOTE]